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      10-19-2019, 11:46 PM   #1
Mr Bill

Drives: 2015 M3
Join Date: Sep 2013
Location: Aliso Viejo

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High Hp 600+ exhaust systems

So I'm wondering if on the high HP 600+ whp cars out in the wild now if we think the dual 2.5" exhaust / 3.5" single exhaust systems are enough?
I know there has been testing in the past on different cars and we're definitely past where dual 2.5" exhausts are efficient at least on those cars. Has anyone tested a true dual 3" system or a 4" system? Were there any improvements?
2015 M3, Signature 18x10 & 19x11, Apex 18x10&11, Apex 18x10.5 square, Bootmod3 with Cary Tune, VRSF intake, Dinan Exhaust, Dinan chargecooler, Dinan Monoballs, Dinan Toe links, Essex AP 9660 & 9449, MCS doubles (full coilover), StudioRSR rollbar, Hotchkis swaybars, Vargas Crank hub fix, Vargas chargepipes, N54 downpipes

Last edited by blackey; 10-20-2019 at 07:03 PM..
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      10-20-2019, 10:28 AM   #2
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Drives: M4 Competition
Join Date: Oct 2019
Location: Madison, WI

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For a turbo charged car, you want upstream pressure to be high and downstream pressure to be as low as possible. You definitely would see a gain from a dual 3" system. Gintani is the only offering I'm aware of. Dual 3.5" would be best, but I don't believe anybody is making one. Fitting it to our car would be rather hard, since the current offerings already have a hard time fitting the space available.

Edit: perhaps consider adding cutouts after the DPs? This would greatly reduce back pressure as needed.

Last edited by Kev608; 10-20-2019 at 11:36 AM..
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      10-20-2019, 12:48 PM   #3
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Drives: '16 MG F80 M3
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AWE makes a full 3" system from the downpipes back, thats what I switched to coming from the typical AA midpipe, stock muffler, when I put on Pure st2+ turbos a few months back. I think they are the only ones making one that large. It sounds incredible, but its hard to gauge any actual HP improvements because I'm still in the process of tuning and dialing in the setup, not done with the fueling side either yet. There are a few online calculators out there, showing the larger dia pipe is definitely needed as you up the HP levels. One I found says dual 2.5" pipes support up to 463hp, dual 3" can support up to 679hp. Keep in mind there are a lot of variables involved here, exhaust gas temp, fuel, intake volume etc... All made more complicated by the fact these are turbo cars and not NA motors.
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