Hey guys, I was talking to my friend (has a WRX) and a mechanic told him to leave the car running for a couple minutes after a hard drive, rather than just shutting it off to let the oil circle through the turbo and cool it down. I was wondering if this should just be for turbocharged cars?

If we dive hard for about 15 to 20 minutes (basically not letting RPMS below 3k), should we let the engine run in idle when we arrive where we are going or is it safe to just shut it down?

Thanks,
-Mike

 

not a big issue with NA cars, but i usually start to keep the rpms low once i am near my house, then i let it idle for about 30 seconds and shut it off

 

This really only applies to turbocharged cars. Especially non-watercooled turbos. Turbo bearing sections build up a lot of heat under boost. The bearing inside will see enough oil flow to keep the bearings cool enough, but if you shut down too soon, the heat from the housing will quickly transfer into the bearing and cook the oil onto the bearing. Water-cooled turbos generally remain cool enough overall not to have to worry about this. And even then, they cool down quickly even after a hard drive. There is very little reason to even use a turbo timer with water-cooled turbos. About the only reason to cool-off a normally aspirated car is to cool down the brakes after hotlapping at a track. You can shut the engine down without any cool-off...

 

Yup only for turbo cars its why the turbo timer was invented. So you can leave your car on and leave without having to sit there waiting. My friends RX-7 has one and the first time I watched him leave the car sitting at idle I was shocked. Later I learned about turbo timers. haha

 

yeah no need for a cool down..

 

This is a BIG ISSUE with turbos. I had to rewire my Radiator Fans to stay on after my car turned off on my last Supra...Turbos suck, too much going on with them.

 

couldn't have said it better.

 

I'm sorry I have to disagree with this part of your analogy. I fail to see why leaving your engine on after some hot laps will cool your brakes. The rule when tracking your car is that don't set your ebrakes to prevent wrapping of the rotors. If you track your car shutting down without cooling off the engine is not necessarily good. You have to let the engine idle for a few minutes before shutting down or your engine is not going to last for a long time. Remember the biggest enemy of any engine is heat. When tracking your car leave it running for a few minutes and open your hood to desipate heat. Mind you this is only done when you're tracking your car or some spirited driving. Turbo needs to cool down because it can warp the blades on the turbo. These things are so sensitive that if you treat it the wrong way turbo failure is imminent even only after a few months.

 

If you actually read what he wrote he's saying the only thing you really need to cool off on a NA car is the brakes.

 

I belive what he is saying is that you don't come to a complete stop while your brakes are cooling down (hense leaving the car on)

 

You can come to a complete stop after tracking your car just don't set the ebrake.

 

Which is incorrect you still need to cool down an NA engine after hot laps. This is common practice when tracking your car it does NOT ONLY APPLY to turbo engines.

 

I agree with RacerB355 and let the engine cool slightly b4 shutting down. IMHO it benefits a non FI engine too somewhat.
C.

 

A friend of mine bought the first run of the Dodge Cummings Turbo Diesel in his truck. We were hoofin' it to Goliad at about 90 to 95mph down Alt US77. We had been running this way for about 30 min. He called me on the phone (I was behind him) and said "let's stop for some lunch at La Bahia" (right on the highway). He pulls off the road and just shuts it off. That turbo must have been Cherry Red when he killed it. The oil in the bearings coked up and stopped the turbo. He got it fixed under warantee, but, he never made that mistake again!

 

^^^^ ^^^^

I'm sorry but I am going to have to disagree with you!! You are so wrong. The only reason you let a turbo cool down is so the oil gets back down to normal operating temps. Period! Like posted earlier most new turbos are water and oil cooled from the factory to prevent the oil from coking up after a hard drive. Even so I always put a turbo timer on all my FI cars becuase they are such cheap insurance!( $99 for a TT )