Quote:
Originally Posted by redpoint5
Another thing I have pondered with regards to hill climbs and efficiency is speed. Consider that it takes energy just to maintain position on a hill. You could burn fuel just sitting in one place at a standstill. Let's say it takes 1hp to just sit there and not move. If you double the horsepower by giving more throttle to the engine, then you are spending 1hp to merely maintain your position on the hill, and 1hp is spent actually climbing it. That would be a very slight throttle opening, and half of the power would be wasted to just maintaining hill position. If you increased throttle opening even more and now were developing 10hp, 9 of those would be spent climbing the hill, and only 1 maintaining. In this example, increasing power from 2hp to 10hp increased hill climbing efficiency from 50% to 90%.
Since just spending time on a hill without climbing it consumes fuel, it follows that getting to the top of the hill quickly reduces the amount of fuel wasted just maintaining position. Getting to the top in 1min instead of 2min reduces this wasted "maintenance" fuel expenditure by half.
The only factor that makes it more efficient to go slower, and this is significant, is wind resistance. There is some sweet spot of speed where getting to the top quickly is balanced by the exponential forces of wind resistance. Finding this ideal speed for various hills seems a daunting task for this limited mind to figure out.
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For some hills different tricks are needed than for other hills, letting speed go down is good for some hills, but one need to let speed go enough down that next downhill will again increase speed with neutral coasting so that next uphill is started again with enough speed, works well when there are continuously hills, but if there is just one hill it can be different story.
I wonder if hill would be endless and I will use only tiny bit more power than driving on flat ground, it would mean that my car would stop and would not even stay on hill, but would start going backwards, how much power one would need to stay at hill?
Even with lowest gear at steep hill, one needs to ask more power from engine so I doubt that it is just 1hp for staying on hill, even 10hp might be bit too little? But hp is bit difficult here as it is torque from wheels multiplied by gear ratios that would be holding car on place at steep hill, bit complicated for my tired brain at this moment, but it is quite a lot of force that 1000kg or more weighting vehicle is making with gravity at 5% slope, I think it is possible to calculate how much power is actually needed.