Engines

Snowmachine engines come in two types, two-stroke and four-stroke. Two stroke engines are simpler, lighter, and cheaper to manufacture then four-stroke engines, "plus two-stroke engines also have the potential to pack about twice the power into the same space because there are twice as many power strokes per revolution than in four-strokes". There are other advantages two-stroke engines have which include not having valves which lowers weight and eases construction. They also can work in any position while four-stroke engines have problems with oil flow unless it is in the upright position. On the other hand, four-stroke engines are more fuel efficient and much quieter than two-stroke engines.

 

http://science.howstuffworks.com/two-stroke1.htm

The picture above is an example of a two-stroke engine. Fuel is pulled in when the piston moves down, then is compressed as the piston moves back up to the top and then the sparkplug ignites the fuel. This drives the piston down the the process repeats itself. In a two-stroke engine the piston moves up and down only once before the period is complete.

http://auto.howstuffworks.com/engine1.htm

The picture above is an example of a four-stroke engine. Fuel is electronically injected, then the piston compresses the fuel and the spark plug ignites it driving the piston down. When the piston comes back up the exhaust valve is opened to allow the gases to escape. The piston moves down again and the fuel is injected again. In a four-stroke engine the piston moves up and down twice before the period is complete.

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