iac steps

[BALLSS]

I am referring to only larger aftermarket TB (52 or 58 mm) that require PCM re-calibration. Not a stock 48 mm TB. M6 cars are not affected by the TPS as much but there are other tune parameters that take info from TPS vdc so making adjustments to the PCM should be done.

Any tuner will do this. If you do a mail order tune most tuners have a form and one of the ?'s is what size TB.

[SSlowBoat]

I am referring to only larger aftermarket TB (52 or 58 mm) that require PCM re-calibration. Not a stock 48 mm TB. M6 cars are not affected by the TPS as much but there are other tune parameters that take info from TPS vdc so making adjustments to the PCM should be done.

Any tuner will do this. If you do a mail order tune most tuners have a form and one of the ?'s is what size TB.

I understand that, the reason i am asking, not trying to bicker, is because I have had more than one tuner tell me only thing that needed to be touched for larger tb was the tps and iac stuff, then a little ve work to smooth out part throttle transitions and stuff. never had anything said about line pressure issues since the tps is doing the same thing as it did stock when properly set up and reading the same, and an aftermarket tb barely helps in the power department u less max effort. at which point, you should have a built 4l60e anyway. all my cars have been autos until now. and have used bbk 58mm or tpis 58mm tbs. it was never mentioned about line pressure or trans tables from more than one tuner, some of who frequent here.

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[BALLSS]

I have had more than one tuner tell me only thing that needed to be touched for larger tb was the tps and iac stuff, then a little ve work to smooth out part throttle transitions and stuff. never had anything said about line pressure issues since the tps is doing the same thing as it did stock when properly set up and reading the same

it is the "re-programmed" TPS stuff that does correct line pressure to be the same as with a stock TB blades. My point is aftermarket TB's need PCM re-calibration as the transmission is affected by lower line pressure if no adjustments are made. It would be TPS vdc is re-calibrated per throttle blade angle to keep the line pressure in the tranny correct to the position of the throttle blades of the aftermarket TB

[Injuneer]

Some thoughts....

The TPS voltage can be anywhere between 0.30 - 0.90 volts at closed throttle. The PCM reads the closed throttle voltage at key on, and sets that voltage as 0% TPP (throttle position percent). While most of the hundreds of data logs I have reviewed show 0.67 volts for a stock, unmolested throttle body and sensor, there is nothing magical about this value, and it does vary somewhat.

I appears the PCM adds ~ 4 volts to the closed throttle value it read at key on, and sets that as 100% TPP, then prorates between those voltages to determine TPP.

DTC 21 for high TPS volts will set if voltage exceeds 2.50 volts at closed throttle (defined as less than 10 grams/second mass air flow) for 5 seconds. DTC 21 will also set if TPS voltage exceeds 4.80 volts at any time. DTC 22 for low TPS volts will set if at any time the TPS volts drop below 0.23. These values are out of the 1995 factory manual, and vary from year to year.

The PCM uses TPP (throttle position percent) for the functions I am familiar with.... example, defining power enrichment (PE) mode boundaries. The shift table in the factory manual is very confusing, because for the 94 and 95 F-Body manuals, the shift table only references various truck applications (LM2, L03, L05, 6.5L Diesel), not the LT1. And while it labels the columns as "TPS" the values appear to be percentages - e.g. 10, 25, 50. I'm not a tuner, but I would assume the shift tables reference TPP (%) and not TPS (Vdc). That seems to be confirmed in the "lt1pcmtuning.com/tips/" writeup.

[SSlowBoat]

Some thoughts....

The TPS voltage can be anywhere between 0.30 - 0.90 volts at closed throttle. The PCM reads the closed throttle voltage at key on, and sets that voltage as 0% TPP (throttle position percent). While most of the hundreds of data logs I have reviewed show 0.67 volts for a stock, unmolested throttle body and sensor, there is nothing magical about this value, and it does vary somewhat.

I appears the PCM adds ~ 4 volts to the closed throttle value it read at key on, and sets that as 100% TPP, then prorates between those voltages to determine TPP.

DTC 21 for high TPS volts will set if voltage exceeds 2.50 volts at closed throttle (defined as less than 10 grams/second mass air flow) for 5 seconds. DTC 21 will also set if TPS voltage exceeds 4.80 volts at any time. DTC 22 for low TPS volts will set if at any time the TPS volts drop below 0.23. These values are out of the 1995 factory manual, and vary from year to year.

The PCM uses TPP (throttle position percent) for the functions I am familiar with.... example, defining power enrichment (PE) mode boundaries. The shift table in the factory manual is very confusing, because for the 94 and 95 F-Body manuals, the shift table only references various truck applications (LM2, L03, L05, 6.5L Diesel), not the LT1. And while it labels the columns as "TPS" the values appear to be percentages - e.g. 10, 25, 50. I'm not a tuner, but I would assume the shift tables reference TPP (%) and not TPS (Vdc). That seems to be confirmed in the "lt1pcmtuning.com/tips/" writeup.

and this is what I was referring to, thanks fred

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