One of the most common modifications that require recalibration of the ECM are changing injectors and changing Mass Air Flow (MAF) sensors.

For the rest of this article, we’re going to assume that you’ve already read the articles explaining basic MAF operation and a model for injectors.  We’re going to discuss how to properly change the tune to compensate for new fuel injectors.

You should also take a look at the article on MAF Calibration as they often go hand in hand.

About Injectors on Ford ECMs

Ford uses the concept of injector slopes, breakpoints and battery voltage latency adjustment to cover the behavior of injectors.   Slopes represent the flow of the injector at high and low pulsewidths.  Breakpoints determine the pulsewidth required to switch from the low slop to the high slope.  Returnless fuel system cars add additional compensation tables related to fuel rail pressure.  When changing injectors, it is best to have a complete set of test data.  If you have good data, the amount of tuning required after inputting full injector data can be extremely minimal – think minutes versus hours with unknown injectors.

• In many cases, injectors purchased from Ford Racing will include all of this information.
• If you’re using a larger OEM injector (Cobra, Lightning, etc.) you can generally obtain valid data from the OEM calibration in which the injectors were used.  Some Ford vehicles which use desirable injectors:
  • 2014 GT500 52# Bosch EV14 (sold by Ford Racing who publish data)
  • 08 GT500 SXH1 48# Bosch EV14 (sold by Ford Racing who publish data)
  • 03 Harley Truck data i.e. EKO2 processor code is recommended by Decipha for 42# “green tops” (formerly sold by Ford racing.  warning: currently heavily counterfeited)
  • 03 Cobra AMZ2 for 39# “blue body” (warning: unusual spray pattern may cause issues with 2V / pushrod cylinder heads)
  • 05-10 Mustang GT CDC3 24# (sold by Ford Racing who publish data)
  • 97/98 Cobra AOL1 or AOL3 24#
  • 94-95 Cobra 24# injector data is NOT recommended.  Look at it sometime and see if you can figure out why.
• If you don’t have complete test data, you can make do.  You will need a wideband.  Recommended procedure:
  1. The rest of this procedure assumes you have a SOMEWHAT sane MAF transfer function.  If your MAF transfer is jacked, you may need to adjust, retune MAF then readjust a few times to get things properly aligned.
  2. Start with the data of the injector closest in size and design to the one you are using (slopes, inj latency, etc.).  If you can’t get any good data on other injectors, then your stock ones will do.  We will call this the “old” injector.
  3. Figure out what the injectors you are installing are rated for (i.e. 24#).  Remember the size of you old injectors (i.e. 19#).  Divide your NEW rated flow by your OLD rated flow.  Make sure your injectors are rated at the same pressure.  24/19 = 1.26 in this case
  4. Multiply both the LOW SLOPE and HIGH SLOPE by the value from above, in this case 1.26.
  5. Set your target AFRs / Open loop targets to a a UNIFORM value.  (i.e. 12.5 for a NA car)
  6. Do a WOT pass on the car.  Observe AFR.  Adjust BOTH high and low slope until actual AFRs resemble the target AFRs you have set up in your tune.
  7. Repeat #6 until the car is as close as possible to what you are commanding.
  8. Let the car idle.  Turn off closed loop if necessary.  Observe AFRs.   Adjust latency (battery voltage table) so that observed AFR is close to commanded AFR.
  9. Drive the car at low – light throttle.  Hopefully, Observed AFRs will be close to commanded AFRs.  If so, skip ahead to #11
  10. If observed AFRs differ significantly from targeted at part throttle, determine how badly they are off.  If they’re really far off, re-adjust in order to get things as close as you can.  After this, make SELECTIVE adjustments to the MAF transfer function at idle in order to achieve targets at idle while maintaining proper operation at light throttle.
  11. Once you have a preliminary set of slopes, latency values it is time to tune battery voltage tables.  First, observe battery voltage and AFR while IDLING.  At idle, the injectors are open the smallest amount of time so changes from battery voltage have the largest effect.
  12. Next turn on headlights, blower motors, brake lights, EVERYTHING you possibly can to put an electrical load on the motor.  Observe changes in battery voltage and AFR.  Make adjustments to the injector battery table in order to compensate for fluctuations.  I.e. if the car goes lean when you turn on the headlights, INCREASE the latency value at the voltage that the ECM reports with the lights on.
  13. Once you have the engine operating in a more consistent AFR range under electrical loan, rev the motor up and make sure that you don’t go too rich when battery voltage increases as a sanity check.
  14. At this point, you’ve probably done a more thorough injector calibration than most tuners will.

This article is being written to answer the most basic questions about what to shoot for when tuning an engine.  This is not intended to be absolutely what you must do – it’s intended to be a starting point for those who don’t know any better.

Prerequisitites

This article will assume you have read pretty much all of the Education section, particularly the article on Modes of Operation.  This article will assume you have a spark-ignition reciprocating piston 4-cycle (stroke) throttle-body fuel injected or multi-port fuel injected engine.  (If you aren’t familiar with these terms, click them!)

Basic Setup Guidelines

• Make sure the ignition system is in good shape before trying to tune a vehicle.  Coil(s), wires, and spark plugs themselves must be in good condition.  Fouled plugs will ruin your day.  Improper heat range or gap will cause ignition issues that will ruin your day.  A rule of thumb is to go one step colder on plugs for every point of compression (i.e. 9.0 -> 10.0) OR half atmosphere of boost (7.75 psi)  and decrease the gap by one third (i.e. 0.045″ stock to 0.030″) for every step colder plug.
• Make sure timing is correct.  “Timing” here means BOTH the mechanical connection between your crank and camshaft AND any adjustment of distribtor, CAS, etc. used to mechanically adjust ignition timing.
• As dumb/obvious as this may sound, you cannot make adjustments on an ECU to fix a mechanical problem. Things like bent valves, damaged pistons, dead coils, defective injectors,  bad sensors, incorrect mechanical timing, etc. are not things that you can fix with a computer.
• If the engine is operating in closed loop operation, it’s fueling behavior will be determined by the operation of the O2 sensor.  DO NOT TRY TO FIGHT THE O2 SENSOR.  Use the O2 sensor to guide your tuning activity i.e. try to get the ECM to make zero changes based on O2 sensor feedback
• Do not try to tune WOT using a narrowband (lambda) style O2 sensor, which is the most common type.
• O2 sensors can “lie” about the mixture.  LARGE camshafts and misfires are the most common culprits for this behavior because Oxygen sensors measure the Oxygen content of the mixture in order to infer lambda.   Large camshafts and misfires both cause “extra” oxygen to be present in the exhaust, which will cause a false lean reading.  If the ECM is operating in closed loop when this occurs, it will generally add fuel when no such trim is required.
• If closed loop O2 feedback is working against you, turn it off.  If you have closed loop feedback turned off, you should monitor conditions with a wideband.

• If you are dealing with a volumetric efficiency type system (i.e. TBI/TPI GM and others) it is a good idea to have your VE values resemble reality.  I.e. if you have 180% volumetric efficiency at idle to achieve stoich, this is bad.  Most “hot” naturally aspirated engines will achieve 85-95% VE, *in a narrow RPM range at WOT*  Some older engines with poor cylinder heads and manifolds will struggle to achieve a 80% VE.  Extremely modern engines will often see a peak VE close to 100% in places.  Motors almost always lose VE at low throttle angles/low MAP sensor readings due to pumping losses created by the restriction at the throttle body.  See the Speed Density article for more.
• If you are dealing with a Ford that uses Load, it is a good idea to make sure your injector size resembles reality so your MAF transfer function and calibrated load values will resemble reality.  The MAF and LWFM articles cover this as well.
• Looking at  a graphical representation of your tune should be a “pretty picture” not a bunch of noise.  Things aren’t going to be straight or perfectly smooth most of the time or you wouldn’t be tuning it but you should see trends.  It does not matter whether you are talking about a MAF or speed density or Alpha-N setup.  You should see clear trends.  The absence of trends or unexpected reversal of trends can often indicate a mechanical issue such as a fuel pump that has reached its maximum flow capacity, misfires, reversion, etc.
• For measuring power, your butt dyno is wrong.  Use a repeatable performance measure, i.e. dyno, accelerometer, 1/4 mile track, etc.
• Use all your senses particularly SOUND when tuning.

Basic Fueling Guidelines

• Best emissions are generally achieved close or at stoichiometric.  This is generally around 14.7 AFR gasoline, or 1.0 lambda.
• Best fuel economy is generally achieved between 15.5:1 AFR gasoline (1.05 lambda) and 16.2:1 (1.1 lambda) for port injected engines.  Newer cylinder heads with fast burn characteristics generally do better with leaner mixtues.  TBI setups generally need to run at least stoichiometric or richer.
• Best power is usually achieved around 0.85 lambda (12.5:1 AFR gasoline) on modern cylinder heads.  Older heads generally require richer mixtures.
• Forced induction engines run richer, mostly to combat knock.  How much richer will depend on the engine and conditions.  Except in rare cases, there is no benefit to ever running richer than 0.75 lambda (11:1 AFR gasoline)
• Oxygenated fuels (Q16, E85, E98/Ethanol, Methanol, Nitromethane) require substantially larger volumes of fuel than “regular” gasoline.  If you have an option for stoichiometric ratio, use it.  If not, it is generally preferable to use injector constants / base pulse width modifiers instead of MAF transfer/VE to tune this out.
• Almost all widebands on the market read in lambda but convert this to an AFR value for gasoline (where 14.7 AFR = 1.0 lambda) to display it.  If you are burning hexane, this is fine.   If you are running any other fuel, think of the desired lambda you wish to achieve and convert this lambda value to AFR gasoline.  I.e. target an AFR of “11.2 :1” to achieve a lambda of 0.77 with E85 at ~7.4 :1 AFR.
• Most pump gasoline as of 2012 in the US is at least 10% ethanol, which means that a true stoichiometric mixture is closer to 14.1 than 14.7.
• Summer and Winter gasoline blends can have dramatically different ethanol contents, especially in colder climates.  Different octanes and brands of gasoline can have a large variation.  Although somewhat outdated, see the gasoline faq for a more in depth discussion of fuel composition and why it matters.
• If you are tuning the vehicle with closed loop O2 feedback disabled, make sure you tune such that the ECM will not have to make big changes to achieve its targets when closed loop is turned on.  This boils down to shooting for around 14.7 AFR (1.0 lambda) in areas where closed loop will operate.
• Get AFRs around idle as smooth as possible in open loop without any feedback or idle troubles will happen.  Do not rely on closed loop to maintain fueling at idle.

Basic Ignition Guidelines

• Your ECU expects the distributor/CAS/other-adjustable-timing-thing to be in a certain spot.  ALWAYS SYNCHRONIZE YOUR TIMING WITH A TIMING LIGHT BEFORE DOING ANYTHING ELSE!@#!#!!!

• Mechanical factors (mostly combustion chamber volume, shape and design) are the primary factors determining optimal timing requirements.  Optimal timing is often referred to as “MBT” or Mean Best Timing.
• Most naturally aspirated engines like to run between 24 and 36 degrees of advance @ WOT at RPM-of-peak-HP
• It is often not possible to achieve MBT due to the engine knocking first.  Knock will destroy even the strongest engine.
• Higher compression motors need less timing than lower compression motors.  Higher compression motors are more likely to be knock limited.
• Forced induction motors need less timing as boost increases.  Forced induction motors are more likely to be knock limited.
• Aggressive camshafts generally let you run closer-to-optimal timing than smaller camshafts.
• Race gas and higher octane fuels generally allow closer-to-optimal timing.
• At a fixed RPM, the engine will generally require less timing at higher load.  I.e. more throttle less timing
• At a fixed RPM and load, the engine will generally require more timing with a leaner mixture.  (One reason to run a slightly richer mix is that you don’t need as much timing to effectively burn it.  There are plenty of exceptions to this and too rich can be a big problem too.)
• At a fixed load, the engine will generally need more ignition advance as RPM increases until around maximum horsepower where timing requirements generally flatten.

• Spark at idle is critcally important for maintaining a stable idle and not having stalling issues.  Too much spark will generally result in hunting/surging.  Too little will generally result in stalling or lumpy idle.  Spark control at/near idle is extremely manufacturer (and sometimes even ECM) specific.
• You can tune ignition timing to some degree by reading plugs but instantaneous acceleration data and/or a dyno while monitoring knock is the best way.
• The trap speed of a 1/4 mile run will tell you about power output but it will not tell you about specific RPMs, just overall performance.
• Your “butt dyno” is totally inaccurate.

Questions you may have coming in:

• How do I determine what is needed? Keep reading!
• What vehicles are compatible? Hardware will work with all 2004 and older Ford vehicles with a J3 port, depending on software support.
• What are the capabilities of Moates hardware? Realtime tuning, logging live data, burning chips, switching between multiple programs
• What hardware and software options are available, and at what cost? Keep reading!
• How do I learn to tune EEC? What learning resources are available? Keep reading!  We’ll provide references.

