Engine vibration or boost noise

[Marco34]

Hi

I noticed this whilst at some lights last week and I couldn't replicate it when I got home. Anyway, it returned tonight.

When idling I rev the car to say 2000, 2500 rpm then let off the throttle the engine settles to idle, but just before there is a small vibration sound, almost like a loose pully or some boost pressure going somewhere. I can see the engine cover vibrate a little for split second then fine at idle.

I've had a remap and the turbo spools much quicker than it did. If I rev it with little boost it seems ok. This only happens when revved from idle and turbo spooling and doesn't always happen. It's fine whilst driving!

Could it be the car struggling to get rid off excess boost whilst going straight to idle? The car runs superb otherwise.

No fault codes in VCDS.

Seems an odd one...

Cheers
Marco

[Marco34]

Just an update - it does it from higher revs to lower revs but not as noticable. It does sound like air or escaping boost but not in a very efficient way. I'm not sure whether mapped cars behave like this due to the extra boost....

[Marco34]

Anyone got any theories?

I've since read the TDis can do this and that a remap with increase boost may well magnify the noise...

[Marco34]

Nobody ever come across this then?

The sound only occurs most noticeably at close to 2000rpm and is loudest (although it's not loud at all and you need to listen for it) when you open the throttle up a fair bit before immediately lifting off the throttle very quickly. It doesn't happen if I ease off the throttle gently.

The sounds has a dry abrasive quality to it, which is why I am concerned about it. However, if it is pressure being released from the turbo then the sound could be likened to a slighlty rougher sounding version of Darth Vader breathing, in a rattly way.

I don't here when driving as much, it's not noticable..

I'll update this last time in the hope someone has heard it before.

Thanks
marco

[Crasher]

It is always difficult to describe noises and even harder to work from the description but your Darth Vader analogy is good as it is the noise I hear a lot of VNT turbo’s make as they age, especially after they have been re-mapped. It isn’t normally anything to worry about but in extreme cases I have seen the turbo compressor explode after the shaft bearings have failed.

[Marco34]

It is always difficult to describe noises and even harder to work from the description but your Darth Vader analogy is good as it is the noise I hear a lot of VNT turbo’s make as they age, especially after they have been re-mapped. It isn’t normally anything to worry about but in extreme cases I have seen the turbo compressor explode after the shaft bearings have failed.

Hi Crasher

Thanks for your reply. My car has only covered 42k miles although it is a 2001. I change the oil every 6 months which usually about 5-6k in the hope of keeping the bearings as good as poss. I'll just see how it goes for now.

Is it the mechanics of the turbo or the air within?

Thanks again Crasher.

Marco

[Crasher]

Both really, the vanes can oscillate as the revs come down.

[kenhodgson]

Ah, useful info. Mine sounds very much the same as your describing -though I always thought it sounded like a bearing rattle but the Darth Vadar description is good.

I only noticed mine when I was at the Nurburgring. Thought I did some damage after I first heard it but 6 months on turbo seems ok.

[Marco34]

Ah, useful info. Mine sounds very much the same as your describing -though I always thought it sounded like a bearing rattle but the Darth Vadar description is good.

I only noticed mine when I was at the Nurburgring. Thought I did some damage after I first heard it but 6 months on turbo seems ok.

Interesting to hear your comments. I think I did have it before but just not as noticable before the remap. If it was anything major I think the turbo would have died by now. I agree that it does sound like a bearing rattle but with the added mix of air!!

I think I'm going to crack on and enjoy driving the car....
By the way, Ken how did you find the Nurburgring?