Jeff Spitzer wrote:

  I don't dispute the
chart that was attached, just PL's interpretation.  The apex seal is
operating in a boundary lubrication mode.  The friction and heat
*generated* at the apex seal boundary is a strong function of the
characteristic of the film.  The reason why apex seals run cooler with more
oil is because they generate less heat IMO.  There is probably heat
transfer in all directions from/to the apex seal throughout the cycle.  As
the seal passes over the plugs it may pick up heat from the housing.  The
seal will most certainly pass heat TO the housing on the majority of the
cold sections of the engine.  The same goes for seal to rotor.

I agree with all this and there is one other factor heating the
apex seal and there is evidense it is the most important factor. When 
the exhaust port opens there is a squirt of high temperature 
exhaust gases passing by the apex seal. Also the trialing apex 
seal is sweeping the hot gases before it at this point in time 
until it too reaches the exhaust port and is subjected to a new 
blast of hot gases from the next rotor flank.

The sides of the apex seals are rubbing just as fast as the center
but the center runs much, much hotter as you can see from this chart.

apextemp.jpg

Jeff, keep a copy of these charts in a notebook and refer to them
the next time the subject comes up :-)

Paul Lamar


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