M-Motronic Engine Management

Gasoline-engine management M-Motronic Engine Management Technical Instruction Published by: © Robert Bosch GmbH, 2000 Postfach 30 02 20, D-70442 Stuttgart. Automotive Equipment Business Sector, Department for Automotive Services, Technical Publications (KH/PDI2). Editor-in-Chief: Dipl.-Ing. (FH) Horst Bauer. Editorial staff: Dipl.-Ing. (FH) Anton Beer, Ing. (grad.) Arne Cypra, Dipl.-Ing. Karl-Heinz Dietsche, Dipl.-Ing. (BA) Jürgen Crepin, Dipl.-Holzw. Folkhart Dinkler. Authors: Dipl.-Ing. (FH) Ulrich Steinbrenner, Dipl.-Ing. (FH) Hans Barho, Dr.-Ing. Klaus Böttcher, Dipl.-Ing. (FH) Volker Gandert, Dipl.-Ing. Walter Gollin, Dipl.-Ing. Werner Häming, Dipl.-Ing. (FH) Klaus Joos, Dipl.-Ing. (FH) Manfred Mezger, Ing. (grad.) Bernd Peter, Dipl.-Ing. Ernst Wild. Presentation: Dipl.-Ing. (FH) Ulrich Adler, Berthold Gauder, Leinfelden-Echterdingen. Translation: Peter Girling. Technical graphics: Bauer & Partner, Stuttgart. Except where otherwise indicated, the above are employees of the Robert Bosch GmbH, Stuttgart. Reproduction, copying, or translation of this publi- cation, wholly or in part, only with our previous writ- ten permission and with source credit. Illustrations, descriptions, schematic drawings, and other particulars only serve to explain and illustrate the text. They are not to be used as the basis for design, installation or scope of delivery. We assume no liability for agreement of the contents with local laws and regulations. Robert Bosch is exempt from liability, and reserves the right to make changes at any time. Printed in Germany. Imprimé en Allemagne. 4th Edition, February 2000. English translation of the German edition dated: August 1999. M-Motronic Engine Management Modern electronics are opening up Combustion in the gasoline engine new perspectives in automotive The spark-ignition or design. The spark-ignition engine is Otto-cycle engine 2 being subjected to numerous, some- Gasoline-engine management times mutually-antagonistic demands. Technical requirements 4 It is now possible to satisfy these Cylinder charge 5 demands – including high specific out- Mixture formation 7 put, modest fuel consumption and low Ignition exhaust emissions – by using systems Function and requirements 10 providing an optimal combination of Inductive ignition systems 13 operating characteristics. Gasoline-injection systems Separate mixture-formation and igni- Overview 16 tion systems deal with parts of the M-Motronic engine management problem: Jetronic controls fuel supply M-Motronic: System overview 18 while the electronic ignition system Fuel system 20 provides optimal ignition control. Operating-data acquisition 28 Motronic combines the two systems. Operating-data processing 38 A computer controls the injection and Operating conditions 42 ignition systems with reference to Integrated diagnosis 58 shared optimization criteria. Electronic control unit (ECU) 62 Digital data processing and micro- Interfaces to other systems 64 processors make it possible to trans- late extensive operating information into program-map-controlled injection and ignition data. Installation of a Lambda oxygen sen- sor and integration of a Lambda control unit in the CPU allow Motronic to meet tomorrow's emissions regulations today. Combustion in the gasoline Combustion in engine the gasoline engine combustion process pressurizes the The spark-ignition cylinder, propelling the piston back down, or Otto-cycle engine exerting force against the crankshaft and performing work. After each combustion stroke the spent gases are expelled from Operating concept the cylinder in preparation for ingestion of The spark-ignition or Otto-cycle1) a fresh charge of air/fuel mixture. The powerplant is an internal-combustion (IC) primary design concept used to govern engine that relies on an externally- this gas transfer in powerplants for generated ignition spark to transform the automotive applications is the four-stroke chemical energy contained in fuel into principle, with two crankshaft revolutions kinetic energy. being required for each complete cycle. Today’s standard spark-ignition engines employ manifold injection for mixture formation outside the combustion The four-stroke principle chamber. The mixture formation system The four-stroke engine employs flow- produces an air/fuel mixture (based on control valves to govern gas transfer gasoline or a gaseous fuel), which is (charge control). These valves open and then drawn into the engine by the suction close the intake and exhaust tracts generated as the pistons descend. The leading to and from the cylinder: future will see increasing application of systems that inject the fuel directly into the 1st stroke: Induction, combustion chamber as an alternate 2nd stroke: Compression and ignition, concept. As the piston