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OK, there is more involved I see Drive at say 11,000 feet up a hill in 3rd at 3/4 throttle and my car runs 60-70 degree's hotter than at the same speed, same throttle (or even more) in 4th. This is much less temp difference at sea level but as its getting older it gets more noticable. Keith temp > On 19 Sep 2005 at 20:56, Keith Park wrote: > > > I do notice that when pulling a hill, the oil temp (meas at the cooler) goes > > up with higher RPM... and down when I shift up to lower RPM. At first I > > thought that maybe the fan was cavitating at higher RPM but when I upshift > > to a lower RPM the engine puts out less HP at the same throttle position > > If you're driving up the same hill at the same road speed then your drive train > is putting out the same power. If we ignore differences in transmission > efficiency, which will be small, then the engine output is the same. > > The result of this is that the only differences to the engine are the changes > in cooling and rpm. There certainly could be cavitation at some point, but I'd > expect that point to be somewhere around the red line, which I think is about > 4500-5000 rpm. The change in rpm will put you in a different place on the power > curve of your engine, and that effect will depend on the exact conditions > you're operating under. > > It's very hard to know for sure that you have exactly the same throttle > opening, and besides, the throttle opening is really not a good indicator of > power output, since the gear changes give you different rpm as well as > different pressure drops across the throttle, different pumping losses, and > different volumetric efficiencies. > > -- > Jim Adney > jadney@vwtype3.org > Madison, WI 53711-3054 > USA > > ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > List info at http://www.vwtype3.org/list | mailto:gregm@vwtype3.org > ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > >