Question: catalic converter on a 1990 corvette

[cornbread8787]

catalytic converter on a 1990 corvette

I want to gut the cats on my 90 vette but was wondering. Will it mess it up?

 

[Hib Halverson]

On a 90, gutting the cats, as long as you do it in a manner that doesn't leave fragments in the front part of the exhaust, it should not cause any problems other than the car will no longer pass any State exhaust emissions tests.

 

[aklim]

Mess what up? It won't trip the O2 sensor up since the sensor is before the cat, IIRC. It has been so long since I saw a stock system but I think it is right.

Will it make more noise? Probably so.

 

[sstearns2]

I want to gut the cats on my 90 vette but was wondering. Will it mess it up?

It will dramatically increase the pollution your car produces for a small gain in power. I think you'd be better off replaceing it with a modern high flow cat. They are not that expensive.

Scott

 

[cornbread8787]

Thanks everybody, I have only had the car for a month. Just wanted to make sure I have another question there is a 1 inch tube that runs from the cat up to somewhere on the motor can any one tell me what that my be?

 

[aklim]

Thanks everybody, I have only had the car for a month. Just wanted to make sure I have another question there is a 1 inch tube that runs from the cat up to somewhere on the motor can any one tell me what that my be?

Yes, it is AIR tube. Air Injection Reaction, IIRC. It pumps fresh air into the cat to help it along at the right times

 

[English Guy]

would the car use more gas with gutted cats?

 

[aklim]

would the car use more gas with gutted cats?

I don't think so. I don't have precats and had a gutted center cat but it got too noisy so I put a real cat back and it didn't use any more or less fuel in any measurable sense.

 

[justin10morrissey]

gutting the cat will show no increase in power in fact most cases a decrease in power...too much turbulence with gutted, the honey comb inside helps direct exhaust out and cleans it at the same time save your time and dont do it. also sound difference is minimalistic

 

[aklim]

gutting the cat will show no increase in power in fact most cases a decrease in power...too much turbulence with gutted, the honey comb inside helps direct exhaust out and cleans it at the same time save your time and dont do it.

also sound difference is minimalistic

Any reports to that one? I haven't seen increase in power of a straight pipe vs a cat unless that cat is bad but I haven't seen any reports of a decrease in power at WOT or any part with a gutted cat.

I don't know about you but the sound difference is huge. Gutted cat is really louder and obnoxious. I had to cat it to make it tolerable.

 

[G Winter]

I don't know about you but the sound difference is huge. Gutted cat is really louder and obnoxious. I had to cat it to make it tolerable.

Any time I have gutted a cat , usually because it was suspect, it has been like putting an amplifier on the exhaust system.

Glenn

 

[nelson84]

Just bolt on a test pipe in place of the cat. They are $50 on ebay.

 

[English Guy]

Any reports to that one? I haven't seen increase in power of a straight pipe vs a cat unless that cat is bad but I haven't seen any reports of a decrease in power at WOT or any part with a gutted cat.

I don't know about you but the sound difference is huge. Gutted cat is really louder and obnoxious. I had to cat it to make it tolerable.

Thanks for that Aklim, I'll leave the cats as they are. I don't want to rattle my neighbours windows when I take off for work in the morning:L

 

[aklim]

Thanks for that Aklim, I'll leave the cats as they are. I don't want to rattle my neighbours windows when I take off for work in the morning:L

I don't know about that but in a parking ramp, I can romp on it and trigger some alarms.

 

[G Winter]

My front cats are in tact, the main cat has a front and back half. When I was installing my clutch I noticed the back half was lose in the case and rattled so I removed it. Just doing that increased exhaust noise.


Glenn

 

[justin10morrissey]

i only had a single cat on mine it goes headers to y pipe to cat then straight back to center glass packs i gutted the cat completely and really dont notice much of a difference its tolerable and has a good rumble never gotten pulled over(knock on wood) mechanic said decrease in power due to turbulence without the honeycomb flow wanna switch to full true duals no cats but it wont pass inspection without a cat

 

[cornbread8787]

there is a tube that runs from the cat to some where on the motor do i need to cap that off or what? got a different cat but it does not have a place for the tube

 

[joshwilson3]

I've read that gutting the cat leaves a place for unburned fuel to sit, which could cause a pop noise. I wonder if the added noise is because of having a gutted cat vs. a straight pipe?

I don't believe you want to cap that AIR tube that goes to the cat. As it might could damage the AIR pump or solenoid as it is trying to pump air out of that hose at certain times. I'd just tie it out of the way somewhere.

I was thinking of removing the cat and having a pipe welded in it's place on my 89 as I suspect it could be clogging. Alot cheaper than getting another cat since I don't have any emissions testing.

 

[Hib Halverson]

Early L98s had only one cat. The tube that some have running from the AIR system down to the cat was there to hasten cat light off after start up. With the cat so far back in the system, cat light off didn't occur soon enough for the car to pass the FTP, so adding AIR, got the cat to light sooner.

In fact, the "pup cats" that are on later L98s exist for the same end....to get catalyzation of the exhaust gases to start sooner. The closer a cat is to the engine, the sooner it gets hot enough for the catalytic reaction to begin.

From a performance standpoint, stock or near-stock L98s don't have much to gain from removal or gutting of the main cat as long as the cat itself is in good condition. The pup cats, however, can pose a restriction and if you remove the pups but leave the main cat, performance will improve slightly, but exhaust emissions, except immediately after a cold start, will remain the same.

Lastly, as many of you have found, the cat convertors also have a part in quieting the exhaust. The turbulence created when the exhaust flows through the cat "brick" definitely quiets the exhaust and when you gut or remove the main cat, you'll always have a louder car.

 

[joshwilson3]

Early L98s had only one cat. The tube that some have running from the AIR system down to the cat was there to hasten cat light off after start up. With the cat so far back in the system, cat light off didn't occur soon enough for the car to pass the FTP, so adding AIR, got the cat to light sooner.

In fact, the "pup cats" that are on later L98s exist for the same end....to get catalyzation of the exhaust gases to start sooner. The closer a cat is to the engine, the sooner it gets hot enough for the catalytic reaction to begin.

From a performance standpoint, stock or near-stock L98s don't have much to gain from removal or gutting of the main cat as long as the cat itself is in good condition. The put cats, however, can pose a restriction and if you remove the pups but leave the main cat, performance will improve slightly.

Lastly, as many of you have found, the cat convertors also have a part in quieting the exhaust. The turbulence created when the exhaust flows through the cat "brick" definitely quiets the exhaust and when you gut or remove the main cat, you'll always have a louder car.

Is there any problems removing the cats, and leaving the AIR intact on the L98? I believe the computer compensates for AIR at the manifold anyways with regards to the O2 sensor.