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I plan on putting on a full exhaust system on my 88 vette. This will replace the pre-cats and the cat. I am also going to remove the Air pump. Will I need to add a chip to the computer?
 

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when ever you baseline your ecm by disconnecting the battery, the ecm will need 15-20 minutes of drive time to adapt to the new exhaust...should not be a big prob, many won't even notice the difference...a custom chip can take care of it, but you will need to datalog and tell the tuner what she likes.
 

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So I can go ahead and put on my exhaust and worry about the chip later? My plan is to put on exhaust w/ in a week… and later down the road I’m going to remove the intake to seal up some oil leaks… but while its off I was going to port and polish the plenum, base and boost up the fuel pressure. After I finished the intake I planed on getting a chip, but that might not be for a few weeks or months:lookinup: . So will I be ok with running full exhaust and no air pump on stock computer for a few weeks? Or will this have a negative affect on performance with out the chip?:huh:

Thanks for your input! :thumbsup:
 

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exhaust now, no worry.

super neat thing with your ecm is the ''knock sensor/ electronic spark control'' that retards spark to minimize danger of engine melt-down (albeit at a major reduction in power) ...hafta go much deeper with mods before you outpace this feature.

bumping up the fuel pressure a bit (3-5 psi) after port/polish plenum should get air/fuel mix back to near perfect with the stock programming already in your chip...the ecm relies on fixed memory to feed the engine during the first 2-3 minutes running (cold start) and at W.O.T. (anything more than 3/4 throttle open) and higher pressure=more fuel --same as a modded chip will do by longer injector 'open' programming...during part-throttle (normal driving) the ecm starts with memory baseline and 'learns' (reprograms itself) to get 'perfect' exhaust discharge = perfect air/fuel input by datfrom the o2 sensor (unless you get wild with mods, exceeding the physical capabilities of components) so fuel pressure is not critical there.

the stock chip program is conservative with spark advance to reduce the manufacturers (gm) warranty exposure, live with poor quality fuel, etc...an aftermarket chip that gets closer to the 'ragged edge' will usually increase power a bit, but premium fuel is mandatory

air pump only affects what goes on inside the exhaust pipes during brief periods and has little effect on anything except increased noise of the pump itself, mpg reduction due to component weight and drive belt friction, etc...no danger to engine in any configuration, questionable environmental impact, local vehicle inspection may mandate retention if oe equipped.
 

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You will be fine until you can purchase a chip, just probably won't run at full potentional but you should still feel a small increase in the seat of the pants. I have no emmissions on mine because SC has no inspection. I have straight duals back to baffled tips. That's it. The only problem I had after I opened the exhaust was the O2 sensor couldn't get hot enough to go into closed loop. So I hooked up a three wire heated O2 sensor for a ZR1 and it works fine now. I ran it through a relay so it comes on when I turn on the key, and the element inside the sensor heats it up.
 
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