TDi turbo noise

[mbames]

Before my smoke test on the MOT yesterday, the tester rev'd the nuts off the car to clear out all the rubbish. The first couple of times he did this, I think just as be backed off the throttle, there was a strange "chattery" noise, I would say a bit like a chavvy sound dump valve.

I did not think that VAG-110 TDi's has such things fitted. Any ideas?

[mbames]

** bump **

Any ideas?

Cheers,

Matt

[chicken_eyebrow]

On a petrol turbo the chattery noise is the sound of excess boost trying to go back through the compressor turbine. But this only happens when you close the throttle and the dump valve doesn't release the boost quick enough (or the DV has been blanked off). Diesels as far as I know don't have a throttle plate so I don't know why the excess boost would be trying to go back through the turbo. I know they run at a much higher psi than petrol turbos so I suppose if excess boost was trapped the noise would be noticeable.

[mbames]

The noise was pretty noticable for the first two applications of HeavyFoot™ and after that I did not hear it again.

[felicia16v]

its just a slight overboost causing the pressure pipe to whistle on the exit of the turbo, they only seem to do when revved with no load on .

the later cars have a silencer on the pipe to eliminate it so nothing to worry about..

[yashicamat]

Mine does this a bit in 1st gear, but I always thought it was the DMF. The turbo does, however, definitely make a 'dump valve sound' (for lack of a better way of describing it) when accelerating with some boost then changing gear at mid-rpms. Nothing like as loud as the 2.0TDi that was in my Octy mk2 though.

[mbames]

its just a slight overboost causing the pressure pipe to whistle on the exit of the turbo, they only seem to do when revved with no load on .

the later cars have a silencer on the pipe to eliminate it so nothing to worry about..

Cool, so nothing to be worried about then I was just slightly concerned as I have the sticky vanes in the turbo problem and have not yet had time to take the thing off and clean it up.

[felicia16v]

yea once you have free'd the vanes up you will hardly ever notice it

[cheezemonkhai]

Before my smoke test on the MOT yesterday, the tester rev'd the nuts off the car to clear out all the rubbish. The first couple of times he did this, I think just as be backed off the throttle, there was a strange "chattery" noise, I would say a bit like a chavvy sound dump valve.

I did not think that VAG-110 TDi's has such things fitted. Any ideas?

There is no dump valve on the 110 as it's a VNT mechanism and so varies the fin angle.

I think that it could be a couple of things.

1) It is clutch/dmf, but since it's in neutral then I doubt this

2) The VNT is stuck and because there is no wastegate the air can't escape and so the turbo stalls. This would be what you can here.

I'd say option 2 is most likely by a long way and that it might be worth getting the turbo off and inspected and if there is an issue off for a recon at somewhere like turbo techniques before it goes bang.

Have you blanked off your EGR system?