ECM question

[Nick90vetteguy]

SO its been about a good year since I put headers/straight pipe exhaust on the vette. I never stopped to think about the ECM. Is there something that SHOULD be changed?

 

[vetteboy86]

SO its been about a good year since I put headers/straight pipe exhaust on the vette. I never stopped to think about the ECM. Is there something that SHOULD be changed?

Anything you do that alters the stock condition and operating parameters of the motor should be followed by appropriate changes to the ECM.

 

[Nick90vetteguy]

SO how can I modify the comp?

 

[Hib Halverson]

Anything you do that alters the stock condition and operating parameters of the motor should be followed by appropriate changes to the ECM.

I'm sorry but, that is not correct. It is not true that anything you do to the engine requires a change in calibration.

As for conversion to headers, no cats and no mufflers, that is a major change. In that case, a different calibration will make the engine run better at wide-open throttle. You may also have problems with the EGR system, such as that discussed in some other threads here on the CAC about EGR performance on modified L98s. The trick, of course, if finding the right cal for that configuration.

 

[Nick90vetteguy]

Ok, how can I find that calibration?

 

[vetteboy86]

I'm sorry but, that is not correct. It is not true that anything you do to the engine requires a change in calibration.

Examples?

 

[Curious George]

1990 C4 is a Speed Density ECM. It is probably running on the lean side now, but you do not realize it, because the computer is doing everything it can to make it run "nominally".

If you are interested in hardware... go to Welcome to www.moates.net! : Moates.Net

Buy the Autoprom. You'll also need the adapter to replace your prom.

Software is free with the Autoprom (TunerPro). You can also use Tuner Cat (TunerCat), but it is not free, but worth the price.

You'll need to do a lot of reading and research in order to put all the pieces together, as there is no "single source" that tells you how to put all this together (and use it), unfortunately.

I tune my 1987 TPI Camaro and 1992 LT1 Corvette with the Autoprom and associated software.

As an example of what Hib is referring to regarding EGR, etc... the cam I used when I replaced the LB9 in my '87 Camaro (305) for an L98 (355 swap), had enough overlap that I could disable the EGR. Before disabling the EGR (when it WAS working correctly), I had a slight hesitation at part throttle. Because of the cam overlap AND proper EGR operation, it was too much. I disabled the EGR and it runs perfect now.

I knew the cam overlap when I was assembling the engine, but did not know if it was going to be enough, apparently, there is enough residual exhaust gas left in the cylinders for "built-in" EGR like the LT4 engine / cam combo. If your cam has at least 49* of overlap you can probably disable your EGR.

CG