YorkshireJumbo wrote:Kevin wrote:I see someone has suggested that brisk acceleration is part of a hypermiling technique, which makes me think that someone has worked out whether or not there is some benefit in it. I dunno, just putting it out there to those that might have a better knowledge or greater access to resources than I have.
But they still cut the engine once they've reached their set speed, so that the engine only runs for a small %age of the time. That technique IS proven to work better for mpg, but it only really works if you are not sharing the road with other users, as their speed varies widely. Unless you plan to drive like that, I'm not sure there are significant benefits.
We're talking about driving with the engine running to maintain a set speed.
Whatever speed you reach and whether or not the engine is cut once the desired speed is reached isn't the area of fuel saving that I'm exploring. The area of fuel saving I'm focusing on (and I accept that it is probably only a small area and that there are many other ways of saving fuel that probably have greater effect) is just the acceleration phase. My gut feeling, is that longer spent in lower gears means the engine uses more fuel for a given distance. So early changing up gears is probably beneficial.
Now, that could mean selecting higher gears very early, almost labouring the engine. But, lets say you want to make reasonable, every-day normal driving sort of progress.
You could gently accelerate, changing gear, lets just say purely for the sake of example, at about 2,500rpm, until you reach whatever speed you want to be travelling at. Or, you could accelerate briskly, still changing gear at about 2,500rpm, until you reach the speed you want to be travelling at. Before this is discected in minute detail (Gareth! luv 'im to bits, but he does like to over-analyse sometimes) I accept various engines, drivers etc may, do, or want to change gear at different engine rpms and that journey time may affect the way people may or may not want to drive at any given moment etc. Just concentrate on whether brisk acceleration or gentle acceleration is better for fuel economy if all other variables remain constant. Otherwise I'll get a headache. I can feel one coming on already.