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Old 12-03-2003, 12:51 PM   #1
JST
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Question Exhaust 2.5'',3.0'' or 3.5''

At first a want to bye a 3'' WRX exhaust to put on my 99 RS_T (8.5psi) but now i just fond a shop how did great hand made exhaust in S-S and mandrel whit the muffler a want. And they did exhaust and the DP all for 200$$$ less than a simple WRX cat-back.

The question is should a go with a big 3.5'' turbo-back exhaust or stay conservative and go with a 3'' or be a bit more conservative and keep my Lachute 2,5'' cat-back and my ASR 2.25 DP???

Need help???
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Old 12-03-2003, 12:55 PM   #2
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How much HP are you hoping for?
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Old 12-03-2003, 01:06 PM   #3
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I would go with a 3" DP and a 2.75" cat back. the reason for this is that most of the exhaust cooling happens in the downpipe. once the exhaust cools the volume of gas decreases. You always want to run the smallest diameter pipe that won't cause backpressure. If you run a pipe that is too big your flow velocity drops off measurably and you loose alot of power. If you are only intending to run 8.5psi then a 3" DP and 2.75" cat back is very well matched.
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Old 01-01-2004, 07:39 PM   #4
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It is just becaise i saw the APS 3,5" turbo/back race exhaust and it look like a good idea!!!
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Old 01-01-2004, 11:07 PM   #5
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i dont know how 3.5" can fit... i have 3" that i did myself at my work, and it was a pain in the @$$

-Jake
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Old 01-02-2004, 07:01 AM   #6
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The bigger the better. Turbo cars do not have to worry about back pressure. The turbo itself is the engines back pressure so after it you wan the LEAST resistance. Turbos would run best with no exhaust at all but that is not an option.

Tats.
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Old 01-02-2004, 11:42 AM   #7
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Quote:
Originally posted by Tats
The bigger the better. Turbo cars do not have to worry about back pressure. The turbo itself is the engines back pressure so after it you wan the LEAST resistance. Turbos would run best with no exhaust at all but that is not an option.
Tats.
While your statement is true, it is also short-sighted financially. The APS 3.5" is around $1300. A TurboXS exhaust (for example) that is 3" would be right around $1000. 2.5" exhaust would probably be even cheaper and still put out enough volume.
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Old 01-02-2004, 01:59 PM   #8
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I agree with 80% of what Tats said. The best exhaust option on a turbo car is none, but 3.5" piping is definately overkill unless you are planning on 500+hp or something crazy like that. Here's a quote from Corky Bell's book. Great book btw.
Quote:
Corky Bell - Maximum Boost

It is easy to get overeager on fitting large-diameter pipes into an exhaust system. "The larger the better" is not the case. As indicated in Chapter 5, there is an exhaust gas velocity that ought not to be exceeded...
He also has a chart which represents the general idea of how big exhaust piping should be on a turbocharged car... He recommends 3.5" piping for a 800-850hp car

Hope this helps
-ben
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