Hi All,

Anytime you can SLOW the temperature change of metal - the longer it lasts. Flexing metal via repeated bends or repeated cooling and heating cycles causes fatigue - so - I don't get it - why would you want to more rapidly cool the engine - what is the purpose??? I am not saying you are "wrong" I just don't understand why you would do that....

I don't, on my 3.2
I don't want to introduce thermal shock.
At 95 degrees, after a 50 miles drive home, its not all that hot in there anyways. Most of the heat is underneath the car.

Trying to rapdily cool the motor is worse than slow cooling.

Not an engineer, but I know this as fact from being around jet engines.

Ideally, the motor will have it's longest life if it never cooled from it's operating temps. That would produce the longerst material life from I've been told.

Those more cautious could mount a low-profile fan under the grill and controlled by a temp.-sensitive relay (ala Japanese radiator fans). Orient the fan so it helps increase the normal flow of heat up and out of the engine compartment.

The more ambitious might use a reversible fan to help the cooling system in low-speed, stop-and-go driving.

Sherwood

I only pop the deck-lid to cool down the engine if I'm going to work on it. Or if I am working in the garage and need some heat :)

If everything is nearly too hot, (inter coolers, seals, turbos, etc.) and the oil is no longer moving, just sitting in the hottest areas...then wouldn't an open deck lid be a good thing? Not really to cool the engine metal faster, just to allow the heat out.

The water cooled 911s have a fan that blows air on the engine (downward I believe) after shutdown. While it will cool down differently than an air cooled engine, Porsche must have had a reason for drawing in relatively cool outside air and blowing it on a hot engine.

The fans in the newer water cooled cars (Porsche and non-Porsche) do not blow on the engine - they blow through the radiator. In the end, the air contacting the engine is hot after ambient air is blown through the radiator. The purpose of fans continuing to blow after engine shutdown is to cool the hot water that is now sitting without movement in the radiator, thus reducing thermal wear on the cooling system - it has nothing whatsoever to do with cooling the engine itself.

The water cooled models have a small fan attached to the deck lid to draw in air and blow on the engine as well as the radiator fans.

when driving my 356 to california during the summer months over the mountains during the day, i will open the rear decklid and in addition try to follow/stay next to a tractor trailer in its shadow - don't laugh it actually works and keeps my small hot engine just below the red on the temp guage.

Never, but mine is a daily driver, no track for me. yet.....

I've had a 996 and know what you mean.

It was probably for heat soak reduction more than anything else after shut down.

Every time. But mostly to make sure nothing is on fire.

;)

Tippy,

That would be my guess as well. Some here pop the engine lid after shutdown to reduce heat soak - Porsche installs a fan on the newer models to accomplish the same thing.

Those with fuel injection, not likely to make a difference. Those with carbs can benefit from keeping the topside of the engine relatively cool because heat soaking the carbs can boil the fuel in them.

Almost always after each track session : have a little look everywhere on the engine ... and refresh the compartment ...

And when we arrive at home...

It's always a pleasure to have a look there :-)

I only really do it at Track or DE events without the e-Brake pulled up to keep the rear brake rotors from warping/deforming or after a extreme hot day of driving L.A. traffic then in the garage lid open.

Plus I like to give the lid struts a break from being compressed all the time.

Sometimes I wonder about the cooking time for salmon in aluminum foil under the hood or seared next to a heat exchanger.

Sherwood

I've heard people suggest when stopping for pits stops that opening up the engine lid after a long drive on a hot day keeps the A/C condenser from building up heat. So when you drive off from a stop your A/C comes up to temp faster.

In the dead of Southern summer, after a long drive with sweltering heat and humidity about, I'll whip in the driveway,...power down,...then open the rear deck.....head inside, to probably get something to drink,.."whatever",.....then head back out to kneel at the rear and LOOK around,..probably touching a few things here and there,...checking to make sure all looks well.

I would presume this would help with the cooldown rate,..but am not quite sure that I've induced a thermal shock.....

I think about (too) the things Sherwood is mentioning....!!!!!!!

Best!

Doyle