A question for the SC'd community. I plan on getting boosted soon. Just curious, is it good practice to "cool down" your engine before shutting her off? I believe this would be true for turbo charged cars.

BTW, I'm counting the days till I'm boosted. Can't wait.

 

In general, the cool down period for turbos is to 1) let the turbo spin down to idling speeds prior to no oil pressure and 2) allow additional cooling to occur in the bearings so oil coking doesn't occur. Supechargers don't spin at anything near turbo RPMs and are directly related to engine speed. No real need for a cool down.

Of course, putting the horse away wet is a recipe for problems. If you just came in from a prolonged hig-speed run (track, etc.), a little bit of ensuring that things have normalized in the cooling department is always a Good Thing. Eliminating temperature spikes from little to no coolant circulation is a good idea.

 

I usually just drive normal after a hard run for a few min although not as critical like jguerdat said.

 

This is an old wives tale. The reason it's now an old wives tale is because it used to be true some years ago. Turbo's were only oil cooled, so if you ran it hard, then shut it right down, the oil left in the turbo would coke, eventually killing it.

These days, however, turbos are oil and water cooled. So even after you shut the car down, coolant is constantly forced through the turbo to cool it down. No more exploding turbos after 30k miles.

That being said, I think it's always a good idea to let a car "wind down" a bit after a hard run. Whether you choose to just drive it easy for a few miles or let it idle in the driveway is up to you, but either should do the trick and let operating temps come down a bit.

 

Thanks for everyone's responses.

 

[QUOTE]Originally posted by heffergm

 

You hit the nail on the head. There is no MECHANICALLY forced cooling... it's done by convection, which in my mind is still "forced", it's just not mechnical (at least in Subby's):

[QUOTE]Thank you for visiting Subaru.com and congratulations on the purchase of your 2002 WRX! We hope that you are enjoying your new Subaru!

Our position regarding turbo cool down is that it is not necessary to perform a 'cool down/idling' procedure, as was recommended with past turbo models. Our current turbo engine has far greater cooling capacity and coupled with technological advances, makes this practice no longer necessary. This explains why information about a cool down is not included in the Owner's Manual.

 

This says to me that the turbo system has to be designed from the start to have a forced cooling system. I don't know one way or the other, but if your particular system doesn't have the coolant reservoir set up in the same manner as the Subaru's, sounds like cooking is still going to be an issue.

 

[QUOTE]Originally posted by MacGyver
This says to me that the turbo system has to be designed from the start to have a forced cooling system.

 

Possibly, but I seriously doubt any aftermarket system will include such a system. Therefore, some form of timer or other cooling system would be required in this guy's case.