ME-Motronic engine management Electronic engine-management systems have advanced to become decisive factors in promoting fuel economy and enhancing the motor vehicle’s environmental compatibility. The engine-management system’s primary assignment is to furnish the torque requested by driver demand while at the same time ensuring maximum fuel economy and minimum emissions. The MEMotronic engine-management system for the gasoline engine (also known as the spark-ignition (SI) or Otto-cycle engine), unites all of the subsystems required to meet this challenge: The electronic throttle control (ETC, or “drive by wire”) regulates the flow of induction air to satisfy instantaneous torque demand, while the fuel-injection subsystem regulates fuel mass. Meanwhile, the ignition subsystem governs ignition timing and the generation of spark energy. ME-Motronic’s capabilities extend even further to embrace coordinated action with other automotive systems designed to enhance comfort, convenience and safety for the user. An example is the way ME-Motronic adjusts torque levels to ensure maximum traction in response to demands from the ABS and ESP systems. Progress in satisfying this highly variegated range of engine-management functions has been marked by evercloser coordination of the individual subsystems. This brochure explains the design concept behind ME-Motronic engine management as well as how the system operates. Conventional Motronic systems are described in a publication from this series entitled “M-Motronic engine management”.
Combustion in the gasoline engine The spark-ignition engine 2 Gasoline-engine management Technical requirements Cylinder charge Mixture formation Ignition Inductive ignition systems
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Gasoline-injection systems Over view
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ME-Motronic engine management The overall Motronic system Cylinder-charge control sy systems Fuel system Operating-data acquisition Operating-data processing Operating conditions Closed-loop idle-speed control Lambda closed-loop control Evaporative-emissions control system Knock control Boost-pressure control Protective functions Improved drivability Cruise control Integrated diagnosis ECU Interfaces to other systems
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ME –M otronic
ME-Motronic system diagram
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Cylinder-charge control systems
Principle of air control using air bypass valve 1 Idle valve (bypass valve), 2 ECU, 3 Throttle valve, 4 Bypass tract.
Cylinder- charge control systems
Throttle-valve control 3
On spark-ignition engines with external mixture formation, the prime factor determining output force and thus power is the cylinder charge. The throttle valve controls cylinder charge by regulating the engine’s induction airflow.
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Conventional systems Conventional layouts rely on mechanical linkage to control the throttle valve. A Bowden cable or linkage rod(s) translate accelerator-pedal travel into throttlevalve motion. To compensate for the cold engine’s higher levels of internal friction, a larger air mass is required and supplementary fuel must be injected. Increased air flow is also required to balance drive-power losses when ancillaries such as airconditioning compressors are switched on. This additional air requirement can be met by an air-bypass actuator, which controls a supplementary air stream routed around the throttle valve (Figure 2). Yet another option is to use a throttlevalve actuator designed to respond to demand fluctuations by readjusting the throttle valve’s minimum aperture. In both
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cases, the scope for electronic manipulation of airflow to meet fluctuating engine demand is limited to certain functions, such as idle control. Systems with ETC In contrast, ETC (electronic throttle control) employs an ECU to control throttle-valve travel. The throttle valve forms a single unit along with the throttlevalve actuator (DC motor) and the throttle-valve angle sensor: This is the throttle-valve assembly (Figure 1). Two mutually-opposed potentiometers monitor accelerator-pedal travel as the basis for controlling this type of throttle-
Fig. 1 ETC system
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