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PowerPoint ® Presentation Chapter 4 Small Engine Fundamentals Four-Stroke Cycle Theory Four-Stroke Cycle Engine Operation Engine Components and Functions.

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Presentation on theme: "PowerPoint ® Presentation Chapter 4 Small Engine Fundamentals Four-Stroke Cycle Theory Four-Stroke Cycle Engine Operation Engine Components and Functions."— Presentation transcript:

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2 PowerPoint ® Presentation Chapter 4 Small Engine Fundamentals Four-Stroke Cycle Theory Four-Stroke Cycle Engine Operation Engine Components and Functions Small Engine Systems Compression Systems Fuel Systems Ignition Systems Lubrication and Cooling Systems Governor Systems Electrical Systems Braking Systems

3 Chapter 4 — Small Engine Fundamentals Gasoline-powered four- stroke cycle engines typically power lawn mowers, snow throwers, lawn and garden tractors, and many other types of outdoor power equipment.

4 Chapter 4 — Small Engine Fundamentals Small engines are designed to perform simple tasks with specific types of outdoor power equipment.

5 Chapter 4 — Small Engine Fundamentals A four-stroke cycle engine completes five events in one operating cycle, including intake, compression, ignition, power, and exhaust events.

6 Chapter 4 — Small Engine Fundamentals An intake event is an engine operation event in which an air-fuel mixture is introduced to a combustion chamber.

7 Chapter 4 — Small Engine Fundamentals A compression event is an engine operation event in which a trapped mixture of air and fuel is compressed inside the combustion chamber.

8 Chapter 4 — Small Engine Fundamentals An ignition event is an engine operation event in which a charge is ignited and rapidly oxidized through a chemical reaction to release heat energy.

9 Chapter 4 — Small Engine Fundamentals A power event is an engine operation event in which a compressed charge is ignited and hot expanding gases force a piston head away from a cylinder head.

10 Chapter 4 — Small Engine Fundamentals An exhaust event is an engine operation event in which spent gases are removed from the com- bustion chamber and released to the atmosphere.

11 Chapter 4 — Small Engine Fundamentals Basic small engine components are used for starting, running, and stopping the engine.

12 Chapter 4 — Small Engine Fundamentals

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14 Valve location determines whether an engine is an L- head or overhead valve engine.

15 Chapter 4 — Small Engine Fundamentals A piston acts as the movable end of the combustion chamber by using the forces and heat created during engine operation.

16 Chapter 4 — Small Engine Fundamentals Piston rings provide a seal between the piston and the cylinder bore and commonly include a compression ring, wiper ring, and oil control ring.

17 Chapter 4 — Small Engine Fundamentals A crankcase houses and supports the crankshaft of an engine.

18 Chapter 4 — Small Engine Fundamentals A typical small engine fuel system includes a fuel tank, fuel pump (on some models), fuel filter, carburetor, and fuel line.

19 Chapter 4 — Small Engine Fundamentals A carburetor provides the required air-fuel mixture to a combustion chamber based on engine operating speed and load.

20 Chapter 4 — Small Engine Fundamentals A throttle plate is used to regulate the flow of the air-fuel mixture to an engine, while a choke plate is used only to assist in cold starting.

21 Chapter 4 — Small Engine Fundamentals An ignition system includes multiple magnets, an ignition armature, a spark plug lead, and a spark plug.

22 Chapter 4 — Small Engine Fundamentals Breaker points control the flow of electricity to other parts of the ignition system circuit.

23 Chapter 4 — Small Engine Fundamentals A solid-state ignition system has a solid- state transistor in the ignition armature.

24 Chapter 4 — Small Engine Fundamentals The lubrication system and its engine oil absorb heat energy and transfer it to the aluminum cylinder block. The cooling air can then absorb the heat energy from the aluminum and transfer it into the atmosphere.

25 Chapter 4 — Small Engine Fundamentals A governor system is an engine system that maintains a desired engine speed regardless of the load applied to the engine.

26 Chapter 4 — Small Engine Fundamentals A mechanical governor uses the gears and flyweights inside a crankcase as speed-sensing devices to detect changes in a load and adjusts the throttle accordingly.

27 Chapter 4 — Small Engine Fundamentals A pneumatic governor uses a movable metal or plastic air vane as a speed-sensing device by registering the change in air pressure around a rotating flywheel.

28 Chapter 4 — Small Engine Fundamentals A small engine electrical system typically consists of an alternator, rectifier, regulator, and 12 V battery.

29 Chapter 4 — Small Engine Fundamentals An electrical system can be set up to produce either alternating current (AC) or direct current (DC).

30 Chapter 4 — Small Engine Fundamentals Small engine braking systems include several components that are designed to stop an engine quickly.


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