why 2.5" how come not 3"

denverlicious · 12-12-2006, 04:51 PM

so im coming from an evo and hoping to get a 335. im just trying to understand why all these exhaust companies are making 2.5" exhausts? From my experience back pressure for turbos arent the greatest thing. Usually a 3" on a turboed car is standard. why is it that the 335er's are using 2.5"

let me know? thanks!

adriver · 12-12-2006, 05:14 PM

cause were talking about a true dual exhaust from the turbo back, not a single exhaust with a x pipe, or just daul tips. were talking basically 7 square inches of exhaust space in a 3 inch to about 5 inches per 2.5 inch pipe, so 10 inches of space.

Cliffnotes, a dual 2.5" exhaust has about 40% more exhaust flow than a single 3"

jgannonloans · 12-12-2006, 05:45 PM

yeah but a dual 3" will flow even more!!!!

ahnh77 · 12-12-2006, 05:55 PM

rule of diminishing returns....larger doesn't always equal any more performance...typically for most turbo cars...a free flowing 2.5 inch piping exhaust seems to do the job of maximizing performance.....plus you have to take into consideration the sound...you want to maximize performance matched with the best sound or tone to the exhaust......

BMW_E90 · 12-12-2006, 11:32 PM

for back pressure, which makes torque.

canucklion · 12-13-2006, 02:59 PM

by your defintion, a 10" exhaust tip will be awesome, like BMW_E90 said, you need some back pressure for torque

Quote:

Originally Posted by jgannonloans

yeah but a dual 3" will flow even more!!!!

Lucid4000 · 12-13-2006, 08:44 PM

They do it so you have something else, to upgrade later...

cm3rc · 12-14-2006, 01:20 AM

i got a 3" custom piping

BMW_E90 · 12-14-2006, 02:28 AM

Quote:

Originally Posted by cm3rc

i got a 3" custom piping

dude post some vid clips yo !

denverlicious · 12-14-2006, 11:13 AM

Quote:

Originally Posted by cm3rc

i got a 3" custom piping

umm? why would you need custom 3" piping arent the 325's NA? for NA cars i know you need smaller piping for backpressure and torque. Your probably losing power. Usually turbo cars need the bigger exhausts due to the volume of air and pressure being forced out from the turbo.

Turbo Squid · 12-14-2006, 11:40 AM

I'm interested in seeing who and how someone will tackle upgrading the downpipes on the 335, I read that a BMW designer said that one of the problem points of a 335 with more power would be that the DP (downpipe) is more prone to overheating and cracking as a result of the greater heat.

From my experience with a turbo car, having a 3" DP is very beneficial, even if it feeds into a 2.5" system. I'd say the DP is a greater priority worrying who's is bigger.

I'd also be interested in seeing an upgraded TIP (turbo inlet pipe) and LIP (lower-intercooler pipe) from the pictures I saw it looks like the stock ones are pretty nice, doesn't seem like there are any "pancake pipes" like there was on the 1.8T. But it's always nice to get the most that you can out of what you have.

denverlicious · 12-14-2006, 12:02 PM

turbosquid is right on the money with the downpipe. From my experiences with my evo, the downpipe made the biggest difference in terms of a turbo back.

im not to familiar with the layout of the 335i's engine so i can really say about the LICP and the turbo inlet pipe. But for sure a 3" dp into a 2.5" exhaust doesnt sound to bad.

12-12-2006, 04:51 PM	#1
denverlicious New Member 1 Rep 15 Posts Drives: 05 evo Join Date: Nov 2006 Location: redondo beach, ca iTrader: (0)	why 2.5" how come not 3" so im coming from an evo and hoping to get a 335. im just trying to understand why all these exhaust companies are making 2.5" exhausts? From my experience back pressure for turbos arent the greatest thing. Usually a 3" on a turboed car is standard. why is it that the 335er's are using 2.5" let me know? thanks!
	Appreciate 0 Tweet Quote

