Abstract: A system and method to control the ignition timing of engine (28) are used to rapidly warm a catalytic converter (52). A controller (8) calculates (402) hydrocarbon efficiency of the converter (52) from a ratio of the integrals of hydrocarbon sensors respectively positioned downstream (48) and upstream (46) of the converter (52). The controller retards ignition timing to a value retarded from nominal ignition timing (416, 426) when the calculated hydrocarbon efficiency is less than a desired efficiency (418).

Abstract: Air/fuel and ignition control of engine (28) are used to more rapidly heat-up a catalytic converter (52). A control system (8) generates a fuel command (100) for fuel delivery to the engine (28) based upon at least an amount of air inducted into the engine. The fuel command is offset by a predetermined amount in a lean direction during a period after engine start to shift the engine exhaust gas mixture towards a preselected air/fuel ratio lean of stoichiometry (106-122). In addition, the fuel command is corrected by a correction value so that the exhaust gas mixture is shifted ore closely to the preselected air/fuel ratio (126-140). Correction values are adaptively learned (300-324) during a portion of the warm-up period from a feedback signal derived from an exhaust gas oxygen sensor (44). Ignition timing and engine idle are also controlled (350-374) to further achieve more rapid warm-up of the catalytic converter (52).

Abstract: An internal combustion engine having a single intake valve which is fed fresh charge by primary and secondary port passages has an essentially flat combustion chamber with the spark plug and primary port passages being arranged to achieve a rapid burn rate.

Abstract: An air-air/fuel throttle body is provided with a secondary throttle valve of a differing diameter and operating in a different cross-sectional area of the throttle body induction passage, the upstream throttle valve being positively connected to the vehicle accelerator pedal to assure a like opening or closing movement of the latter throttle valve upon movement of the accelerator pedal, the construction assuring that main control of the flow of air and changes in manifold vacuum will be retained by the lower smaller diameter servo operated throttle valve operating in a smaller cross-sectional area.