# custom exhaust



## Charles Devine (Aug 22, 2007)

Ok so while working on my axle replacement tonight I looked back at the cats and just past them I see this rinky dink exhaust pipe. WTF! like it litterly its only 1 inch in diameter... does anyone have any exhaust systems with good quality audio of a 2.8? I'm looking at going to a shop having them remove the resonator and using a 2.5 inch pipe all the way back to a muffler.

The youtube clips I'm finding are all 2.7t and or sound like crap!

I'd like to aslo note I'm looking at passat's as well as they are the same motor.


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## vr6ninja (Mar 20, 2007)

I've never understood the reaction to change the diameter of the pipe right away. By increasing your diameter you're potentially decreasing the velocity of your exhaust gas. 

For a moment assuming flow is incompressible:

flow rate out of the engine = velocity x cross section of the pipe

That would be decreasing your gas velocity by 40% = (1 inch / 2.5 inches) * 100

Ok so assume the flow out of the engine is compressible:

The formula for that function is more complicated as density plays a roll and so a slight increase in diameter could reduce the density pushed through the pipe. I can't answer how much but an inch and a half seems like a large increase to me.

As for sound, I have yet to find a decent sounding 2.7t exhaust on youtube. I haven't changed my exhaust because i haven't found an affordable system that sounds good to me. I've looked at Eisenmann and Supersprint but of course those are an arm and a leg, on the cars I've heard them on they sound really good but then again I haven't heard them on a 2.8 or a 2.7t.


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## showtime212 (Mar 5, 2005)

On my 2.8 12v A4 i put 2.5 cat back deresonated with a straight thru magnaflow muffler with dual tips its sounded really good. My avant has 2.5 downpipes with hollowed cats a magnaflow x-pipe and straight thru magnaflows on it. It needs resonators though because its a little raspy up high but sound like an R32 down low


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## Charles Devine (Aug 22, 2007)

ya that's the kind of sound I'm looking for all around I don't want to kill people but be able to hear a nice rumble


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