12-12-2006, 05:14 PM	#2
adriver Enlisted Member 2 Rep 43 Posts Drives: soon to be Join Date: Nov 2006 Location: soon to be back iTrader: (0)	cause were talking about a true dual exhaust from the turbo back, not a single exhaust with a x pipe, or just daul tips. were talking basically 7 square inches of exhaust space in a 3 inch to about 5 inches per 2.5 inch pipe, so 10 inches of space. Cliffnotes, a dual 2.5" exhaust has about 40% more exhaust flow than a single 3"
	Appreciate 0 Quote

12-12-2006, 05:45 PM	#3
jgannonloans FOR SALE 15 Rep 279 Posts Drives: jet black 335i Join Date: Oct 2006 Location: Philly iTrader: (0)	yeah but a dual 3" will flow even more!!!!
	Appreciate 0 Quote

12-12-2006, 05:55 PM	#4
ahnh77 chichen 6 Rep 233 Posts Drives: e90 325xi Join Date: Sep 2006 Location: san francisco (south beach), ca iTrader: (0)	rule of diminishing returns....larger doesn't always equal any more performance...typically for most turbo cars...a free flowing 2.5 inch piping exhaust seems to do the job of maximizing performance.....plus you have to take into consideration the sound...you want to maximize performance matched with the best sound or tone to the exhaust...... __________________ ......... ............ ..........
	Appreciate 0 Quote

12-12-2006, 11:32 PM	#5
BMW_E90 Major 57 Rep 1,035 Posts Drives: 325i Join Date: Jul 2005 Location: California iTrader: (11)	for back pressure, which makes torque. __________________
	Appreciate 0 Quote

12-13-2006, 08:44 PM	#7
Lucid4000 Major 57 Rep 1,190 Posts Drives: 335i AW Sport 6MT Join Date: Jan 2006 Location: NYC!! iTrader: (5) Garage List 2006 330i Sport [0.00]	They do it so you have something else, to upgrade later... __________________ Mobile Addictions 718.877.7700 or info@mobile-addictions.com www.mobile-addictions.com
	Appreciate 0 Quote

12-14-2006, 01:20 AM	#8
cm3rc Colonel 85 Rep 2,221 Posts Drives: 2006 E90 Join Date: Dec 2005 Location: Ferndale MI iTrader: (8) Garage List 06 325i [0.00]	i got a 3" custom piping __________________ www.socale90.com
	Appreciate 0 Quote

12-14-2006, 11:40 AM	#11
Turbo Squid Model 23 Rep 283 Posts Drives: Fast and Loud Join Date: Nov 2006 Location: San Francisco, CA iTrader: (0) Garage List 1999 M3 [0.00] 2001 ML55 AMG Desig ... [0.00] 2001 BMW X5 4.4 (SOLD) [0.00] 2003 VW Jetta 1.8T ... [0.00] 2007 335i (SOLD) [0.00] 1966 Pontiac GTO [0.00]	I'm interested in seeing who and how someone will tackle upgrading the downpipes on the 335, I read that a BMW designer said that one of the problem points of a 335 with more power would be that the DP (downpipe) is more prone to overheating and cracking as a result of the greater heat. From my experience with a turbo car, having a 3" DP is very beneficial, even if it feeds into a 2.5" system. I'd say the DP is a greater priority worrying who's is bigger. I'd also be interested in seeing an upgraded TIP (turbo inlet pipe) and LIP (lower-intercooler pipe) from the pictures I saw it looks like the stock ones are pretty nice, doesn't seem like there are any "pancake pipes" like there was on the 1.8T. But it's always nice to get the most that you can out of what you have. __________________ “No man has the right to be an amateur in the matter of physical training. It is a shame for a man to grow old without seeing the beauty and strength of which his body is capable.” ~ Socrates
	Appreciate 0 Quote

12-14-2006, 12:02 PM	#12
denverlicious New Member 1 Rep 15 Posts Drives: 05 evo Join Date: Nov 2006 Location: redondo beach, ca iTrader: (0)	turbosquid is right on the money with the downpipe. From my experiences with my evo, the downpipe made the biggest difference in terms of a turbo back. im not to familiar with the layout of the 335i's engine so i can really say about the LICP and the turbo inlet pipe. But for sure a 3" dp into a 2.5" exhaust doesnt sound to bad.
	Appreciate 0 Quote