Originally Posted By: Shannow
Google Books Link from Vehicle thermal Management Systems Conference and Exhibition (VTMS10)
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The first two runs examine the effect of engine power by varying engine load. The results show a 10$ reduction in engine load only reduces fluid temperatures by a little over 1C, and lap times ((Nurbergring) by less than 5 seconds. A 10% increase has a similar opposite effect. The small effect of fluid temperatures is due to the relativley small change in heat rejection with reduced load. Engine speed has a much greater effect on heat rejections than load so that for a constant power condition a high engine speed and low engine load condition will reject more heat than a low speed high load condition.
Quote:
Firstly, the effect of one of the key assumptions in the analysis was tested. Vehicles are driven around the Nurburgring in their most aggressive condition whcih means using the gearbox in manual mode. This is simulated by setting aggressive gear up and down shift speeds in the cycle generation (e.g. change up at 6500RPM and down at 3,500RPM.
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The effect of varying the set up-shift speed in three comparisons shows the strong link with cooling performance described above. Increasing the upshift speed, hence raising the average engine speed increases heat rejection and fluid temperatures by about 2.5C for a 300RPM increase, and 3.5C for a 500RPM increase. A 500RPM drop in up-shift speed shows a reduction of about 2.5C. This case also shows a drop of only 1.3s in lap times confirming that limiting engine speed is an effective way of controlling excessive temperatures without a dramatic impact on performance.
Goes on to explain the difference in full auto and auto sport modes (2,000 to 4,000 RPM ranges and 2,000 to 5,000RPM respectively).
Also looks at the effect of gradient, 3C difference between having a gradient for a section and removing it.
As always, will try to find the paper itself...but they are the words.
For the parts I can see in the link, it looks like they are talking mostly about coolant temperatures, not oil sump temperatures. Plus the first 4 pages (536-539) can't be seen to give more info. Also see Section 3, and Figures 3 & 4 which are plotting coolant temperatures. I see no plots for oil temperatures.
Section 2.2.3 however does mention the effect of reducing the coolant system flow by 18%, which made the oil temperature increase twice as much as the coolant temperature. Goes to show that the oil temperature is very sensitive to the coolant system performance, because the less heat you take out of the pistons and other parts that heat up from combustion, the more heat the oil will have to absorb.
As I said earlier, the cooling system can't take all of the heat of combustion out of the engine (even with a good cooling system), and the less effective the cooling system is, the more the oil temperature in the sump will increase as shown by your link. Also realize that pushing the car hard on the track is going to tax the cooling system, which will increase the cooling system's overall bulk temperature and make it less effective, which will enable even more heat rejection into the oil. Many things are going at the same time that are intertwined. And if you don't have any kind of oil cooler, it doesn't take very long while pushing a car really hard on the track to get oil dangerously hot.
