Rob:

**The two points I was trying to demonstrate were simply that 1) the optimal theta PP is a moving target that is dependent on several factors, including rpm and 2) that theta PP is an indication of the inefficiency of the engine.**

Ooooeeee, I'm not gonna answer how wrong that is. I'm going to let a real, graduate engineer correct you on that one. I sure don't want to be a snob. <g>

Have at it, engineering, graduate snob. <hehehehe>

Walter