04-10-2012, 05:35 PM
Two Stroke Internal Combustion Engines
TWO STRO.PPT (Size: 254.5 KB / Downloads: 140)
This type of engine is commonly found in applications such as;
lawn and garden equipment
dirt bikes
small outboard motors
Two stroke engines have advantages over four stroke:
simplified construction (no valves)
fire once every revolution for a significant power boost
Great power to weight ratio
The two stroke cycle
The two stroke engine ignites every revolution of the crankshaft. These engines overlap operations to reduce parts while maintaining power.
After the fuel air explosion, the piston is driven down. As the piston reached the bottom of it’s stroke, the exhaust port is uncovered. Most of the gases are driven out.
When the piston has bottomed out, the intake port is uncovered. The new fuel enters and is ready for compression and combustion.
When the fuel mixture is being compressed a vacuum is created in the crankcase. The vacuum opens a reed valve and sucks air/fuel/oil in from the carburetor.
Disadvantages of a two stroke
The engines do not last as long due to poor lubrication.
You have to mix two cycle engine oil with gasoline. $$$$$
The engines do not use fuel efficiently.
These engines produce a lot of pollution.
Summary
Two stroke engines are great for the power to weight ratio and their simple design, however, due to there pollution concerns these engines will be harder to find.