Piston moves up the cylinder bore from BDC to TDC.Downward motion of the piston creates a vacuum (i.e., negative air pressure), which draws the air/fuel mixture into the engine through the open intake valve.Intake valve is open and the exhaust valve is shut.Piston descends the cylinder bore from top dead center (TDC) to bottom dead center (BDC).During the 4-stroke cycle, the intake and exhaust camshafts open and close the intakes and exhausts at precise times. The intake and exhaust valves regulate the air/fuel mixture that enters and exits the cylinders.

After these four events, the cycle is complete and ready to restart. A piston motion, either upward or downward, is defined as an event. Read : Motorcycle Ignition Systems: What Are They and How do They Work? What Are the Strokes of a 4-Cycle Engine?Ĥ-stroke engines have four valves so that pistons can go through four events to complete one 4-stroke cycle. But higher compression ratios can reduce durability and require more expensive higher-octane gasoline. In some applications, a higher compression ratio can provide more power. The compression ratio describes the relationship between total cylinder volume and compressed volume.įor example, a compression ratio of 10:1 (also known as '10 to 1') means that the chamber squeezes 10 parts air/fuel volume into 1 part of that volume at the end of the compression stroke. These characteristics have propelled 4-stroke technology to the top of the passenger vehicle market today! CompressionĪir/fuel compression before ignition improves combustion efficiencies. They also separate oil from fuel, which significantly reduces carbon monoxide emissions. When it comes to emissions, 4-strokes mechanically separate each event, reducing unburned fuel emissions. How Does a 4-Stroke Engine Work?Ĥ-stroke engines provide a good balance of power, reliability and efficiency.

Most modern internal combustion engines are 4-stroke engines that run on gasoline or diesel fuel. What Is a 4-Stroke Engine, and How Does a 4-Stroke Engine Work?Ī 4-stroke engine is a common type of internal combustion engine. If you want to learn more, consider enrolling at the Motorcycle Mechanic Institute (MMI)! 1 With MMI’s technical training curriculum, students can take motorcycle mechanic courses to develop skills for servicing motorcycle engines – including those with 4-stroke engines.Ĭontinue reading to learn more! You’ll discover how 4-stroke engines work and how they differ from 2-stroke engines. This guide will give you a brief, effective overview of 4-stroke engines.

Whether you're currently working in the field or are considering becoming a technician, it's critical to understand how different types of engines work – including 4-stroke engine technologies! 4-stroke engines power everything, from motorcycles and cars to lawn mowers and generators.

4 stages of combustion