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my exhaust too small in diameter?

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Old Apr 28, 2014 | 11:08 PM
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Default my exhaust too small in diameter?

im gonna be running a LQ4 with 799 heads p&p milled .025, torquer v2 cam, ls6 intake, 3 7/8" longtube headers, with dual 2.5" exhaust ran into a dual 2.5" y pipe with 3" outlet into a dynomax vt single 3" inlet and single 3" outlet muffler, my question is, is the 3" gonna be too restrictive? im also gonna be running a 3" electric cutout after the y pipe. all input is greatly appreciated. reason why im running a single in/outlet muffler is this is going on a nissan 240sx and there isnt much room to work with. and i want it as quiet as possible til i open the cutouts.

Last edited by masonS13; Apr 29, 2014 at 02:33 AM.
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Old Apr 28, 2014 | 11:33 PM
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I see no problems. Thats bigger than the Intermediate pipe I have on my soon to be 224/228 cammed ls1. I have a similar header/ypipe but then the factory ( believe 2 3/4" ) into the f-body style crossflow magnaflow muffler. before the cam it was Quiet at idle and controlled loud at WOT. I love that muffler choice.
unless you are pure race non street I say you are good. A bigger pipe tends t omean scrape from what I hear. But hey I'm no expert just a fellow forum user
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Old Apr 28, 2014 | 11:40 PM
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Since you plan on running a cutout I'd run a Y-merger with a 3.5" exit on it and continue to run 3.5" pipe into a 3.5" cut-out. After the cut-out run a 3.5"-3" reducer and run 3"pipe the rest of the way on back through the 3" in/out muffler. The reason to go with the 3.5" pipe after the 2.5" dual pipes is to not bottle neck the flow, ant least when the cut-out is open.
FYI, dual 2.5" and a single 3.5" pipe have about the same amount of flow.

As far as you muffler choice I just go with a regular Dynomax Ultra Flo Welded muffler with running a cut-out, and I would go with the largest one you can fit without running into issues.

Last edited by 99Bluz28; Apr 28, 2014 at 11:52 PM.
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Old Apr 28, 2014 | 11:51 PM
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Mods and hp in sig cutout open on dyno was worth 5rwhp over stock 2.75" exhaust and muffler.
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Old Apr 29, 2014 | 02:36 AM
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Originally Posted by 99Bluz28
Since you plan on running a cutout I'd run a Y-merger with a 3.5" exit on it and continue to run 3.5" pipe into a 3.5" cut-out. After the cut-out run a 3.5"-3" reducer and run 3"pipe the rest of the way on back through the 3" in/out muffler. The reason to go with the 3.5" pipe after the 2.5" dual pipes is to not bottle neck the flow, ant least when the cut-out is open.
FYI, dual 2.5" and a single 3.5" pipe have about the same amount of flow.

As far as you muffler choice I just go with a regular Dynomax Ultra Flo Welded muffler with running a cut-out, and I would go with the largest one you can fit without running into issues.
Ahh. I see. That's definitely a better idea. I'll be doing this instead. Thanks for the advice! Only problem is finding a used 3.5" electric cut out lol.
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Old Apr 29, 2014 | 12:28 PM
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Anybody got any more input or advice?
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Old May 1, 2014 | 03:19 PM
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Bump.
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Old May 1, 2014 | 03:49 PM
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I'll think you be on the money with the advice you have. The only question now is tips or turndowns? Get on it!
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