Vehicle Compatibility

• Hardware is compatible with all year/model Ford vehicles that have a J3 port.  This generally covers 86-2004 model years.
• If you already have a binary file (bin) or hex file (hex) that is tuned for your vehicle. you can use one of our chips.
• If you need to make changes (tune) to get your vehicle where you want it, you are limited by software support.
• Some ECMs are simply not supported in software that works with our hardware because of lack of definition information.
• It’s important to check for software support before purchase. If you have an uncommon vehicle (for example, a 1995 Festiva) you may be out of luck with our products.
• We need certain information to tell if your vehicle is supported. (click)  Email us to check before purchase!

Overview of Tuning Process

• Determine your target vehicle boxcode and strategy.
  • The Boxcode is typically a 3 or 4-digit letter/number code on the EEC computer. ( ‘A9L’  or ‘T4M0’ for example)  This represents a calibration for a particular engine/transmission using a particular strategy.
  • A Strategy is the set of procedures that the ECM follows to run an engine.  Combined with a calbration, this determines how the engine will operate.
    • The strategy will determine things like whether a MAF or MAP sensor is used, how spark and fuel are calculated, how idle is controlled, etc.
    • Each strategy needs a definition (or ‘def’) to work.  The definition tells the software how to interpret the binary and display it in a format you can understand with tables and real-world values.
    • For instance, the A9L boxcode, belongs to the GUFB strategy.  The A3M boxcode also belongs to the GUFB strategy.  You can change a bunch of parameters on a A3M computer and have it run 100% identical to a A9L computer.
• Review your software options in terms of availability.
  • First: figure out which software supports your box code.  Support varies from package to package.  Check with each software vendor for the most up-to-date supported options.
  • Next: download software and install it.  You can check out the interface and features at this time without paying for anything.
  • Finally: After you have found a software package with an interface that you like which supports your strategy, go to our web store to purchase.  You will need to have already installed software prior to purchasing in order to provide us with information to license it.

• Determine your tuning needs to guide your purchases.
  • Do you just need to burn chips?
  • Do you want to be able to make changes while the vehicle is running? (emulation)
  • Do you want to be able to log vehicle parameters while the engine is running? (datalogging)
  • Do you want a more accurate measure of the air/fuel mixture? (buy a wideband)
  • Decide what capabilities you need and then purchase hardware as appropriate.

• Install hardware.
  • Clean that J3 port PROPERLY!
  • To clean the J3 port, you generally must remove the case from the ECM, gently rub the J3 port with Scotchbrite or a mildly abrasive kitchen scrubber.  (‘mildly’ is important – you do NOT want to rub hard enough to remove the copper traces from the circuit board!)  A final clean with brake clean, starting fluid  or another mild solvent doesn’t hurt.  A properly cleaned J3 port will have a very, very slight crosshatch visible on the ‘fingers’ of the connector.
  • Golden rule: ALWAYS TAKE THE KEYS OUT OF THE IGNITION (CAR OFF!!!)  WHEN INSERTING OR REMOVING THINGS ON THE J3 PORT. Failure to do so can result in a fried ECM, fried chip/QuarterHorse or both.
• Install USB drivers
  • The same USB drivers are used for all Ford products
  • USB driver is a free download from the webstore, it comes with config instructions. (download)
  • If you need more visual directions, there is an install guide available on the Moates support site.
  • If you have trouble with the install, there is troubleshooting guide available on the Moates support site.

• Setup software and perform initial configuration
  • Establish communications, check settings – this procedure will vary depending on software package you are using.
  • Select the appropriate strategy for your box code and load any appropriate definition files.
  • Program hardware with a calibration to serve as a starting point.  A stock tune with a few key parameters modified to suit the vehicle at hand is great.  You’re just looking for something good enough to get the car to fire and (hopefully) idle.
  • If you are datalogging, select and configure datalogging payload matrix (PIDs) – i.e. what you’re interested in monitoring.

• Gather performance data, analyze it, and make changes toward an optimized result.
  • Parameters are gradually adjusted to achieve desired targets.
  • This is an iterative process, where adjustments are made and the results are evaluated followed by further adjustments.
  • Please see our subsequent chapters on Ford Tuning (available separately).
    • Basic Tuning Techniques and Common Examples
    • Advanced Tuning and Tricky Combinations

Chapter 2: Hardware Selection and Installation

Several types of hardware are available and needed depending on desired functionality.

Laptop PC

• Windows XP/Vista/7 are all compatible with the Ford tuning software.
• Something 5 years old or newer is recommended (no old 486 machines!).
• Internet access is recommended to facilitate licensing and software installations.
• USB ports (at least 1) are required. All needed cables are included with the hardware.
• If logging wideband, a serial-to-USB converter may be needed. ($37 on our webstore – link)

F3 Chip modules

• These modules install onto the J3 port of the EEC box.
• One per vehicle, $60 per unit – link.
• J3 port MUST be thoroughly cleaned, both sides, before installation!
  • Disassemble case, scrape off coating with non-metallic scraper or fingernail.
  • Clean both sides with Scotchbrite, not sandpaper.
  • Don’t be too rough, just polish it to a nice crosshatch, not down to the copper.
  • Clean with paper towel and alcohol or toluene.
• Two-position switch capable with user-added toggle.  Directions for switching are on support site.  (link)
• Reprogrammable many times using Jaybird.

Jaybird mini-USB chip reader/writer

• Small size, low cost, $75 – link.
• Allows reading and writing of the F3 modules.
• No datalogging or emulation with the Jaybird. No EEC box reading.  Most basic chip programmer available.

Quarterhorse Realtime Emulator and Datalogger

• Hardware unit is $249 – link.  All cabling is included, along with ferrite shields and USB bulkhead connections.
• Optional rotary switch ($30 – link) can be used to select from several different programs on the device, switching on-the-fly.  Works for EECIV ONLY.
• Fits onto J3 port like a chip module –  port MUST be clean as with F3 modules.
• On some early EEC boxes, several components will need to be gently bent out of the way for clearance during installation.

• The Quarterhorse is an integrated unit that can do several things:
  • Realtime Emulation
    • Changes in the calibration take effect immediately while engine is running.
    • No disturbance in engine operation or communications.
    • Changes in software are synchronized on the Quarterhorse.
  • Datalogging
    • Requires special definition file with ‘patch code’ written for the QuarterHorse, allowing RAM on the EEC to be shadowed onto the Quarterhorse.
    • Unprecedented access to variables and sensor values through the QuarterHorse without additional datalogging hardware.
    • Logging rates in excess of 5 kHz possible.  Most software logs around 20 Hz, which is great for tuning.
  • EEC Reading
    • EEC must be installed and powered in-vehicle with QH installed.
    • You can read the tune from the EEC box and save it to file.
    • This can be done with a stock EEC to acquire the base calibration.
    • You will be able to harvest the active calibration that has been programmed with a flash programmer this way.

Burn2 with F2A and F2E adapters

• The Burn2 ($85 – link) is a general purpose chip programmer that can be used for many different devices.
• When used with the F2A adapter ($10 – link), it can be used to read/write F3 modules.
• If the F2E adapter is added (another $10 – link), you will be able to read EEC boxes.
• No emulation or datalogging – this is a simple chip programmer only.
• This hardware combination is best suited for people that plan to tune vehicles from many different manufacturers.  If you plan on tuning exclusively Fords, consider the Jaybird as a less expensive alternative.

F8 chip module with Destiny programmer

• No emulation or datalogging – this is a simple chip with switchable tunes.
• Available exclusively through our distributor DP Tuner
• The $165 F8 module holds 8 switchable tunes and can be reprogrammed in-vehicle without removing the chip from the EEC!
• The $150 Destiny programmer is used with a 4-pin switch cable while F8 module stays installed on EEC.
• Once programmed, the $30 rotary switch can optionally be connected as a calibration selector.

Wideband O2 Sensor and Controller

• Used to sense your engine’s Air-Fuel ratio through exhaust gas analysis.
• Units such as the Innovate DB-Red LC1 Gauge Kit /w/ O2 ($209 – link) are very affordable.
• Software (discussed separately here) supports direct logging of the Innovate device data using a serial interface.  This is the preferred method of logging wideband data because it avoids all the pitfalls of using analog signals.
• Analog outputs from the wideband (such as the LC1) can be connected directly to the EEC in some cases (unused EGR pin on A9L for example).
• Wideband O2 readings critical for tuning fueling parameters.

Chapter 3: Software Selection, Installation, and Licensing

Several different software packages currently work with our hardware.  Cost varies considerably considerably from package to package along with capabilities.  Each software package also has its own unique flavor of interface – you will probably like one better than another.  Luckily, you can download and check them out prior to purchase.  Also remember that support for various box codes / strategies varies considerably from package to package.  It is important to investigate not just whether there is ANY support for a particular strategy but whether the items you require to tune your vehicle are supported – definition files vary considerably from software to software.  Fortunately, the availability of ‘trial’ versions makes it possible to ensure you to find a software package that fits your needs without having to purchase each one.

Binary Editor ( http://www.eecanalyzer.net )

• Written by Clint Garrity.
• Currently has the largest user base.
• Cost is $80 for the base application which is registered to a specific PC.
• Includes many of the most common and popular definitions (GUFB, etc) with no additional cost.  ( this list has almost all the “free” definitions along with some pay defs )
• Other ‘premium’ encoded definitions available at extra cost ($50-150+) from the definition author.
• Tends to benefit from a faster/newer laptop. Code is a bit heavy, so older PCs are taxed.  Think 2Ghz P4 / 512Mb ram realistic minimum.
• Includes EEC reading, chip reading and burning, datalogging, and emulation capabilities when used with the appropriate hardware.
• Also includes logging for wideband (Innovate, PLX, etc).
• Also includes optional support for standalone dataloggers, J2534 interfaces.
• Companion software EEC Analyzer is available for an additional $50. Not necessary, but it helps with data interpretation.
• Licensing occurs after you install the software from the available downloads, through a menu item within the BE and EA software programs.
• Both BE and EA licenses can be purchased from the webstore with information from the program.  See webstore product page for further instructions.

EEC Editor ( http://www.moates.net )

• Written by Paul Booth.
• Fairly lightweight software – does not require a very fast PC to work well.
• Cost ranges from $20-65 for each strategy depending on options.
  • EEC-IV is $20 for editing DEF (emulation and chip burning) plus $25 for datalogging (DLM) .
  • EEC-V is $10 more ($30+$35).
  • In order to have a comprehensive tuning solution for a typical fox body Mustang, you would need to order the GUFB def ($20) and the GUFB DLM ($25) along with a QuarterHorse.  This would allow you to tune any number of vehicles using the A9L, A3M, etc. processor codes.  You can also burn chips with the Jaybird/BURN2+F2A for any strategies you have purchased.
• Includes logging for Innovate Wideband (LC1, LM1, etc) at no additional charge.
• List of available supported strategies is listed on the webstore.

TunerPro RT v5 ( http://www.tunerpro.net )

• Written by Mark Mansur.
• Software license is optional (nag screen) but encouraged for $30.
• Editing portion of software *extremely* lightweight – can run well on older PCs.  Parts of logging engine considerably more demanding.
• Many definitions are available for editing only, see Tunerpro.net and our website for details.
• Editing, chip burning and emulation are supported by TPRT V4 and TPRT V5.
• Datalogging using the QuarterHorse is supported by TunerPro RT V5 via new the ADX format.  See here for updated definitions.
• QuarterHorse vehicle support is very limited compared to other software, but some of the most popular ones (GUFB CBAZA etc) are well-developed and available at time of writing (December 2010)

Flash & Burn Interface ( Moates/TunerPro )

• This is a low-level utility for reading and writing F3 chip modules using Jaybird or  BURN1/BURN2 + F2A
• Capable of reading EEC boxes using BURN2+F2A+F2E.  Does not work with QuarterHorse
• If you have a raw binary file ( bin ) you can use Flash n Burn to program a F3 chip module
• No cost, can be downloaded from the webstore.

F8 Destiny Utility ( http://www.moates.net )

• For use with a Destiny and F8 multi-position in-situ chip module.
• Allows easy management of stacks of tunes on the module with PC-based selection.
• No cost, can be downloaded from the webstore.

USB Driver ( Moates.net / FTDI )

• Needed to allow PC to communicate with the USB hardware (Quarterhorse, Jaybird, BURN2, etc).
• In many cases, working drivers will be detected by Windows via plug n play.
• If you need more visual directions, there is an install guide available on the Moates support site.
• If you have trouble with the install, there is troubleshooting guide available on the Moates support site.

