The IC engine has separate fuel injection control for each cylinder with the injector (9) near to the inlet valve (7). The air duct comprises a main duct (5A) with a flow control valve(6) and a parallel secondary duct (5B). For low settings of the throttle pedal, and for idling speed, the main air valve is shut. For increasing throttle settings the air valve is progressively opened, with the process control computing the combined effect of both air ducts. The fuel is dispersed as a spray near to the ignition point with the airflow from the secondary duct providing a lateral flow to layer the fuel/air mixture. This enables a lean burn control to be used. No separate flow control valve is required for the secondary duct.
