On 09/04/2016 11:42, Dave Plowman (News) wrote:
In ,
Roger wrote:
What any car's 0-60 time may be is totally irrelevant to where the
maximum acceleration occurs anyway. Unless comparing apples to oranges.


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.

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.

A colleague of mine at Rover studied this is some detail, and plotted a
graph of 0 - 30 times (admittedly not 0 - 60) against power to weight
ratio for a wide range of vehicles. He found a very strong correlation.

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?


Why compare a bike engine with V8 car engine?

If you take the same car and equip it with a high revving petrol engine,
and then swap the engine for diesel which produces the same power but at
a lower speed (with a suitable matching gearbox in each case) there will
be very little difference in the accelerative performance - even though
the level of drama may be different.
--
Cheers,
Roger
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