Chapter 4: Suggested Techniques for Effective Calibration of EEC Systems

Vehicle Inspection and Preparation

• CRITICAL part of the tuning process. Start here, really.  If you fail here, you will never succeed.
• Several areas of the vehicle should always be analyzed before you begin the effort.
  • Smoking – learn to identify fuel (black) vs. oil (grey-blue) vs. coolant (white/sweet smelling).  You cannot fix oil smoke or coolant smoke with a tune.
  • Compression – you should have all cylinders within 10% compression of each other.  If smoking, damage to old spark plugs or general appearances make you suspicious of the motor’s health, check it before you start.  It’s a lot easier to deal with a motor with poor compression BEFORE you beat the snot out of it in the course of tuning it.  Many people skip this but it is something to think about because a motor that is already hurt is very likely to blow up or experience a catastrophic failure during tuning.
  • Check base timing, adjust as needed. (all vehicles with a distributor)
  • Evaluate TPS voltage.  Minimum/maximum values should be within acceptable limits.  Check for reversed wires – voltage should increase as throttle opens.
  • Look at MAF intake routing, make sure there are no obvious vacuum / intake leaks between the MAF and the intake valves.  Think cracked/split/loose hoses, bad gaskets, open ports, dry rotted couplers, hoses connected both before and after the MAF, …
  • O2 sensors should be operational without any exhaust leaks before the sensors.  For some reason, cut and soldered “extensions” for long tube headers often cause problems.  Plug and play extenders are *highly* recommended.  If you know that you do not have proper stock O2 sensors, REMEMBER TO TURN OFF O2 FEEDBACK!!!
  • If you are using a wideband sensor, you need to make sure there are no exhaust leaks before the wideband.  Flex tubing, poor joints between headers- midpipes and cracks in tubing can all create havoc.
  • If applicable, pay attention to which bank the wideband is installed in – bank-bank differences can be a powerful diagnostic tool.  Pay attention to how far the wideband is from the engine’s exhaust ports – there is always some lag between combustion events and measurement.  When things are changing quickly, this is critical.
  • Widebands need calibrated periodically, generally in free air.  Wideband sensors need replaced periodically.  Leaded fuel kills them very quickly.  Proper care and feeding of widebands is crucial to their effectiveness.
  • Be aware of catalytic converters.  Always tap them (GENTLY) and listen for suspicious noises that would indicate a catalytic converter that is degrading.  Clogged cats can rob literally hundreds of horsepower.  It is possible to place a wideband sensor AFTER a catalytic converter but remember that the cat will very slightly skew readings.
  • Make sure you have enough fuel pump and injectors for the power level you are looking for.  For a V8, “Injector size in #/hr * 14 = max hp” is a crude rule of thumb.  There are tons of injector calculators to be found if you want a better idea.
  • Ensure that fuel pressure is sane.  40psi with no vacuum reference is generally about where most OEM regulators are set.  You should be able to see a difference in fuel pressure between key-on-engine-off, idle and blipping the throttle.  Fuel pressure should be lowest when vacuum is highest.  Fuel pressure should increase when you blip the throttle as manifold pressure increases.
  • You need a MAF capable of metering enough air for your power goals.   There are ways to increase the metering capacity of a given meter, but tuning that properly is an advanced topic.  Keeping it simple: get a meter that can handle your airflow needs.
  • You need a functioning alternator and battery.  Battery voltage plays a role in crucial things like injector opening time and coil charge duration.  If your charging system is not functioning correctly, your tune may drastically change if/when you fix it.  Rule of thumb: if your battery voltage ever drops below 13 volts with the motor running, you will run into trouble.
  • On a similar note, underdrive and overdrive pulleys can cause real issues.  Pay attention if you see them.
  • Check for emissions hardware ( purge, smog pump, EGR, etc. ) that is missing.  In many cases these items can be disabled but you need to pay attention to what is present compared to what the ECM expects.
  • Basic maintenance should not be overlooked.  If it is important for a “normal” car it is twice as important in a performance application.
    • Spark plugs: correct heat range, appropriate gap, not fouled.  Consider power level, fuel and ignition system.  AVOID PLATINUM PLUGS FOR PERFORMANCE APPLICATIONS!!!  Copper or iridium will serve you much better.
    • Plug wires: no cracks/arcing, properly crimped ends, appropriate length so there isn’t too much tension
    • Firing order: firing order is determined by the camshaft (mostly) not the block or computer.
    • Spark boxes: great for distributor engines, unneeded/problematic for mod motors
    • Coil packs: Coil-per-cylinder (99-04 generally) applications like ***OEM*** coils best. (according to Dave B.)  MSD, Accel, Granatelli, … are all cause for concern especially with boost.
    • Oil and coolant: always check fluids before starting.  Quick check, potentially horrible consequences if low/out.
    • Fans / overheating: it is always a good idea to check that radiator fans work.  A car that overheats cannot be tuned.
    • Belts and Idlers: All serpentine belts must be in good shape.  Cracks, missing ribs, etc. will all cause problems.  Any idler pulleys must spin freely.
    • Tension:  Belt Tensioner should not be extended fully with the engine off.  Adjust belt length so that tensioner is in the lower third of its adjustment range with the motor off.  (i.e. it can move 2/3 through its range to increase belt tension – it should be mostly compressed when motor idle)  This is particularly important for supercharged applications.
    • Fuel filter: Fords are *horrible* about clogging fuel filters.  Especially if the car has been sitting for any significant period of time, change the fuel filter.  Motorcraft/OEM filters seem to hold up better than many cheap aftermarket ones.
    • Fuel age and type: Gasoline degrades with time.  Do not expect fuel that is more than a month or two old to be of the same quality as fresh gas.  Be particularly careful with heavily oxygenated fuels (i.e. VP Q16) and alcohols (ethanol, methanol, E85, etc.) in contact with fuel system components for large periods of time.
    • Clean air filter and MAF.  Oiled filters generally cause MAFs to get dirty.  Clean MAFs only after they have had a long time to cool – hot MAF+liquid=death.  Clean *GENTLY* with brake clean, starting fluid, or other organic solvents.
• Remember, you can’t fix mechanical or electrical issues by reprogramming the ECM!!! The results you achieve with tuning will only be as good as the material you start working with.  Garbage in, garbage out.

Datalogging: What’s important and what does it mean? What should we be interested in? What to select?

• There are certain sensors that you will almost always want to keep an eye on because they are critical to engine operation:
  • RPM – how fast the motor is spinning
  • MAFV / MAF counts – a “raw” value representing the reading from the MAF sensor
  • Airflow – a value calculated  by the ECM from the raw sensor MAF voltage that represents how much air is being ingested by the engine.  This is often represented in some form of “real world” value, like Kg/hr or Lbs/min
  • Load – from 94-2004 “Load” is the main factor involved in determining spark advance.
  • Spark Advance – when the ECM is commanding sparks to be fired.
  • TPS – Throttle Position Sensor.  How far open the throttle is, i.e. how hard you’re pressing the gas pedal
  • ECT – Engine Coolant Temperature(how hot or cold coolant flowing through the engine is)
  • IAT – Intake Air Temperature (how hot or cold air entering the engine is)
• Depending on what you are trying to do, there are other items you may want to pay attention to as well.
  • Injector Pulsewidth – How long the injectors open.  This can be useful both for “sanity checking” and to ensure you do not run out of injector – there is only a fixed time available at a given RPM to fire injectors.
  • HEGO1/2 – Heated Exhaust Gas Oxygen sensor.  Measures the presence or absence of oxygen in the exhaust in order to try to determine whether the motor is running rich or lean.   Watching the raw HEGO voltages can give you some kind of very basic indication of fueling.  These sensors experience a large change in voltage in a very small area centered around a stoichiometric mixture ( 1.0 lambda or about 14.7:1 Air-Fuel Ratio or AFR)
  • STFTs – Short Term Fuel Trims.  These are IMMEDIATE changes the ECM makes in response to HEGO readings in order to steer the air-fuel mixture towards desired targets.   If your EEC uses STFTs effectively (i.e. all modular motors) then these are generally more effective as a tuning tool than looking at raw O2 voltages.
  • LTFTs – Long Term Fuel Trims.  These are the long term difference between programmed values and target values.  Think of them as the average of STFTs over a long time.  If your EEC uses LTFTs effectively (i.e. all modular motors) then these are one of the most effective pieces of data provided by the stock computer for tuning fueling.
  • WBO2 – Wideband Oxygen meters can measure a much wider range of rich-lean conditions than standard HEGOs.  Having wideband data is often preferable to HEGO/STFT/LTFT.  In many cases (i.e. 86-95 in my opinion) it is often easier to disable closed loop operation/the O2 sensors completely and tune the car exclusively using a wideband.
  • ISC Integrator (‘integrator’) – this represents the difference between how much air the EEC is using to hold and idle versus how much it is commanded to hold in the tune.  Critical for proper tuning of larger camshafts and larger displacement engines.
  • Boost/MAP/Pressure – Although MAF systems do not differentiate between boost and vacuum, it is often very handy for sanity and safety to have an idea of how much pressure there is in the intake manifold.  For positive displacement blowers (roots, TVS, twin-screw) make sure you take pressure readings AFTER the blower on the lower plenum.
  • Pressure drop across injectors / FPDM duty cycle – most 99-04 cars control fuel pressure electronically.  These values are critical to a properly operating fuel system on these vehicles.

Recalibration: Modifying Parameters and Values to Achieve a Target

• First step: decide on target operating parameters for the engine
  • This may seem obvious, but something as simple as “make the most power” or “improve fuel economy” isn’t going to be be enough.
  • Second step: take a general goal like “make the most power” and decide on appropriate engine conditions to achieve that goal.
  • If you read these rules of thumb and say “this isn’t right for my engine” – GREAT.  You already know more than the audience these rules are aimed at.
    • If in doubt, “0.8 is great” – blatant simplicity.  Quoted me to once by someone who did OEM calibrations for Honda for a living.  It is very difficult to break anything due to fueling from running a vehicle at 0.8 lambda (about 11.6:1 AFR Gasoline)
    • 1.0 Lambda represents a stoichiometric mixture – exactly enough oxygen is present in the air to burn all the fuel supplied.  This is normally the best mixture for minimizing emissions.
    • Most vehicles make best power around 0.85 to 0.88 lambda (12.3 – 12.7 AFR Gasoline) – slightly richer than stoich
    • Most vehicles achieve best fuel economy at around 1.05 to 1.1 lambda ( 15.2 to 16.0 AFR gasoline)
    • Most vehicles need more ignition advance as RPM increases
    • Most vehicles need more ignition advance under cruising/low-throttle conditions than WOT
    • Knock is most likely close to peak torque, at high loads/low RPMs or at peak horsepower
• Next step: Get familiar with the strategy your vehicle uses.  Fueling, timing, idle, open-closed loop and just about everything else vary considerably from one strategy to another.  Being familiar with the strategy your ECM uses will help you figure out which tables to modify to acheive the results you seek.
  • eectuning.org is a good place to learn more.
  • the ‘Education’ section of moates.net is another good place to get information
• After you figure out where to look: set up what you can based on what you already know
  • Setup Engine Displacement / displacement of one cylinder
  • Setup injector size
  • Setup a reasonable rev limiter based on what you know of bottom end and valvetrain
  • Setup a reasonable (perhaps a little high to start) value for target idle
  • Setup a reasonable base calibration for MAF sensor.  If sensor came with a calibration sheet, this would be great time to use it.
  • Setup a reasonable target air fuel while in open loop
  • Setup a reasonable timing map.  A stock timing map adjusted for mods is always a good place to start.
  • Setup a reasonable pattern from switching from closed loop to open loop.
  • Enable or disable hardware such as O2 sensors, EGR, Purge/Evap, automatic trans
  • If you take your time to create a sane starting point before you turn the key on you will save yourself countless hours of time!
• Finally: Start your engines (and your datalogger) and make final adjustments
  • Are air fuels not matching what you command in open loop?
    • Three pieces of the fueling puzzle:  MAF transfer, Injector slopes(size), Injector offset (battery compensation – latency)
    • How do you tell what is going on?  STFTs, LTFTs (if O2s are enabled) combined with a wideband.  STFTs/LTFTs are great while O2s are active – i.e. part throttle
    • Leanest at idle, small pulsewidths but perfect at WOT/higher throttle -> increase battery offset
    • Lean – rich – lean patches as you gradually increase throttle -> wrong shape of MAF curve.  systematically tune it
    • Entire range of engine operation uniformly off from commanded values -> either injector slopes (size) or entire MAF transfer function is off.  Let load determine which one to multiply/divide in order to fix things
  • Idle issues?
    • Make sure your MAF transfer table, injector slopes and injector offset are sane before trying to fine tune idle!
    • Follow the integrator – a good place to start is to add the integrator (or subtract if it is negative) from the Neutral Idle Air table (in neutral) or Drive Idle Air table (if in Drive for automatic cars)
  • Performance
    • ALWAYS TUNE FUELING FIRST BEFORE TACKLING TIMING!  You are *much* more likely to break your engine if your mixture is wrong.  As long as your timing is good enough to light the mix, you can tune fueling adequately.
    • Tuning timing without a dyno is hard.  Accelerometers and a dragstrip can provide crude but repeatable feedback.

