The physics of cars - a question sequence.

[Dave Plowman (News)]

Thank gawd for that.

And has anyone ever denied that? Although I think you mean a lower gear.

Now all you need to do is persuade Mr Camp.

[dennis]

The answer to that is easy..

the biggest engine as you rev it to maximum revs and pop the clutch transferring all the kenetic energy in one go. The more energy you can get into storage the faster it will accelerate for that instance.

[Roger Mills]

Apart from you, do you mean?

Although I think you mean a lower gear.

Yes, of course. My "different" gear would obviously need to be lower to get the effect I described.

I don't think he needs persuading.

[Roger Mills]

The fact remains that a car's power to weight ratio (*not* engine torque to weight ratio) is a pretty good indicator of accelerative performance.

[Roger Mills]

Now who's comparing apples with pears?

[Dave Plowman (News)]

And on most cars, that would simply result in wheel spin. Turning any useful acceleration into smoke heat and noise. Congratulations, Dennis.

[Dave Plowman (News)]

Please quote where I have. You'll find that impossible.

No. He thinks the best acceleration takes place at maximum BHP. The whole reason this started. And he is wrong then as now.

[Dave Plowman (News)]

It's an oft quoted figure for the masses. Same as BHP is all important to bar room mechanics. But it doesn't tell the full story. Only that car makers tend to produce roughly similar engines.

But I'll ask you a question. Take a high revving bike engine with a very high specific BHP per litre and put it up against a lightly stressed but torquey V8 etc in vehicles with the same power to weight ratio. Which one will accelerate better?

[Dave Plowman (News)]

I was never ever discussing 0-60 times in this particular discussion. It's merely a pub bore benchmark.

I would remind you of what this discussion was about, but if you don't know by now, no point.

[michael adams]

michael adams

...

[Roger Mills]

I don't need to try very hard, do I? Just look at your very last statement (below) in *this* post!

I thought from what you wrote above that the truth had finally dawned on you. But I was wrong!

[Fredxxx]

If you can understand the OP's question, you will accept that there are scant details to provide an answer.

I was commenting on the assertion that torque is an irrelevance to the acceleration of a car where 0-62mph times were mentioned. The OP's question was something like 40 posts ago in this specific thread.

[Fredxxx]

If you want the least confusing measurement of power then use Watts, or even KW. They are also an SI unit.

If people here don't know how to calculate power from torque and revs, then they ought to excuse themselves from this discussion and learn.

[Dave Plowman (News)]

And? Just what you find in that worth pasting without comment?

[Dave Plowman (News)]

Then please quote me saying you *won't* get better acceleration in a lower gear?

Either you're trolling or you haven't grasped what this thread is about.

[dennis]

How does that differ from having too much torque? If its going to make the tyres spin then they will spin however you input the same rate of energy.

[michael adams]

Your instructing me, that I should tailor my useage i.e. use BHP, so as to pander to those very same "bar room mechanics" who you choose to sneer at.

michael adams

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[Dave Plowman (News)]

Torque still matters even for a 0-60 time, unless you were using some form of CVT specifically designed for a very narrow band output.

Early BMW 4 valve per cylinder car engines were extremely peaky. Later units used variable valve timing to improve the torque curve - but had no more peak BHP. The acceleration times with the later engines were better. And the car felt far more lively in general driving.

[Dave Plowman (News)]

It's not commonly used in the UK for engine outputs. That is still BHP - in the same way as we still used MPH. Although PS is creeping in. But they can all be converted directly.

I've been saying that for weeks. ;-)

[Dave Plowman (News)]

Sneering at those who only 'know' BHP and don't understand torque. And therefore argue black is white.

The trouble with 'power' is it means different things to different people.

BHP is the common term in the UK for car engines. But it does need to be used correctly.