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Engine Cycles

Engine Cycles. Engine Cycles. Introduction to Engine Cycles. For an engine to operate, a series of events must occur in a “ specific sequence”. This “Series of Events” is as follows:. Fill the cylinder with a combustible mixture. This is referred to as “ INTAKE ”.

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Engine Cycles

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  1. Engine Cycles Engine Cycles

  2. Introduction to Engine Cycles • For an engine to operate, a series of events must occur in a “specific sequence”

  3. This “Series of Events” is as follows: • Fill the cylinder with a combustible mixture. This is referred to as “INTAKE”. • Compress this mixture into a smaller space. This is referred to as “COMPRESSION” • Producing Power,the mixture ignites which causes it to expand. “POWER” • Exhaust the burnt gases from the cylinder. “EXHAUST”

  4. The result of these events is power. • To produce sustained power, the engine must repeat this sequence over and over again. • One complete series of these events in an engine is called a cycle.

  5. Engine Cycles • Most engines have one of the two types of cycles: • Four-Stroke Cycle • Two-Stroke Cycle

  6. Four-Stroke Cycle What are those 4 parts to the cycle again?

  7. Four-Stroke Cycle • In the four-stroke cycle engine, there are four strokes of the piston, up & down then up & down again during each cycle. • Then it starts over again on another cycle of the same four strokes. • This cycle occurs during two revolutions of the crankshaft. • Most engines today operate on the four-stroke cycle.

  8. Four Stroke Cycles

  9. 4-Stroke Cycle Engine in Action

  10. Intake Stroke • The intake stroke starts with the piston near the top and ends shortly after the bottom of its stroke. • The intake valve is opened, allowing the cylinder to receive the fuel-air mixture as the piston moves down. • As the piston moves down, it creates a vaccuum • The valve is then closed, sealing the cylinder.

  11. Compression Stroke • The compression stroke begins with the piston at the bottom of the cylinder and rises up to compress the air-fuel mixture. • Compressed air-fuel is easier to ignite! • Since the intake and exhaust valves are closed, there is no escape for the fuel-air mixture and it is compressed to a fraction of its original volume.

  12. Power Stroke • The power stroke begins when the piston almost reaches the top of its stroke and the fuel-air mixture is ignited. • As the mixture burns and expands, it forces the piston down. • The piston being pushed down creates power! • The valves remain closed so that all the force is exerted on the piston.

  13. Exhaust Stroke • The exhaust stroke begins when the piston nears the end of its power stroke. • The exhaust valve is opened and the piston rises, pushing out the burned gases. • When the piston reaches the top, the exhaust valve is closed and the piston is ready for a new four-stroke cycle.

  14. Advantages of 4-Stroke • good fuel economy • quiet

  15. Dis-advantages of 4-Stroke • more moving parts • expensive to make

  16. Examples of Four-Stroke Cycle Engines • Cars • Trucks • Tractors SCOOTERS!!!

  17. So, that was the theory. Let’s see these engines work

  18. Camshaft & OHV

  19. OHV with pushrods. No Overhead CamNote: ElectricalPoints, Condenser, Coil, and Battery

  20. Engine Cam

  21. Any Questions

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