Data Analysis and Evaluation

• Once captured, the operational data can be analyzed and used to guide calibration effort.

(More to come!)

(below this line is draft / coming soon as of 2010-11-30)

Chapter 4:  Software/Hardware Initial Configuration with Tuning Session Start-Up Examples

• Physical installation of hardware is shown in more detail from Chapter 1 overview.
  • F3
  • Jaybird
  • Quarterhorse
  • F8/destiny and switch
  • Wideband

• Installation, licensing, initial configuration, and detailed hardware synchronization procedures for each software are explained and examples detailed. Initial basic calibration load-up for different hardware, as well as basic payload creation for datalogging, are explained and illustrated for each.
  • USB Driver
  • BE/EA
  • EEC Editor
  • TunerPro RTv5
  • Flash & Burn
  • F8/Destiny Utility

1. Data Analysis and Evaluation
   1. Once captured, the operational data can be analyzed and used to guide calibration effort.
   2. Several examples of logged data values and how they relate to calibration parameters are provided.

Chapter 6:

Case Studies: Example Modifications, Vehicle Combinations, and Rules of Thumb

1. Key Issues and Vehicle-Specific Examples
   1. How do many of the popular modifications on these vehicles affect the tuning approach?

i.      Bigger MAF

ii.      Bigger injectors

iii.      Cold plugs

iv.      Nitrous

v.      Gears and converter

vi.      Auto vs Manual

vii.      Emissions delete / racing modifications

viii.      Cam, heads

ix.      Headers/exhaust

x.      Cold air intake

1. 1. We look at a walk-through of important considerations and the thought process of tuning several different example combinations, with real-world dyno results.

i.      A9L/GUFB Fox Body, 1993 N/A 331 stroker, 24# injectors, cam, headers, 5spd.

ii.      CBAZA, same as above.

iii.      03/04 Mustang

iv.      SC A9L

v.      SC 03/04 Cobra

vi.      F150 Truck

1. 1. Achieving an Optimized Result: When is it good enough?

i.      What are your goals?

ii.      Do you plan for future modifications?

iii.      Rules of thumb for AFR and timing, NA vs boost.

iv.      What is safe vs aggressive?

>

>

>

> Vehicle Compatibility

>

> All year/model Ford 2004 and earlier with J3 port are compatible

***with our hardware*** but there may not be software support for particular models.

> Some vehicle year/model applications are simply not supported in the

> software because of lack of definition information. It’s important to

> evaluate the availability of your desired application as ir relates to

> the software selection process. You may be out of luck (for example,

> 1995 Festiva or such uncommon target).

http://support.moates.net/ford-strategies-supported/

http://support.moates.net/ford-box-code-strategy-cross-reference/

>

>

>

> Overview of Tuning Process

>

> Determine your target vehicle boxcode and strategy

>

>                                                                i.

> Boxcode is typically a 4-digit letter/number code on the EEC computer.

> This is the calibration code.

http://support.moates.net/ford-information-we-need-to-help-you/

>

>                                                               ii.

> Strategy is the ‘parent’ definition structure to which a boxcode belongs.

Each strategy is the set of procedures that are executed on your ECM to run an engine.  Sometimes more than one strategy can successfully run on a given ECM.  Normally we do not make many changes to the procedure part of strategies while tuning vehicles.  Instead, we change tables, functions and constants so that the engine receives what it needs to run well.  Each “box code” represents a configuration of a particular strategy for a particular engine.

>

>                                                             iii.

> For

instance, the A9L boxcode  belongs to the GUFB strategy.  The A3M boxcode also belongs to the GUFB strategy.  If you compare A9L.bin and A3M.bin the files will be almost identical because they use the same strategy but are configured for different vehicles by Ford.  If you get a definition (also called def) for the GUFB strategy, you will be able to edit both A9L and A3M binaries because they use the same strategy.

……….

>                                                             iii.

> J3 port MUST be thoroughly cleaned, both sides, before installation!

***IMPORTANT***

……………….

> Chapter 5:

>

> Suggested Techniques for Effective Calibration of EEC Systems

>

>

>

>

>

> Vehicle Inspection and Preparation

>

> CRITICAL part of the tuning process. Start here, really.

> Several areas of the vehicle should always be analyzed before you

> begin the effort.

>

>                                                                i.

> Check base timing, adjust as needed.  On older Fords, pull “spout” timing connector either by distributor (86-93) or on passenger fender side (94-95).  Adjust distributor to achieve 10 degrees base timing with spout removed.  Reinstall spout before tuning.

>

>                                                               ii.

> Evaluate TPS voltage, make sure it is in range through motion.

Vehicles are very sensitive to improper TPS voltage.  TPS being too low or too high can cause the ECM to not enter the correct idle mode.

TPS should be between 0.95 and 1volt with throttle plate closed.  This can be checked using QH quite nicely.

>

>                                                             iii.

> Look at MAF intake routing, make sure there are no gross vacuum / intake leaks.

http://support.moates.net/tuning-maf-systems-and-air-leaks/

See how much or little of that you want to put here.

>

>                                                             iv.

> O2 sensors should be operational, exhaust should be leak-tight at

> least that far back.

OEM Ford O2 sensors work a million times better than cheap aftermarket ones.

Ideally, a wideband sensor is to be installed in addition to the factory O2s rather than instead of one.

If this is not possible, it is greatly preferable to remove a secondary (Post-catalytic converter) O2 sensor.

If a primary O2 sensor has the be removed in order to install a wideband, make sure closed loop operation is disabled.

>

>                                                              v.

> Basic maintenance should not be overlooked.

>

> 1.       Plugs and wires

1a. PLUG GAP IS REALLY IMPORTANT

1b. Appropriate plug type is really important (Copper, Silver (Brisk for 3v)).  Iridium plugs are ok for applications with extremely strong spark boxes or CDI systems.  Avoid platinum plugs like the plague.

>

> 2.       Oil and coolant

>

> 3.       Fuel filter and fuel age/quality/octane

>

> 4.       Clean air filter and MAF

>

>                                                             vi.

> Ensure that fuel pressure is as expected through operating range.

>

> Remember, you can’t fix mechanical or electrical issues with reprogramming.

> Tuning is about more than just flipping chips, so make sure your

> vehicle is in good shape!

This really can’t be stressed enough.  Tuning a car that isn’t running right is like putting a bandaid over a gangrenous wound!  The first step to tuning a car properly is to make sure it is mechanically sound!

>

>

>

************I’m not sure I would get into datalogging just yet because we haven’t talked about recalibration yet.****************

> Datalogging: What’s important and what does it mean? What should we be

> interested in? What to select?

>

> RPM

> MAFV

> Kg/Hr

> Spark

> HEGO1/2

> TPS

> ECT,IAT

> Load

> WBO2

>

***********************************Snip*********************************************************************************************************

>

>

> Recalibration: Modifying Parameters and Values

>

The purpose of recalibrating an ECM is to produce the behavior you desire, and by doing so hopefully improve performance, emissions or other operating characteristics.  Normally, there are two stages to this process.

First, parameters within the strategy are altered to match physical parameters of the engine.  Engine displacement, injector size are the primary values here.  Also, the MAF transfer function should be altered to match the MAF that is installed on the vehicle.  You can often “rob” a MAF transfer function from another vehicle’s strategy when using the MAF from another vehicle.

Next, operating parameters are changed in order to achieve the actual running conditions desired for the particular engine.  In many cases, simply adjusting the “configuration” items for the strategy in the first step will make then engine run great but there are almost always small changes that can be made to optimize performance.

>

> What are the most common values we will need to modify?

>

i.     Displacement – how large the engine is

ii.      Injector slopes – define how much fuel flows through

injectors, aka injector size

iii.      MAF calibration – defines how much air enters the engine as

a function of MAF voltage.  aka MAF transfer function iv.      Rev limiters – protect the engine from being damaged by over-revving

v.      Speed limiters – protect the driver from his/her own stupidity

vi.      EGR delete, PATS delete, secondary O2 delete – turn off items that are not present or not desired.

>

> How do we know which values to change, and by how much?

>

(repeat / correlate with above)

First step: calibration data should match actual equipment specification

example: If you have a 347 stroker with 30# injectors your strategy should be configured to match these physical parameters

Next step: start your engines, identify problems and goals.  There are hundreds (if not thousands in some cases) of parameters you can change.  Before starting on tuning, it’s good to have an idea of what’s not right, what you’d like to improve and what you can leave alone.  This may sound basic, but maintaining some kind of focus is really important to working effectively.  Examples of things you might want to work on are improving idle, improving wide open throttle performance, decreasing fuel consumption.

After figuring out what aspects of running the engine you want to work on, it is time to get the data you need to achieve your goals.  By selecting appropriate items for datalogging, the QuarterHorse allows you to view, log and replay the same data that your ECM uses to run your engine.  Instead of blindly guessing which values you need to change in order to get the engine behavior you seek, you can use this process of logging, analyzing logged data and a little math to make appropriate changes.

Now specific tasks in the tuning process will be examined in detail.

This will be presented as a mixture of theory and practice.  The next chapter will serve as a guide for how to adapt the programming of your ECM to suit specific modifications (cold air kits, injectors, motor transplants, etc) and will be attempt to be primarily hands-on.

Routine tuning processes: (these are going to need more explanation, I’m just running out of steam tonight)

Basic setup – Slopes, injectors, MAFs, sane spark tables

WOT / Open loop fueling – MAF transfer, inj slopes, stabilized fuel table

Closed loop fueling – O2 trims, MAF transfer

Power tuning – Dyno, spark tables

Idle tuning – idle RPM drive, neutral, Drive idle air, neutral idle air, integrator, gains, etc

Dashpot – role, tuning, scalars, preposition

>

>

>

> Chapter 6:

>

CASE STUDIES AND HANDS ON PRIMARILY.  Theory / processes in previous chapter

>

>

>

>

>

> Key Issues and Vehicle-Specific Examples

*MAKE MORE SPECIFIC*  General procedures covered above

>

> How do many of the popular modifications on these vehicles affect the

> tuning approach?

>

>                                                                i.

> Bigger MAF

>

>                                                               ii.

> Bigger injectors

>

>                                                             iii.

> Cold plugs

>

>                                                             iv.

> Nitrous

>

>                                                              v.

> Gears and converter

>

>                                                             vi.

> Auto vs Manual

>

>                                                           vii.

> Emissions delete / racing modifications

>

>                                                          viii.

> Cam, heads

>

>                                                             ix.

> Headers/exhaust

>

>                                                              x.

> Cold air intake

>

> We look at a walk-through of important considerations and the thought

> process of tuning several different example combinations, with

> real-world dyno results.

>

>                                                                i.

> A9L/GUFB Fox Body, 1993 N/A 331 stroker, 24# injectors, cam, headers, 5spd.

>

>                                                               ii.

> CBAZA, same as above.

>

>                                                             iii.

> 03/04 Mustang

>

>                                                             iv.

> SC A9L

>

>                                                              v.

> SC

> 03/04 Cobra

>

>                                                             vi.

> F150 Truck

>

> Achieving an Optimized Result: When is it good enough?

>

>                                                                i.

> What are your goals?

>

>                                                               ii.

> Do you plan for future modifications?

>

>                                                             iii.

> Rules of thumb for AFR and timing, NA vs boost.

>

>                                                             iv.

> What is safe vs aggressive?

>

>

Before you read this, make sure you have read Theory: Alpha-N, Theory: Mass Air Flow and the FordOverview.  Although not essential, it wouldn’t hurt to have at least read about Speed-Density operation as well.  This page will assume you have read and understood these pages.  This is a somewhat complicated topic and will require you to put several pieces together so don’t feel bad if you have to read this a couple times.

About the table and why it is critical

The “Load with failed MAF” (“LWFM” from here forward) table(s) are found in almost all MAF Ford Strategies.  Most strategies that make use of IMRCs (Intake Manifold Runner Control – valves that restrict air entering the engine in order to increase tumble and velocity) have two LWFM tables instead of one and  switch from one LWFM table to the other as the IMRCs open and close.  The main purpose of the LWFM table is to estimate the amount of air going into the engine without using the MAF sensor or a MAP sensor (if present) to provide the ECM with an “emergency” fallback method of running the engine in the event the MAF sensor fails.

The LWFM table is also important for normal operation of the motor because Load from the MAF (this is “Load” – the Ford-specific calculated cylinder filling value calculated from the MAF sensor, RPM and engine displacement) is “sanity checked” against the LWFM table to determine if the MAF is providing reliable information.  If there is too large of a difference between calculated Load and the LWFM table, the ECM may ignore the MAF even if it is providing valid information! This happens most commonly in forced induction situations (where load is greatly increased compared to a naturally aspirated car) but can also occur in cars with aggressive camshafts.  If you are making changes to a MAF transfer function and you are not seeing any changes in engine operation, double check your LWFM table!  Further, most strategies use “Anticipation logic” to predict airflow.  This prediction logic is based off…  Surprise… The LWFM table!  Having a sane LWFM table is neccesary for the aircharge anticipation logic to work.  You can disable this but it’s generally not necessary if you tune the LWFM table properly.

