HowAutowork.com
In a two-stroke petrol engine, lubrication occurs by mixing oil with the petrol so oil passages are not needed. And if like many two-strokes, air-cooling is used instead of liquid cooling. There is no need for cooling passages in the cylinder head. Another difference between four-stroke and two-stroke petrol engines is how they deliver if fuel mixture to the cylinder. In a two-stroke petrol engine, separate passages called ports let fuel mixture into the crankcase and cylinder and exhaust gasses out. They covered and uncovered by the piston, has not moved ups and downs the cylinder.
In the four-stroke petrol engine, the inlet and exhaust ports are opened and closed by valves. This valves needs a system to control how they work, the valve is held in place by a valve guide with a spring on its stem. A rocker arm is attached to a station re-shaft that allows the arm to pivot, the rocker arm can presses and releases the valve spring so that the valve opens and closes.
Let us run the cycle again. The pistons moves up the cylinder. The top of the piston covers the exhaust port, the bottom uncovers the inlet port. If fuel mixture enters and circulates in the sealed crankcase below the piston, the pistons rises and compresses the mixture above it. As spark plugs ignites it and it burns. Pressure from the expanding gases pushes the piston down in a power strike, the top of the piston uncovers the exhaust port and let exhaust gases escaped. The bottom of the piston covers the inlet port and forces fuel mixture up into the now open transfer port. The piston reaches bottom dead center and the crankshafts forces it back up to repeat the process.
Notice which events occur above the piston, compression of the air-fuel mixture into the combustion chamber, combustion for the power stroke and excavanging of the exhaust gases. Notice the events that occur below the piston, intake into the crankcase, free compression of the air-fuel mixture in the crankcase and the transfer of mixture from the crankcase through the transfer port and into the combustion chamber.
Transcription by:
Scribe4you Transcription Services