924Board.org

[augidog]

Coming home Friday I noticed that the car was running with much more low end on the highway.Sounded great.Deep purr with power. I thought maybe something cleared the exhaust.
Then- performance drastically dropped as the new leak in opened up further behind the cat.The purr soon turned into a roar.
I'm guessing that for a couple of minutes the exhaust was tuned perfectly to the motor.Is there any way of getting that back?There must be a formula.
Header?
larger pipe?
I'm running a stock system now.
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1978 924 95 mile daily driver.
Audi TB/POR174M/High Flow Cat/2.25" exhaust
I knew that positive thinking thing wouldn't work.

[Smoothie]

A free-er flowing exhaust is better for hp at higher speed, but a more restrictive exhaust is better for torque, so exhaust systems are designed to provide a compromise between the two. There's a device - an exhaust tip with a variable spring-loaded flap that stays more closed at low speeds to provide more torque and gradually opens up as speed increases to improve HP at higher speeds. I don't have any personal experience with it (and it wouldn't make sense to use on a turbocharged car because the turbo provides resistance at lower speeds and becomes more free-flowing at higher), but it makes sense to me for a NA car and should work, but you'd have to change your whole exhaust system to a larger diameter to get the high end HP gain.
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"..it's made in Germany. You know the Germans always make good stuff."


'82 924T, US version, dark green metallic, 5 speed Audi 016G gearbox