LWFM table is a classic example of an Alpha-N control strategy – it’s purpose is to provide a very crude estimation of airflow entering the engine when the MAF signal is absent or the ECM thinks it is unreliable.   The LWFM table uses only two inputs – throttle position (aka “TP”) and RPM to determine Load.  Here is a picture of a typical LWFM table: (screenshot from Binary Editor / GUFB strategy)

Here you can see the X axis is RPM and the Y axis is RELATIVE Throttle Position volts.  Each cell represents the Load that will be used to calculate fueling and timing when the ECM thinks the MAF is bad.  For example, idling with the throttle closed (0 volts relative)  around 700 RPM the ECM will assume a Load of .1602 and make appropriate fueling and timing changes.

The importance of the LWFM table varies considerably from strategy to strategy.  A rule of thumb is that the newer of an ECM you are using the more picky it will be able the LWFM table.  Fox Body and most early EECV (pre-99) are fairly tolerant of inappropriate LWFM tables where 99+ ECMs are generally much, much, much more picky.

Tuning the LWFM Table

Tuning the LWFM table is pretty simple:

First, set the Aircharge WOT multiplier, Anticipation logic scalars, etc. to make the ECM as tolerant of a bad failed MAF table as possible

Second, GUESS!   Yes, guess.  Enter values that you think are sane for the setup, starting with the stock LWFM table as a guideline.  A few examples:

• If you put in aggressive cams, decrease the LWFM table at low RPMs and throttle angles while increasing it at higher RPMs and throttle angles.
• If adding a positive displacement supercharger (roots, twin screw) multiply the whole LWFM table by approximately the highest pressure ratio you will see.
• If you add a centrifugal blower, multiply a column of the LWFM table by the pressure ratio you achieve at a given RPM

Third, drive around and log throttle position (TP Relative), RPM, Load.  Compare the Load values you log with the LWFM table.  Start changing entries in the table so they get closer to the load you really see at given TP and RPM conditions.

Note: Turbo cars present a very big challenge to this strategy due to the amount load can vary with throttle position due to spool time.  This is a very tricky case and often the only solution is to try and maximize allowed error before the LWFM table becomes active and also disable Aircharge Anticipation and other functions dependent on the LWFM table.

As stated in our overview of MAF systems, one of their main weaknesses are air leaks.  Whenever air can enter the engine without going through the MAF, weird things happen.

There are two principal kinds of leaks that wreak havoc on MAF systems – constant leaks (like a unplugged vacuum port) and mechanically induced leaks (such as a Blow Off Valve or Bypass Valve that vents to atmosphere.)  Each leak has a tendency to affect the system differently.  In this article, we will try to take a look at what “should” be happening, what changes with a leak and what kind of odd things you can look for while tuning to identify a leak.

Reversion presents an additional problem for MAF systems.  Reversion is the technical name for when air changes direction and reverses flow.  MAFs are not one way systems – they will measure air flowing into the engine and then meter the same air flowing out of the engine when there is severe reversion, causing unreliable MAF readings.

Constant leaks

This kind of constant leak in a MAF system is the classic “vacuum leak” where a gasket, coupler or piece of tubing in between the MAF and the engine does not seal properly.  In this case, air can enter the engine without passing through the MAF.  Because air has entered the engine without passing through the MAF sensor, the MAF sensor reads artificially low.  An engine operating in open-loop mode will tend to run very lean.  A motor operating in closed loop will see very large positive trims as the computer uses the O2 sensors to add fuel to compensate for the lean condition.

The air leak provides more air for the engine at idle which will make the idle rise or sometimes “hunt” or bounce around unstably.  Generally, the idle system will also try to compensate.  On Fords you will see the ISC Integrator (“Integrator”) swing negative, indicating the ECM is allowing less flow through the idle valve than is commanded in the tune.  It is very common for the Integrator to get stuck at the minimum allowed value and have the car still idle higher than commanded.

Most MAF systems use the MAF for calculating appropriate timing values as well as fueling.  With a vacuum leak throwing off the system, the ECU thinks there is less air entering the engine than their really is.  This will mean that “load” values will be artificially low, which generally leads to timing being artificially high.  In severe situations, this combination of issues (less fuel, more timing) is a recipe for melting engine components if it goes unchecked.

Mechanically induced leaks

Bypass valves are the most common source of mechanically induced leaks although idle, purge and other vacuum operated solenoids can all be a problem.  MAF systems require these valves to be re-circulated so that air leaving the valve re-enters the intake AFTER the MAF so it does not get measured twice.

Blow off valves on turbocharged vehicles are often vented to atmosphere.  This unfortunately will severely confuse a MAF system.  When the valve opens, air that has already passed through the MAF and been “counted” is released into the atmosphere instead of entering the engine.  The ECU will supply enough fuel for all the air that has passed through the MAF while only a small portion of this air actually entered the engine.   This causes the engine to run very rich and can cause stalling or other problems when letting off the gas and the BOV opens.  Once the valve closes again and the car burns off the excess fuel delivered, things slowly return to normal operation.

Supercharger bypass valves can present the same kind of issues when they are allowed to vent to atmosphere. (or when there is a leak in the piping allowing air to recirculate.)  Failing to catch an air leak with a supercharger bypass will result in the MAF curve having a sudden change when the valve closes.  This will require complete re-tuning of the MAF transfer function once fixed so it is best to catch it early.

Reversion

Reversion is most common in engines with very large camshafts operating at low speeds such as close to idle.  Situations where MAFs read unreliably due to reversion can generally be greatly improved by moving the MAF further from the throttle body.  Increasing the volume of the intake between the MAF and the throttle body is also effective at smoothing out the pulses of air coming from an engine with a radical camshaft.  It is normally possible to get a reliable enough MAF signal in most circumstances.  Even extremely wild cams that draw 3-4″ of vacuum at idle can be tamed with an appropriately designed intake system.

Another form of reversion that is troublesome to MAF systems happens with poorly designed supercharger bypass valve systems.  In most of these systems, the pipe connecting the outlet of the bypass valve connects with the inlet of the supercharger at an angle where recirculated air flows backwards through the intake.  This causes any reverse-flowing air to be metered multiple times by the MAF, leading to unreliable operation.  This can almost always be remedied by adjusting the angle of the pipe from the bypass so it points at the inlet of the supercharger directing the flow of recirculated air away from the MAF.

Reversion is very obvious if you are logging the MAF signal. Looking at a graph of a “normal” MAF signal versus time, it will look like a line that could have been drawn without reversing the direction of travel.  The same graph of a MAF impacted by reversion will look very “shaky” and jagged, changing direction many times in a short period of time.

If you’re completely new to burning chips, you may want to take a look at the Beginners’ Guide before reading the rest of this article.  You will probably still need to read this guide in order to choose the correct programming parameters unless you’re in the situation where you’re programming a chip that is the exact same size as the chip you are replacing.  Programming chips with offsets comes into play in two situations:

1. If the chip you are programming is of a larger capacity than the binary file you are putting on it, you need to use an offset to ensure the tune ends up in the right spot on the chip.
2. Switching adapters which hold multiple programs require the use of offsets to fit multiple programs on a single chip for a switching adapter.

Both of these cases will be covered in this article.

Chip Offsets With a Single Tune:

We’re going to assume you have either TunerPro or Flash n Burn open at this point and the chip physically oriented correctly.  If you need help with this, look at the Beginners’ Guide before continuing.  We will be selecting the correct buffer and chip addressing to ensure the chip is burned properly and can be used.

When in the software:

1. Select the type of chip you’ll be programming from the drop-down menu. This will likely be either the AT29C256, 27SF512, AT90F040 or Moates J3 adapter (F3/F3v2).
2. Pick the ‘Load file to buffer’ option, and navigate to the file you want programmed on the chip. Select it, and it will be loaded to memory on the PC. Take note of the file size indicated in the message window. (You can typically “hover” over the filename before opening it and Windows will pop up an information box iwth the file size)  It will likely be one of five sizes: 4k, 16k, 32k, 56k or 64k bytes.
   • The file you have loaded will determine your buffer addressing (start/end)
   • 4k byte = 0000/0FFF
   • 16k byte = 0000/3FFF
   • 32k byte = 0000/7FFF
   • 56k byte = 0000/DFFF
   • 64k byte = 0000/FFFF
3. In the top right part of the window you will see the Chip Addressing offset values that need to be changed. The buffer addressing along with the chip size will determine what offsets you need to use. (Flash n Burn usually automatically selects sane offsets based on your chip type and file size in order to place your buffer at the end of the chip, where it usually belongs.)
   The following table summarizes what offsets you need to use depending on chip used and file size:

   File Size	Chip	Buffer Start -> End	Chip Start -> End
   4k (4096)	AT29C256	000000 -> 000FFF	007000 -> 007FFF
   16k (16384)	AT29C256	000000 -> 003FFF	004000 -> 007FFF
   32k (32768)	AT29C256	000000 -> 007FFF	000000 -> 007FFF
   4k (4096)	27SF512	000000 -> 000FFF	00F000 -> 00FFFF
   16k (16384)	27SF512	000000 -> 003FFF	00C000 -> 00FFFF
   32k (32768)	27SF512	000000 -> 007FFF	008000 -> 00FFFF
   56k (57344)	27SF512	000000 -> 00DFFF	002000 -> 00FFFF
   64k (65536)	27SF512	000000 -> 00FFFF	000000 -> 00FFFF
   32k (32768 EECIV)	F3/F3v2	000000 -> 007FFF	032000 -> 039FFF
   56k (57344 EECIV)	F3/F3v2	000000 -> 00DFFF	032000 -> 03FFFF
   64k (65536 EECIV)	F3/F3v2	000000 -> 00FFFF	032000 -> 03FFFF
   216k or 224k (EECV)	F3/F3v2	“bank” format: non-linear!	convert to 256k!
   256k (EECV)	F3/F3v2	000000 -> 03FFFF	000000 -> 03FFFF

   While the correct values are often selected, you can manually enter them.  For a single-tune single-chip scenario, you generally want the buffer (or file content) to be placed at the ‘end’ of the chip. The notable exceptions to this rule are 32k EECIV Ford tunes (which need to start at 0x32000 and end before the end of the chip) and 216k/224k Ford EECV bins (which are not in linear memory format and need converted to 256k before programming).

   
   To do this manually:

   • Ensure Buffer Addresses are correct for the file size you have loaded.
   • Adjust the Chip Addressing start value and end value until the end value is the maximum value for the chip AND buffer address values are correct.
   • A short list of common chip addressing settings:
     • 64k bin: 000000 start 00FFFF end ( SST27SF512 chip )
     • 32k bin: 008000 start 00FFFF end ( SST27SF512 chip )
     • 16k bin: 00C000 start 00FFFF end ( SST27SF512 chip )
     • 4k bin: 00F000 start 00FFFF end ( SST27SF512 chip )
     • 56k Ford EECIV bin: 032000 start 03FFFF end ( Ford F3 chip )
     • 256k Ford EECV bin: 000000 start 03FFFF end ( Ford F3 chip )
     • 112k Ford EECV bin: SPECIAL need other software ( Ford F3 chip )
     • 216k Ford EECV bin: SPECIAL need other software ( Ford F3 chip )
     • BEB files CANNOT be programmed with FnB / TP.  Must program using Binary Editor
     • eBIN file CANNOT be programmed
4. Once you are satisfied with the offsets, perform a normal Erase/Blank/Program/Verify cycle!  Consult the Beginners’ Guide for more information.

Using Switching Adapters:

Using our switching adapters (G2X, G3, GX, TwoTimer, F3, F3v2,F8) requires programming chips using offsets of making “stacked” bin files.  Switching adapters use chips that are larger than an ECU requires, allowing the extra space to be used for multiple programs.  The “extra” space gets divided up into chunks, each of which can store an individual tune.  There are two approaches to creating proper chips for use with switching adapters, both equally valid:

1. Lump all tune files together on your PC into one bin file “stacked” which is the same size as the chip, program chip at once.
   • The “Bin Stacker/splitter” function in TunerPro can be used to prepare a single file from a group of tunes.  (You can also use a hex editor or other tool)
   • This “stacked” file contains all the tunes and can then be programmed like a “normal” file using TunerPro, Flash n Burn, etc.
   • “Normal” programming cycle: Erase, Blank check, Load tune/buffer, Program chip, Verify.
   • Entire chip gets programmed at once, all tunes for the ECU get programmed on the chip in one operation as part of the “stacked” file.
   • Requires preparation of new “stacked” file and reprogramming of entire chip if any individual tune changes.
2. Program the chip multiple times, once for each tune, different small selected area of chip Program/Verify cycle instead of whole chip.
   • Instead of relying on a program to create a “stacked” file, knowledge of chip addressing is used to place tunes at correct places within a chip.
   • Programming cycle changes slightly: Erase, Blank check happens at very beginning of cycle ONLY ONCE.  Does NOT happen before every Program/Verify operation, like normal.
   • Erase/Blank is followed by multiple Program, Verify operations.  Each operation is for one tune.  Each operation will have different start/end addresses which are a portion of the chip.
   • Does NOT require preparing any special files in advance – uses the same bin files which would be used for single-tune programming.
   • If you want to chance a tune which is already programmed, the entire chip must be erased and all tunes individually reprogrammed.

