On cold mornings lately I have noticed a loud grating noise from the enigine.

Seems to come on betwen 1000-2000rpm and stop at 2000

After a few minutes of driving it goes quiet for the rest of the journey.

Am i right in thinking its the wastegate? and does this sudden increase in noise bode badly?

Any ideas guys?

Jono

The wastegate only opens when you lift off the throttle, so i would think it's unlikely to be that.

Si

Just reading the symptoms again. My wastegate is much more audible when cold becuase the secondary air pump(octy RS) comes on for a few minutes, then all settles down.

The wastegate only opens when you lift off the throttle' date=' so i would think it's unlikely to be that.

Si[/quote']

Are you saying that boost when coming off the throttle is vented through the waste gate?

If so I'd be worried for the longevity of my turbo.

I took my Octy RS in to Pillings last week for noisy start up. Sounds like a diesel for a couple of minutes then goes back to normal. Garage said all perfectly normal in colder weather and down to air pump. There is a thread on here somewhere about noisy start up - you could search to find it. It is quite a racket though - was a bit worried before I took it into garage.

No, the wastegate only opens when the actuator diaphram moves. The actuator is set to a certain psi (0.8 bar in the Octy RS, i think) and opens the wastegate into the exhaust to stop the turbo over boosting. Correct me if i'm wrong, but a certain amount of boost is let out when you lift off, and the rest goes out the dump valve.

No, the wastegate only opens when the actuator diaphram moves. The actuator is set to a certain psi (0.8 bar in the Octy RS, i think) and opens the wastegate into the exhaust to stop the turbo over boosting. Correct me if i'm wrong, but a certain amount of boost is let out when you lift off, and the rest goes out the dump valve.

Got to admit that I don't rightly know...you're probably correct.

However what I do know is that if you hear a rasping sort of noise then the boost is being vented through the wastegate instead of via the dv and this is bad for the turbo.