How long should I wait for the cooldown when I idle before shut off?
Turbo Cooldown
- Thread starter jerseyguy123
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if your at idle, you can shut it off.
On a modern vehicle, about 0 seconds.
- they will be designed for either passive cooling techniques or run a small pump
- the last few minutes into a residential area are usually pretty tame
- with as many turbos as there are out there now, there would be widespread knowledge if this was a problem.
the cooldown problem stems back from the 80s when turbos were new and add-ons didn’t have the engineering we have today. Or maybe (I have no firsthand experience here) if you are bringing the car in off a hot lap at a track.
OR (I do have experience here), if towing heavy and they are barely glowing soft red, 30 seconds off the interstate. In that case I’ll let it idle a few minutes.
I can’t see what vehicle you’re asking about.
If you aren’t towing heavy then probably idle and shutdown. I have an EGT gauge on my Ram and I let it cool down under the 400F range prior to shutting it down. If I have the time I will let it go down closer to 300F.
Honestly letting it idle so it doesn’t run dry is probably just as big of a deal.
Just my $0.02
Unless the engine was seeing a lot of boost in the previous few minutes, I wouldn't wait at all. On most modern turbos, coolant continues to circulate through the turbo by convection, even after the engine is off, which helps prevent oil coking. I'd still give it a bit of idle time after coming off a racetrack or something.
This depends on the circumstances prior to shutdown too. After track use, a spirited drive or as you approach home from a commute?
Do you have a water cooled turbo?
Do you have a water cooled turbo?
Early 80s and 90s vehicles tended to use bushings instead of bearings for the turbo. Add that alot were air cooled not water cooled hence why many people put turbo timers on their vehicles. If the vehicle was turned off without cooling down you could get coking on the bushings.
If you drive normal, just turn it off.
If you have a hot hatch or "sports car" with a turbo and you were in high boost a lot before shut down. Example: I take the back roads to work, so I am on high boost every morning hitting the corners. I get the 1/16th mile cool down where I have to drive the speed limit in the industrial park. I do 2 large circles in the parking lot at 2,000ish rpm and idle the car for about 20-30 seconds above 1,500 rpm as the oil pressure hardly flows any oil at idle to give the cooling water and oil enough flow to pull heat away. Some cars (not mine) have a circulation pump that runs after shut down. My example is a worst case street scenario.
If you have a hot hatch or "sports car" with a turbo and you were in high boost a lot before shut down. Example: I take the back roads to work, so I am on high boost every morning hitting the corners. I get the 1/16th mile cool down where I have to drive the speed limit in the industrial park. I do 2 large circles in the parking lot at 2,000ish rpm and idle the car for about 20-30 seconds above 1,500 rpm as the oil pressure hardly flows any oil at idle to give the cooling water and oil enough flow to pull heat away. Some cars (not mine) have a circulation pump that runs after shut down. My example is a worst case street scenario.
Doesn't matter. This issue is taken care of in modern turbo motors.
If it has water coolant lines it doesn't need any cool down period. When the engine shuts off the convective flow will reverse normal water flow direction hot coolant (heated by turbo) rising up to the head and cooler coolant drawn up though the turbo.
It's a modern car with a water cooled turbo. You don't even have to think about it.
I thought newer turbos run coolant through them on some sort of thermostatic switch so the turbo can properly cool.
they usually either do it by convection or with an electric pump.
For diesels I would avoid turning it off during an uphill trailer pull.
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Gas engine egtd don't really cool down. Hooefully it has coolant surrounding the bearing.
No, not always. There is a guy who rebuilds Mini Cooper turbos and he said he gets a high # of them with coked turbo shafts, some really bad ones. They are water cooled and I can assume the extreme Mini's, the owner's know how to babysit their turbos. Yet he still gets coked turbos in on a regular basis he said. He is an advocate of cooling down "pushed" turbos.
if there is some concern about coking, I would add that oil selection plays a part here. This was an issue with prior turbos, such as the bushing-type Volvos back in the … (?) 80s or 90s? I have only run synthetic in the 3 turbo’d cars under my care.
Agree with the comments regarding late models not being as critical of cool down times. I still have my 87 Buick GN that I bought new in 87 and that is one turbo vehicle I do let idle a minute or 2 after driving....no water cooling in that design and oil sits and cooks when shut off.
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