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Idle speed, sometimes simply called "idle", is the rotational speed an engine runs at when the engine is idling, that is when the engine is uncoupled from the drivetrain and the throttle pedal is not depressed. In combustion engines, idle speed is generally measured in revolutions per minute (rpm) of the crankshaft.
The result is an engine that fails to maintain idle RPM and frequently stalls. A jammed actuator may be freed simply by cleaning it. However an actuator that has stopped working due to a fault in its servomotor will need replacement. Air leaks in either the stepper housing or pipes will cause elevated idle RPM.
An air-cooled engine uses all of this difference. In contrast, a liquid-cooled engine might dump heat from the engine to a liquid, heating the liquid to 135 °C (water's standard boiling point of 100 °C can be exceeded as the cooling system is both pressurised, and uses a mixture with antifreeze) which is then cooled with 20 °C air.
Fuel enrichment during cold-start is achieved by altering the timing of the main injectors based on engine temperature. The idle speed is also fully controlled by the digital Motronic unit, including fast-idle during warm-up. Updated variants ML 2.10.1 through 2.5 add MAF Mass Air Flow sensor logic and direct fire ignition coils per cylinder.
Some idle management technologies are so comprehensive, they are able to manage the engine's on/off ignition while retaining control of auxiliary functions, such as vehicle climate, anti-theft, operator security, and more, even when the engine is powered off. Idle reduction can also be achieved by more efficient control of stop lights [34] and ...
An engine that runs too hot or too lean may produce an environment conducive to allowing unspent fuel to burn. An idle speed that is too fast can leave the engine with too much angular momentum upon shutdown, raising the chances that the engine can turn over and burn more fuel and lock itself into a cycle of continuous running.
Just before the piston reaches TDC, ignition begins. In the case of a SI engine, the spark plug receives a high voltage pulse that generates the spark which gives it its name and ignites the charge. In the case of a CI engine, the fuel injector quickly injects fuel into the combustion chamber as a spray; the fuel ignites due to the high ...
A cold start is an attempt to start a vehicle's engine when ambient temperatures are much lower than its normal operating temperature. [1] A cold start can be difficult for an engine due to higher viscosity of oil and fuel in cold temperatures.