Because in new engine there is no flow of fuel initially. And the piston moves from BDC to TDC.
The initial movement is powered by electric motor until fuel arrived to the engine and combustion takes place steadily.
Wouldn't the initial movement affect the cylinder walls in terms of initial tear and wear due to loss of oil or lubricating agents on the cylinder walls? This is because volumetric efficiency might be affected considering the wearing away due to loss of oil. What do you think?
Hi guys, the engine is 'cranked' over by a starter motor (usually electric, some larger engines have pneumatic units). These suckers can rotate the engine at about 150 to 200 rpm, whilst this is happening, the fuel system is delivering fuel to the carburettor or fuel injectors whilst the ignition system is being energised as well ( in the case of petrol engines) in the case of diesel engines, the heat generated by the compression process is enough to ignite the diesel.
The pistons are supported by piston rings. These rings have several important jobs to do. They seal of combustion gases from the ignition process to stop them entering the sump. They control the oil by not allowing it to go past the piston. They support the piston, Heat transfer for cooling etc; the rings are usually under estimated in there job.
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