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Q about a 2.5" exhaust

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Old Jun 2, 2005 | 11:20 AM
  #1  
Race4Ralliart's Avatar
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Q about a 2.5" exhaust

hey, I just went to my muffler shop to get a quote to have a custom cat back made. I want a 2.5" with a magnaflow muffler/resonator. The old man running the place today tells me that I'm not going to get anything out of opening the pipe up. I know its not going to be a huge gain but I already have the rrm downpipe and I can't justify spending $300 on an axle back when I can have the whole catback made for aroun $200. So does this guy not know what he's talking about? I would think a 2.5" with the downpipe would give a little more gain if not a sufficiant one.
thanks, Cameron
Old Jun 2, 2005 | 04:41 PM
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i think a 2.5"may give you one or two hp. a 2.5" pipe is pretty big.
Old Jun 2, 2005 | 05:57 PM
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with just the dp, willl it give more gain? yes and no. i have a 2.5" catback (no dp) and dyon'd before and after. i actually lost about 1 lb of peak torque, BUT, i gained torque after peak for about 1000 RPMS. I also gained about 3hp, but the hp band was also shifted up for a much longer period after peak. overall gains were noticable, but not earth shattering.

however, 2.5" will make other future mods more noticable.
Old Jun 2, 2005 | 07:14 PM
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Spend your money how you will, but that little diffrence between a stock pipe and a 2.5" custom, is not a great return for the money. 1-2 hp for $200 is sad. Go with the magnaflow muffler, looks and sounds great, for less money.
Old Jun 4, 2005 | 05:45 AM
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I thought our stock pipe WAS 2.5". If it's not, than what is it?
Old Jun 4, 2005 | 06:24 AM
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Stock is 2.25"
Old Jun 7, 2005 | 07:44 PM
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stock is 2 1/8"
Old Jun 7, 2005 | 08:52 PM
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u sure i thought it was 2 1/4?
Old Jun 7, 2005 | 09:07 PM
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the RRM down pipe is 2 1/4 i would keep the rest of the piping the same only go larger if you plan to add a turbo soon but if you were going to do that just wait,maby a 2 1/2 cat might help " stainless steel flex section. 2.25 inch diameter is tuned for balanced torque and top end horspower. Expect 10 h.p. "
Old Jun 8, 2005 | 10:37 AM
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Stock pipe is 2.25" O.D., 2.125 I.D.
Old Jun 8, 2005 | 05:09 PM
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Originally Posted by ikeing
the RRM down pipe is 2 1/4 i would keep the rest of the piping the same only go larger if you plan to add a turbo soon but if you were going to do that just wait,maby a 2 1/2 cat might help " stainless steel flex section. 2.25 inch diameter is tuned for balanced torque and top end horspower. Expect 10 h.p. "
I hope you arent saying that a 2.5 catback is going to add 10 hp, because it wont. Maybe 4-5 if you are lucky.
Old Jun 8, 2005 | 06:13 PM
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Originally Posted by BLKRalliArt04
I hope you arent saying that a 2.5 catback is going to add 10 hp, because it wont. Maybe 4-5 if you are lucky.
He's quoting RRM on their downpipe
Old Jul 10, 2005 | 01:08 AM
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Most exhaust shops will do pressbends anyways so the exhaust will neck down to 2.25" ID if your using 2.5" OD pipe to begin with. That is something to keep in mind!

I will be dynoing soon a car with a stock pulley and the other one with the lightened underdriven pulley. Besides that I have a CAI I made along with a 2.5" pressbent catback exhaust system I made. The exhaust system has a resonator and an open Ebay style muffler. Tha point I want to make here is gains with a CAI & Catback should be noticeable over stock. The car rvs better and has more throttle response.
Old Jul 17, 2005 | 08:19 PM
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soooo, everyone is saying that just get a muffler and get someone to weld it on?? and its not worth it to upgrade the pipeing?? right??

Cause I wanna do something to my exhaust and I live in canada and i am not buying an axel back from rrm for 400 shipped/customs and crap you know in Canadian dollars. so yeah you guys know what I am trying to say here. i just want something done to my exhaust and i would like to know whats the best for the money!? thanks guys

Last edited by Red Dragon; Jul 17, 2005 at 08:22 PM.
Old Jul 17, 2005 | 08:34 PM
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It depends on where you want to go with your RA. An improvement in piping will net more gains down the road. If all your after is look and sound then nobody will know the difference unless they look under your car.


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