135i\E82's running turboback's

[J x K]

For those of you who don't know what a turboback is, it means full exhaust from "turbo-back".

I have a question for you guys. Sometimes when I'm cruising, not gear dependent, I can occasionally "hear" my exhaust drone suddenly get louder out of nowhere. It's usually at a steady RPM while I'm just cruising. Not a big whoop, just seeing if anyone else has these same symptoms. I freak out sometimes thinking its my fuel pump failing so I WOT to see if everything is OK, and car runs normal. Weird?

*Sidenote: It's not me just "trippin", its literally exactly how I described it. Please share if your car does the same thing. It's not really a question of "I wonder if my car does it". If your car does it, you will definitely know.

Please share your experiences if you have the symptom described above.

[bryce]

it happens to me sometimes. i've realized that it's when i ever so slightly change the throttle position, though (barely less or more gas). it does exactly what you described. i bet it can be traced to some wastegate action

[Dmacc]

Same thing happens to me, but I can only notice it when I'm cruising on the freeway in 6th around 70, and if I give it the slightest bit more throttle, the tone changes dramatically and there's a lot more drone.

By the way I only have secondary cat delete and muffler delete and I get this problem

[LA-Bimmer]

Yep...when I went from stock to catless DP and full Berk exhaust. Just like you said. First time I thought something came a little loose and was perhaps an exhaust leak (since it was shortlyafter install). I checked all the connections when I got home, all was good. Only occasionally when cruising... a little blip of the gas and goes back to normal.

[BahamaBart]

Originally Posted by LA-Bimmer

Yep...when I went from stock to catless DP and full Berk exhaust. Just like you said. First time I thought something came a little loose and was perhaps an exhaust leak (since it was shortlyafter install). I checked all the connections when I got home, all was good. Only occasionally when cruising... a little blip of the gas and goes back to normal.

What your describing is drone or tonal frequency that is generated via the exhaust gases moving threw the exhaust. The exhaust system picks up the frequency and resonates it. No different than a trumpet - you have to push just the right amount air threw it to generate a sound. I'm running just an axle-back and in 6th gear between 2,700-2,900 a frequency develops which resonates in the cabin = drone. However this does not occur in any other gear at the same rpms.

Resonators and mufflers are designed to cancel out these frequencies.

[J x K]

Originally Posted by BahamaBart

What your describing is drone or tonal frequency that is generated via the exhaust gases moving threw the exhaust. The exhaust system picks up the frequency and resonates it. No different than a trumpet - you have to push just the right amount air threw it to generate a sound. I'm running just an axle-back and in 6th gear between 2,700-2,900 a frequency develops which resonates in the cabin = drone. However this does not occur in any other gear at the same rpms.

Resonators and mufflers are designed to cancel out these frequencies.

we're not talking about drone. we're talking about a sudden dramatic change in exhaust tone while cruising w/ static throttle pressure. it's really weird.

[jojo135]

Waste gate opening more is only logical explanation.

[BahamaBart]

Originally Posted by J x K

we're not talking about drone. we're talking about a sudden dramatic change in exhaust tone while cruising w/ static throttle pressure. it's really weird.

Okay. How re-creatable is it? Tone appears, you blip throttle, it disappears ........if you settle back to were you where does it re-appear? Only in 6th?