Occasional louder exhaust tone and burbles (n54 135i)

[Nuggetsa]

Hi Guys,

I'm currently having an issue where my exhaust tone will suddenly change to a harsh deep tone (similar to drone), also resulting in much louder burbles.

The issue doesn't seem to affect power output, however, it sounds terrible and has started to occur more often, while lasting for much longer.

It can occur randomly, however it usually starts under slight load (around 2.5k rpm, uphill), switching between normal tone and the harsh tone for the remainder of the drive.

No check engine lights appear, with no codes either. Happy to take some logs if that assists in finding the problem, or if this is normal.

Important information:

• Current running fully catless setup (custom exhaust with resonator near tips).
• Running MHD Stage 2, V10 (charge pipe, BOV, 7.5-inch intercooler)
• Brand new set of Eldor coils and spark plugs about 1-2 months ago

[ShocknAwe]

What kind of gasket/interface are you using at turbos and at downpipe/midpipe?

[Eyeman]

Have you had your car long? When I come off the highway, etc my car will be louder and then it will noticeably change tons. I've heard this related to closing of turbo wastegates. That might be what you are noticing.

[iminhell1]

Vacuum leak at wastegate actuator.

[Nuggetsa]

Originally Posted by ShocknAwe

What kind of gasket/interface are you using at turbos and at downpipe/midpipe?

I've current got vrsf downpipes, so the standard v-band clamps from turbo - downpipe, and gaskets from the downpipes - custom exhaust

Late reply as I've been fairly busy

[Nuggetsa]

Originally Posted by Eyeman

Have you had your car long? When I come off the highway, etc my car will be louder and then it will noticeably change tons. I've heard this related to closing of turbo wastegates. That might be what you are noticing.

I've had the car for a little over a year now. Currently at 90,000 kms (56,000 miles).

I have also read something similar, but it can happen within 60 seconds of leaving my driveway, and stays for awhile regardless of throttle movement

[Nuggetsa]

Originally Posted by iminhell1

Vacuum leak at wastegate actuator.

Would you recommend checking the vacuum lines between boost solenoids and wastegate actuators?

I havnt recieved any codes, such as the 30FF.

[ShocknAwe]

I'd replace all your vac line, easy DIY. Could be the dp/mid gasket given your setup, those fail on my car every 30k or so and create similar symptoms you describe. Also easy DIY.

[Nuggetsa]

Originally Posted by ShocknAwe

I'd replace all your vac line, easy DIY. Could be the dp/mid gasket given your setup, those fail on my car every 30k or so and create similar symptoms you describe. Also easy DIY.

Cheers, I'll definitely give both of those a check-over and see if it resolves the issue.