I need help to determine an equation which takes a mixture of fuel and
air and gives me the force experienced on a piston in a cylinder of a
combustion engine at various crank angles.  My limited thermodynamics
knowledge doesnt allow me to analyize it over time (or crank angle). 
In addition, compression ratio (otto cylce efficency) and rate of
volume change changes burn time along with mixture of fuel.

I don't know if mixture of fuel plays directly into the equation or if
it is only done thru the energy relased in the combustion equation.

Summary:
 1. Force vs crank angle in a combustion engine.
 2. Needs to take into account RPM, Compression Ratio, and Mixture.
 3. Mixture can be any combination of N2O, H2O, Methanol, Ethanol, and
various octane pump gas.


Background:
This information will be used for this Excel spreadsheet that I am
creating which will be used for public learning purposes only.  It
will allow a user to enter engine specifications for 2 different
configurations and see how it effects theoretical power output through
out an rpm range or crank angle.  Its really cool and helpful for the
learning process of engines.   Since this is meant for free usage, I
have set a low price since I dont have alot of money nor am I charging
for its use.  This is for the pursuit of knowledge.