GM: TPI Forced Induction

Good Choices (simple)

You have three choices for tuning forced induction on a TPI ECM (i.e. 7730).

  1. Not REALLY a good option, but a simple one: use stock code, hack it around to be ok at WOT by power enrichment tables.  This is ugly and only has a possibility of working for low boost setups.   Do not do this unless you really don’t care how the car runs except at WOT and you are too lazy to choose another option.
  2. Use Code59 on your ‘7730  (see – a modified version of the $58 code that came in the Syclone/Typhoon turbocharged trucks) For this to work, some wiring mods are needed.  (See here for more wiring info, here for more general info) This is not for the faint of heart, but represents a much better solution overall because you are using code that understands what forced induction is.  Code59 isn’t perfect, but it’s arguably the best option readily available that works with OEM hardware.
  3. Code59 on a ‘749 ECM.  This is pretty similar to #2 above, except you get some additional stuff in the ‘749 that will make it easier to say run P+H injectors.  Rewiring will be needed.  The ‘749 is also setup to control boost via PWM and an external solenoid which can be handy for turbocharged applications.

You should plan on buying a Wideband O2 (such as the Innovate LC1), something to datalog with (APU1, ALDU1) and something for realtime emulation (APU1, Ostrich2) along with a G1 chip adapter in order to tackle a project like this and have any degree of success.  You could do it without some of these tools, but you probably wouldn’t be reading this webpage for advice if you didn’t need them.

You will genererally need to install colder spark plugs, (maybe) a spark box, larger injectors (32, 36 or 42lbs would probably be good place to start.  Use an injector calculator to figure out how big you should go based on power goals), a 2bar or 3bar MAP sensor to replace your 1bar factory sensor, sometimes an upgraded fuel pump(s).

Good Choices (Complicated)

The other worthwhile option to mention is using a LS1/LS2 ECM with EFI live.  This requires extensive hardware and wiring changes but has great rewards in terms of an upgraded ignition system, more reliable triggering (i.e. no Optispark) and much more powerful and capable ECMs with advanced features.  See EFI Connection 24x / 58x pages for more information on this upgrade.  You can get EFI Live from us after you’re done.

Bad Choices

While I’m at it, a lot of people ask about FMUs.  This is a quick explanation of how they work and why they’re a band-aid (at best) not an effective tuning solution:

  • FMU is a rising rate regulator
  • It causes fuel pressure to increase at a fixed ratio with boost pressure (usually 8:1 to 12:1)
  • Fuel delivery (approximately) increases by the difference in sqrt of fuel pressure.  I.e. 40 -> 60 psi = sqrt(60) / sqrt(40)
  • An FMU can generally get fueling approximately ok SOMETIMES but more often than not it results in an overly rich mixture and inconsistent fueling across different RPMs.
  • With 35 psi base pressure and 8psi of boost, a 8:1FMU will be delivering close to 100psi of fuel pressure!  Because it raises fuel pressure so much, there is a significant strain placed on the fuel pump and injectors.  Fuel atomization (and therefore power) suffers a lot at extreme pressures with most injectors.
  • Most importantly, FMUs do nothing to adjust spark to compensate for boost.
  • Bottom line: FMUs are a cheap, hackish bandaid supplied to minimally make things work by running the car artificially rich instead of properly adjusting the mixture and timing for boost.

The “Good Choices” above are ways of doing things the “right” way.  It’s a lot more work, but you can get the car to run a *lot* better than with an FMU.  Making appropriate adjustments for ignition timing will also let you run a LOT higher boost than with just a FMU.