Patent ID: 7568467

Claim:
A method, comprising: determining first, second, and third positions of a crankshaft in an engine during one of a piston expansion stroke and a piston compression stroke within a cylinder; determining first, second, and third cylinder pressures corresponding to the first, second, and third crankshaft positions; determining first, second, and third cylinder volumes corresponding to the first, second, and third crankshaft positions; determining the logarithm of the first, second, and third cylinder pressures and the first, second, and third cylinder volumes; and determining whether a point defined by the logarithm of the third cylinder pressure and the logarithm of the third cylinder volume is within a predetermined limit of a line defined by the logarithm of the first cylinder pressure and the logarithm of the first cylinder volume as well as the logarithm of the second cylinder pressure and the logarithm of the second cylinder volume.