Rob,

 

>>Consider a perfect ottocycle engine with perfect fuel. Mechanically the engine can survive whatever pressure the fuel can generate and the fuel burns infinitely fast. In this perfect world, with no cylinder leakage and no heat transfer, the cylinder pressure at any theta after ignition on the power stroke is always the same, no matter where ignition takes place. If the fuel is ignited at TDC, then the entire charge is combusted at TDC and Theta PP is also at TDC. Now, the piston sees the maximum possible pressure force at every inch of downward travel. Energy is force times distance so this has to extract the most shaft power from the fuel charge.<<

 

That is an interesting concept.

 

But I don’t think it is even  theoretically true.   I think if you apply some boundary condition analysis you will come to the same conclusion.

The configuration you suggests  does not appear to take into account the effects of the connecting rod-crankshaft geometry.

 

It is not the simple area under the  expansion curve that results in the power.  It is the correct integration of the expanding pressure curve, with the contribution of each point on the curve a function of  sin(theta-crankangle).

 

It is not a desirable design to arrange the combustion event  so that  the maximum pressure point in the combustion cycle gets multiplied by  zero (0=sin (zero degrees)  in the integration of the pressure-expansion curve to arrive at the torque applied to the crank shaft. 

 

Regards,  George