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The only moving parts inside simple two-stroke engines are the crankshaft, the connecting rod, and the piston. It is the same simplicity in design, however, that causes a two-stroke engine to be less fuel-efficient and produce high specific levels of undesirable exhaust gas emissions. At the bottom of the power stroke, the transfer ports, which ...
Snowmobiles Usually have one to four cylinders and can be both 2-stroke or 4-stroke, normally in the in-line configuration; however, there are again some novelties that exist with V-4 engines; Small portable appliances such as chainsaws, generators, and domestic lawn mowers most commonly have one cylinder, but two-cylinder chainsaws exist.
Animation of a two-stroke engine. A two-stroke (or two-stroke cycle) engine is a type of internal combustion engine that completes a power cycle with two strokes of the piston (one up and one down movement) in one revolution of the crankshaft in contrast to a four-stroke engine which requires four strokes of the piston in two crankshaft revolutions to complete a power cycle.
Boxer crankshaft configuration. Most flat-twin engines use a boxer configuration for the crankshaft and are therefore called "boxer-twin" engines. In a boxer-twin engine, the 180° crankshaft moves the pistons in phase with each other, therefore the forces generated by one piston are cancelled out by the other, resulting in excellent primary balance.
The shaft of the four-stroke piston rotates twice as fast as the shaft of the two-stroke piston, and the two-stroke part always runs at half speed. This ensures that both parts work optimally regarding fuel consumption at all times. The same principles apply to having two distinct engines, but the design of the M4+2 is much simpler.
When the transfer is complete, the piston is on the compression stroke but the exhaust port is still open, an unavoidable problem with the two stroke piston port design. To help prevent the piston pushing fresh mixture out the open exhaust port the strong acoustic wave (produced by the combustion) from the expansion chamber is timed to arrive ...
Many two-stroke engines use a crankcase-compression design, where a partial vacuum draws the fuel/air mixture into the engine as the piston moves upwards. Then as the piston travels downward, the inlet port is uncovered and the compressed fuel/air mixture is pushed from the crankcase into the combustion chamber.
Animation of the Atkinson differential engine 1932 Junkers Jumo 205 diesel aircraft engine. One of the first opposed-piston engines was the 1882 Atkinson differential engine, [7] which has a power stroke on every rotation of the crankshaft (compared with every second rotation for the contemporary Otto cycle engine), but it was not a commercial success.