The Characters between Two-Stroke Engine and Four-Stroke Engine
Two-stroke engine and four-stroke engine are two popular engines which are widely used in the model RC airplane. When we talk about the difference between the two engines from diagnosis, repair and maintenance, we should learn clearly about differences of them on the valve mechanism, method of lubrication and mixture composition.
As we all know, two-stroke engine does not have a valve, and it's a simple structure. It is needed to fire for each cycle, while the four-stroke engine should fire for once every other cycle. Two-stroke engine can run on any location. It is very important in some equipment such as chain saws. Standard four stroke engines may happen in failure when oil sloshing, unless it is upright. If this problem was solved, that will greatly increase the flexibility of the engine. Two-stroke engine can't work continuing for such a long time like a four-stroke engine. The lack of precise lubricating system means that the two-stroke engine parts wear faster. Two-stroke engine will produce a worse pollution on the air. In addition to the above difference, there are also some differences in the two engines.
Difference in valve mechanism
Four-stroke engine transfer the rotation of the crankshaft to the camshaft through the timing chain, in the process of the camshaft rotating, the inlet and exhaust cam push the rocker arm swing, and makes the inlet and exhaust valves open and close regularly under the action of valve springs. Two-stroke engine depends on the certain pressure produced by the mixture entered into the crankcase to control the open and close of the inlet and exhaust of the piston, and then finish the scavenging and exhaust movements.
Difference between lubrication methods
Four-stroke engine piston connecting rod mechanism adopts the crankshaft splash lubrication method; cam shaft, rocker arm and valve are all adopts the pump pressure lubrication method. Two-stroke engine always uses the mixed lubrication or separation method. As for the separation lubrication, the crankcase of crankshaft connecting rod assembly, cylinder, piston assembly is all depend on the oil, gas and air mist to form the lubrication. The lubricating oil has played a role of lubrication, cooling, sealing and cleaning, it will also affect the wear of the parts and its service life.
Differences in the combustible mixture
Four-stroke engine combustible mixture is composed of gas and air while two-stroke engine is made up of petrol, oil and air.
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