mark kibort

Here are a few screen shots of the gauges during thunderhill through qualifying.
interesting to see that in the long left sweeper, the pressure progressively goes from 5.5bar to 4 bar by the turn end.... also that same reduction in right turns as in the turn 3 sweeper. i came in the hot pits , and went back out with the oil temp being clearly seen. on the cool down lap with lower RPM, only right hand turns , would give a huge spike in oil temp, mainly because the oil temp is measured at the dipstick and was uncovered. proof that the oil is moving away from the dipstick on right turns, but thats a given.

so, the oil is always as high as the dip stick, which should submerse the pump pick up. interesting this phenom doesnt happen when RPM is at full tilt.

the pictures are :turn 2 the longest sweeper at 80mph constant speed
top speed down main straight 135'ish

turn 3 the longest R sweeper at 60-65mph constant speed

then two pictures of the right handers under lower RPM (on gear taller on cool down) with the oil temp sensor uncovered for 300F readings)

Mark Anderson

I wonder what it would show if you drove flat out? ��

Speedtoys

Is your oil temp seriously 325d?

mark kibort

i belive the oil dipstick was getting uncovered on right hand turns, becasue the filll level was 3/4 before qualifying. i put about 1/2quart in before the race, and it didnt happen again..... even with a taller gear in the right turns during cool down. but it does show there is a lot of movement of the oil when not quote full. makes sense as the dip stick is slightly on the right side so the oil moves left on right turns.but, if the dipstick is covered by proof of the temp reading, the oil pickup is well below the oil level.

Speedtoys

So..your pan temp is really 325d? Not sure I followed that..

Imo000

So the probe reads hotter when becomes uncovered in the engine?

GregBBRD

Oil steam hotter than liquid oil.....everybody knows that!

Imo000

Everybody on this board knows but me? Aren't you a bit overly pretentious?

GregBBRD

My comment was 100% sarcasm. (Oil steam?) I have no idea, just like you, how the sender would read hotter when uncovered.

jorj7

Greg,

Every one knows magic motors run hotter when not in contact with oil. It's the nature of the beast.

Well, its also true with real motors, but that you know.

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erioshi

Has anyone actually measured the ambient air temp inside the engine block of a running 928 engine? Both coolant and oil draw heat out of the engine and we run both fluids through coolers to help reduce buildup of heat in those fluids.

Given the actual temperatures seen by the physical components that contain combustion, I suspect the ambient air temperature inside the block of a running engine is probably much hotter than either the coolant or oil temperatures. The bottoms of the pistons and the cylinder walls are probably radiating a tremendous amount of heat into the airspace inside the block. Additionally, that airspace is largely static, without the kind of high volume airflow that would be necessary to use air as a cooling force inside the block.

Interestingly, some two stroke engine designs actually do route fresh air from the intake through the engine block on on it's way to the combustion chamber. It works in those applications, but would reduce the efficiency of a four stroke engine.

Just a thought.

Oh - here's a link to get you started on the "oil steam" idea...
http://www.drivenracingoil.com/news/...tion-problems/

M. Requin

Very interesting! Thanks for the link.

Imo000

Shiiiit and I almost believed it was true.

GregBBRD

Sorry, sarcasm is easy to loose, in print.

GregBBRD

I had a long discussion about Willow Springs and its unique "issues" about oiling, with good friend Dwain Dement (Vision Motorsports), this last week.

Currently, Dwain's expertise is directed at the 997/997/Boxster/Cayman engines and what it takes to make them survive on the track. He "over sensored" one of these engines that had Motec and got back some really interesting data.

Turns out that turn #6, where the cars get "really light", is the disastrous corner for these engines. The pick-ups get completely uncovered and the oil pressure drops to zero.

Interestingly enough, because the stock oil pressure sender also has a tiny orifice (like the 928 oil pressure sender), this only registers as an oil pressure drop on the stock gauge, but is much more dramatic in reality.