sundog

Having just finished my rebuild of my 964 motor, I can attest to the oil cooling aspect of these motors. There are piston squirters that continuously spray oil on the bottom of each piston. Also, a huge amount of oil is delivered to the cam towers, and carries heat away from the top of the heads. It's an amazing piece of engineering.

Dan V

Here's an example of an "Oil Cooled" 911 which raced flat out for over 4 hours with the front oil radiator effectively non-functional. It completed the 25 hour race...

...They radioed Rich, who
had called in the problems, to try shifting at 5,000 rpm
instead of 6,300 and see if that helped. The oil temperature did not come down.
It normally ran at about 215F and was now running at 250F. Plenty hot enough for an engine failure. Examination after the race revealed that the
main oil line running back from the front radiator had been crushed flat.
With backing off not helping while costing precious
seconds per lap, the crew decided to go for it.
Shift points went back up, the oil temperature held steady, and the
team's lead increased to 5 laps with four hours to go. In
the early morning hours, Robinson ticked off the
team's fastest lap time. With two hours to go, the car
came in for the final pit stop, dropping the lead over the
second place car to 3-1/2 laps.
But the team figured that second place car would also have
to make one more pit stop. If their car held, that ought to
be enough. Minutes ticked by with agonizing sloth as Smith drove
the final stint. Would the car hold? (It did and won).

The Nugget March 2006

SimonExtreme

Excellent story! I am sorry that my "red herting" comment has sparked off such a debate. I have no real issue with "air cooled" and air certainly does pay a significant part. I was just trying to say that we mustn't forget the role oil plays.

However, I guess that as air also cools the oil (and water in the later cars!) air can be considered rather important.

It still doesn't get away from the fact that the standard 996 engine has real issues that do need to be considered. In the UK, I know of enough problems on cars that haven't seen the track to think it isn't just trackday driving that is the problem. And if spirited driving on the road is a problem, then I would suggest the engine isn't fit for purpose. Or maybe Porsche should put out an official warning "You may think you own a sports car, but please don't use it like one"

wprater

Sad to hear there is such an issue with the 996 motor. Glad I just got my "new to me" 997 and I love it! Heading to PRI (Seattle) in August.

cobalt

Pistons and cylinders are cooled by air vs a water jackets used on the 996 therefore air cooled. The dry sump and oil cooler play the part of keeping oil temperatures down. Try running a 911 engine that had the unfortunate problem of having a mouse nest built inside the cowling or lost its fan belt (yes the battery will fail before you blow up your engine). No air flows over the cylinders and the engine will fail eventually no matter if the oil was circulating properly or not. Remove the air diverter/baffles from the engine and you will create dangerous hot spots. The 914 and VW engines are similar and are strictly air cooled with a wet sump and no oil cooler. These rely 100% on the baffles and fan to cool the engine and oil. The 911 engines produce more hp, higher revs and compression, higher temps. The oil needs to be maintained at a constant temp to prevent it from thermal break down and that is where the dry sump and oil cooler come into play. So both keep the engine running cool. The air being the primary cooling and the oil is kept cool to work properly and lubricate.

Superunknown

I heard very recently that 996 engines are notoriously unpredictable. That you could replace the head gasket only for the engine to blow 10k miles later. Where as with the 964 you get an engine rebuild at 100k miles for £3.5k and its good for another 100k miles. Reliability kind of put me off going for a 996, especially as Porsche dont put warranties on cars over 10 years old or 100k miles...

DrJupeman

Well said! They are definitely air cooled cars.

How many quarts of oil go in the dry sump GT3?

Anyone catch the Lime Rock Le Mans race where the Flying Lizard car ran the last 20-30 minutes with no water. Thank goodness for the air cooled origin of the engine, eh!

blake

I think it is 8.5 quarts, give or take .5. That FLying Lizards story is truly amazing...

-B

springer3

The early 911s had oil coolers bolted to the engine about where the power steering pump goes on the 3.6. I recall air-cooled VWs also had a small oil cooler atop the engine.

Oil does remove heat from the bearings, but that is a minor heat source. The biggest heat source is the combustion chamber. The cylinder heads are the hottest non-exhaust part of any engine. The oil cooler is small. Compare the size of the engine-cooling fan to the oil cooler fan. My guess is less than 10% of the engine cooling is from circulating oil. The oil cooler keeps oil temperature cool for long oil life, but as the race story shows, the engine needs the oil cooler only to keep the oil at a healthy temperature.

The 964 engine is air-cooled.

jimq

same on the 996TT