As a rule of thumb, tunes start at the end of the chip and count down.  i.e. “Tune 0” is in the highest addresses on the chip, or the top slot in a stacked bin.  “Tune 1” will be the next lower slot.  Some adapters have chips which can hold more tunes than there are address lines for switching.

Each switching adapter we sell has different numbers of available slots, slot sizes and corresponding chip addresses start/end:

• G2X: 27SF512 chip (00000/0FFFF), 16x 32kbit/4kbyte slots on chip:
  1. F000/FFFF
  2. E000/EFFF
  3. D000/DFFF
  4. C000/CFFF
  5. B000/BFFF
  6. A000/AFFF
  7. 9000/9FFF
  8. 8000/8FFF
• G3: 29F040 chip (000000 / 07FFFFF), 16x variable size slots, Ex remote required, addressing varies according to settings on adapter
• GX: 29F040 chip (000000 / 07FFFFF), 16x 64k slots, Ex remote required, addressing varies according to size of base file.
  • There are 16 slots on the chip.  Each slot is 64k ( 0x0FFFF) in size.
  • Tunes smaller than 64k typically need to be top-justified so that they END at the end of each window
  • When using the Ex remote (or no switcher – floating switch inputs) slot “0” will be at the end of the chip and bigger numbers on the Ex remote will mean slots closer to the beginning (0x000000) of the chip.
• TwoTimer: 27SF512 (00000/0FFFF), 2x 256kbit/32kbyte slots, idles in “high position”
  1. 8000/FFFF
  2. 0000/7FFF
• F3 (version one – switch pin and 2 tunes): special case.  Cannot program entire device at once, stacking NOT possible.  Program chip twice, manually change state of switching pin during programming. Note: “Erase chip” function does NOT erase whole chip, only erases the “bank” selected by the jumper
• F3v2 (version two – 4 pin connector and dial switch, 8 tunes): special case.  Cannot program entire device at once, stacking NOT possible.  Program chip multiple times, manually change state of switch during programming to select different slots. Note: “Erase chip” function does NOT erase whole chip, only erases the “bank” selected by the switch
• F8: special case.  Use F8 device utility to prepare and program tunes.

What makes engine management tricky is that even the best theoretical models fail to accurately represent physical behavior in certain situations.  All engine controllers would use the same logic and procedures for running the engine 100% of the time if there was a perfect engine control strategy.  Instead, most engine management schemes incorporate several different modes of operation in which different sensors dictate fuel and timing requirements.  Also, engine controllers have specific logic dictating when to switch between different modes of operation based on different demands from the driver and different engine conditions.  Some of the most common mistakes made by people starting out (hell, even experienced tuners too) are changing some of the “main” functions in order to try to fix a problem that is being caused by a secondary table or the computer operating outside its normal mode(s).  Better understanding of the various modes of operation will help pinpoint what needs to be changed in a tune.

It would probably be a good idea for you to have read the other articles about Injectors, Speed-Density, Mass Air Flow, and Alpha-N before reading the rest of this.

Some basic vocabulary:

• ECM, ECU, Engine computer : used interchangeably to mean the computer operating the fuel injectors and running the engine
• RPM : Revolutions Per Minute – how fast the motor is spinning
• MAP : Manifold Absolute Pressure – (usually) the pressure of air entering the motor
• ECT : Engine Coolant Temperature sensor – sensor used to measure the temperature of coolant circulating through a motor.  Sometimes called different things by different manufacturers.  I will use ECT here
• IAT : Intake Air Temperature sensor – sensor used to measure the temperature of air entering the motor.  Sometimes called different things by different manufacturers – I will use IAT here.
• MAF : Usually used as a shorthand for Mass Air Flow Sensor / Meter
• MAP : Manifold Absolute Pressure Sensor – a sensor that measures the pressure of air in the intake manifold
• Idle Valve : A electromechanical valve controlled by the ECM that allows air into the engine in order to control engine speed.
• Displacement : the volume swept by a piston descending from the top to the bottom of the cylinder bore.  More here.
• AFR : Air Fuel Ratio – the ratio of air to fuel present in a combustible mixture.  Usually stated as a ratio, i.e. 14.7:1 for the stoichiometric AFR for gasoline.  Stoichiometric AFR varies from fuel to fuel.
• Lambda : similar to AFR, except usually expressed as a number where 1.0 represents a stoichiometric mixture for all fuels.  Lambda and AFR are the same concept expressed in different units.
• Stoichiometric : a mixture containing the precise amount of oxidants required for complete combustion of all fuel present.  See here or here for more information on chemistry involved.
• Injector : a special type of solenoid that allows fuel to flow through it when energized (more)
• Pulsewidth : the length of time the engine computer applies electricity to the injector, or how long the injector is commanded to be open
• Flow Rate : The amount of fuel an injector flows once open.  These values are typically given in units of cc/min or lbs/hr at a specified fuel pressure. (injector flow rate varies with the square root of fuel pressure.)
• Latency : the length of time after the injector is turned on before it achieves its linear flow rate.

Goals of Engine Management

Although the answer is somewhat obvious (“make the engine run as well as it can”) it is worth a closer look at what engine management systems try to achieve and why.  Operating optimally normally means one of several things:

1. Making the most power possible without engine damage happening
2. Consuming as little fuel as possible in order to make a specific power output (maximizing efficiency)
3. Minimizing emissions

Most of the time engine management systems aim for more than one of these at once, i.e. Fuel efficiency while minimizing emissions or power and efficiency.  Generally, you cannot have your cake and eat it too when it comes to engine management because the physical conditions required to achieve optimal fuel economy are vastly different than those required to achieve optimal power production.  Minimizing emissions frequently conflicts with BOTH power and economy!

So how do engine management systems deal with the conflicting requirements of economy, emissions and power?  The answer is the title of this section – engine management systems switch between different modes of operation based on input from the driver, measurements from sensors and how they are programmed from the factory.  Sometimes in the course of tuning it is necessary to change not only configuration parameters of an ECM but also how it switches from one mode of operation to another.

Common Modes of Operation

Different ECMs will have different modes of operation and different rules for switching among them.  Many modes of operation exist to service requirements common to all engines, leading to many modes of operation being shared between different engine management implementations:

• Cranking: This is the first task for an ECM – help an engine transition from being spun by the starter to spinning on its own propelled by combustion.  This might not sound like a very difficult task, but there is a LOT involved!  While cranking, cam and crank sensors need to be monitored so the ECM can determine how fast the motor is spinning and what angle the crankshaft is at in order to provide accurate ignition timing, injectors have to be fired in order to deliver enough fuel to get the engine moving, the ignition system has to deliver sparks at an opportune time to ignite the mixture, (in some cases) the idle valve needs to be opened to allow enough air into the motor to get it running on its own…  And more sometimes!  Combine this with (typically) the lowest operating voltages because the alternator is not providing electrical energy and you have a potentially tricky situation.
• Startup: Once the engine is spinning under its own power, the fun can start.  There are often special rules that change the behavior of the ECU immediately after the engine starts.  Idling higher to prevent stalling is a common task in startup mode.  Many engines add additional fuel and change timing in order to try to help the engine warm up to desired operating temperature faster.
• Open Loop: This is a critical mode for the overall operation of the engine.  Open-loop mode is the mode used most often for performance, but it is important all the time.  Open loop operation uses a control strategy like MAF, Speed-Density or Alpha-N to determine fueling and ignition parameters to use to run the engine.  If tuning parameters related to open loop are incorrect, the motor will never run optimally.
• Closed Loop: This is an important mode for fuel economy and emissions.  In Closed Loop mode, the fueling and ignition values from Open loop are adjusted using feedback from additional sensors (usually Oxygen sensors).  Small imperfections in a tune can be corrected in closed loop, letting the ECU maintain much closer control over operating conditions than is possible with open loop alone.  There are usually limits to how large changes can be made by closed loop, which can lead to diagnostic error codes.  (Too Lean / Too Rich / O2 sensor)
• Power Enrichment: (aka “PE” mode) This is a subset of Open Loop operation where engine conditions such as AFR and ignition timing are adjusted with the goal of maximizing power.  Frequently, TPS readings close to wide open throttle serve as a trigger for PE mode.
• Tip-in: Sudden changes are a problem for all control strategies.  When the TPS sensor indicates the throttle has changed quickly enough, the ECU can enter Tip-in mode where
• Decel Fuel Cut Off (DFCO): When you take your foot off the gas, many ECMs will shut off fuel injectors in order to decrease fuel consumption and help promote engine braking.
• Dashpot: Many ECUs implement some form of digital dashpot using the Idle Valve.  The idea here is to prevent stalling when the throttle plate closes suddenly by opening the idle valve enough to gradually bring the engine to idle.
• Idle: At idle, the ECU tries to maintain engine speed while little or no load is placed on the engine.  Idle is often one of the trickiest states to control well.  Usually a mixture of airflow control (via Idle Valve or Drive-by-Wire), spark control and fuel control is used.  Strategies for controlling idle vary immensely among manufacturers.
• Limiting/Protection: Engines have limits – how fast they can safely spin, how much boost they can handle, how fast the car can safely travel.  Part of the ECM’s job is to monitor engine conditions and take measures before damage occurs.  Frequently, spark or fuel will be cut off until engine conditions return below a pre-set limit.

More to come later on this topic…

Before you read this, you should already have read the articles on Injector Theory and Speed-Density.  This article will not make much sense without the background information in those articles.

First, vocabulary:

• ECM, ECU, Engine computer : used interchangeably to mean the computer operating the fuel injectors and running the engine
• RPM : Revolutions Per Minute – how fast the motor is spinning
• MAP : Manifold Absolute Pressure – (usually) the pressure of air entering the motor
• ECT : Engine Coolant Temperature sensor – sensor used to measure the temperature of coolant circulating through a motor.  Sometimes called different things by different manufacturers.  I will use ECT here
• IAT : Intake Air Temperature sensor – sensor used to measure the temperature of air entering the motor.  Sometimes called different things by different manufacturers.  I will use IAT here.
• Displacement : the volume swept by a piston descending from the top to the bottom of the cylinder bore.  More here.
• AFR : Air Fuel Ratio – the ratio of air to fuel present in a combustible mixture.  Usually stated as a ratio, i.e. 14.7:1 for the stoichiometric AFR for gasoline.  Stoichiometric AFR varies from fuel to fuel.
• Lambda : similar to AFR, except usually expressed as a number where 1.0 represents a stoichiometric mixture for all fuels.  Lambda and AFR are the same concept expressed in different units.
• Stoichiometric : a mixture containing the precise amount of oxidants required for complete combustion of all fuel present.  See here or here for more information on chemistry involved.
• Ideal Gas Law : PV= nRT (Pressure times Volume equals moles of gas times ideal gas constant times temperature)  More to be read about this here.
• Moles : a measure of how many atoms are present.  See here.
• Induction stoke :  the part of a 4-stroke engine’s cycle in which air is drawn into the cylinder by the piston.  See here for more information if you are not familiar with a 4 stroke engine’s operation.

Many ECMs (particularly older ones) use extremely slow processors to run an engine, especially by today’s standards.  In addition to doing all the math required by Speed-Density to calculate airflow, the processor often has many other extremely timing or IO-intensive tasks, such as processing crank and cam sensor inputs, firing spark plugs and firing injectors.  Additionally, most of these processors lacked floating-point units (short explanation: pieces of a chip that understand what fractions and decimals are) limiting their ability to accurately represent a model that involved lots of numbers with a fractional component.   Bottom line: engineers had to come up with ways to simplify and speed up the math involved in speed density in order to get older, slower, cheap microcontrollers to be able to run an engine.

Obviously, different manufacturers implement things differently.  In the remainder of this article, we are going to explore briefly how Honda and GM simplified the ideal speed density system to make it more practical to implement on cheap hardware.

