[BenN]

Ok, so i may be imagining things here, but on my 120d F20 - when changing gear at certain rev's i've managed to hear what sounds like a slight dump/hissing sound. Its loud enough for me to hear inside the car with the windows up. Since i'm still running the engine in, ive not had much of a chance to try and figure out what circumstances make this more noticeable.

Have never heard this before on a diesel, so i was pretty surprised unless im hearing something else usually associate the 'noticeable sound' with higher performance petrol engines. I guess the car has some sort of waste gate on it, its the noticeable hiss that i found unusual - although ive only heard it a few times.

Anyone know what conditions promote this - lol?

[JonF1982]

I get that too on my 116i.

[logiclee]

The petrol model's have a wastgate to control the exhaust gas flow and a recirculating dump valve that dumps pressure back into the intake.

The Diesel doesn't have either it has a VNT system, you may just be hearing the changes to gas flow across the compressor blades.

Cheers
Lee

[Scouser]

i can hear it on my 116i petrol want to make it so i can hear itt louder whats the best thing to do? induction kit ???

[ovekvam]

I haven't heard it myself on the 116i, but I've heard that spectators on track events hear it from the outside. Since the turbo is very small, I guess there is not all that much air going through the valve. You would have to install some kind of whistle on it....

[yoodog]

I have 120d f20 as well, and when I push it to the limit, and than drop the accel pedal, I can hear it blowing off. And some times not in one step but in clear 3 steps. It has nothing to do with gear switching. Blow off simply lets the air out when you stop accelerating, similar thing happens while gear-shift. If you have turbo, you can have it. For 120d f20, I was not able to locate it on real oem, even though 125d has it clearly because it is twinturbo and pressure is higher =)

[westphone]

In Sport or Sport+.... In the mountains more than one third travel of throttle started to get the hissing sound (thought we were chased by an angry bird ha) At more than three quarter of throttle waste gate dump sound I guess is more prominent.

My amateur test through OBD port our turbo only gets up to 0.5 bar (－ish), so the sounds probably won't be that loud....

[Avian]

It's as simple as this. You have a turbo. Enjoy the sounds that come along with it.

[Bob UK]

The twin port turbo gives a little rasp when you push the revs up and I thought it was a problem until I had a loaner with 300 miles on it that sounded exactly the same.