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Discussion Starter #1
I am hearing a sound when I turn my engine off that goes on for a few seconds, initially I thought it was an air leak but I now think that it is the front turbo spinning.
Would really appreciate some third party feedback, has anyone else noticed this on their car?
I think that this is happening because of the position the engine is in when it stops, so if piston 1,2, or 3 is in a position where it is just starting the exhaust stroke, then it could be leaking through the barely open exhaust valve and keeping the front turbo spinning for a short while.
It does sound a bit far fetch, but this is the only thing I can come up with.

Ideas anyone, please.
 

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LOL, its a healthy turbo. Its a good thing

You have uprated turbos to ball bearing i guess?

the reason why you can here the turbo spinning still is because of the revs it spins at and the bearing are in good condition and allowing it to free wheel until, well until it stops.
 

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Discussion Starter #3
LOL, its a healthy turbo. Its a good thing

You have uprated turbos to ball bearing i guess?

the reason why you can here the turbo spinning still is because of the revs it spins at and the bearing are in good condition and allowing it to free wheel until, well until it stops.

Awesome, thanks for the advice. I am really relieved.
They are Garret 2860-5's so ball bearing turbos, one less thing to worry about before my session on the rolling road :).
 

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lol use to hear that every time .

just think , your turbo's spin up to and over 250,000 rpm depending on what boost your running so it will take time for them to come down and thats exactly why you are ment to give them time to slow down before you turn off the engine

( or just have a turbo timer )
 

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yup roller bearing turbos do this, normal journal bearing turbos slow down much quicker due to the higher friction on their bearings compared to roller bearing turbos.

Healthy roller bearing turbos will still spin after stopping the engine even if you just leave the car idling and then stop the engine.

Note: The turbo timer is not really to allow the turbos to slow down (due to the point about idling above), its more to allow sufficient oil and water to help cool the turbo core before you switch off after hard driving. (if you dont oil tends to bake on the bearing surfaces, carbonise and wear the bearings much quicker). Turbos that do not have water cooling are particuarily liable to this (your GT2860-5s are oil lubed/cooled and water cooled so dont worry!). I find its much easier to chill out your driving for the last few miles of your journey and let everything cool rather than use a turbo timer.
 

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lol use to hear that every time .

just think , your turbo's spin up to and over 250,000 rpm depending on what boost your running so it will take time for them to come down and thats exactly why you are ment to give them time to slow down before you turn off the engine

( or just have a turbo timer )
250000 rpm?? i think thats too much you are saying i would say close to 100000+/-
 

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yup roller bearing turbos do this, normal journal bearing turbos slow down much quicker due to the higher friction on their bearings compared to roller bearing turbos.

Healthy roller bearing turbos will still spin after stopping the engine even if you just leave the car idling and then stop the engine.

Note: The turbo timer is not really to allow the turbos to slow down (due to the point about idling above), its more to allow sufficient oil and water to help cool the turbo core before you switch off after hard driving. (if you dont oil tends to bake on the bearing surfaces, carbonise and wear the bearings much quicker). Turbos that do not have water cooling are particuarily liable to this (your GT2860-5s are oil lubed/cooled and water cooled so dont worry!). I find its much easier to chill out your driving for the last few miles of your journey and let everything cool rather than use a turbo timer.
i was just being basic about the turbo timer lol

but agreed on chilling the driving down after a spirited drive as i use to do that too when i was driving my R32 at high speeds
 

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Actually it IS to let the turbo slow down ....
Or am I to assume its ok to turn off the oil supply to the bearing (s) with the turbo spooled up....if its cold ?

A good plain bearing turbo would seize if it was turning at anything much greater than what speed it runs at at idle, if you turned the oil pressure off to it...

The core cooling down is definatly correct, but the spindle speed is the most important thing prior to turning the engine off.
The ball bearings are just less pedantic about oil supply and more durable when abused ( by being turned off early)
 

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Actually it IS to let the turbo slow down ....
Or am I to assume its ok to turn off the oil supply to the bearing (s) with the turbo spooled up....if its cold ?

A good plain bearing turbo would seize if it was turning at anything much greater than what speed it runs at at idle, if you turned the oil pressure off to it...

The core cooling down is definatly correct, but the spindle speed is the most important thing prior to turning the engine off.
The ball bearings are just less pedantic about oil supply and more durable when abused ( by being turned off early)
yup agree about the shaft speed when you put it like that. I was thinking that most people dont get the turbos up to 100,000rpm and then just shut the engine off!.. usually there is some slowing down period coast to pits / car park etc and usually by that time the turbos have slowed down a lot!!.

Defo agree that rollerbearings are more tolerant to lack of oil, which is why they take a good few seconds to stop spinning when the engine is stopped whereas plain bearing turbos stop much more rapidly ( presumeably as the shaft touches the plain bearing surface as the oil film its suspended on drains away).
 

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Discussion Starter #11
What is actually happening is not that the turbos are spinning from a previous boost, I get this spin down even if I just start the car leave it to idle for 20 secs and the stop it. I don't even rev it and when it stops I get the turbos spinning.
I assume they will still spin up slowly on idle.
 

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Yep, turbos will still be spinning on idle so you still get the noise even if you havent boosted the car at all.

I only got the 'spinning down' noise after upgrading to 2860-5's, like others have said above, its because they are roller bearing jobbies.
 

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Discussion Starter #13
Yep, turbos will still be spinning on idle so you still get the noise even if you havent boosted the car at all.

I only got the 'spinning down' noise after upgrading to 2860-5's, like others have said above, its because they are roller bearing jobbies.
Well, thats exactly what i've got. Thanks
 

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my 2835s spin down for about 5-10 seconds... when new or newly refurbished its a nice gentle whoooshhh as they spin down but as they get used and abused they get noisier as they spin down but don't be too alarmed by that.
 

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