Valve overlap defines the phase in which the intake and exhaust valves are open simultaneously, and is the prime factor in determining the amount of residual gas remaining in the cylinder. Parameters Exhaust-gas turbochargers Air-fuel mixture Here the energy employed to power the Operation of the spark-ignition engine is compressor is extracted from the exhaust contingent upon availability of a mixture gas. The engine does not provide the steady-state requirements of an engine power to the flywheel at idle. Each cated to each metering slit. A diaphragm upper chamber is connected to a separates the upper and lower chambers metering slit and its corresponding con- of the valve (Figures 18 and 19). The nection to the fuel-injection line. The combination of air and fuel common to Overview actual injected fuel quantity is regulated conventional injection systems. 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.
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. Basically, fuel metering is carried out a by the mixture control unit. The correct zero position in the switched-off position of the plate is transmitted to the phase. control plunger by a lever. The management engine’s pumping losses, leading to engine ingests a mixture of fresh air and lower fuel consumption. The Throttle valve ramps on the camshaft lobes determine completely open both the points and the rates at which the valves open and close (valve timing) to define the gas-exchange process, and Fresh gas charge with it the amount of fresh gas available for combustion. Clutches are often used to control compressor activation.
Since this point, the K-Jetronic has now become particularly impor- tant with regard to maintenance and repair. Throttle valve Dynamic pressure charging The power produced by the spark- A supercharging (or boost) effect can be ignition engine is directly proportional to obtained by exploiting dynamics within the mass airflow entering it. Unless otherwise stated, the above are all employees of Robert Bosch GmbH, Stuttgart. 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 pressure and holds the delivery pressure (system regulator then closes the return-flow port pressure) at about 5 bar. The amount of air drawn in by tronic system also allows for engine the engine is measured by the air-flow variations and permits the use of facilities sensor which, in turn, controls the fuel for exhaust-gas aftertreatment for which distributor.