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Old 03-07-2006, 06:25 PM   #1
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Default Gutting a stock downpipe?

Has this been tried? Doug has been asking around my hometown about getting a custom downpipe made for my car. As some of you know, the stock downpipe consists of a small pipe inside a larger one, which I am assuming is for heat insulation. One exhaust tech thought we might be able to simply pull the smaller pipe out of the larger case and bolt up the resulting product as a larger-diameter downpipe.

What are your thoughts on attempting this? Is it a waste of time and effort? What is the purpose of the stock DP'* two-layer design?
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Old 03-07-2006, 08:22 PM   #2
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Don't know if it'* been tried [in the words of Bart Simpson: 'I didn't do it!' ], and not to hijack the topic, but what is the alternative?...is there a source for aftermarket downpipes [especially for a L27]?...what good is my considering PEMs if the stock downpipe is the biggest exhaust restriction?!...since I have 2.5" stock exhaust & a high-flo CAT [& am told that I can't out-flow my stock muffler], wouldn't it make sense to replace the pesky downpipe first?
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Old 03-07-2006, 08:27 PM   #3
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Travis at www.hulkspeed.com is working on a downpipe for S2 Bonnevilles. Contact him through the site.
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Old 03-07-2006, 09:35 PM   #4
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If no one can give us a good reason not to do it, we're going to do it.
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Old 03-07-2006, 10:08 PM   #5
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Quote:
Originally Posted by Mortehl
Travis at www.hulkspeed.com is working on a downpipe for S2 Bonnevilles. Contact him through the site.
As with the rest of my project, we're trying to do it more cheaply than the aftermarket alternatives. I think we might give this idea a try.
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Old 03-08-2006, 01:34 PM   #6
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I think its worth a try, You mite just come up with a whole new Mod for us
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Old 03-08-2006, 01:43 PM   #7
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Oh.. I'm sorry I wasn't clear. I know the reason you're considering doing it yourself is to control costs... I brought up Travis because I think he had the same idea.
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Old 03-08-2006, 01:45 PM   #8
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Well when I get home from work it'll get done or I'll destroy the downpipe... I'm not sure what will happen yet.
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Old 03-08-2006, 02:22 PM   #9
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Let'* take a moment and thank these two guys for gutting, gluing, reaming and dremeling this car away in the interests of power.

Guys...credit where it'* due.. you are doing stuff most of us are afraid to try on our cars. Make it work and we will follow.
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Old 03-08-2006, 02:37 PM   #10
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Well Bill..... lol..... I just got off the phone with Doug, and we might be holding off on the downpipe for right now. In light of some new information, it might be more beneficial for me to keep a stock DP into the 2.25" exhaust than trying to funnel the exhaust from a 2.5" or 3" DP into the smaller 2.25" pipe. We'll wait to see what some of the gearheads think, but it might kill horsepower and torque to create a 'bottleneck.' Doug has a Thunderbird friend with a supercharged 5.4 V8, and he had an exhaust setup that did a transition from 3" to 2.5", back to 3". If you can believe it, I guess he lost something like 60hp at the wheels because his exhaust couldn't get out of the car efficiently. Maybe Doug will chime in here and give better details.

Anyway, we're thinking a stock DP might be the best idea, since at least it will create a uniform exhaust path all the way through. We're open to suggestions, though. Fire away, boys!
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