The physics of cars - a question sequence.

[Roger Mills]

That's not a misuse of power - it's just an error of fact!

[Roger Mills]

I think you might have some difficulty trying to install a bile engine in a car!

I'm saying that it's the most significant factor. I would expect a diesel car to perform similarly to a petrol car with the same power to weight ratio - as indicated by the figures which someone quoted to other day.

But when you start comparing apples with pears by speculating about putting a bike engine in a car, you are shifting the goalposts more than somewhat. Your hypothetical bike engine probably wouldn't do so well because you wouldn't to able to deliver near maximum power - and I stress the word *power* - to the wheels for as large a proportion of the time.

[stvlcnc43]

How about examining the facts and admitting that you're wrong. An egine develops full power at one speed only. Now weasel out of that.

[Dave Plowman (News)]

Could be either. But it does prove the point I made earlier. Power can be a general expression used which may be perfectly well understood in a context. But not when discussing the difference between power and torque.

[stvlcnc43]

You're not really "into" cars and motoring. are you?

[Dave Plowman (News)]

Really? There are several around. Although more what you'd call sports cars.

They may have a similar 0-60 time or whatever, but how they perform in a single gear is likely very different. The very point I was making about torque versus power.

I was merely commenting on power to weight ratio. That may be a reasonable guide to performance where the engines are similar. But doesn't take into account how the vehicle will perform in a single gear if the engine type varies wildly. For that, you need to know about the torque output of the engine.

[Dave Plowman (News)]

Seems to apply to an awful lot on here. Doesn't stop them thinking they are, though.

[Roger Mills]

No need to. I've never said anything which is inconsistent with that. I can only assume that you've *mis*-read all my posts on the subject!

[bert]

In article , Vir Campestris writes

Isn't that where we started?

[Fredxxx]

OK - I was thinking of turbo-diesels.

[Fredxxx]

Yes, but didn't we start in ignorance of the gear?

[Vir Campestris]

A lot of modern diesels have a flat torque curve. Not a flat power curve.

The few I've driven feel as if the power band is horribly narrow compared to my car - which has peak torque at 4800...

Andy

[Vir Campestris]

Power corrupts, absolute power corrupts absolutely :P

Andy