Tach Vs. Hobbs Time

Dylan Smith wrote:

In article , John Roncallo
wrote:

Why? Do the Archer's engine components wear less at high RPM than an
engine on an Arrow?

Yes they probably do wear less. They are under less load for the given
circumstance. Cylinder pressures are much higher in an engine at 65%
power 2300 RPM than they are at 65% 2480 RPM.


But a far greater effect will be the additional wear from friction of
running at 2480 RPM instead of 2300 RPM - a significant increase in the
number of friction cycles per hour. I'd say the Archer's engine
will wear more quickly.


Wear is a function of pressure and velocity. Mechanical dynamic friction
is a function of mostly pressure. High cylinder pressures cause high
mechanical pressures everywhere , journal bearings, piston side forces
etc. With both cases of high and Low RPM at equal power output the wear
should for the most part be relatively equal.

The absolute which case is better argument and where is the exact equal
wear points as far as RPM goes will probably never be much more than an
educated guess but it should be clear that the lower loaded Archer
engine should be allowed more RPM than the higher loaded Arrow engine
even if they were the same exact engine, which they are not.

John Roncallo