Greg Lab

When I bring my 993 into garage, and shutdown, I often open the rear deck lid to assist the engine in cool down. Is this OK to do? Or is that perhaps hurting something with the fan ducting. I saw many drivers doing this at the track, and I started doing it with my 930 Turbo track car. On really hot days in summer, I will place a fan on behind the 993 as well. Just don't want it to cook in hot garage in Houston TX... So do you think this is a good practice, or overkill?

CalvinC4S

Overkill, no need and fruitless

BobbyT

Porsche engineers have this covered:

The engine has a system that activates the engine bay blower to dump hot air if the engine temperature is high. This system is active for 20 minutes after the ignition is turned off if the detected air temperature in the blower outlet pipe on the left side of the engine is above 104F. If the air temperature in the duct rises above 167F, the blower is activated at low speed until the temperature drops below 158F.

If this system is working correctly, a few minutes after you park the car, if the engine is hot enough, you will hear a click followed by the whoosh of the fan.

Mine comes on if the oil temperature is around 225F or above when I park the car.

993_Pilot

probably overkill for normal operations, but I see lots of people do this to help speed up the cooling, between runs at the Auto-X. I have even done it myself at the AX, but never timed it to see if it made any real difference.

NP993

I just don't understand the logic of this at all. Let's say the engine is at 200 degrees F during operation. You pull into your garage and shut it off. From that moment onwards, the engine is not going to get hotter -- it's going to cool off. Opening the decklid might possibly encourage the engine to cool down ever so slightly faster, but if it does, it's a minuscule difference from not lifting the lid. Regardless, what does the speed by which the engine cools off after use affect anything?

Plus, heat doesn't wear an engine out -- RPM's do. That is, your engine does not wear because it is warm, it wears because it is in operation. It's bad if it's too hot or cold while in operation, but heat itself does not wear out an engine.

Also, the reason you lift the lid on the track is because you have another run to do soon, and you want the engine to cool down as much as possible before then. Still, it probably makes virtually zero difference. There's a big old grille on top of the decklid that provides plenty of space for the hot air to escape...

race911

Well, heat sink happens. And heat does wear an engine out. Much rather run one of these things on the 'Bahn at 6K in 6th (if possible) @ 220F oil temp, than running-around-town 3-4K @ 250+ that many of the no external oil cooler 2.7L cars saw in their day.

Even so, lifting the lid is more of the "it's cool, I'm one of the guys who knows what I'm doing" activities at the track.

NC TRACKRAT

If you forget to close the rear deck lid, the engine compartment light will run down the battery.

Kein_Ersatz

At the track for DE's it would seem to let the radiating heat out quicker (anecdotally), I usually let it idle for 5-minutes with the deck up before shutting off the engine after a DE run. YMMV

Since it is up, I may just leave it up until I head out for the next session. Plus it never hurts to look at the engine bay a lot to admire the craftsmanship and make sure noting is a miss.

And it pays homage to the air cooled lineage.

tracke30m3

I leave my deck lid open for a few hours after I get home based on the premise that having the heat escape faster may be good for the rubber and plastic bits (hoses, vacuum lines, connectors, wires) inside the engine compartment.

May also extend the life of the deck lid shocks and engine bay insulation?

Whether this works or not I don't really know but it sure doesn't do any harm.

Allen

I raise my lid after a ride too. Maybe it makes no difference to the car...but I like doing it...so it makes a difference to me. Kinda like washing it when it's clean...I do that too. Oh...and I also removed my engine undertray...

Linnm

If you are concerned about engine heat I suggest that you jettison the pan that is under the engine.

Greg Lab

Oh that's a great idea about removing the pan under engine. What's it there for anyway? Any tricks to removing it?

Ocean Blue C2S

CalvinC4S,

It's good to see you're back on line! Missed you now for a while... missed the Cave Creek analysis... now you will have the Escape 3011 nearby! That should keep your group in Arizona busy...

Air-cooled Greetings from Canada... the bad sledding is almost over!

Bert

Stealth 993

I leave my spoiler up, but that is more so the airbox doesn't get heat soak.
You can turn the car on, but don't start it, this will kick on the electric fan, & cool the engine way better then leaving the deck lid open.

TheOtherEric

Well, yes and no. Temps in/on the engine vary greatly. The entire intake stays very near ambient no matter how hard you're driving on the track. But the heat exchangers (headers) get crazy hot. When you shut down, that heat moves up into the engine, then into the intake, etc.

While I agree with Noah & others that raising the hood is useless, I actually do leave my ignition "on" after track sessions so that the aux blower runs for 15-20 minutes. At least it cools off the headers, which gets that heat away from the engine. I've found that it does cool down the engine bay, but if you forget and leave it running, it'll kill your battery!