I live on a pretty serious ridge line and getting home works the engine pretty good. I'm usually in 1st gear for a good portion of the end climb before my house. Sometimes after I park the fans kick on.

I usually open the engine lid to let the heat dissipate but should I just be letting the fans go to work? It seems like letting the heat swell with no ventilation isn't ideal long term.

 

I personally prefer to open the engine compartment. Heat dissipates faster than with the engine blower (in my opinion) + it doesn't use the battery's power. I honestly don't think that a 100$ plastic blower using 4 thin air stripes as fresh air source (throught the rear spoiler) can do a better job that a whole opened hood dissipating heat from bottom to top... Just my 2 cents! But I'm curious to see what people on Rennlist have to say on this subject! I'm here to learn!

 

Leave the engine cover closed and let the fans do their job. They are acting as a heat exchange, whereas if you just open the lid open you are only using the surrounding atmosphere for the heat exchange. Your engine is not really getting that hot driving up and down hills in SF. Also, the water cooled motors don't really suffer from the same heat related problems as the old air-cooled (oil only) engines. In a turbo-charged car, there is a pump that circulates water through the turbo after shutdown that does the same thing as your engine fans.

I do request that you don't crash the front end of your car on severe dips in town there. I see folks doing that with 911s every time I am out there on a business trip.

 

I leave the rear lid closed so the fan can kick in if necessary to cool the engine... also run a floor fan at the rear of the car on high when I park her. Hook up the trickle charger to insure that the battery is charged fully even if the rear deck fan turns on.

 

Ha! I'm actually in the east bay, not in sf.

 

^^^ Fair enough. I still don't know why I came to DC instead of SV. That was a dumb move. DC is a dump compared to Palo Alto.

I honestly wouldn't stress out about the engine temps too much. My dad and I have done a ton of events in his 89 turbo during 90+ F days at Sebring and still remember having to dial it back a bit because the oil temperatures were getting pretty high. Your water-cooled motor is more than fine with city driving.

 

Something I learned years ago is to let the engine idle for a couple of minutes after a hard run before shutting it down. It lets the oil and coolant circulate with the fans on and cools the engine down to normal temperatures.

 

I would generally agree but the fan doesn't exhaust, it blows air in and in an enclosed garage it's just more hot air being circulated. I typically open the lid and lock the car so the engine compartment light goes out.

 

Isn't the 991 engine compartment more closed up to retain the heat for emission controls, efficiency, fewer 'cold' engine starts?

 

I say leave it closed and let the fans do the work - I agree that it's important to keep the area around the car cool (keep the garage door open or run a floor fan if it's really hot).

This reminds me of personal computers. In the old days, some people ran their computers with the cover off in order to cool the processor better - and the processors over-heated. In turns out the cases are designed to maximize air flow with the fans - taking the cover off breaks the design. I'm not sure if the same logic applies to the 911, however, my bet is that the Porsche engineers thought this through and have an efficient design.

 

I leave the lid closed and let the fan do its work. Pulling air through a sealed compartment forces cooling air to move past locations that might not be cooled as effectively if only simple convection is at work and the sources of air aren't controlled. It's not like Porsche hasn't thought of how to cool these engines.

And +1 on letting the engine idle for a short period after a hard run. A little bit of gas is cheap peace of mind for cooling internal parts, but I only do this when the oil temp is a tick above the reading I get for a normal drive. I don't go by the water temp as I know Porsche decided not to give us a true value on that gauge.

 

After seeing the fan run with the lid open, I now leave it closed.

 

+1 I like to do a cool down lap around the neighborhood to get the oil temp down to 225F or lower.

 

I've read somewhere that in the .2 version, the spoiler will raise and the fans will run when very hot. Not seen it happen on mine yet.

 

Porsche has probably thought of this and would direct you to open the engine lid if it were an issue. But they, just like every other car manufacturer, have determined that its ok to leave the hood closed after a drive.