Engine cool-down

[adias]

There is a thread on another forum re cool-down of water-cooled flat-sixes. What is the consensus about shutting down an air-cooled engine after a spirited drive especially on a hot day?

I tend to drive slower the last few miles and let the engine idle for a couple of minutes at the parking spot.

[Quicksilver]

I drive generally drive it to the house and then park it.

Unless your engine is over temp to begin with your only issue is the oil. If you are using a good quality oil there shouldn't be an issue.

(Now if you have a Turbo, that is a different story. Getting the heat out of the turbocharger should be in the back of your mind. You'd want to run the engine out of the boost long enough to cool it down. A common item is a "turbo timer" which idles the motor for a set time or you could look at a turbo after oiler that keeps the oil flowing for a while to help cool it down.)

[mo-mon]

If I let it idle for a minute or two before shutting it down, I noticed that my engine doesn't "puff" a bit of smoke when I start it (3 days to a week) after.

[safe]

Originally Posted by adias

There is a thread on another forum re cool-down of water-cooled flat-sixes. What is the consensus about shutting down an air-cooled engine after a spirited drive especially on a hot day?

I tend to drive slower the last few miles and let the engine idle for a couple of minutes at the parking spot.

I guess you don't drive it 10/10ths all the way to your house/garage so just shut it of!

I usually get half a lap cool down on a track day, after that I shut it off. In my experience a spirited drive is pedestrian compared to 20 minutes of track time.

[T77911S]

turbos are more critical of this than NA cars. synthetic oil (for the turbo) is a big plus along with clean oil. (my opinion) all that helps to prevent coaking in the turbo. as far as clean oil i think the coaking is the dirt in the oil hardening in the turbo.

i tried idling my 77s to see if it made a difference and i could not tell as far as smoke on start up.
if you are running it hard and oil temps are up I would drive it slow to cool it down some before shutting it down.
the problem with idling is it really does not cool as good as if you just drive it slow.

i usually drive my 930 slow for several miles when i know i will be shutting it down for the day.
now my brother use to idle his for a good 10-15 minutes.
i will give him credit, he always had an oil analysis and it always came back good. he now has 140k on his car and it still runs very well.
mine? i had coaking in the turbo at 50k due to PO. (i assume hot shutdowns and dyno oil).

[Tippy]

My understanding of metal, is you want the slowest cool down possible. So, like you said, doing a few minutes of slow driving to bring a hot motor down to normal operating temps before shutting down would be better than just shutting a hot motor down immediately.

[GH85Carrera]

At the track after a 20 minute session, they give you one lap to cool down. Mostly for the brakes. At Laguna Secca in Monterey in the dead of summer is it 72 degrees. It is easy to cool down the brakes and engine. At Robeling Road near Savanna, GA it is 100+ degrees and 90% humidity. The last thing you want to do is sit in the car driving slow. I have done both tracks in my 85 Carrera, and both are great but the weather at Laguna Secca is lots more comfortable.

At both tracks and the many autocrosses I have run I just shut it down after a driving to a good safe parking spot. As mentioned above, it is a different story if you have a turbo.

Driving home on public roads it is almost impossible to be much of a hoon if you like not getting tickets. I guess it depends on where you live. I live in a neighborhood so they last mile to the house is normal traffic and easy driving.

[T77911S]

oh, one other thing I do, I will pop the hood on the 930 when it is really hot out, BUT,i don't drive it that much in the summer.
I also have a big fan in the garage and I have popped the hood and turned the fan on when I have not been able to do a drive cool down.

I got to drive it today. going home at lunch and not hot yet.

[gtc]

Mine needs some speed and engine revs to cool down, so idling in the driveway for a few minutes before shutdown would just get the engine hotter.

[wildthing]

Define hot.

Because of the traffic here in the afternoons, my needle is very close but still below the 250 deg line (top most white line) as I get home. I do nothing special. I just shut it down. The garage does get warm though and reaks of that old Porsche/VW Beetle engine smell.

[adias]

Originally Posted by wildthing

Define hot.

Because of the traffic here in the afternoons, my needle is very close but still below the 250 deg line (top most white line) as I get home. I do nothing special. I just shut it down. The garage does get warm though and reaks of that old Porsche/VW Beetle engine smell.

Right... 230 to 250F. Re the garage car smell... like that too.

[HaroldMHedge]

My 87 manual has the following bold text in it concerning stopping the engine.

"Do not stop engine immediately after hard or extended driving. Keep engine running at increased idle for about two minutes to prevent excessive heat build-up before turning off engine."

Harold
87 Carrera Coupe

[juanbenae]

Originally Posted by wildthing

Define hot.

The garage does get warm though and reaks of that old Porsche/VW Beetle engine smell.

love that smell! that's why I sold the turbo and got another air cooled car after a mere 10 months. when I have those that might appreciate it over I also have them soak up a wiff of the interior that is the same identifiable VW Porsche Mercedes vintage aroma. more that three have shown me goose bumps after a hit of my original non sunroof headliner air freshener...

I don't drive on the track any more so my cool down lap has become the journey through my neighborhood home. respect the hood & everything is cool.

wouldn't a water cooled car run fans on the radiators until even the garage has cooled downed?

[86 911 Targa]

I just park the car in the garage,
and open the rear deck lid for a while.

Gerry

[wildthing]

This was the temp as I exited the freeway, so I suppose my cool down run is my last mile which is at 40mph and 30mph.

[T77911S]

Originally Posted by wildthing

Define hot.

Because of the traffic here in the afternoons, my needle is very close but still below the 250 deg line (top most white line) as I get home. I do nothing special. I just shut it down. The garage does get warm though and reaks of that old Porsche/VW Beetle engine smell.

i would at least lift the deck lid to let the heat out. just my opinion.


its funny, when my brother would let his 930 idle in my yard, it would kill the grass where the turbo was. there would be about a 2ft circle of dead grass the next day

[carreradpt]

I always back into the garage, open the rear deck, turn on my garage fan (mounted 7' high aimed directly at the motor), check the oil, shut the motor down and close the door, leaving it open about a foot. I know pretty anal, but... I do this to always remember to check the oil primarily, but also to let the heat escape the garage quicker. And I still get to enjoy that great aircooled oil/exhaust garage smell.

[GH85Carrera]

Originally Posted by carreradpt

I always back into the garage, open the rear deck, turn on my garage fan (mounted 7' high aimed directly at the motor), check the oil, shut the motor down and close the door, leaving it open about a foot. I know pretty anal, but... I do this to always remember to check the oil primarily, but also to let the heat escape the garage quicker. And I still get to enjoy that great aircooled oil/exhaust garage smell.

I used to check the oil after virtually every drive. Now after a couple of decades of owing the car I know the oil gauge really gives a valid range. If it is pointing above 9:00 I don't bother checking the dipstick.