Turbo Whirring - I Think

[stu306]

Well I just traded in my 97 GT for a 95 GT4. Wow there is no comparison!

Since I am new to the Turbo's excuse the ignorance!

When I am changeing up, I feel the turbo kick in, then when I lift off the accelerator to change gear I hear a whirring noise almost a rattle sometimes. Any ideas? Is this bad?

The car came fitted with a AVC-R and HKS Turbo timer, I don't think there are any mods apart from an induction kit. I don't believe there is a dump valve fitted.

Is this air passing the compressor wheel I am hearing? If this is the case am I best to fit a dump valve?

[dawesy]

could be compressor surge (also refered to as wastegate chatter)

is it any thing like this (need to listen at gearchange) if it is then no need to worry

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[stu306]

That's exactly what the sound is. Thanks for the assurance that it is normal. I understand why you get the noise. Just curious as to why this happens, is it wear on the turbo? I assume it doesn't happen from new?

Thanks again

[cmarshall]

That's exactly what the sound is. Thanks for the assurance that it is normal. I understand why you get the noise. Just curious as to why this happens, is it wear on the turbo? I assume it doesn't happen from new?

Thanks again

Mine only chatters like that when i let off the throttle slowly otherwise its just through the OEM d.v which is fairly loud.

[dawesy]

if there is no dump valve and an induction kit then that's why you can hear it.

what you are hearing is caused by what happens when you lift the throttle:-

the compressed air between the turbo and the throttle butterfly has no where to go and back flows out the turbo but as the blades are still spinning it gets chopped up and also causes a judder in the spinning compressor wheel.

[cmarshall]

if there is no dump valve and an induction kit then that's why you can hear it.

what you are hearing is caused by what happens when you lift the throttle:-

the compressed air between the turbo and the throttle butterfly has no where to go and back flows out the turbo but as the blades are still spinning it gets chopped up and also causes a judder in the spinning compressor wheel.

Mine has the oem d.v though why does it only do it when i let off slowly. All it has is a HKS induction kit