Automotive Engineering; Digital Powertrain Control Systems

Traditionally, the term powertrain has been used to include the engine, transmission, differential, and drive axle/wheel assemblies. With the advent of electronic controls, the powertrain also includes the electronic control system (in whatever configuration it has).

Moreover, certain vehicles employ electronically controlled clutches in the differential (transaxle) for traction control. Electronic controls for these major powertrain components can be either separate (i.e., one for each component) or an integrated system regulating the powertrain as a unit.

This latter integrated control system has the benefit of obtaining optimal vehicle performance within the constraints of exhaust emission and fuel economy regulations. Each of the control systems is discussed separately beginning with electronic engine control.

For a typical engine, there are at least seven different engine-operating modes that affect fuel control: engine crank, engine warm-up, open-loop control, closed-loop control, hard acceleration, deceleration, and idle. The program for mode control logic determines the engine-operating mode from sensor data and timers. All the above modes will be discussed in detail.