The torque on my Toyota Verso doesnt really climb until around 2000rpm, I was under the impression I would be better keeping the engine above this rpm as the engine is producing more torque for a given amount of pedal movement, than keeping it below where I need to press the pedal more as it is underpowered. But some of the posts above about staying under 2000rpm make me question whether Im right.
Though it is very dull to always change gear before the turbo spins up. I usually keep the revs between around 1500-3000rpm.
Is it petrol or diesel?
And if it's a diesel, are you sure it's the torque or the power you're noticing? Power of course being a multiple of torque and engine speed.
Most diesel engines produce their peak torque at below 2000rpm these days, but it should also be noted that the peak torque is the point in the rpm range where you are getting the most complete burn of the fuel in the cylinder per revolution. Not necessarily the point where it's using the least fuel... OK, sorry, perhaps not the best explanation, but whilst using a diesel's strong torque to accelerate it quite quickly but without revving to high (where the engine becomes inefficient) is more efficient than in a petrol, but may also not be quite as fuel efficient still as trickling it very slowly along, changing gear before the turbo spools up even.
Unlike in a petrol engine, the amount of diesel squirted into the engine by your injectors is directly proportional to how hard you press the accelerator. So tickling it gently of course will yield the best results. Accelerating hard before the turbo spools up will of course be very poor for your fuel consumption, as you won't be accelerating very much (because of lack of turbo pressure) but you're still using lots of fuel.
Driving a diesel for optimum economy is a trial, as it requires some quite different approaches depending on your speed, engine speed, incline and all sorts of other variables. Driving a petrol for maximum economy is much easier, as you just need to lay off the loud pedal as much as poss... That said though, of course a diesel will give you much better economy anyway!
Fifth Gear tested the recent Porsche 911 and got 30 mpg out of it, and i think it had well over 300bhp.
I remember Gordon Murray saying about his own McLaren F1 (he designed it by the way for those that don't know) that he used to get 26mpg whilst cruising down the motorways at "normal" traffic speeds (ie. 75-80mph). That's with a 6.1 litre V12 that produced 627bhp! Might've had a fair bit to do with the F1's low weight of just over 1100kg though in fairness...
Have had 32mpg out of a 1995 4 litre V8 Beemer 5 series myself on a 70 mile run before... That said I'm sure it was much easier to achieve 30mpg out of a new Porsche though, seeing as they have direct injection and are pretty efficient for a modern large capacity petrol engine.
When you drive a car harder that may mean lower gear and/or more throttle. So that means more losses, more heat loss, more unburned fuel exiting the exhaust, not to mention the effects of variable valve timing and about a million other things.
