Patent ID: 7774124

Claim:
A method of determining the composition of a fuel blend from a first fuel and at least a second fuel to operate an internal combustion engine having at least one combustion chamber, wherein fuel blends of different composition combust at different optimal ignition angles with an optimal degree of efficiency, the method comprising: varying an ignition angle; and determining a degree of efficiency of the internal combustion and a parameter that is a function of the degree efficiency of the internal combustion as a function of the varied ignition angle; wherein the composition of the fuel blend is determined from at least one of: a change in the degree of efficiency of the internal combustion when the ignition angle is varied; a change in the parameter that is a function of the degree efficiency of the internal combustion when the ignition angle is varied; the ignition angle as a function of the degree of efficiency of the internal combustion; and the parameter that is a function of the degree efficiency of the internal combustion.