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Discussion Starter · #1 ·
On an '82, Is there any reason that the cat cannot be removed and replaced with a straight pipe?


I have nice free-flow mufflers, but the car is just as quiet as it was with factory exhaust. I assume the reason is the Cat restricting the sound flow.
 

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Hi Bill, the cat is cutting the sound, you are correct. Have you got a good friend that does inspections? They check (or are supposed too) for the cat to be there. I went around that by registering as historic/collector. Limited to 1000 miles/year, but no inspection requirement either.

:cheers:
 

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Discussion Starter · #3 ·
Hey Tim... Yeah I will problably license as a historic. No inspection required.

But will cat removal affect performance, etc...? Will engine run OK without it?
 

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Removing the Cat will help performance- less restriction in the exhaust. The computer should be able to adjust with no problem.

:cheers:
 

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You could develop issues with the O2 sensor. After removing the cat con (btw, do not plug the air pipe, either remove the air suystem or leave it open, if you plug it your air pump is pushing air into a dead end) run the car and jumper the a & b ALDL pinouts just like you do for going into field service mode for reading codes. The CEL will flash at a steady pace. Fast = open loop (checking sensor voltage) and slow is closed loop (each flash is a cross count where the lambda value passes stoich. 14.7:1) anyway, after warmig up the lamp should keep flashing slow, if it goes to fast again it's going out of closed loop, the sensor will be too cold and needs to be moved closer to the header, preferrably to a collector. The cat con produces massive amounts of heat, that's why the sensor is placed right before it (can't put it afterwards as the rear section uses the oxygen in the air from the air pipe for the oxydizing section and this would give a false O2 signal)
 

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I forgot they used that air line into the cat. TT is correct in that it may cause some problems with the O2 sensor heat, and then switching from open to closed loop. Later years they (GM) moved the sensor to the exhaust manifold just before it connects to the pipe and got rid of the air tube to the cat.
 

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Discussion Starter · #7 ·
OK, I'm starting to understand how it works.

What if I were to remove the Cat, gut it, then put it back?
 

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Applies to that too, if you hollow it out the cat is non functional and will not generate heat needed to ehat the O2 sensor, IF you run into closed loop issues move the sensor towards the engine.
 

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Discussion Starter · #9 ·
Applies to that too, if you hollow it out the cat is non functional and will not generate heat needed to ehat the O2 sensor, IF you run into closed loop issues move the sensor towards the engine.
Thanks TT and Tim...

I'll probably go with a hi-flow Cat. They are around $120...
 
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