Turbo grand prix overboost fuel cut?

[Guest]

Does the factory chip from gm have a fuel cut feature if boosting more then factory specs? if so, can someone here explain what happens? Does it cut the fuel essentially shutting the car down till you lift off the gas?

This isn't on a TGP car, I am just running a boosted 3.4 in my fiero and using the stock computer with a aftermarket chip Mask $24 designed to handle boost so the timing and fuel tables have been set up for boost.

It seems on my setup anything over 11-12 ish psi the car cuts out. I beleive its a fuel cut issue because the car falls on its face, and won't refire till I let off the gas. No matter what I set my plug gap to, the same problem happens every time, right around 4200 rpm or so in 4th gear, and even in third sometimes with enough load on the motor but at the same rpm.

has anyone dissected the $24 or $24a mask and can tell me if my suspicions are correct and if there is a way around this problem? I want to run 14+ psi and this problem is standing in my way.

[Joseph Upson]

Does the factory chip from gm have a fuel cut feature if boosting more then factory specs? if so, can someone here explain what happens? Does it cut the fuel essentially shutting the car down till you lift off the gas?

This isn't on a TGP car, I am just running a boosted 3.4 in my fiero and using the stock computer with a aftermarket chip Mask $24 designed to handle boost so the timing and fuel tables have been set up for boost.

It seems on my setup anything over 11-12 ish psi the car cuts out. I beleive its a fuel cut issue because the car falls on its face, and won't refire till I let off the gas. No matter what I set my plug gap to, the same problem happens every time, right around 4200 rpm or so in 4th gear, and even in third sometimes with enough load on the motor but at the same rpm.

has anyone dissected the $24 or $24a mask and can tell me if my suspicions are correct and if there is a way around this problem? I want to run 14+ psi and this problem is standing in my way.

Since you are using $24 code which is specific for the Fiero the TGP madness will not apply to you and yes the the TGP code has a limit at around 10 psi eventhough the boost table goes higher than that. The only way I know to get around it is to modify the chip code which requires programming knowledge or use a diode at the MAP sensor with a voltage just below the peak boost voltage the code will allow before fuel cut so that it never sees it and therefore never activates the boost cut.

In your case from what I recall in all the times I have programmed the $24 boost code available only for the 85 ecm, there is no limit to prevent reaching 14 psi, so it's possible your chip rev limit may have been set to low or something else is going on.

I'll have to dig up the code again and take another look. In the TGP code you can set the fuel/spark restore rpm also which would reduce the stall time after hitting the rev limit. You may want to check out the tunerpro site and download the program and load the $24 code into it and look through the tables. I'm not sure if the boosted version is available for it though. I have a registered version of Tunerpro and Tunercat and Tunercat is the program I used for the Fiero code.

[Guest]

Maybe I am running the $24a then. The computer I am using is a 88 v6 computer. Maybe there is a difference in the 88's and the 85's

Hey Joseph, I am not hitting a rev limiter, and when I turn the boost down, I can rev the car to the moon. Its just that when I want to turn the boost up past 11 psi the car shuts down shortly after reaching 11+ psi. It takes about 2-4 seconds for the car to shut off after going 11+ psi of boost.

My map is hitting around 4.6 volts and in that area when the car shuts off.

You think I should swap to the 85 ecm and throw that in my car? Think this will fix my boost problem?

I can only assume allthe pins in the harness are the same from 85 to 88? I would think it would just be plug and play between computers.