another exhaust thread: 3" too big?

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Mar 31, 2003 | 12:37 AM

LS-1st-Gen

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From: Houston

another exhaust thread: 3" too big?

What do you guys think?? I want my car to be reasonably quiet, but still sound like a '67 camaro should, that is, badass and pretty loud, but not toooo loud, I want to be able to hold a conversation while driving down the road. So what do you guys think?? Ive found 2.5" and 3" x pipes on summit, both reasonably priced, and im thinking dynomax super turbos, or 3 chamber flowmasters, but im not sure yet. I want to have this stuff ready to go to the muffler shop by the end of the week, or at least have the mufflers and xpipe in the mail by then. By the way the LS1 is internally stock, and will be for a while.

-Gordon

Apr 1, 2003 | 04:37 PM

Nine Ball

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From: Houston, TX

Re: another exhaust thread: 3" too big?

Stick with dual 2.5" exhaust until your LS1 is making 500+ rwhp under boost or naturally aspirated. Then go to 3" duals.

Too big and you lose alot of torque on the low-midrange, unless you install some very expensive merge collectors on the headers, which would require the least amount of backpressure beyond them.

Tony

Apr 1, 2003 | 08:09 PM

John B

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Re: another exhaust thread: 3" too big?

<blockquote>quote:<hr />Stick with dual 2.5" exhaust until your LS1 is making 500+ rwhp under boost or naturally aspirated. Then go to 3" duals.<hr /></blockquote>I'm going to have to disagree with Tony on this one. Granted, I already had a cam in my motor but going from 2-1/4" true duals to my extremely large 3-1/2"/3" dual exhaust picked up way too much power (+53 RWHP/49 RWTQ) which tells me that if you have long tube headers, go with the 3" duals now rather than replace the system later.

Apr 1, 2003 | 10:36 PM

LS-1st-Gen

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From: Houston

Re: another exhaust thread: 3" too big?

And what if i dont have long tubes??

Apr 3, 2003 | 08:34 PM

John B

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Re: another exhaust thread: 3" too big?

<blockquote>quote:<hr />And what if i dont have long tubes?? <hr /></blockquote>If you have stock manifolds it probably doesn't matter what you use because you'll never make decent power. If you have a decent set of mid lengths (like the MACs) I'd still go with 3" and an "X" pipe.

Apr 10, 2003 | 09:34 PM

Boosted One

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Re: another exhaust thread: 3" too big?

I would have to agree with John. I have 3" duals on my car, with stock manifolds and bone stock engine. It sounds Fantastic!! I haven't had it on a dyno but the first pass ever at the track was 12.3, and that was driving miss daisy out of the hole!

Frank

Apr 11, 2003 | 08:17 AM

Nine Ball

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From: Houston, TX

Re: another exhaust thread: 3" too big?

John, you didn't finish reading my reply:

<blockquote>quote:<hr />Too big and you lose alot of torque on the low-midrange, unless you install some very expensive merge collectors on the headers, which would require the least amount of backpressure beyond them.
<hr /></blockquote>The ONLY reason your combo is working is because you have those merge collectors. Remember that C5s have true dual exhausts (2.5") and we have extensively dynoed tons of different combinations with the factory midpipe and with a custom 3" X-pipe equipped midpipe setup (both longtube setups with aftermarket catback, as well as dual cutouts).

Dual 3" midpipes killed low/midrange torque on those Vettes on anything less than 475-500 rwhp. They also had a more peaky looking HP curve instead of the nice broad curve.

When Judson first ran 10s in his 346ci car, he tried and tried to do it with dual 3" exhaust, but actually went quicker once he put some 2.5" reducers and went with dual 2.5" . I did the same thing and also went quicker.

Tony

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Apr 11, 2003 | 01:27 PM

John B

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Re: another exhaust thread: 3" too big?

<blockquote>quote:<hr /> The ONLY reason your combo is working is because you have those merge collectors. <hr /></blockquote>Tony, I would agree that the merge collectors are certainly helping my combo out, however, even the exhaust mfgrs tpically recommend 3" duals for over 400 HP applications.

I certainly can't argue with your or Judson's results but then again, I have always tried to optimize my complete exhaust as a system, not just the pipe size. All I know is that if you pick up power when your system is disconnected then you had better do something about it like enlarge it. Since open headers display the ultimate "no backpresure" I find that a good exhaust system should duplicate this. If the power falls off, then something isn't engineered correctly.