StephanieT said:
There is no need to let the turbo "cool off" after driving. The only time it might be necessary is if the car is shut off while under boost.
Stephanie
I Feel that I should point out that your statement is misleading..
There is infact no "Need" to let the turbo spool down, but I highly recomend it.
The time that the turbo will need to finally be replaced, will probably be just as the car is off waranty if you don't treat the double snail with a bit more respect than that.
It's not the fact that it's liquid cooled that cures all, it just helps. The turbo spools up to over 100,000 Rpm and is supported by bearings that are lubricated by the engine oil. As soon as you kill the motor, you kill the oil that the turbo needs to prevent massive damage to the bearing.
So, what you read in the book is fine, however the reality is that the damage will not be visible until it's too late and you are paying for it.
If you take the time to wash and wax the car, take the time to let the power gods rest a bit before removing the oil.
30 Seconds is perfect, it also has a nice way of leveling the temperature of the block just before the heat spikes as the engine is shut off.
Do not wait those 30 seconds with the A/C on if possible, it will make it worse.