What is this odd knocking noise?

[jj1010]

I suddenly heard this knocking sound coming inside the cabin. I have a AA catted GESI Downpipe and everything else is stock. Have had the DP installed for around two weeks now and had no issues. Didn’t even drive that hard today and suddenly it start making this knocking noise once I came home. Engine seems to be fine I checked. Opened the front hood and didn’t hear any knocking noises. In the outside also I can hear this sound. I seem to be able to only hear it when I’m inside the cabin.

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[NocturnalEmber]

I suddenly heard this knocking sound coming inside the cabin. I have a AA catted GESI Downpipe and everything else is stock. Have had the DP installed for around two weeks now and had no issues. Didn’t even drive that hard today and suddenly it start making this knocking noise once I came home. Engine seems to be fine I checked. Opened the front hood and didn’t hear any knocking noises. In the outside also I can hear this sound. I seem to be able to only hear it when I’m inside the cabin.

Put the car in neutral and see if the noise goes away; I'm not expecting it to, but something is better than nothing.

The car is stationary, so you can reasonably eliminate anything suspension or propulsion related since no load is being placed on the chassis either aside from what the car would normally see at rest anyway.

Its rhythmic, so I'm going to go with the drive belt or possibly the AC compressor clutch.

Edit: actually that sounds like it might be the downpipe contacting something under the car.

 

[itzTang]

Put the car in neutral and see if the noise goes away; I'm not expecting it to, but something is better than nothing.

The car is stationary, so you can reasonably eliminate anything suspension or propulsion related since no load is being placed on the chassis either aside from what the car would normally see at rest anyway.

Its rhythmic, so I'm going to go with the drive belt or possibly the AC compressor clutch.

Edit: actually that sounds like it might be the downpipe contacting something under the car.

but he opened the front hood and nothing...

 

[Eastwood]

Put the car in neutral and see if the noise goes away; I'm not expecting it to, but something is better than nothing.

The car is stationary, so you can reasonably eliminate anything suspension or propulsion related since no load is being placed on the chassis either aside from what the car would normally see at rest anyway.

Its rhythmic, so I'm going to go with the drive belt or possibly the AC compressor clutch.

Edit: actually that sounds like it might be the downpipe contacting something under the car.

I was gonna say waste gate actuator hitting the vband, but as you said car is stationary. But really we're all just guessing

 

[omfgzilla]

Check the V-band on the turbo again. Bolt might have gotten loose, or it could be the bolts that tie the downpipe to the bracket. It's the only thing i can think of.

 

[FitmentIndustries]

Don’t panic! Since the engine bay sounds healthy, your motor should be totally fine. Because the noise is only heard inside the cabin, your aftermarket downpipe is simply expanding from heat and physically tapping against the underside of the car. It is very common for new exhaust parts to shift, stretch, or loosen slightly after two weeks of heat cycles.
The Main Culprits:

The Crossbrace? The downpipe shifted or rotated, causing it to hit the metal chassis brace right under the exhaust.
The Heat Shields? The flimsy aluminum shielding in the transmission tunnel is bent and vibrating against the wider pipe.
Loose Bolts? The upper V-band clamp or the mounting brackets loosened up, letting the exhaust swing around.

The Fix
Let the car cool down, jack it up, and give the exhaust a hard shake to replicate the noise. Look for scratched metal where it’s rubbing. To fix it, loosen the clamps, physically pull/rotate the pipe to get a finger-width of clearance all around, bend the heat shields away by hand, and retighten everything down hard.

To narrow it down, does the knocking happen mostly at idle and over bumps, or does it speed up with your RPMs?

 

[jj1010]

Update I think it may have been because I overfilled the gas… I don’t know how in the hell that would make a noise but after I drove it for a while and the gas lowered it stopped making the sound. This is interesting..

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