How does a 4-stroke engine work?

2 stroke scooters are almost a history. These days almost all vehicles (scooters or bikes) are equipped with 4-stroke engines. This is because 2-stroke engines deliver low fuel efficiency eventually low mileage and also greater levels of pollution. On the contrary, 4-stroke engine vehicle delivers enhanced performance, fuel efficiency and greater mileage.

A four-stroke engine is characterized by a/an
Intake stroke
Compression stroke
Combustion stroke
Exhaust stroke

It is these characteristics that aid in transforming fuel into motion. One-stroke cycle implies single complete down or up movement of the piston. In a 4-stroke engine there exists 2 complete up and then 2 complete down movement of the piston for the engine combustion.

The engine cycle starts with the intake stroke. In the intake stroke, piston moves down and the intake valve opens up. Fuel mixed with air is taken in the cylinder and in the combustion chamber. Then, in the compression stage, the fuel-air mixture is compressed as the piston moves back and then up. The correct mixture of air and fuel is ascertained by carburetor. In this stage of compression there is no heat transfer in the fuel-air mixture. With the decreased volume of the mixture, gas pressure increases in the combustion chamber. Next, as the piston reaches the top, the spark plug ignites the gasoline in combustion stroke finally bringing the piston down. As the piston hits bottom, the exhaust valve gets opened and the pressure of burning fuel pushes the combustible products out of the cylinder through exhaust valves.

How does the piston move up and down?
By the crankshaft throw, the piston basically moves up and down. It is the revolution of the crankshaft that provides with two strokes to the piston. Thus in a four-stroke engine for the piston to move complete 4 strokes, the crankshaft need to turn twice. Again one must know that the degree of crankshaft travel is not same for all the four strokes of the piston.

Latest Comments. Share Your Opinion

  1. ravi

    this is for you ravi.

  2. sushant

    but why does the piston move down at the begining of the suction/inlet stroke?….i mean what makes it go down???and similarily what makes it come up again at the start of the compression stroke???the engine hasnt started and the flywheel still doesnt have enough rotational energy…….

  3. madhukar

    can u pls tel wat makes piston move up n down nd how does speed increases by shifting gears……pls reply me

  4. madhukar

    how does the gears work

  5. madhukar

    maintainnence tips of engines

  6. subhadip sinha

    maintainance tip of 4 stroke engines

  7. saran

    what is the starting position of piston when the fuel intake.then how the piston help to rotate the wheel…

  8. saran

    for one rotation of wheel how many time the piston process done???????????

  9. avinash

    how racing bike engines brakes while using slipper clutch

  10. deepak

    how does bikes got spoiled , hoe their engin got rested and geting out of condition

  11. sasi

    how many times piston beat per second

  12. yesudas

    how many times piston beat per second

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