rises, it compresses 3rd stroke: Combustion and work, the mixture in preparation for the timed 4th stroke: Exhaust. ignition process, in which externally- generated energy initiates combustion via Induction stroke the spark plug. The heat released in the Intake valve: open, Fig. 1 Exhaust valve: closed, Reciprocating piston-engine design concept Piston travel: downward, OT = TDC (Top Dead Center); UT = BDC (Bottom Combustion: none. Dead Center), Vh Swept volume, VC Compressed volume, s Piston stroke. The piston’s downward motion increases VC OT the cylinder’s effective volume to draw fresh air/fuel mixture through the passage s exposed by the open intake valve. Vh UT Compression stroke Intake valve: closed, Exhaust valve: closed, OT Piston travel: upward, Combustion: initial ignition phase. 1) After Nikolaus August Otto (1832 –1891), who UT unveiled the first four-stroke gas-compression engine 2 UMM0001E at the Paris World Exhibition in 1876. As the piston travels upward it reduces The ignition spark at the spark plug Otto cycle the cylinder’s effective volume to ignites the compressed air/fuel mixture, compress the air/fuel mixture. Just before thus initiating combustion and the the piston reaches top dead center (TDC) attendant temperature rise. the spark plug ignites the concentrated This raises pressure levels within the air/fuel mixture to initiate combustion. cylinder to propel the piston downward. Stroke volume Vh The piston, in turn, exerts force against and compression volume VC the crankshaft to perform work; this provide the basis for calculating the process is the source of the engine’s compression ratio power. ε = (Vh+VC)/VC. Power rises as a function of engine speed Compression ratios ε range from 7...13, and torque (P = M⋅ω). depending upon specific engine design. A transmission incorporating various Raising an IC engine’s compression ratio conversion ratios is required to adapt the increases its thermal efficiency, allowing combustion engine’s power and torque more efficient use of the fuel. As an curves to the demands of automotive example, increasing the compression ratio operation under real-world conditions. from 6:1 to 8:1 enhances thermal efficiency by a factor of 12 %. The latitude Exhaust stroke for increasing compression ratio is Intake valve: closed, restricted by knock. This term refers to Exhaust valve: open, uncontrolled mixture inflammation charac- Piston travel: upward, terized by radical pressure peaks. Combustion: none. Combustion knock leads to engine damage. Suitable fuels and favorable As the piston travels upward it forces the combustion-chamber configurations can spent gases (exhaust) out through the be applied to shift the knock threshold into passage exposed by the open exhaust higher compression ranges. valve. The entire cycle then recommences with a new intake stroke. The intake and Power stroke exhaust valves are open simultaneously Intake valve: closed, during part of the cycle. This overlap Exhaust valve: closed, exploits gas-flow and resonance patterns Piston travel: upward, to promote cylinder charging and Combustion: combustion/post-combus- scavenging. tion phase. Fig. 2 Operating cycle of the 4-stroke spark-ignition engine Stroke 1: Induction Stroke 2: Compression Stroke 3: Combustion Stroke 4: Exhaust UMM0011E 3 Gasoline- engine Gasoline- management engine management Technical requirements Primary engine- management functions The engine-management system’s first Spark-ignition (SI) and foremost task is to regulate the engine torque engine’s torque generation by controlling all of those functions and factors in the The power P furnished by the spark- various engine-management subsystems ignition engine is determined by the that determine how much torque is available net flywheel torque and the generated. engine speed. The net flywheel torque consists of the Cylinder-charge control force generated in the combustion In Bosch engine-management systems process minus frictional losses (internal featuring electronic throttle control (ETC), friction within the engine), the gas- the “cylinder-charge control” subsystem exchange losses and the torque required determines the required induction-air to drive the engine ancillaries (Figure 1). mass and adjusts the throttle-valve The combustion force is generated opening accordingly. The driver exercises during the power stroke and is defined by direct control over throttle-valve opening the following factors: on conventional injection systems via the – The mass of the air available for physical link with the accelerator pedal. combustion once the intake valves have closed, Mixture formation – The mass of the simultaneously The “mixture formation” subsystem cal- available fuel, and culates the instantaneous mass

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