Four-stroke engine explained

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[img] the movement in either direction of a mechanical part (such as a piston) having a reciprocating motion, Archives of Pearson Scott Foresman (2020)

A four-stroke engine, also known as a four-cycle engine, is a type of internal combustion engine commonly used in most cars, trucks, motorcycles, and many other applications. It operates on a cycle of four distinct phases to convert fuel into mechanical work.

Here are some key facts about four-stroke engines:

  1. Four Strokes: A four-stroke engine completes four distinct phases or strokes in two revolutions of the crankshaft. These phases are intake, compression, power, and exhaust.

  2. Intake Stroke: During the intake stroke, the engine's intake valve opens, and the piston moves down the cylinder, allowing a mixture of air and fuel to enter.

  3. Compression Stroke: In the compression stroke, both the intake and exhaust valves are closed, and the piston moves upward, compressing the air-fuel mixture. This compression increases the mixture's temperature and pressure.

  4. Power Stroke: The power stroke is initiated when a spark plug ignites the compressed air-fuel mixture. This rapid combustion generates high-pressure gases that force the piston down the cylinder. This downward motion of the piston is what drives the engine's crankshaft and produces mechanical work.

  5. Exhaust Stroke: After the power stroke, the exhaust valve opens, and the piston moves up the cylinder, expelling the burned gases from the previous combustion cycle.

  6. Fuel Efficiency: Four-stroke engines are generally more fuel-efficient than two-stroke engines because they separate the intake and exhaust cycles. This separation reduces fuel wastage and leads to better efficiency.

  7. Environmental Benefits: Four-stroke engines tend to produce fewer emissions and are considered more environmentally friendly compared to two-stroke engines. They are compliant with stricter emissions regulations.

  8. Common Usage: Four-stroke engines are the standard for most automotive applications, including cars, trucks, and motorcycles, as well as in various industrial and power generation applications.

  9. Lower Noise and Vibration: Four-stroke engines tend to produce less noise and vibration compared to two-stroke engines, making them more suitable for a wide range of applications, including passenger vehicles.

  10. Wider Torque Range: Four-stroke engines typically provide a broader and more usable torque range, which is advantageous in various situations, such as driving cars and trucks.

  11. Lubrication: These engines rely on a separate lubrication system to ensure proper lubrication of moving parts. Oil is not mixed with the fuel, as is often the case in two-stroke engines.

  12. Reliability and Durability: Four-stroke engines are known for their reliability and durability, with longer service intervals compared to two-stroke engines. Regular maintenance includes oil changes, air filter replacements, and periodic timing belt or chain adjustments.

  13. Popularity: Four-stroke engines have become the standard in the automotive industry and are widely used in a wide range of applications due to their fuel efficiency, reduced emissions, and broad torque characteristics.

While four-stroke engines are the dominant choice in many applications, it's important to note that they are not without their drawbacks, and the choice between two-stroke and four-stroke engines depends on the specific requirements and constraints of the application.