Answer / asdf

4 stroke is more efficient than 2 stroke in terms of fuel
consumption and emission.

But in terms of power, 2 stroke is more efficient. it
produces power in 1 revolutions of crankshaft than 4 stroke
in which 2 revolutions required..

Moreover, the world's most powerful engine is turbocharged
2 stroke diesel engine of around 1,00,000 hp developed by
Aioi works, Japan..

some one had made a mistake in the answers shown above
informing 4 stroke is better in power...

Answer / vachanti madhu

4 Stroke engine is more efficient primarly because of the
prescence of valves which precisely control the flow of
charge into the chamber and exit the exhaust gases with
proper timing which is hard to achieve by ports in a 2
stroke engine.

Answer / sawan taylor

In terms of mechanical efficiency 2 stroke is better.

And in terms of thermal energy 4 stroke is better.

Answer / dane huisman

A Four Stroke is more efficient when it comes to fuel
consumption because the four stroke engine has intake and
exhaust (poppet) valves. The exhaust valve allows all the
exhaust to escape every time, and the intake valve lets in
the same ammount of fresh fuel every time. The two stroke
engine is less efficient in this because it has ports that
do not get all the exhaust out every time causing not as
good of a gas mixture.
The Two Stroke Engine is more efficient than the Four
Stroke. The Two Stroke Combusts every time that the piston
hits TDC (Top Dead Center), where the four stroke fires
every other time the piston hits TDC because the four
stroke has to push the exhaust out of the valve. Therefor,
the two stroke fires two times in the time that the four
stroke fires once, making it more efficient in power.

Answer / mechy08

A four stroke engine is more efficient than 2-stroke due the
following reasons:-

1.)For the same size of cylinder, Some of the power and
compression stroke get wasted due to the presence of ports.
Improper combustion due to the mixing of burnt gases with
fuel.

2.)The fuel consumption is four stroke is less and the
combustion power in four stokr engine is greater there by
reducing the emmission of smellier gases.


3.)prescence of valves which precisely control the flow of
charge into the chamber and exit the exhaust gases with
proper timing which is hard to achieve by ports in a 2
stroke engine.

Answer / manoj prabahar

Four stroke engine produces less pollution than two stroke,
since there is no valves the the little amount of fresh
charge escapes so it gives less mileage, but power produced
is more in two stroke since cycle of operation is 2, rather
in 4 stroke its 4. The power produced in 2 stroke engine is
app twice the 4 stroke for the same capacity engine....

Answer / md. alamgir

It is matter of optimization. Efficiency can be determined
by specific fuel consumption. It can not be said in one
line that a four stroke engine is more efficien.

In four stroke engines, the higher amount of fuel is burnt
in a shorter period. However, combustion may have been
improved by good timing and good supply of air. Power
weight ratio of four stroke engine is less and hence
initial cost may be less.

A two stroke engine also can also be designed for same
specific fuel consumption. However, its power weight ratio
is higher than four stroke engine. It requires bigger space.

Considering all concerned matters, an engine has to be
selected for the required purpose.

Answer / david

The four stroke engine is more efficent, because of the
controlled flow of fuel into the motor, plus a four stroke
engine has two revolutions to every crank, whereas a two
stroke has one revoluion to every crank.

Answer / javeed ahmed

.)For the same size of cylinder, Some of the power and
compression stroke get wasted due to the presence of ports.
Improper combustion due to the mixing of burnt gases with
fuel.

2.)The fuel consumption is four stroke is less and the
combustion power in four stokr engine is greater there by
reducing the emmission of smellier gases.


3.)prescence of valves which precisely control the flow of
charge into the chamber and exit the exhaust gases with
proper timing which is hard to achieve by ports in a 2
stroke engine.A Four Stroke is more efficient when it comes
to fuel
consumption because the four stroke engine has intake and
exhaust (poppet) valves. The exhaust valve allows all the
exhaust to escape every time, and the intake valve lets in
the same ammount of fresh fuel every time. The two stroke
engine is less efficient in this because it has ports that
do not get all the exhaust out every time causing not as
good of a gas mixture.
The Two Stroke Engine is more efficient than the Four
Stroke. The Two Stroke Combusts every time that the piston
hits TDC (Top Dead Center), where the four stroke fires
every other time the piston hits TDC because the four
stroke has to push the exhaust out of the valve. Therefor,
the two stroke fires two times in the time that the four
stroke fires once, making it more efficient in power.four
stroke engines having more thermal efficiancy than two
stroke engines that gives good fuel economy .

Answer / sys

4 stroke is more efficient than 2 stroke because
---the friction in 2 stroke engine is more than 4 stroke
engine.

---and the valve mechanism is better than ports.

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