chuckbdc

When you get your 991 you can amuse yourself watching the water temp rise, the oil temp rise to match and then exceed it by 10-20 degrees, and then pushing the sport button and seeing the oil temp come down fairly fast to 10-20degrees cooler than the water.

PS - I asked the tech where to oil cooler was and he said there was a combined water and oil cooer system on the top of the engine. In my ol 911SC I had an oil radiator (installed at the factory in place of the loop that was standard but that is another story). I never could get the water temperature guage working on my 911 SC.

GSIRM3

In addition to all the computer gizzmo stuff at work, you have to consider the heat transfer effectiveness of water vs oil. I believe water is better at heat transfer than oil, so based on that alone, you would expect the water to heat up faster than the oil. You also have to consider the mass of the water vs the oil, and the mass flow rates of the two through the engine during warmup.

I am not a fluids expert, but I did stay at a Holiday Inn Express last night.

chuckbdc

Better get your fluids checked asap.

GSIRM3

I value your advice and will get fluids checked asap.

Quadcammer

this is not unusual

draxa

I have read this thread with great interest.

One issue still niggles with me; early on in my Rennlist days - I'm guessing 2005/6 or thereabouts - a member with a great deal of knowledge in such matters wrote a terrific treatise on the function(s) of the oil in our engines. I read it avidly and what I most recall taking from it was his statement that the main function of the engine-oil is cooling, not lubrication.

This was certainly news to me then; however, reading this thread there appears to be learned opinion inferring that that may not actually be the case. Or am I mistaken?

Thank you anyway, gentlemen, for the time taken to enlighten the dorks here!



ps: there once was a man called OCBen.....sounds like the start to a limerick, I know, but really, times like this Ben would've swooped in having found exactly that earlier thread.

chuckbdc

I don't think anyone here was making the case that the "main function" was cooling. Oil lubricates best at the specific optimal temps for which it is formulated, so keeping it there is the goal of oil regulatory systems. Ditto for other engine systems. And many work together, hence the software to convert that knowledge into mechanical effects.

draxa

OK. I think perhaps I was led astray by the first two sentences in this paragraph of Chuck's:

"Not so much the oil though. Because, while coolant is channelled to dissipate heat, oil is only pumped where its needed for lubrication- and as its needed for lubrication all the time, its pumped all the time. Coolant, meanwhile, is controlled by temperature. Very little flows below a certain point, while maximum flow is only attained under conditions of high ambient temp and full engine load. There is in other words a great deal of coolant overhead capacity. The distinction here perfectly explains the varying temps, with no computer and just one rheostat."

In fact he only deals with a specific function of the oil - lubrication - whilst not necessarily excluding any other functions.

WCE

Yes, and notorious for eventually leaking (after the warranty period of course) and requiring an engine drop to repair. Let's hope Porsche fixed this!

simsgw

It is not the case. Cooling is a function of oil, especially in the air-cooled Porsche engines, but the primary purpose is always lubrication. Just as the primary purpose of measuring the oil temperature is to infer the temperature of the most hard-working components. It is cheaper to do so, and the temps reported are closer to everyday values that drivers understand, than if we measured and reported the cylinder head temp, let alone the exhaust valve temps. Measuring the stress on the bearings of an operating engine requires a completely different class of sensor of great cost.

All those possibilities meld into an idiot light in family sedans and because most of us put our cars through a wider range of situations, sports cars report the temperature of oil and water-based coolant as well as oil pressure and other tidbits.

Gary

chuckbdc

And lets face it, enthusiasts enjoy seeing the colorful computer graphic display that is redundant with analog guages to the far left and right of the comprehensively instrumented dash (the hard to see ones just behind where I set the steering wheel).

I imagine that next year the configurator will offer a moderate cost option to store the data for analysis on personal computers, to pour over after a drive. A somewhat higher cost option on the GT3 will be real time transmission (along with tire pressure) back to the to the pit to get one ready for the session after lunch. Proof that racing technology improves the breed will be evident when Porsche gets back into F1 and a hunderd other things are clocked, cell phones have terabit memories, and apps are available to analyze and display the data.

At some point, it may be possible to get a red warning light, as a reasonable cost option.

Slow afternoon here.

simsgw

I can tell!

SteveFromMN

All I want is a good old fashion dip stick. Is that too much to ask for?

simsgw

Well, it does impose annoying limitations on the designer you know. And since it isn't as reliable as an electronic gauge we prefer an electronic read-out when the minor extra cost isn't an issue. I must say the one on the 991 is much more pleasant to use than the one on my 997.

Gary

chuckbdc

You can get an old fashion dip stick at any Porsche service department, speed shop, swap meet, and some junk yards. You may have to get an old fashion Porsche, and a garage drip pan to make old fashion use of it.