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What Noise Does Back Pressure Make?

getyayayaout

By getyayayaout,
in Engines & Forced Induction

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getyayayaout Enthusiast

getyayayaout

Posted
Posted

Have a stock exhaust on my car, but bigger front mount and boosted to 10psi at about 4k rpm. after 4000rpm there's a shockingly loud noise, i can hear it through my open window. sounds like a machine gun going off from under the car. back pressure from the stock exhaust (once had a 3'' cat back) or something more sinister? also, car loses no power...

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https://www.sau.com.au/forums/topic/386988-what-noise-does-back-pressure-make/
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JustinP Mentor

JustinP

Posted
Posted

Loose bolts on turbo or exhaust manifold.

Have a stock exhaust on my car, but bigger front mount and boosted to 10psi at about 4k rpm. after 4000rpm there's a shockingly loud noise, i can hear it through my open window. sounds like a machine gun going off from under the car. back pressure from the stock exhaust (once had a 3'' cat back) or something more sinister? also, car loses no power...

GTR_JOEY Grand Master

GTR_JOEY

Posted
Posted (edited)

Blown gasket in ur exhaust somewhere I reckon....

Would need to hear it

Upload a video

Machine guns are loud, hope u wear hearing protection while driving heh heh

Edited by GTR_JOEY
getyayayaout Enthusiast

getyayayaout

Posted
  • Author
Posted

I think it could be a blown gasket in the exhaust somewhere leaking, or like I said back pressure going back to the turbo. But im not really an expert. don't think my iphone mic would pick it up cause the wind noise would be a factor i reckon..

Blown gasket in ur exhaust somewhere I reckon....

Would need to hear it

Upload a video

Machine guns are loud, hope u wear hearing protection while driving heh heh

GTScotT Grand Master

GTScotT

Posted
Posted

backpressure = silent killer

kidding. it doesnt make any noise..

id say ask a mechanic as its extremely hard to e-diagnose a noise in these cases. as already noted, it could be denotation/exhaust leak/rattling bolts/machine gun hiding under the car.

:action-smiley-069:

Rolls Grand Master

Rolls

Posted
Posted (edited)

You have the extremely common peak torque misfire.

Caused by bad spark due to spark plugs, spark plug gap, coil packs, ignitor, increase boost on stock ecu causing massive overfueling making the mixture even harder to ignite, boost leaks etc will also cause the car to run even richer etc also compounding the problem.

Start at the start and work your way through the list, I am confident it will be one of these things. Misfires are still very loud with a stock exhaust.

Really bad detonation?

Detonation is never loud, it is just a pinging noise like marbles in a can.

Also you can't hear back pressure, back pressure is just high pressure in the exhaust. Blow into a straw vs blowing through a pipe, does it make a machine gun popping noise? lolol

Edited by Rolls

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