Custom Made exhaust please help

ThomasMartin · 07-18-2007, 09:35 AM

Hey Guys

I know many of the popular exhausts have a 3" downpipe tampered down to 2.5" and following 2.5" all the way to the rear. If i may ask a stupid question why cant you run it 2.5" all the way from the downpipes? will that decrease power?

Thanks.

Cadillac Johnson · 07-18-2007, 11:15 PM

You can, and it will work just fine.

Since a dual 2.5in exhaust is good enough to handle 600+whp your not going to have much, if any performance gain by going to a dual 3in exhaust. Much less just adding 3in downpipes to a 2.5 exhaust.

CASHBY · 07-19-2007, 04:03 AM

only hard part is the Turbo Exhaust Outlet is 3 inch..... so really the Downpipe has to go from 3 inch and tapper to 2.5 inch. The stock downpipe is 3 inch diameter but actually has a pipe in the inside that is only about 2 inch at the turbo outlet, maybe even smaller.... you can make an aftermarket DP like that... but not worth it.

ThomasMartin · 07-19-2007, 04:07 AM

Quote:

Originally Posted by CEA 3

only hard part is the Turbo Exhaust Outlet is 3 inch..... so really the Downpipe has to go from 3 inch and tapper to 2.5 inch. The stock downpipe is 3 inch diameter but actually has a pipe in the inside that is only about 2 inch at the turbo outlet, maybe even smaller.... you can make an aftermarket DP like that... but not worth it.

Can i then make a 3" downpipe and complete 3" cat back system not taper down at all? will that effect the turbo spooling negativly at all?

CASHBY · 07-19-2007, 04:13 AM

Sure you can do that. We made a bit more power with our 3 inch downpipe then we did with the 2.5 inch downpipe. however some will say 3 inch isnt needed for the ammount of power the 335 puts out... or its potential power it will put out.... 3 inch all the way back is fine and you will not have any negative effects at all....

ThomasMartin · 07-19-2007, 05:17 AM

Quote:

Originally Posted by CEA 3

Sure you can do that. We made a bit more power with our 3 inch downpipe then we did with the 2.5 inch downpipe. however some will say 3 inch isnt needed for the ammount of power the 335 puts out... or its potential power it will put out.... 3 inch all the way back is fine and you will not have any negative effects at all....

Thank you very much for the help you one of the only guys here that has answered all my question, once again thanks and ill keep you updated on the progress

07-18-2007, 09:35 AM	#1
ThomasMartin First Lieutenant 28 Rep 321 Posts Drives: BMW 335i Coupe Join Date: Jun 2007 Location: South Africa iTrader: (0)	Custom Made exhaust please help Hey Guys I know many of the popular exhausts have a 3" downpipe tampered down to 2.5" and following 2.5" all the way to the rear. If i may ask a stupid question why cant you run it 2.5" all the way from the downpipes? will that decrease power? Thanks.
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07-18-2007, 11:15 PM	#2
Cadillac Johnson Free taco with stolen base 28 Rep 639 Posts Drives: 335i? GTR? RS5? Join Date: Jun 2007 Location: Milwaukee iTrader: (0)	You can, and it will work just fine. Since a dual 2.5in exhaust is good enough to handle 600+whp your not going to have much, if any performance gain by going to a dual 3in exhaust. Much less just adding 3in downpipes to a 2.5 exhaust.
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07-19-2007, 04:03 AM	#3
CASHBY 168 Rep 2,114 Posts Drives: E90 335 "done up" Join Date: Dec 2006 Location: GARAGE iTrader: (2)	only hard part is the Turbo Exhaust Outlet is 3 inch..... so really the Downpipe has to go from 3 inch and tapper to 2.5 inch. The stock downpipe is 3 inch diameter but actually has a pipe in the inside that is only about 2 inch at the turbo outlet, maybe even smaller.... you can make an aftermarket DP like that... but not worth it.
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07-19-2007, 04:13 AM	#5
CASHBY 168 Rep 2,114 Posts Drives: E90 335 "done up" Join Date: Dec 2006 Location: GARAGE iTrader: (2)	Sure you can do that. We made a bit more power with our 3 inch downpipe then we did with the 2.5 inch downpipe. however some will say 3 inch isnt needed for the ammount of power the 335 puts out... or its potential power it will put out.... 3 inch all the way back is fine and you will not have any negative effects at all....
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