rickdm

I am heading for my first hot weather DE of the year in my 3.2 Carrera. I am running 20W-50 dino oil, and my question is; how hot should I let it get before I pull of the track? In the past at the end of a hot run I am at about 250 (which seems a little high), and even in a little cooler weather I have been around 220. When would you pull off, considering of course that giving up any seat time is not something I look forward to doing.

Thanks,
rickdm

bgiere

250 is pretty hot. I had high oil temps in my Carrera and cup car and found that a slightly lower viscosity oil will reduce temps. 20w50 has a higher coeffecient of friction (think of stirring honey) and has probably sheared to a lower weight. Try Redline 10w40, it will give you better protection than any 20w50 and can handle temps well above 250. Dave at Redline will give you some advice if you call him.He is a great resource. The long term solution is to consider an oil cooler besides the one you have now. There are many kits available which can be fitted. In the Texas heat i would imagine that is what you will need to do if you are doing DE's long term. BTW, make sure your cooling fan is coming on....Should kick in at 250.

APKhaos

WHen you see 250 its time to take it easy or pull into the pits for a cool down. Your engine is oil cooled more than air cooled, and has expanded close to its limit at that temp. [Yes, the 3.2, like all Porsche air/oil cooled engines, expand considerably from cold to limit temps]. Its not so much an oil film issue, it becomes a mechanical tolerance issue.

Next track day, try removing your rhs fog light. Its an easy job [one 17mm nut from under the bumper takes it off] and it gets a LOT more air flowing through the cooler. My 85 had the same problem when really going hard on a hot day. The fog light hole helped, and fairing in the area so that the air had nowhere to go BUT through the cooler fixed it for good.

Here's a pic with the fog light removed:

rickdm

Tony, I will take some tools with me to the track to see if I can get the foglight off. Right now my thought is that I will go until my temps hit about 240 since 250 seems to be the upper limit. I am just going to have to avoid the red mist long enough to look ay my gauges

rickdm

Bull

I have seen charts published of relative engine wear at differing operating temps. The wear increases rapidly above 245+ degrees. There might be something in the PCA website Tech archives on this.

APKhaos

Rick,
All you need is a deep 17mm socket, a 6" [or longer] extension, and a socket wrench. Need to check this, but I think the connections break outside the fog light housing. Its been a while, so I don't trust my memory on that point.

RedlineMan

Indeed;

Anything North of 240 is where you start to see HP losses. This has been demonstrated in dyno testing. 220 is a good limit if you can get there. I would also suggest a thinner oil. I prefer synthetic. The factory uses 0w after all.

When things get extreme, it is about volume, not pressure. Volume = cooling for the bearings.

The 911 is not an easy chassis to install a truly efficient cooling system on without removing some sheetmetal, but any gains you can get are worthwhile.