Bosch Gasoline Engine Management: SI Engine Torque & Primary Functions (Page 1)

This is a scanned page from a Bosch gasoline-engine management reference (likely a Bosch technical handbook). It opens the chapter "Gasoline-engine management" with two sections. "Technical requirements, Spark-ignition (SI) engine torque" explains that engine power is determined by net flywheel torque and engine speed, and that net flywheel torque equals combustion force minus internal friction, gas-exchange losses, and torque consumed by engine ancillaries. Combustion force depends on three factors: air mass trapped after intake-valve closure, the simultaneously available fuel mass, and ignition timing. "Primary engine-management functions" describes the system's core task of regulating torque generation, then covers two subsystems: cylinder-charge control (in Bosch systems with electronic throttle control, ETC, the subsystem sets required induction-air mass and throttle opening; on conventional injection systems the driver controls the throttle directly via the accelerator pedal) and mixture formation (calculating instantaneous mass fuel requirement to set injection duration and timing). Figure 1, "Driveline torque factors," diagrams the torque path from engine inputs (air mass, fuel mass, ignition angle) through combustion output torque, subtracting gas-transfer/friction and ancillary losses to give flywheel torque, then through clutch and transmission losses/conversion ratios to final drive force. Legend items: 1 ancillary equipment (alternator, A/C compressor), 2 engine, 3 clutch, 4 transmission.