An Exhaust system----restrictions, etc....

clairvoyant · 08-04-2010, 02:52 PM

What is the most restrictive point from an exhaust system (downpipes, catbacks, midpipes, etc) on 335i?
Is it the catalytic converter or the shape/bent of the exhaust system itself?
Thank You

RoundelM3 · 08-04-2010, 03:55 PM

Pipe diameter would be no. 1, with catalysts/mufflers and any bends that reduce the pipe diameter following after. Catalysts aren't all that restrictive, but they are Federally mandated, and in some states, like Texas, it's a huge fine if you remove them from a licensed street vehicle. Doesn't apply to vehicles that aren't street-driven, though.

A "catback" refers to an aftermarket exhaust system that bolts directly to the catalytic converter(s) and goes all the way back to the exit point. Most of these feature larger diameter pipes and high-flow resonators and mufflers. The other option is usually just free-flow mufflers that attach at the same point as the stock mufflers.

08-04-2010, 02:52 PM	#1
clairvoyant Major 88 Rep 1,032 Posts Drives: Bavarian Manure Wagon (BMW) Join Date: Oct 2007 Location: 45°19′20″N, 75°50′0″W iTrader: (5) Garage List 2007 335i [5.24]	An Exhaust system----restrictions, etc.... What is the most restrictive point from an exhaust system (downpipes, catbacks, midpipes, etc) on 335i? Is it the catalytic converter or the shape/bent of the exhaust system itself? Thank You
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08-04-2010, 03:55 PM	#2
RoundelM3 Major General 1952 Rep 7,073 Posts Drives: 15 F80 M3, 22 G01 X3 30i Join Date: Apr 2010 Location: Clayton, NC iTrader: (2) Garage List 2015 BMW M3 [8.25] 2022 BMW X3 [9.87]	Pipe diameter would be no. 1, with catalysts/mufflers and any bends that reduce the pipe diameter following after. Catalysts aren't all that restrictive, but they are Federally mandated, and in some states, like Texas, it's a huge fine if you remove them from a licensed street vehicle. Doesn't apply to vehicles that aren't street-driven, though. A "catback" refers to an aftermarket exhaust system that bolts directly to the catalytic converter(s) and goes all the way back to the exit point. Most of these feature larger diameter pipes and high-flow resonators and mufflers. The other option is usually just free-flow mufflers that attach at the same point as the stock mufflers. __________________ 2015 F80 ///M3 Sedan 7DCT Tanzanite, 2022 X3 sDrive30i 8AT Brooklyn Grey
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