C4 Tech/Performance L98 Corvette and LT1 Corvette Technical Info, Internal Engine, External Engine

Smog Pump and Cats elimination

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Old Jun 1, 2006 | 07:13 PM
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Default Smog Pump and Cats elimination

How hard is it to eliminate the cats and the smog pump. I was told I would see about 30 HP increase by eliminating these. I am not worried about emmisions anymore since the car is over 20 years old. Basically what should I be looking to do for it to be done right...is it worth the trouble? TIA (I might do this once the car gets outta the shop)
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Old Jun 1, 2006 | 07:17 PM
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the pump is easy... so are the cats, really...

but yours is an 85, right? it has one central cat.

The downside will be noise... noise out the ***... and if your area ever starts sniff tests, it would be a royal PITA to get it passed.

The cabin of the C4 is damned near an echo chamber. It will take whatever noise you start with and make it louder... yuck.

What I would do is this... loose the factory exhaust... add a set of long tubes. then a pair of high flow bullet cats, an xpipe and then a cat back out to the rear bumper.

it will flow like a bitch, gain 40+ hp, not deafen you and not stink up the joint.

the other side of the noise factor, many towns are cracking down on loud exhaust... you don't want nuicence tickets...
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Old Jun 1, 2006 | 07:23 PM
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Yup 85, factory exhaust has been long gone and it has hooker comp headers going back into flow masters I think. X pipe huh
Originally Posted by bogus
you don't want nuicence tickets
I do like it loud though. I was thinking borla sqaure tips on the ends when I was done BUT right now I have to figure out why my pipes are so carbon filled. I stick my finger in and it comes out black With all of these exhaust mods would it play havoc on the ECM? Thanks bogus
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Old Jun 1, 2006 | 10:38 PM
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I haven't found any extra noise at all. I have more noise from going to a larger tire then from exhaust mods.

Cats will take some time grinding off and then bending pipe to fit. Not fast or easy unless you buy a cat-less Y or something.

Air, can take some time to. There is that hard to reach pick up filter below the A/C.
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Old Jun 1, 2006 | 10:48 PM
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Originally Posted by bogus

it will flow like a bitch, gain 40+ hp, not deafen you and not stink up the joint.


Originally Posted by bogus
the other side of the noise factor, many towns are cracking down on loud exhaust... you don't want nuicence tickets...
The Harleys get away with straight pipes around here. I know of a few guys that actually ride with ear plugs in because their bikes are so fudgin loud.
I better never get pulled over for my Vettes pipes, (borla).
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Old Jun 1, 2006 | 10:50 PM
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Originally Posted by red_johnny
How hard is it to eliminate the cats and the smog pump. I was told I would see about 30 HP increase by eliminating these. I am not worried about emmisions anymore since the car is over 20 years old. Basically what should I be looking to do for it to be done right...is it worth the trouble? TIA (I might do this once the car gets outta the shop)
Any chance that somebody is yanking your chain? Listen to Bogus.
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Old Jun 1, 2006 | 11:24 PM
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You'd get back about 10 by taking the main cat off altogether, and 0 from the AIR eliminator.

Removal of the AIR is a weight-savings/cosmetic modification, as it doesnt really take anything to spin it. If you find a belt that will work and deletes it altogether, I'd like to know.
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Old Jun 1, 2006 | 11:31 PM
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I'm running a highflow cat ($50) and muffler eliminator pipes.

I think you'd like the sound. The cat is just enough to soften it up. Not really any resonance either.
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Old Jun 2, 2006 | 07:10 AM
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Thanks for all the input guys. I am still going to remove the smog pump and I have to see what kind of cats are on there right now. Once I find out what I have I then can decide what I am going to do. I love the sound of a non-restrictive exhaust. Ahhh, the roar.
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Old Jun 2, 2006 | 11:46 AM
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I did this a few days ago...

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Old Jun 2, 2006 | 11:57 AM
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Originally Posted by Steel Breeze
I did this a few days ago...



SWEEEEEEEET!
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Old Jun 2, 2006 | 12:23 PM
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Originally Posted by vader86
You'd get back about 10 by taking the main cat off altogether, and 0 from the AIR eliminator.

Removal of the AIR is a weight-savings/cosmetic modification, as it doesnt really take anything to spin it. If you find a belt that will work and deletes it altogether, I'd like to know.
I can't remember where I saw it or who makes it. Somebody is marketing a braket made out of billet aluminum with an idler pulley and low friction bearing. The stock belt will work just fine, and really cleans things up under the hood. I wish I could remember who makes them, they're out there!

Adam.
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Old Jun 2, 2006 | 12:58 PM
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Originally Posted by Hole-Shot
The Harleys get away with straight pipes around here. I know of a few guys that actually ride with ear plugs in because their bikes are so fudgin loud.
I better never get pulled over for my Vettes pipes, (borla).
I live in Torrance, CA. For those of you who don't know the area, it's rather, uh, LOADED. I have seen everything from Ferrari to Maybach around here. Big money.

However, up on the hill, Rancho Palos Verdes, the town PD actually set up an exhaust check for motorcycles. Apparently, it's illegal to modify motorcycle exhaust. And they were nailing Harley owners left and right.

This is not an isolated trend. Yuppies in general are into this quiet thing... and don't want anyone else to have fun. Up in NJ a few years ago, someone built an expensive housing development... around the corner was a sprint car track (Bridgeport)... the yuppies cried, and won. The track now has an 11pm curfew. It's bull****. The track was there first. Those whiney assed, entitled pecker heads need to get a line drawn.

On the other side, Sebring Intl Raceway has been there since 1952. It's been a year round track since about 1988 or so. About a mile away is a housing development that has grown with the track. Essentially, they live in harmony. However, a local club started drag racing there. That wasn't the problem, the problem was that the club officials could not run a tight schedule, so the races ran into the 1~2am time frame. After having been warned, they sorta tightened up, but they still could not always make the midnight curfew.

Between the noise issues, the inability to meet curfew and the insane amount of garbage they left on the track (rubber/oil/junk) SIR kicked them out. The road racers started complaining about the rubber on the track.

I like enough noise so I know it's there, but when it gets annoying, starts to resonate, I draw the line.

Last edited by bogus; Jun 2, 2006 at 01:03 PM.
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Old Jun 2, 2006 | 01:02 PM
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steel Breeze, thats awsome. I am going to do that soon. Going to do a search to find a "how to". Then I will work on the cats. I want to find a AC delete bracket and a smog delete bracket.
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