Hi this is probably a daft question at low speed when accelerating not too hard you can slightly hear the boost from the turbo and a dumping noise when you come off throttle. A little like a dump valve. I'm.assuming this is normal. Obviously if you boot it you hear the supercharger.

I'm pretty sure from what you are describing that's the normal noise!

Yes this is normal, you are hearing the turbo spin upto speed, then when you lift off the wastegate opens to release excess exhaust pressure.

It's normal, enjoy !!

Cheers guys thanks

Let me guess, you haven't driven with the windows open for a while? And thanks to the sunshine, now you have?

I've noticed it for a while as I try my best to drive with the windows down coz it sounds good. but as it sounds a little like a dump valve and there isn't one, I thought I'd pop the question.

Keep the windows down, now you know what it is try this,

Put your foot hard down at low revs (1500 rpm) as you feel the surge of power coming on, snap the throttle up quick and you'll get a good wastegate noise as it releases all that pressure :-)

It's childish but it will make you smile!!!

Ha ha ha

I sometimes go on and off throttle just to hear it

It does have a dump valve - just a recirculating dv. Dv \ wastegate \ bov same thing yes?

We're talking about the little whistle when one gets off the loud pedal under about half-throttle, I presume? Go any faster, and you won't hear it for engine noise; go any slower, and you won't hear it then, either.

Worth reading when you have Supercharger,  Supercharger Whine,

Supercharger & Turbo Charger, & just Turbo.

 

Turbo,

Charge Pressure Control, page 49.

 

See page 11 on,

13 & 18 Supercharger Whine. 2,000-3,000 rpm

http://volkspage.net/technik/ssp/ssp/SSP_359.pdf

(this is the engine up to 125 kW, but mechanically the same as the 132-136kw, but Max Power is different & at 6,000 rpm)

I like to boot it and then slowly come off the throttle, you get to a point at such little throttle that the waste gate is fluttering.

Makes a great noise and makes my car sound like it belongs in a Fast and Furious film.

Fitting an ITG turns everything to 11 though! :-p

If this turbo system is like any other...

Dumpvalve (or in this case recirculation valve) dumps any boost pressure upon releasing the throttle. It protects induction parts, especially in throttle bodies which when closed would other wise become pressurized, as well as the turbo itself which would otherwise suffer from backflow "chatter".

Wastegate, a valve on the turbo which opens to maintain a safe maximum boost pressure (in this case I believe ecu controlled). Without a wastegate the boost pressure would continue to rise as the rpm of the engine did, consequently being fatal for the engine.