V6 Tech 1967-2002 V6 Engine Related

Back Pressure?

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Old Nov 24, 2002 | 07:58 PM
  #1  
Zomie's Avatar
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From: Michigan
Back Pressure?

Well I fried my cat, actually its falling apart?!?!

So should I just put in a straight pipe? What about Back Pressure and performance lose?
Old Nov 25, 2002 | 07:36 PM
  #2  
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From: Lubbock TX
Back pressure is waaay overrated....But the sound may suffer if you just gut it. A straight pipe will sound better, but you'll need an O2 simulator (search for one at www.slponline.com ) to keep from having an SES light.

-Jeremy
Old Nov 26, 2002 | 01:20 AM
  #3  
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You have a '95 so w/ the OBD1 you'll be just fine doing the straight pipe. No O2 simulator needed since you don't have any after the cat.

::BTW The other guy is right... a gutted cat will probably sound like ***... then again it could be a sound you dig. Personally I'd go w/ the pipe through the gutted cat... if you gut the cat and do nothing more you'll have this weird echo-ish sort of sound

Last edited by MysticTeal 95 V6; Nov 26, 2002 at 01:23 AM.
Old Nov 26, 2002 | 01:44 AM
  #4  
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mine didn't sound too bad... barely noticed a difference, except my car was studdering and stalling at naythign above an idle due to a compeltely blocked up CAT.
Old Nov 26, 2002 | 02:46 AM
  #5  
oil pan 4's Avatar
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If you don't like the sound of no cat you could put in a glass pack in it's place.
I will help cut down on any rasp if you run with one.
Old Nov 26, 2002 | 02:52 AM
  #6  
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straight pipe will sound a little better. the gutted cat sound is so hard to differentiate unless you are an exhaust expert. i had a gutted cat and could not hear it till a friend pointed it out to me. nobody else could tell, but yeah its different. and yeah, dont sweat the back pressure.
Old Nov 26, 2002 | 03:52 PM
  #7  
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Originally posted by 1fastV6
straight pipe will sound a little better. the gutted cat sound is so hard to differentiate unless you are an exhaust expert. i had a gutted cat and could not hear it till a friend pointed it out to me. nobody else could tell, but yeah its different. and yeah, dont sweat the back pressure.
It does have a slightly different sound like you mentioned Its really hard to describe... its almost like a wet sorta sound lol, sorry for the description but its unique. Any regular person around the car wouldn't notice it of course but when you give it gas you can hear that sound coming from the area of the cat. I guess its the exhaust coming out of a smaller diameter pipe... going into the hollow cat then entering another smaller diameter pipe? It makes that sound w/ any engine... I gutted a friends cat on his '94 Z thinking it was causing some probs after 125K miles on the clock but ended up putting a high flow cat in its place.
Old Nov 27, 2002 | 05:49 PM
  #8  
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There was a guy at my local dyno shop who showed up in a 99 LS1 A4 Z28. He came with his cut-outs open and left the caps at home. We dynoed a couple of times and he made 270-272 rwhp/330-335 rwtq. The car sounded a little weak. So I took some small plates, vice-gripped and clamped them on his cut-outs to try to block it up some and his numbers jumped up. He pulled like 295-297 rwhp/360-365 rwtq with the cut-outs capped up. He was very surprised.

Back pressure is actually very important on cars, especially street cars were most of your racing is low-mid, where grunt is needed.
Old Nov 27, 2002 | 05:56 PM
  #9  
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CANTONRACER, i somewhat agree, but zomie has a 95 3.4. thats a world of difference from that guy with a 99 LS1. and a cutout is free flowing. that too is different from having a cat or not. everybody has differences towards cutouts, but i have proven to myself over and over again that my trap speeds with it open were always 2 mph faster than with it capped. maybe just coincidence for me i dont know. my ET was constant but the trap speed was diff.
Old Nov 27, 2002 | 07:43 PM
  #10  
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I've got a similar setup on my 94 3.4L. I've got the Flowmaster 3" catback along with a SLP CAI and not cat. It sounds pretty good and I haven't noticed any low end loss.
Old Nov 27, 2002 | 08:39 PM
  #11  
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What I am curious about is the tubing dia of the exhaust that comes with a 3.4 or 3.8 f-bod vs a LS1 or LT1?
Old Nov 27, 2002 | 10:36 PM
  #12  
ImportKILLER's Avatar
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From: I'm in the Bay, Trick
Stock V6: 2 1/4"
V8s: 2 3/4"

If we're talking about "I"-Pipes here...
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