delvon daily wrote:
>John_H wrote:
>
>> The commonly used formula is HP equals torque in ft-lb x rpm divided
>> by 5,252, in which case the lines will cross at 5,252 rpm.
>
>Thanks for explaining one is just a mathematical construct of the other.
>Why do they even bother if one is just a mathematical twist of the other?
>
>Why not just have one curve?

Because it matters not where the lines cross as the power curve is
calculated directly from the torque curve based on actual dynamometer
readings (since power can't be measured directly).

The most relevant points on those curves are the peaks and rpm at
which they occur since they serve to indicate an engine's power band
(the rev range over which it performs most efficiently). This might
help.... https://en.wikipedia.org/wiki/Power_band

Also relevant might be the tendency of sales folk (and others) to
quote maximum torque in isolation of rpm as if it were a performance
indicator when it really means jack **** since flywheel torque isn't
what appears at the drive wheels (unless it's a Tesla).

--
John H