"Roger Mills" wrote in message
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On 07/04/2016 15:25, michael adams wrote:


And so my question is this.

If the engine is running at maximum power, and thus the crankshaft
is turning as fast as possible, then how is it possible for less than
maximum torque to be delivered to the flywheel ?


Because the torque which the engine produces at wide open throttle varies with speed.
If you plot torque against engine speed, you get a curve which is convex upwards. Peak
torque typically occurs at 3000 - 3500 rpm.

If you then calculate power at each speed (speed x torque) and plot that, you get a
different curve. That rises steadily with speed until it reaches its peak - maybe at
5000 rpm, and then starts to drop off again.

So, at peak torque, the engine is producing more torque than it is at peak power.
Because power is the product of speed and torque, it continues to rise even after the
torque has peaked.

So, to return to your question, you can get more torque - but less power - out of an
engine by running it a speed lower than its max power speed.

Or, to put it another way, peak torque and peak power don't occur at the same speed as
each other.

Hope that helps!

Thanks. I found a website with the curves etc.

" Typically, the torque peak will occur at a substantially lower RPM
than the power peak."

My problem really is that the above statement isn't intuitively
obvious. To me, at least.

I suspect understanding these things requires the ability
to visualise the interplay of at least two different
cocepts at the same time; that once that's been achieved
then it all fits into place; but for people who've never
bothered with this, beyond a certain age, without 3 D models
and intensive tuition it may be a bit of a lost cause.

Especially when there's so much else out there to get
confused about.

Which people who have been familiar with these concepts
since their youth may find a bit difficult to understand.


michael adams

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