Can I Run A Straight Pipe For An Exhaust - BMW Forum -
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#1 (permalink) Old 12-30-2004, 10:42 AM
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I have a rotted cat, and instead of paying a couple hundred for a new used one i wanted to go ahead an run a two and a half in single pipe through the exhaust into a new muffler like a dyno max, i was wondering what the side effects of this would be i already have hesitation when i accelerate and i think its because of the exhaust i was wondering if opening the exhaust like that will have any dramatic results on the motor in a bad way. i have a 85 535i straight six. Thanks
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#2 (permalink) Old 12-30-2004, 11:15 AM
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You will be getting rid of the much needed back pressure that your engine must have!
You will lose most of your low end torque.
And you can burn up a valve.
Why don't you just get a high flow cat or even something cheap just for the time being until you can get the right one?
Th eguy I got my '86 from had taken the cat off. When I replaced it I couldn't believe the low end I all of a sudden had.
You will be much happier if you just put another cat on it!

Dave G.
'89 635csi
'86 528e - Sold
'84 528e - Soon to be 533i
'96 Jeep Cherokee 4WD
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#3 (permalink) Old 12-30-2004, 02:47 PM
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Better check on your state's smog check process. Here in California, you could never get away with that...they'd fail you for 1) removing the cat, 2) modifying the original exhaust system and probably 3) spewing too much pollution out the back.

<span style='color:green'>1994 325i </span>- - - 75,000 mi.
No mods - - - very happy as is!
<span style='color:green'>1995 525i </span>- - - 154,000 mi.
No squeaks or rattles... unreal!
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#4 (permalink) Old 12-30-2004, 03:49 PM
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you would have HUGE torque loss. and lets face it the 535 needs that torque

<span style='font-size:11pt;line-height:100%'><span style='color:blue'> theres no replacement for displacement </span></span>
im so hardcore. i dont even have cup holders
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