Abstract: Alcohol concentration level of flex fuel is estimated based upon in-cylinder ionization signals. The in-cylinder ionization signals are integrated and the rotational completion point of a chosen percentage of the integration total is identified as the integration location for the operating conditions under observation. The calculated integration location correlates with alcohol concentration level of flex fuel, and the integration calculations provide a basis for a virtual flex fuel sensor that provides calculated estimates of alcohol concentration rather than direct sensing using an expensive physical flex fuel sensor.

Abstract: Alcohol concentration level of flex fuel is estimated based upon in-cylinder ionization signals. The in-cylinder ionization signals are integrated and the rotational completion point of a chosen percentage of the integration total is identified as the integration location for the operating conditions under observation. The calculated integration location correlates with alcohol concentration level of flex fuel, and the integration calculations provide a basis for a virtual flex fuel sensor that provides calculated estimates of alcohol concentration rather than direct sensing using an expensive physical flex fuel sensor.

Abstract: Maximum braking torque timing in an internal combustion engine can be determined by calculating the net pressure change in an engine cylinder during combustion. The second derivative of the net pressure change is then calculated. The spark timing of the engine is then varied until the maximum acceleration point of the net pressure change is aligned with top dead center.

Abstract: Maximum braking torque timing in an internal combustion engine can be determined by calculating the net pressure change in an engine cylinder during combustion. The second derivative of the net pressure change is then calculated. The spark timing of the engine is then varied until the maximum acceleration point of the net pressure change is aligned with top dead center.

Abstract: Mass fraction burned in a cylinder of an internal combustion engine is determined by measuring an ion signal across a gap of a spark plug and identifying an inflection point of the ion signal. The mass fraction burned is determined using an expression that includes a constant. A value for the constant is determined using the inflection point of the ion signal, and the mass fraction burned is determined using the expression and the constant.