Bill Freeman wrote:

  OK, it depends a LOT on what kind of racing we are talking about as to
the real duty cycle of a racing motor.  One example may be useful.

The take home??   The duty cycle of road racing cars is *low*, they

can't hold

full power for more than a few (like 5-10) seconds, then down the gears
for a corner at 0-25% power, then back on the power.  Not like climbing out
at 100% and cruising all day at 75%.

Bill

  I agree Bill, but what's your point and how is it relevant to what most
of us are trying to do?

  As an example lets say a race prepped peripheral ported 13B installed in
some sort of road racing chassis produces 350HP @ 9000 RPM. I would agree
that it sees very little time at 100% duty cycle as it circles the track.
But this isnt really relevant in determining how durable the basic 13B will
be in powering my airplane at 180HP @ 6000 RPM. I would suggest that this
same race car as it circulates the course is at or above 180HP/6000RPM for
a considerable amount of time. Now if we knew how long that would be a
number that would have some relevance to the discussion of how durable a
13B can be in an aircraft application which is operating in the 180HP
range. And whether or not you can make any assumptions on durability in an
aircraft based on race car performance.

Mike Wills

 
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