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Dry sliding friction force is independent of sliding rate, at least in theory. However, hydrodynamic friction force generelly varies with the square of the change in rate. The journal bearings in the engine are purely hydrodynamic as are the pistons.
Increases in cylinder pressure don't have much effect on ring coefficient of friction, but they have a direct effect on the contact force and hence the frictional force.
-----Original Message-----
From: elippse@sbcglobal.net
To: lml
Sent: Tue, 5 Dec 2006 6.37PM
Subject: [LML] Friction loss
Friction or Coulomb* loss is independent of sliding rate. However, the friction loss in pounds, when multiplied by rate, yields hp. As rpm goes up, so does the friction hp. Also, as rpm goes up, engine power, at a given MEP, also goes up proportionatly. It would seem that the friction hp would maintain a certain percentage of the overall power input, and I'm not sure how this would cause a change in SFC. Also, I'm not sure of the effect of increased MEP on the coefficient of friction. Does it go up with the increased pressure of the rings against the cylinder walls at higher MEP? Keeping MEP max certainly cuts down on pumping loss! I seek enlightenment!
*Charles Augustin de Coulomb
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