Quote:
Originally Posted by johnlvs2run
.....2) Your comment about keeping rpm close to 3000 rpm is interesting, but seems counterintuitive due to more stress on the engine, a longer time going up the hill and seems it would put more stress on the cooling. Would going a lower gear at higher rpm actually help the cooling?....
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Ah,
Talking about counter-intuitive!!
Kinetic Energy = WV^2/2g
This is one form on an equation for moving a mass up a hill. Work out some numbers and one quickly sees that going up a hill faster simply takes more energy.
Since we are trying to save fuel, it makes sense that going up the hill slower takes less energy (think force times distance divided by time or F * D / T). However, taken to an extreme, going up a hill in first gear may use more fuel than going up in third for example.
I always watch the FCD in the Insight when going up hills to get a feel for what works best.
In the case of the hills by LaCross, going up in third was way better than a higher gear, and keeping the speed to around 30 mph.
Regarding engine cooling.... About 1/3 of the HP generated by an engine goes into the radiator as heat. If we go up the hill slower, use less energy, then it goes that there should be less heat as well, and less cooling requirements from the radiator. However, again taken to an extreme, going to slow lowers the air velocity through the radiator, and thus at some point would heat it up higher because of the slow speed.
In my case, the lower engine temperatures I saw told me that the speed, engine rpm, and gear worked, because engine temperature was lower than going up in forth, with more engine load.
Jim.