Turbo Spooling On The Over Run.

Retrogamer

1.9 TDi PD130 engine with KKK turbo.

Got a bit of a weird issue on my car where the turbo is sometimes spooling up on the over run.

It only happens if i've been either flooring it through the gears for a bit, or if the engine has been running for some time (30 mins or so)

It's got a performance exhaust so i can hear the turbo whistle as normal pulling away and stuff but recently if i'm driving at say 1500rpm, hold it there and turbo is silent the moment i take my foot off the throttle it makes the same turbo spooling (whistle) noise as if i was pulling away.

It's not the "coo" noise you sometimes hear from Garrett turbos. Any ideas?

Not using any oil so and free of smoke on boost so would suggest turbo seals are ok and no boost leaks.

arcon5

Pressure relief valve?

Stigy

VAG TDI engines all have a relief valve noise constant with most turbo cars when you let off the accelerator during picking up speed, usually when changing up a gear. It's not always that noticeable but I notice it on my 1.9-TDI as I did on my older A3 1.8T. I'd imagine, as yours is 'modified' a more prominent noise would to be expected?

Retrogamer

After doing some reading on the TDi forums it seems when the engine has heated up enough on the over run it will dump some fuel into the engine to cause the turbo to spool slightly so that it's quicker to get to full boost again when you put the foot down.

I've had it for 2 years now and the exhaust fitted for most of that but never noticed it doing this until recently.

I know the relief valve you're thinking of that you can hear when gunning it and shifting gears. This is a little different though.

If i pull away like a granny up to 2000rpm i can hear the turbo whistle up to that rpm. If i hold it revs there the whistle goes away until i let off then you can hear the turbo begin to spool a little again. If you dip the clutch or the revs go below 1500rpm then it doesn't do it.

I'm hoping it's just the thing described above. Just a bit weary about it as i know KKK turbos aren't up to much.

1952573

Sticky vanes?

Retrogamer

I'm not sure to be honest. Still pulls & boosts as normal with no error codes or EML. I know they're famous for having sticky vanes. I've got some VAGcom software on route so hopefully that might shed some light on it.

Rambosmum

I noticed this a few months ago on my 1.9 TDI golf. Last week the turbo went and I've just had a new one fitted.

Retrogamer

Rambosmum wrote: »

I noticed this a few months ago on my 1.9 TDI golf. Last week the turbo went and I've just had a new one fitted.

How many miles were on it?
Was yours the PD150 engine?