Method for low and high IMEP cylinder identification for cylinder balancing

Abstract

A system and method for identifying the cylinders having the lowest (“weakest”) and highest (“strongest”) Indicated Mean Effective Pressure (IMEP) utilizes engine speed derivative and/or higher order derivative values typically available in an engine control module by virtue of the need to detect misfire. A delta parameter is calculated that is indicative of the difference between the engine speed derivatives and/or higher order derivatives for the “weakest” and the “strongest” cylinders. Control action is then taken to balance the cylinders, based on the delta parameter, by first increasing torque for the “weakest” cylinder, by at least one increasing spark advance, increasing fuel, decreasing dilution (EGR) or slowing decay of fuel control on cold start. Once the weakest cylinder has been balanced, the control action is then directed to increasing torque of the new “weakest” cylinder.

Dependencies are inferred from the claim text.