four stroke cycle

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© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only

Basic Engine Parts

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Camshaft

Used to open and close valves.

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Valves Used to let gases

into and out of the combustion chamber.

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Fuel is burned inside the engine’s combustion chamber to produce heat and pressure

Engine components convert that pressure into rotating motion

Engine Operation

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Engine Operation

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Piston Travel Terms:(TDC, BDC)

Top dead center (TDC)piston is at its highest point in the cylinder

Bottom dead center (BDC)piston is at its lowest point in the cylinder

Piston strokedistance the piston slides up or down

from TDC to BDC

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Piston Travel

(TDC, BDC)

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Four-Stroke Cycle

Two complete crankshaft rotationsare required to complete thefour-stroke cycle

Almost all automobiles usefour-stroke-cycle engines

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1. Intake Stroke Intake valve is open Exhaust valve is closed Piston slides down and forms a

vacuum in the cylinder which draws fuel and air into the engine

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2. Compression Stroke

Piston slides upward and compresses (squeezes) the air-fuel mixture, making it more combustible

Both valves are closed

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3. Power Stroke Both valves are closed Spark plug fires, igniting the air-fuel

mixture. Piston is forced down, rotating the

crankshaft

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4. Exhaust Stroke Piston moves upward Intake valve is closed Exhaust valve is open Burned gases are pushed out the

exhaust port

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Four-Stroke Cycle

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The End