GM: Base Pulse Width (BPW)

Ideally, n = PV /RT and then injector pulse = n / injector flow constant

GM introduce the concept of “Base Pulse Width” or BPW to reduce the “V” and “R” terms.  Basically, the BPW is how long the injectors need to be open in order to fill cylinders at 100% volumetric efficiency at a standardized temperature.  The BPW is then multiplied by the Volumetric Efficiency table (which is no longer a VE table in the ideal sense of the word) to determine fueling at different load and RPM conditions.  This is then modified further by coolant and intake air correction tables to account for temperature.  This cuts the number of math operations more or less in half.  The idea behind Speed-Density is being applied in a way that is less math-intensive.

Honda: Required Fuel Value (ReqFuel)

Ideally, n = PV /RT and then injector pulse = n / injector flow constant

Honda took a different approach to the problem of simplifying Speed-Density.  Basically, the MAP sensor and RPM values measured by the ECU are used to index a LUT that contains (more or less) a desired fueling value.  Looking at the math above, Honda essentially pulls the final desired injector pulse (n / injector flow constant) out of a table.  This required fueling value is then scaled by various tables indexed by ECT and IAT which attempt to correct for variations in air temperature.  Honda reduces about half a dozen math operations to one table lookup and a couple of additional easy math operations.  Again, the principles of Speed-Density are being applied in a non-ideal way that attempts to capture what is going on in a way that is fast to implement on slow chips.

Be prepared to do a lot of reading in the numerous side links on this page.  More information that is beyond the scope of this overview will be available.

“Mass Air Flow” (MAF, for short) is a method of measuring airflow into an engine in order to supply an appropriate amount of fuel and adequate spark timing. First, vocabulary:

• ECM, ECU, Engine computer : used interchangeably to mean the computer operating the fuel injectors and running the engine
• MAF : Usually used as a shorthand for Mass Air Flow Sensor / Meter
• Vane Air Flow Meter (VAFM, “Flapper” type meter) : An early type of air meter rarely used today that relies on air pressing against a metering plate (“flapper”) to provide an airflow signal
• Karman Vortex air meter : A type of air meter that not used very much anymore that creates and counts vortexes (air disturbances) in order to measure airflow.
• Hot-Wire MAF : A type of MAF Meter that uses a thin wire heated by an electric current to directly measure air mass.  The most common type of MAF today
• Hot Film MAF : A type of MAF Meter that uses a metal film heated by an electric current to directly measure air mass.  Another type of MAF that is found today.
• TPS : Throttle Position Sensor
• MAP : Manifold Absolute Pressure Sensor – a sensor that measures the pressure of air in the intake manifold
• Displacement : the volume swept by a piston descending from the top to the bottom of the cylinder bore. More here.
• AFR : Air Fuel Ratio – the ratio of air to fuel present in a combustible mixture. Usually stated as a ratio, i.e. 14.7:1 for the stoichiometric AFR for gasoline. Stoichiometric AFR varies from fuel to fuel.
• Lambda : similar to AFR, except usually expressed as a number where 1.0 represents a stoichiometric mixture for all fuels.  Lambda and AFR are the same concept expressed in different units.

Types of MAF Meters and General Operating Principles

Hot Wire MAFs and Hot Film MAFs are the dominant technology in use today.  Earlier style meters (Vane/Flapper, Karman) required an external temperature sensor in order to provide a meaningful airflow reading.  Hot Wire and Hot Film sensors are often found coupled with a dedicated air temperature sensor but they do not strictly require one because the method in which they generate a signal accounts for the temperature of the air they meter.  If you want to learn more about meters, read up here.

ECMs generally have a routine (usually called the “MAF transfer function” or something similar) that converts the raw sensor readings into an airflow value. Sometimes this is a real-world unit (such as g/s or lb/hr) and sometimes it is a purely arbitrary synthetic unit that merely defines the shape of the curve. MAF transfer functions for hotwire MAFs are usually an exponential curve. The shape of the curve is usually determined by the physical characteristics of the sensor. The metering range of the sensor is usually determined by the cross-sectional area of the housing it is in. This means that an easy way to increase the amount of air a given MAF can meter is to put it in a pipe with a larger cross-sectional area. The new MAF transfer function can be approximated (usually fairly closely) by multiplying the old transfer function by the difference in cross sectional area.

Example Question: a meter in a 2″ diameter round housing can meter 1000g/s. The same meter in a 4″ diameter round housing will measure how much air?

Answer: First, find cross-sectional area of 2″ diameter pipe.  Area of circle = pi * r^2.  Diameter = 2 * radius. Radius = 1″, area = 1 * pi.  Second, find cross-sectional area of 4″ diameter pipe.  Area = 4 * pi.  New area / Old area = 4 / 1 = 4.  Multiply original airflow (1000g/s) by ratio of area (4) to get maximum value of 4000g/s.  Note that each individual point in a MAF transfer function can be multiplied in this manner to rescale.

MAF Systems

From here on in this guide, “MAF” and “MAF Systems” will refer exclusively to systems using Hot Wire MAFs and Hot Film MAFs. The reason for this is pretty simple: these type of sensors (at least theoretically) are capable of measuring air mass without the need for significant compensation for air density (i.e. altitude changes, forced induction, changes in air temperature).  In practice, many control strategies use other sensors to try to increase the accuracy of the MAF by additional adjustments but it is not strictly necessary.  MAF sensors do not know what “boost” or “vacuum” are – they deal exclusively with airflow.  If you are trying to make the transition from tuning mostly Speed-Density systems to MAF Systems, be very cautious with timing values as the same trends and rules do not apply to both systems.

Fueling with a MAF system is about as simple as it can get.  It goes something like this:

1. The raw sensor output is converted to an airlow value
2. The next step after determining airflow is to figure out how much fuel is needed to achieve a “target” AFR (more on AFR targets later) which is usually achieved by multiplying by AFR expressed cleverly (see footnote)
3. Finally, the desired fuel value is achieved by multiplying/dividing by a value (injector constant, injector slope, async BPW, …) to account for injector size.  Also any battery compensation is added.  (See Theory: An Injector Model for more information)
4. Done!  At this point, we have an injector pulsewidth!  PulseOut = (MAF_Transfer(RawMAFSensor) * TargetLambda * injector size) + injector latency

There is no “standard” way of doing timing with a MAF system, but all variants basically calculate a value that represents how much air is entering the cylinder each time the motor turns over.  It goes something like this:

1. Start with the same airflow value from step one of fueling. (MAF signal -> MAF Transfer)  This tells us the amount of airflow per unit time.
2. Measure how fast the motor is spinning (RPM) and from this calculate how many revolutions happened during the same time frame as our MAF sample.
3. Multiply/divide airflow by engine revolutions to get airflow / rev.  Most engine management stops here (GM, Subaru, Mitsufeces, …) and spark tables are indexed in grams/rev.  This is a measure of engine load (with a lowercase “l” to denote that we are talking about something different than “Load”, explained next)
4. Ford (and others?) instead use a “Load” (with an uppercase “L” to denote that we are talking about something different than “load”) value that is calculated by multiply/dividing airflow/rev by engine displacement to get a measure of how full the cylinders are relative to their maximum capacity naturally aspirated at sea level with certain air conditions.  If you’re at all familiar with Speed-Density, this should sound somewhat familiar because it is a concept VERY similar to Volumetric Efficiency.
5. Timing tables are usually in the form RPM x calculated load.  MAF timing tables will display a very different characteristic shape than RPM x MAP tables common in Speed-density systems.

Now that we have some concept of cylinder filling (“Load” or “load”), we should return to a piece of how fueling happens in a MAF system: target lambda/AFR.  Usually the same measure used to determine appropriate ignition timing is used to determine an appropriate target AFR/lambda.  In these cases, there is a table that dictates target lambda/AFR indexed by RPM and load.  Sometimes, RPM and TPS is used to determing target AFR instead of calculated load.

Strengths of Mass Air Flow

1. Extremely accurate fueling and spark delivery across a diverse range of engine conditions (at least while in steady-states): the holy grail for engine management. A properly set-up MAF system can adapt to changes in weather and altitude with ease.
2. Minor changes to engine equipment (i.e. headers, minor camshaft changes, intakes that do not significantly alter the placement of the MAF) do not require recalibration of the ECM.

Weaknesses of Mass Air Flow

MAF systems are known for having these issues:

1. MAF systems are extremely intolerant of vacuum leaks.  Any leaks between MAF sensor and engine generally cause all manner of odd problems, running lean in most cases due to un-metered air making it into the engine.
2. MAF sensors can be extremely sensitive to how they are “clocked” – merely rotating the sensor at a given spot in the intake tract can be sufficient to significantly change its output.
3. MAF sensors require laminar flow to read 100% accurately.  True laminar fluids do not exist so this introduces some degree of inaccuracy to MAF sensor readings.  Placing MAF sensors near bends, size transitions or obstructions where flow is less laminar greatly magnifies this issue.
4. A MAF sensor can be a flow restriction in cases where the MAF housing is the smallest portion of the intake system.
5. Hot-wire MAF elements are very fragile.  Debris can destroy delicate wires easily.  Dirt and oil deposits can build up on the sensor element, adversely affecting readings.
6. MAF systems have a relatively poor response to transient conditions, such as sudden throttle changes.  This is explained by the time it takes air to move from the MAF sensor where it is measured to the cylinder where it can be involved in combustion.
7. MAF sensors are not “one-way” sensors – reversion from a camshaft with large amounts of overlap can cause air to be metered on its way in to the engine and then again on its way out resulting in an artificially high MAF reading.  This can almost always be fixed by placing the MAF sensor sufficiently far from the throttle body, however doing so comes at the expense of making transient response even worse.

It may seem like there are a lot of weaknesses of MAF systems, but it is truly hard to emphasize just how amazing and important the strengths are.  It is no secret that the majority of OEMs today are implementing MAF systems as the primary control strategy.  There is a good reason for this, namely that engines can be controlled much more precisely (with the goal of meeting stricter and stricter emissions standards) with a MAF system than any other type of control strategy.

Note: I say “Multiply/divide” multiple times because multiplication and division are very similar operations but division is generally much slower on microcontrollers and other “small” processors often found in ECUs.  For this reason, most division is implemented as multiplication by carefully changing the scale of one of the operands.

If you do not have a strong background in physics and chemistry, be prepared to do a lot of reading in the numerous side links on this page.  This isn’t intended to be a brutal presentation of the topic, but theoretical concepts are necessary in order to be able to understand what is going on behind the scenes.

Speed-Density is a method of estimating airflow into an engine in order to supply an appropriate amount of fuel and adequate spark timing.  First, vocabulary:

• ECM, ECU, Engine computer : used interchangeably to mean the computer operating the fuel injectors and running the engine
• RPM : Revolutions Per Minute – how fast the motor is spinning
• MAP : Manifold Absolute Pressure – (usually) the pressure of air entering the motor
• ECT : Engine Coolant Temperature sensor – sensor used to measure the temperature of coolant circulating through a motor.  Sometimes called different things by different manufacturers.  I will use ECT here
• IAT : Intake Air Temperature sensor – sensor used to measure the temperature of air entering the motor.  Sometimes called different things by different manufacturers.  I will use IAT here.
• Displacement : the volume swept by a piston descending from the top to the bottom of the cylinder bore.  More here.
• AFR : Air Fuel Ratio – the ratio of air to fuel present in a combustible mixture.  Usually stated as a ratio, i.e. 14.7:1 for the stoichiometric AFR for gasoline.  Stoichiometric AFR varies from fuel to fuel.
• Lambda : similar to AFR, except usually expressed as a number where 1.0 represents a stoichiometric mixture for all fuels.  Lambda and AFR are the same concept expressed in different units.
• Stoichiometric : a mixture containing the precise amount of oxidants required for complete combustion of all fuel present.  See here or here for more information on chemistry involved.
• Ideal Gas Law : PV= nRT (Pressure times Volume equals moles of gas times ideal gas constant times temperature)  More to be read about this here.
• Moles : a measure of how many atoms are present.  See here.
• Induction stoke :  the part of a 4-stroke engine’s cycle in which air is drawn into the cylinder by the piston.  See here for more information if you are not familiar with a 4 stroke engine’s operation.

Basic Goals and Method

The goal of Speed-Density is to accurately predict the amount of air ingested by an engine during the induction stroke. This information is then used to calculate how much fuel needs to be provided and may also be used for determining an appropriate amount of ignition advance.

The theoretical basis for this is the Ideal Gaw Law (more here.) rearranged to solve for “n” (the number of moles of gas present :

• n = PV / RT

In order to use n = PV / RT to calculate the amount of air a motor ingests during the induction stroke we would need:

• P is pressure in the cylinder immediately after the intake valves close.
• V is volume, which we know from engine displacement.
• R we know (it’s the Ideal Gas Constant see here for more)
• T is the temperature of the gas in the cylinder immediately after the intake valves close.

