Quote:
Originally Posted by euromodder
While you're likely getting the best fuel mileage that way - low rpm, probably low(ish) steady speed - you're not getting the most bang for your gallon of fuel.
In those conditions, your engine is burning its fuel less efficiently in terms of HP / gallon.
But because these cruising conditions require so little HP, you still get good fuel mileage.
It feels contradictory, but it isn't  |
I believe that is nicely put what is challenge of trying to figure out what is way of getting lowest fuel consumption, even with hill climbing going with lowest HP that one can is best, it is just that below certain rpm lower gear can provide that low hp figure from much more favorable spot from BSFC table, which is then reason to downshift, then only challenge that remains is to know what rpm is too low.
Lugging engine at uphill is probably too low
My speed goes down to 50kph on long hills, my normal driving is around 80kph, I think 50kph was below 1400rpm and there is not much of any power left, throttle would need to be nearly floored to maintain the speed and engine is really not liking to go.
Wheel power might be quite low on that situation already.
Two choices for situation, downshift and keep hp low or originally at down of the hill push more throttle and request quite bit more hp to maintain speed which you can stay at top gear.
In such situation downshifting is better as requested hp will be lot less, even it will be less efficient and even there will be more losses because of high rpm.
Luckily there is only few hills that I need to do that, rest are those low throttle, low rpm on top gear type of hills, but that shows how one have to adapt to hills, also one need to plan ahead, see what is other side of hill, is it flat or is there downhill and plan accordingly, if there is downhill one can let speed decrease lot more as downhill will increase speed again with neutral coasting, if there is level ground, then it would be accelerating with engine, where one has to figure out if it is better to ask more hp at hill or at level ground?
That is why trying to get lower consumption is also more interesting at hilly ground as it is far more challenging, requiring a lot of planning.