Gasoline- engine management Technical requirements Spark-ignition (SI) engine torque The power P furnished by the spark- ignition engine is determined by the available net flywheel torque and the engine speed. The net flywheel torque consists of the force generated in the combustion process minus frictional losses (Internal friction Within the engine), the gas- exchange losses and the torque required to drive the engine ancillaries (Figure 1), The combustion force is generated during the power stroke and is defined by the following factors: The mass of the air available for combustion once the intake valves have closed, rThe mass of the Simultaneously available fuel, and The point at which the ignition spark Initiates combustion of the air/fuel mixture Fig 1 Primary engine- management functions The engine-management system's first and foremost task is to regulate the engines torque generation by controlling all of those functions and factors in the Various engine-managementsubsystems that determine how much torque is generated. cylinder-charge control In Bosch engine-management systems featuring electronic throttle control (ETC), the "cylinder-charge control" subsystem determines the required inductionrair mass and adjusts the throttle-valve opening accordingly. The driver exercises direct control over throttle-valve opening on conventional inyection systems via the physical link with the accelerator pedal. Mixture formation The mixture formation subsystem calr cuiates the instantaneous mass fuel requirement as the basis for determining the correct injection duration and optimal inJeclion timing. Driveline torque factors 1 Ancillary equipment (alternator a/c compressor, etc i, 2 Engine, 3 Clutch, 4 Transmission Alf mass (fresh induction charge Fuel mass Combusrion oulput torque Engine Drzue Engine theel lorce Tiers Ignition anoie (ring point] Gasrransier and Melton Anoiiiaiies Clutchicorivener losses and Conversron ratios Transmission losses and conversion ratios Clutch output torque torque YllSSlm UMMti-nts ~s