No argument there all I'm saying is that in addition to having cooked bearings the blades in the turbo can also warp because of exessive heat. Turbos now maybe watercooled like you said I am just speaking in general. It is still a good rule of thumb that you idle the engine before shutting your engine off on hard drives. You know just to be on the safe side burning extra onces of fuel is a lot cheaper than replacing the whole turbo.

Based on what? What ill effects will occur on a NA motor? A healthy motor should run within a safe temperature range. I was in a bit of a rush when I posted originally in this thread, but I should clarify that by cooling down, I am referring to running a cool down lap where you are not loading up the motor nor the brakes. This should allow the brake temps to drop sufficiently, and if for whatever reason your motor is running hot, it will likely cool down to normal operating temperature by the end of the lap. Either way a rapid shut down of a NA motor after a hot lap will have no ill effects unless the engine is actually overheating(so long as the overheating is from a lack of cooling capacity as opposed to a loss of coolant or cooling system failure). And if a failure is a cause of excess heat, the only way to cool the motor will likely be to turn the motor off.

And you should take a cool down lap to cool the brakes, even if you do not pull the e-brake. The pads remain in slight contact with the rotor and that area of the rotor will not be exposed to ambient air and may cause uneven cooling.

Could you please explain how a turbo timer works? I had never heard of such a thing.

It's just an electronic device that leaves your motor running for a set amount of time after you take the key out of the car. Allows you to be able to cool your turbo without having to sit in the car and wait.

ball bearing turbos do not need to be cooled down.

Doing a cool down lap is good for the car don't get me wrong. A cool down lap is sometimes not enough to cool all the components of an engine after a several hot laps around the track. If you think I'm wrong then so be it then I'm wrong. Remember not all engines that do hot laps on the track are always healthy. Any engine expose to this kinds of conditions will need all the help it can get. It can shorthen an engines life by not doing a little preventive measures. Show me any metal that doesn't fatigue, warp or crack under exessive heat then I just might believe your analogy. Do what you wish shut your engine down after hard driving it's not my engine. After all I don't know what I'm talking about and I base all these theory out of nothing. Goodluck with your engines people.

AFAIK, cool down laps are more to cool the brakes than anything else. Speaking of which, I just cooked my rear brakepads at Mosport today and I'm done for the weekend. I have a spare set of fronts on hand, but never expected to go through a set of rears this fast.

If you are running a motor that is overheating at the track, then you should probably not be running it at the track. There is a difference, as I said before between a motor that has a cooling system malfunction, and simply not enough cooling capacity. In the latter, the cooling system is working fine so once you remove the excess load, you will immediately see the temperature dropping. If you have an outright malfunction of some sort, depending on what the problem is, it may either remain running hot or cool down very slowly. If the problem is severe enough, the temperature will rise even with no load. In a case where the motor can cool down might be beneficial, but the other 2 circumstances will not help one bit. In all three cases of malfunction, you should probably think twice about putting the car on the track in the first place. Chances are you won't get more than a few laps in anyways.

But I'll tell you what, if you think you know what you are talking about and have some theory about it, then by all means, explain it.