Two stroke engine
Two stroke engine is a kind of internal combustion engine
which completes power cycle in 2 stroke. That is up and down movement of a
piston during one complete revolution of crankshaft. First two stroke engine
was patented by Dugald Clerk in the year 1881. Since then this type of engine
was used. Generally spark ignition two stroke engine is used to carry
lightweight and compression ignition is used to carry heavy goods.
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Two stroke cycle operation |
The main principle of two stroke engine is inlet and
compression stroke takes place in half rotation of crank shaft and power and
exhaust stroke takes place in another half stroke of crankshaft.
These types of
engine have high power to weight ratio. Since, the power stroke is achieved in
every revolution, it produces constant power .This is the reason why this type
of engine is used in chainsaw. Also, it is less expensive and easier to
construct. There is no valve in two stroke engine like in four stroke engine. In
two stroke engine , we have to mix engine oil with fuel as there is no chamber
to hold engine oil. The main disadvantage of two stroke engine is engine parts
wear fast as there is lack of proper lubricating system and it produces
pollution as the engine oil is burned with fuel in combustion chamber.
Four Stroke Engine
Four stroke engine is also an IC engine in which 4 different
strokes takes place in a complete cycle. Unlike two stroke engine, four stroke
engine uses valves and it has complex structure.
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Four stroke cycle operation |
The inlet stroke takes place
when piston moves from top to bottom. The compression stroke takes place when
piston moves from bottom dead center (lowest point to which piston can travel)
to top dead center (highest point to which piston can travel). Similarly, when
piston travels from TDC to BDC, the power stroke is completed and piston moves
from bottom to top in exhaust stroke. Four stroke engine last longer than two stroke engine as there is provision of
lubricating engine parts thus reducing wear of parts. It produces more power
making it suitable to carry heavy goods. It produces less pollution as well. The
main disadvantage of four stroke engine is it produce power once in two
rotation of crankshaft
Difference between 2stroke and 4stroke
- The general difference between 2 stroke and 4 stroke are
- Two stroke produces power in every rotation of crankshaft whereas four stroke produces power in every 2 rotation of crankshaft.
- Two stroke engine wear more fast than four stroke engine because of lack of proper lubricating system but there is a system for lubrication in four stroke engine.
- Two stroke engine are lighter and easy to construct but Four stroke engine is heavier and complex to construct with valves
- Two stroke engine produces more pollution as engine oil gets burned with fuel which doesn’t happen in 4 stroke engine
From the above description it is easier to choose between
two stroke and four stroke engine with proper reason
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