Cool Down
03-25-2018, 04:55 PM
#1
Racer
Thread Starter
Cool Down
I have read nothing in the manual about this. I have always preferred to not just shut a car down after a spirited drive. What is recommended? They say that idling is not good for the motor but upon returning home I let it idle for about a minute and a half until the rear hood fan turned off.
03-25-2018, 05:04 PM
#2
Generally people recommend that you let the car idle for a minute of so after a really spirited drive. The VTG turbos run very hot and it supposedly is good for the turbos to let them bleed off a little heat. It is pretty rare for me to drive it like a bat out of hell and then immediately stop and turn it off (I don't track it). By the time I hit a few stop lights and come to a stop at my house or elsewhere it has cooled off sufficiently.
03-25-2018, 05:06 PM
#3
Banned
No cool down necessary. This procedure originated in the 930 days - the turbos back then were only oil cooled. Today they are both oil and water cooled and there is an automatic fan that comes on as much as half an hour after running the car, which you guys all know.
03-25-2018, 05:06 PM
#4
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Any turbo car / truck can benefit from letting it cool and cycle "cooled" oil through it after a hard run. Hence the advent of "Turbo Timers".
Never shut a turbo vehicle off directly after a hard run.
Never shut a turbo vehicle off directly after a hard run.
03-25-2018, 05:26 PM
#5
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Though water cooled turbos are cooled passively by convection after shut down, it’s never a bad idea to drive the last couple of miles easily and allow everything to cool off ahead of time. Idling the car for a minute or two once you stop is just fine too, but driving the car also allows the brakes to cool down as well, which helps with uneven pad transfer to the rotors once you’ve stopped.
03-25-2018, 05:26 PM
#6
I generally take a few minutes to drive the car around at around 25-40 MPH and a maybe 30 seconds before turning it off. In this way the oil is recirculated and cooled down to a point that it can be shut off. That is assuming that the oil/water temperatures are around normal high. If at track or spirited drive and oil/water temperatures are in the 200's then longer cool down drive before shutting off.
The fan on top does nothing to cool the engine down and it is to keep the power steering, alternator cooled down as they will get crazy hot with a hot engine sitting right underneath them. BTW, it doesn't draw air out it pulls it in.
The fan on top does nothing to cool the engine down and it is to keep the power steering, alternator cooled down as they will get crazy hot with a hot engine sitting right underneath them. BTW, it doesn't draw air out it pulls it in.
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03-25-2018, 06:58 PM
#9
Three Wheelin'
One of the issues with my old Audi S6 were tiny cracks in the heads of the AAN turbo's. Even though there was an afterrun pump that would circulate the coolant, the intense heat left in an engine run hard and shut down could lead to those cracks. So, with any turbo I have driven, from my son's 1.8, through the AAN to the 911 TT, I always drive it lightly for a few miles before shutting it down.
While I have never heard of cracked heads in a 997, there is no reason to mistreat machinery.
Ed
While I have never heard of cracked heads in a 997, there is no reason to mistreat machinery.
Ed
03-25-2018, 08:06 PM
#10
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2 mins is a small investment into the longevity of your turbos / engine.
Period!!
Period!!
03-25-2018, 08:29 PM
#11
Three Wheelin'
Not to mention, synthetic oils nowadays have a lot higher flash point than the old dynasaur motor oils.
03-25-2018, 08:51 PM
#12
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As mentioned the bearing housings are water-cooled. However the VNT turbine housings aren't >>I am seeing cracking from the EGT sensor in towards the center of the housing. The bearings housing VNT lever/bushing area is also cracking due to extreme heat and hot shutdowns. The water cooling protects the bearings and turbine wheel, but the turbine side seals are taking a beating.
I'd recommend at least 30 to 45 seconds of cool down idle. At the end of the day, you question what the previous owners did.. A 60 to 130 pull and a quick gas fill up with the engine shut off at the pump LOL
I'd recommend at least 30 to 45 seconds of cool down idle. At the end of the day, you question what the previous owners did.. A 60 to 130 pull and a quick gas fill up with the engine shut off at the pump LOL
03-25-2018, 10:53 PM
#13
When i am about to arrive at home, I start to get the my area, 45 mph, then 25 mph. Thats about 1-2 miles. Thats enough cooling. I wont intentionally let it idle in my garage.
Unless some of you guys use it on track or live besides the free way.
Unless some of you guys use it on track or live besides the free way.
03-26-2018, 01:59 AM
#14
Burning Brakes
Same here. I don't idle but drive very lightly last 1-2 miles before getting home without getting the turbo's to do any boost. Now that i think about it does oil and coolant still circulate through even if the turbos are not boosting? Sorry if its a stupid question as i don't know much about turbos, i just love how they plant you into the seat.
Last edited by 996pp; 03-26-2018 at 03:03 AM.
03-26-2018, 02:36 PM
#15
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