I have an 87. I have had the engine rebuilt. I am installing a T-56 in place of the 4+3 when I get finished. I have a little hotter cam then stock. I would like to remove the enviro junk and rework the ecm. I'd like to dump the air pump (I understand is only works during warm up feel free to correct me if I'm wrong). I would not mind running cats in the exhaust system. Do the pre cats help to light off the main cat? My questions are:

Can I make changes to the factory ECM (I mean besides just the tune)?
Can I eliminate the EGR?
Should I eliminate the EGR?
Do I need to keep the factory ECM for my gauges?
What peramiters can be changed in the factory ECM? beside the tune
What would I gain by going to a aftermarket ECM?
Can I gain performance by going to a aftermarket ECM?
Will I/Should I go from a MAF to a speed density?
What questions should I ask that I am not asking?

 

Yes

1.Yes
2.matter of choice; will get violent arguments both way

IIRC Only the digital ones run from ECM

Everything .

1.Easier to tune
2.No ,plenty running wild combos with stock ECM ( and a corresponding tune )

SD is cleaner install ( no MAF on intake ) but harder to tune with major mods

 

Are you required to have the car emissions checked? If not, you should be able to a lot of the things you want.

The 87 uses a replacable chip and there are tuners that can create a chip for you based on engine mods you have. Don't bother with the ones you can buy from the catalogs; those really don't do much more than turn the cooling fans on earlier. The 87 and earlier ECM's are pretty basic compared to the later ones.

You can remove the AIR pump with no problems; no codes will be set. You just need an AIR eliminator bracket or simply remove the plumbing and leave the pump unit. The system only works when the engine is cold.

As far as the pre-cats, they help to reduce emissions while the main cat has not warmed up. Note that the 87 has only one O2 sensor and it sits just below the driver's side exhaust manifold. There are no other O2 sensors. You can run true duals if you want (assuming no emissions testing) and keep the existing sensor in the same location. If you still have the factory exhaust manifolds, stay with 2 1/4" pipe all the way back. If you are considering headers, go with a 2 1/2" pipe.

I don't think there is anything to be gained by removing a working EGR. Doing so will set a code and the SES light, but it won't usually affect driveability. It does provide for faster warmup.

I think that going to a speed density system may also require a matching ECM and probably some extra wiring. That may not be worth doing unless you are considering more mods down the road. I would consider going with a later car rather than doing a change to a speed density system. 89 and later manual trans C4's have the ZF 6-speed so you won't have to deal with the T56 conversion stuff.

 

Guys thank for your responses. Is there any books that give a novice tunner a basic knoledge of what the ECM does and what it controls?

 

The basic book you need is called a Factory Service Manual.

Another good book is "How to Tune & Modify Chevrolet Fuel Injection" by Ben Watson.

 

Some bed time reading
http://www.noid.org/~lj/PCM%20Tutorial/PCMtutorial.htm

Is for LT1 computer (PCM ) but operating principles the similar