Many of the things required to calculate the amount of air the engine ingests using the ideal gas law are missing, unavailable or at least incomplete.  Some notable points where reality is less than ideal:

1. Our MAP sensor measures the pressure differential caused by the downward stroke of the piston in the intake manifold, not pressure in the cylinder as the intake valves initially close.
2. We are assuming that there is no residual exhaust left in the chamber to contribute to “poisoning” of the intake charge.
3. Camshaft overlap (i.e. when both intake an exhaust valve are open simultaneously – see here) makes fluid flow modeling considerably more complicated.
4. T that we need is the temperature of the gas in the cylinder.  This is not usually MEASURED – instead it is ESTIMATED from the temperature of air in the manifold (IAT), the temperature of the cylinder heads (ECT) and other factors.  “RT” is often referred to as the “density correction term” as it tries to account for how air density varies with temperature.  Density correction is arguably one of the biggest problems with speed-density. (more on this later)

Speed-Density introduces the concept of Volumetric Efficiency (VE) to account for the differences between what it can observe and what is really going on.  (mostly problems 1-3 above)  Roughly speaking, VE is the ratio between the amount of air actually present in the cylinder and the amount of air we predict would be in the cylinder using MANIFOLD pressure (MAP) instead of cylinder pressure for our “P” Pressure term, REVOLUTIONS Per Minute (RPM) times Displacement (Volume / REVOLUTION) for our “V” term and an air temperature value estimated from some combination of ECT and IAT for our “T” term.

A motor said to be operating with 100% VE has the same amount of air actually in the cylinder as predicted by n = PV / RT.  Most engines operate at considerably less than 100% VE in most operating conditions.  The difference between actual airflow and theoretical maximum airflow is termed “pumping loss.”  Some engines (most notably Honda engines ) can achieve slightly greater than 100% VE in certain conditions.  Most engines operating under forced induction can be thought of to have a VE greater than 100% in some conditions.

Speed Density ECMs generally have one or more VOLUMETRIC EFFICIENCY (VE) tables that are a critical item to be adjusted.  These tables allow predicted airflow values to be more closely adjusted to observed reality.

Strengths of Speed-Density

Speed-Density has many things going for it:

1. Pressure sensors do not pose any restriction to the flow of air into the engine, unlike a MAF sensor.
2. MAP sensors respond to changing conditions very quickly, enabling it to have fairly good transient response especially compared to Mass-Air-Flow
3. Compared to a carburetor, it allows much more control over the mixture at different engine loads
4. Simplicity: all the sensors required are extremely reliable.

Weaknesses of Speed-Density

Speed-Density is known for having several notable issues:

1. Density correction, density correction, density correction.  You might not think that temperature is that big of a deal, but trust me it is!  Seasonal changes can wreak havoc on speed-density systems.  Superchargers or turbochargers that compress air and raise its temperature from adiabatic heating cause significant changes in density that must be accounted for.  Altitude can also be really problematic.  Many systems incorporate Barometric Pressure sensors to try to address this, but it’s an imperfect correction.
2. Large camshafts with extremely low vacuum due to high overlap close to idle.  Camshafts that have low or pulsing vacuum close to idle present a challenge for Speed-Density.  MAP sensor averaging can help.  Alpha-N blending can help.  It is still very tricky to use speed density to predict airflow with a pressure sensor with camshafts that do not build an appreciable amount of vacuum.
3. Volumetric Efficiency tables can be very time consuming to tune.
4. Engine modifications generally produce volumetric efficiency changes requiring re-tuning.
5. Quite a lot of math is required to do Speed-Density “by the book.”  Because of this, most manufacturers implement something kind of like theoretical speed-density and cut corners or combine math operations in order to allow faster execution on puny computing hardware.  (Remember, most ECUs made prior to 2000 have a slower processor than the average inexpensive cellphone circa 2010)

Sanity Checking a Speed-Density Tune

There are a few rules that transcend particular manufacturer implementations:

1. Volumetric efficiency rarely changes suddenly.  VE tables should almost always have very gradual changes.
2. VE usually DECREASES as pressure DECREASES (i.e. more vacuum = less VE)
3. VE usually maxes out at an RPM close to peak engine torque at maximum observed load, which is usually where peak cylinder filling occurs.
4. Remember that VE tables are not the only thing that controls fueling.  Temperature correction tables (ECT, IAT) are often implemented as multiplier/divider tables.  Don’t forget about injector battery tables either! (see the separate article on Injector Tuning for more on this)

Alpha-N is also sometimes called “TPS maps” because the only sensor that is used for determination of fueling is the Throttle Position Sensor.  (And measured RPM, or how fast the motor is spinning)  Fuel and timing requirements for the engine are expressed as a function of RPM and TPS.

Alpha-N is used most of the time in tricky situations:

1. When the MAP sensor or MAF sensor has failed and the primary control strategy is deemed to be invalid.  Something-is-better-than-nothing is the idea.  (“Load with Failed MAF” is an example from Ford-land)
2. In conjunction with ITBs (Individual Throttle Bodies) due to the extremely low vacuum created by them (making Speed-Density tricky) and the desire to avoid needing to fit a potentially restrictive Mass Air Flow sensor (making MAF impossible).  Again, something-is-better-than-nothing is the idea.
3. In conjunction with ITBs and MAP as a load multiplier. (PowerFC D-Jetro for GTR Skyline, most notable example)  ITBs + Boost – Alpha-N output is multiplied by a MAP sensor to come up with a composite load index.
4. In conjuction with Speed-Density and some kind of blending algorithm.  This approach is often used with very large camshafts that pull little vacuum at idle.  Basically, TPS and MAP are allowed to contribute varying amounts to the overall load calculation.   Net result: more stable and meaningful load index close to idle when MAP sensor readings are unstable.  Found on the Electromotive TEC3 among others.

Alpha-N is very poor at dealing with hills (think about engine load going up and down hills at a constant throttle position), temperature variations and just about anything else that you’d care about except close to wide open throttle where it does fine.

Understanding your fuel injectors is one of the most important things you can do to ensure that fueling is appropriate for your engine.  First, some vocabulary:

• ECM, ECU, Engine computer : used interchangeably to mean the computer operating the fuel injectors and running the engine
• AFR, Air – Fuel Ratio : the ratio between how much air and how much fuel an engine is receiving or how “lean” or “rich” it is running
• Solenoid : a solenoid is an electromagnetic electromechanical device.  It operates by using electricity moving through a coil to generate a magnetic field which moves a plunger. (more)
• Injector : a special type of solenoid that allows fuel to flow through it when energized (more)
• Pulsewidth : the length of time the engine computer applies electricity to the injector, or how long the injector is commanded to be open
• Flow Rate : The amount of fuel an injector flows once open.  These values are typically given in units of cc/min or lbs/hr at a specified fuel pressure. (injector flow rate varies with the square root of fuel pressure.)
• Latency : the length of time after the injector is turned on before it achieves its linear flow rate.

Everything you ever wanted to know about injectors but never knew to ask

Injectors are pretty simple devices: turn on the electricity, wait till the fuel starts flowing.  Right?

Not quite…

Injectors are mechanical devices – once electricity is applied, the injector needs to move from its resting position in which no fuel flows to its open position where fuel is flowing at its published flow rate.  The problem is that this transition from “closed” to “open” is far from instant – some larger injectors can take several milliseconds to open fully.  During this time, injectors do not flow at their linear flow rate.  How long injectors take to open varies from injector to injector largely due to mechanical reasons.  Fuel pressure can also affect injector latency because of the force applied by fuel on injector internals.  And most importantly, the amount of electricity you supply to the injector controls how much magnetic force coils inside the injector can create.  Bottom line: when your battery voltage decreases (such as when cranking) your injectors take longer to open and fuel injector latency increases.

Tuning for Injector latency

Most engine computers have some kind of table to compensate for injector latency.  They can be called many things – “Injector Battery tables” or “Injector battery offset” or “battery tables” but they frequently look very similar: a table of how long to open the injector before it achieves linear flow (“latency”) versus measured battery voltage.  The idea here is that the ECM opens the injectors for a period of time (from the battery tables) to compensate for variations in injector opening time versus battery voltage.  If you change injectors, you probably need to update your battery tables, too.  If you vary fuel pressure, you may want to try changing the battery tables as well as other tables to account for changes in latency.

A basic method for tuning injector latency requires a wideband and a multimeter (or better yet, datalogging battery voltage from the ECU).  Follow this procedure:

1. Start by hooking up you multimeter or starting datalogging battery voltage.  If you are using a multimeter, use a voltage source close to the ECM if possible.
2. Fire up the car and hold it at a few thousand RPM.  Observe battery voltage – it should be fairly high. (13.8 – 14.5 volts, depending on the vehicle)
3. Gradually, let the car return to idle while keeping an eye on battery voltage.  Many vehicles will run anywhere from 0.75 to 0.1 volts lower at idle compared to cruising RPMs.
4. Problems with battery tables can contribute to hunting or unstable idle.  Once the car is idling, do everything you can to put an electrical load on the car – turn on headlights, turn on the stereo, turn on the fan for the climate control inside the car.  As you do so, keep and eye on battery voltage and observed air fuel ratio.
5. If you see the car run progressively leaner when you turn on electrical accessories and voltage drops, start increasing injector latency at the battery voltage you observe until you minimize changes in air fuel ratio when changing electrical load.  This will result in a curve with a steeper slope.
6. If you see the car run progressively richer when you turn on electrical accessories and voltage drops, start decreasing injector latency at the battery voltage you observe until you minimize changes in air fuel ratio when changing electrical load.  This will result in a curve with a flatter slope.
7. If you feel really adventurous, you can disconnect the large cable between the alternator and the + side of the battery (or sometimes a wiring distribution block) while the car is running.  When you do this, the battery will stop charging.  Voltage you observe at the ECU will decrease as the car consumes the battery’s charge.  You can generally tune a much wider range of the battery table by doing this but it is much more of a pain to do and will eventually drain your battery to the point the car will not run.
8. Note: these injector battery tuning methods assume the car is reasonably well tuned close to idle and will idle at a reasonably steady AFR.  Doesn’t need to be perfect, but you may do more harm than good messing with injector battery tables when the tune is jacked.

Another sign that your battery tables may be off is when the car runs poorly at small throttle angles compared to large throttle angles.  Sometimes changing latency is a quick way to fix a car running too rich / too lean that runs well close to wide open throttle.  Latency changes will have a large effect at low pulsewidths (i.e. closed throttle) but will have comparatively little effect at high pulsewidths (i.e. open throttle.)

You shouldn’t be afraid to adjust injector latency as part of tuning but always remember that it is a BROAD SWEEPING CHANGE THAT WILL AFFECT HOW THE ENGINE RUNS EVERYWHERE.  If you have a problem in a specific load condition, chances are your problem is elsewhere.  When you start seeing PATTERNS of problems (i.e. closed throttle too lean, close to idle where battery voltage too lean, hard starts/cranking when battery voltage lowest, etc.) then it is worth looking into whether a latency adjustment can solve your tuning issue.

You can always sanity check your injector battery tables visually.  Injector latency always increases as battery voltage drops.  If you look at a 2D graph of battery voltage versus latency, it should always be relatively smooth.  As voltage increases, injector latency should level out and change much more slowly than at lower voltages.  This is not a Ford thing or a Honda thing – this is a universal thing that all cars that use fuel injectors will follow.

Tuning for Injector Flow

We haven’t said that much about injector flow up to this point, but it is equally important to having your engine run correctly.  Injector flow is the “obvious” thing that most people change when installing different injectors.  Most older systems account for injector flow with a “fuel constant” (it is called many different things in different systems such as… ) – when you change the size of injectors, you multiply the fuel constant by the difference in flow between your old injectors and your new injectors.  For example:

1. Fuel constant = 16.4
2. You have 24lb/hr stock injectors
3. You install 32lb/hr stock injectors
4. 24 (old) / 32 (new) = .75
5. New fuel constant = old fuel constant * change in injector size = 16.4 * .75 = 12.3

Keep in mind, this is just a guideline to get you close.  You can use the injector size / injector constant to make sweeping, global changes to fueling if your tune is off everywhere.  You *should* be able to get a tune very close to where it was before an injector change by changing nothing more than battery tables and an injector size / injector constant.

Some systems (Ford, GM LSx, newer Dodge / DCX Hemi, others) use a dynamic flow model of injector behavior rather than a single “injector constant.” These systems try to more precisely account for the flow of injectors by modeling how injector flow changes as a function of how long they are open.  Most ~87-2009(ish) Ford uses the concept of injector slopes.  There is a “low slope” and an “high slope”, along with a threshold to change from one to the other and often a minimum pulsewidth.  The injector slopes can be thought of as TWO injector flow constants and the ECM changes from one to the other as the injector opens.  When changing injectors on Fords or other manufacturers that use dynamic flow models, a good starting point is to scale both slopes (or all members of a dynamic flow table) uniformly by the predicted difference in injector flow rate.  An even better approach is to copy values from another OEM calibration that uses the injectors you have installed.  Some injector suppliers (but not many – Injector Dynamics is the one that comes to mind) do dynamic flow testing and can supply you with data precise enough to plug in.