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its spools down 1-2-3.... the point is to cool down the turbo before you turn off the engine....so u dont hav ethe hot oil sitting in the turbo :)

give it 2 min's or just drive for a coupl do fminutes on your way back before turnign the car off
 

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aldolicious77 said:
its spools down 1-2-3.... the point is to cool down the turbo before you turn off the engine....so u dont hav ethe hot oil sitting in the turbo :)
Almost right. It does indeed "spool down" 1-2-3. And you do want to cool it down if you have been running high boost.

But regardless of boost the turbo is always spinning, and it can take up to two minutes for the turbo to "spin" down. It is such a low-friction bearing that the turbo will spin at higher-than-normal rpm for a long time, even though it isn't "spooled" (producing boost), when the engine is idling. Our turbos have an "oil bearing" - it is entirely dependent on the oil film for the bearing surface. Turn off the engine, you have no oil pressure, the bearing surface collapses - if your turbo is still spinning at high rpm, it could be enough to squeeze the residual oil out and get metal-on-metal contact.

At the very least, let it idle for 30 secs, and avoid "blipping" the throttle prior to engine shut-off. The longer you let it idle, the more you can be certain that the turbo has spun all the way down. Since learning this little factoid, I've been doing a 1-1/2 to 2 minute idle before shutoff, whenever practical.
 
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