Patent ID: 7383816

Claim:
A method of operating a multiple combustion chamber internal combustion engine comprising: advancing an ignition timing of a first subset of the combustion chambers from an operating ignition timing until a knock event is detected while concurrently operating the remaining combustion chambers at the operating ignition timing; determining a first knock margin of the first subset of combustion chambers in relation to a difference between the operating ignition timing and the ignition timing at the knock event; advancing the ignition timing in a second subset of the combustion chambers from an operating ignition timing until a knock event is detected while concurrently operating the remaining combustion chambers at the operating ignition timing; determining a second knock margin of the second subset of combustion chambers in relation to a difference between the operating ignition timing and the ignition timing at the knock event; and determining a characteristic of a fuel supplied to the combustion chambers in relation to the first and second knock margins.