removing cats - much HP gain?

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Nov 3, 2004 | 10:15 AM

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Burning Brakes

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From: Muskogee, Oklahoma

removing cats - much HP gain?

Do you gain much horsepower by removing cats and replacing with an X-pipe?
Loose any torque? Friends say I will loose HP and torque?

Nov 3, 2004 | 10:27 AM

grinder11

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I have a '00 'Vert and just "gutted" the cats-still there for visual. I have a 3.15 gear and motor is all stock. Stock manifolds on exhaust, too. I did install a LS6 intake, however. It is an A4 with stock converter. I had an LS1 edit done by Howell Engine Developments and have a few bolt-ons, including Flowmasters, a 160 stat, Granatelli MAF, but no underdrive pulley. I have run many high 12 second runs, with a best of 12.89@109.97. I believe that you will pick up 10-20 h.p., if you have some or all of the aforementioned bolt-on's done. Good luck, and don't forget your emissins check, as there is none here, YET!

Nov 3, 2004 | 05:36 PM

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Burning Brakes

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From: Muskogee, Oklahoma

Nov 3, 2004 | 06:04 PM

Roofless

Drifting

Joined: Jul 2001

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From: Tucson AZ

St. Jude Donor '11,'13

i msut disagree with the above. There is no way in my opinion that you are going to pick up 10/20 HP with those add ons alone. The gutted cats are going to smell and that is about it as far as what you are going to get from that option.

Nov 3, 2004 | 06:07 PM

Mitch C

Melting Slicks

Joined: Jun 2001

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From: Davie Florida

You will normally pickup 10 RWHP on a modded H/C car, less than that on a car that is internally stock. You will also get a fuel smell inside of your car. Not to mention the fact that removing your cats is illegal.

Last edited by Mitch C; Nov 3, 2004 at 06:10 PM.

Nov 3, 2004 | 07:05 PM

Y2Kvert4me

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From: Gone

CI 6-7-8-9-10 Veteran

St. Jude Donor '03

I've run my car a lot both ways, and although I don't have numbers, I can give you my driving impressions.

I have the FLP header system which allows me to switch between cats and no cats quite quickly.

With cats = Quieter, more punch off the line at lower rpms. It feels more responsive and snappier.
W/O cats = Noticibly louder, and pulls much harder at higher rpms (4k+) than with the cats,

I usually run it w/o the cats, and have done so for the past year and a half or so. I recently had to put the cats back in my car for an emissions test, and I absolutely do notice it doesn't pull as hard in the higher rpms since putting the cats back in. A definite hp loss. But it does seem more responsive at low rpms.

From this, I'd say you do gain peak hp going catless, but w/o tuning, probably lose a little low-rpm torque. I have not had any tuning done, and if you tune specifically for no cats, I'm sure you can probably gain more.

As for smell, I absolutely hate the sulphur stink of a cat-equipped car under a hard load. I much prefer the scent of old-skool hp and don't at all find the smell strong, offensive, or overpowering when running catless.

Nov 3, 2004 | 08:36 PM

GVZO6

Racer

Joined: Dec 2003

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From: MENOMONEE FALLS WI

Cats

Alot Of Noise,and Smell ,3 Rwhp Loss

Nov 4, 2004 | 07:33 PM

tcmc5

Drifting

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From: Chapel Hill NC

My stock LS1 6sp + TPIS headers, DrGas x-pipe (in place of cats), ported throttlebody, Z06 exh. = 345rwhp 344rwtq. I'd say the x-pipe/cat delete was worth about 15hp on my car. No smell.