Abstract: A method for calculating actual air charge temperature uses values of coolant temperature, ambient temperature and engine air flow. These parameters affect the intake manifold temperature which, in turn, affects the amount of heat that is transferred to the air from the manifold. The time constant associated with the manifold temperature keeps the actual air charge temperature from instantaneously achieving a steady state condition. A time constant in the actual air charge temperature calculation substantially tracks the time constant associated with the change in temperature of the manifold as it responds to changes in air flow conditions. This actual air charge temperture value can then be used to calculate an accurate air-fuel ratio.

Abstract: A system and method of predicting the temperature of the bed of a catalytic converter positioned in the exhaust system of an internal combustion engine.

Abstract: In a closed loop fuel control system for an internal combustion engine having a catalytic converter in its exhaust system, a first zirconia sensor in the exhaust system upstream from the catalytic converter generates a signal indicative of air-fuel ratio in gases before catalytic treatment, a second zirconia sensor in the exhaust system downstream from the catalytic converter generates a signal indicative of air-fuel ratio in gases after catalytic treatment and a cascade feedback control system including both zirconia sensors controls the rate of flow of fuel or air to the engine in response to both sensor signals and a reference to maintain a constant stoichiometric air-fuel ratio in the exhaust system for maximum catalytic converter efficiency in simultaneous oxidation and reduction. The engine fuel system reverts to open loop operation during wide open throttle, closed throttle and cold start operation.