On 3/31/2016 3:33 PM, Clive George wrote:
On 31/03/2016 14:25, Dave Plowman (News) wrote:
In article ,
Clive George wrote:
On 31/03/2016 01:22, Dave Plowman (News) wrote:
In article ,
Clive George wrote:
On 31/03/2016 00:43, Dave Plowman (News) wrote:



I
won't disagree with that, but don't think it's terribly useful, because
generally people are concerned with the fastest way of getting between
two road speeds (eg 20-60). And for that, the fastest way is to choose
the gear such that the engine is at or closest to maximum power, not
maximum torque. Ie change up late, not early.

The discussion was about where on the *engine's* output maximum
acceleration occurs. Not about achieving the best 0-60 mph or anything
else.

To most of the people in this discussion, the discussion is about how to
achieve maximum acceleration during normal (or rather 'spirited')
driving, at whatever start and end speed the situation requires - and
the answer to that is to choose the right gear to get as near to maximum
power as you can, not maximum engine torque.

To you it seems to be only about at which point when you're racing from
0 to whatever are you accelerating fastest - which I agree is max torque
in first gear.

Is that an adequate summary of the two positions?

Peak power revs is normally a point where your acceleration is dropping
right off. For the best 0-60, standing quarter, or whatever you would
normally change up before you reach peak power (as long as you have
another gear available). You change up somewhere beyond peak torque so
that in the next gear you are going back through the torque peak again.
Exactly where you change is also partly determined by how much time you
lose in the gearchange; you might decide to start in second if you have
a low first ratio, or to reduce wheelspin. If you are drag racing in a
Landy you probably would not use low ratios!

Power, revs, and torque are inextricably linked but I think that most
mechanical engineers who go back to the basics think of it being the
torque which provides the mechanical force at the wheels (and hence the
acceleration).