97 l67 IFR values same?

**timboku** · 07-23-2016

Anyone know why 97gtp pcm has a flat IFR value across the board like an NA? Only year it's like that. 98 up l67s have a slopped IFR. Would it be benifical in putting slopped IFR values in a 97 that is being tuned for a turbo?

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**Turbocharged400sbc** · 07-23-2016

its the evolution of the hardware/OS as GM went through obd1/1.5/2

the v6 vehicles didn't need as much work to get to pass emissions and didn't get the R&D time that the v8 cars did for mpg/emissions.

the slight change in njector flow rate due to its "perceived" pressure differential (fuel press vs manifold) wasn't as important as them sorting out the 4t65e's drivability

I can only imagine what their breadboards looked like as they went through the major pcm hardware upgrades in just 4 years

**timboku** · 07-23-2016

Would it hurt/help to put the slopped IFR of later models in a 97 for a turbo build? Or stick with flat value even for 80lbs injectors?

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**Turbocharged400sbc** · 07-23-2016

I would say to experiment, and see if things change, it may not on a stock car, on a moded it may. though im partial to the 98/99 as being the best pcm/system before the damned Enhanced EOBD2 of the 00+

the 96/97 "obd2" sure seems like and OBD1.5 with refinements and without all the damn Com issues now that the knock system was integral in a "zit"

**timboku** · 07-23-2016

Hahah agreed...use the 98 all the time...first time working with a 97....you can take a 98 pcm and out it in a 97 can you..lol?

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