What Noise Does Back Pressure Make?

[getyayayaout]

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...

[abr33]

Really bad detonation?

[JustinP]

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]

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 January 1, 2012 by GTR_JOEY

[getyayayaout]

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

[toffy]

Stick a straw in your mouth and blow as hard as you can.. then you will know the sound of back pressure . I'd say something is loose and rattling by your description

[hypergear]

back pressure makes no sound. It can make your EGT goes very high and causing issues for motor and turbo. Possibly some sort of leaks in the exhaust side.

[joeyjoejoejuniorshabadoo]

missing can make that noise as well... check your plugs

[MBS206]

Back pressure goes "Om nom nom nom"...

[GTScotT]

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.

[Missileman]

Yes it does, it kind of sounds like stepping on a duck

[SargeRX8]

Machine gun = misfire.

[JustinP]

Back pressure sounds like this:

http://www.youtube.com/watch?v=YK18wQA-tHs

[Manuel Kasko]

Hahaha how was their driving when they decided to demo it for the reporter! Nearly side swiped a car

[Rolls]

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 January 8, 2012 by Rolls