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Four Stroke EnginesFour Stroke Engines

How does a canon work?How does a canon work?

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Engine OperationEngine Operation

Gasoline & diesel engines convert chemical energy into Gasoline & diesel engines convert chemical energy into mechanical energymechanical energy

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11stst stroke: Intake stroke stroke: Intake stroke

Gasoline and diesel engines have to go through 4 strokes to Gasoline and diesel engines have to go through 4 strokes to create power to move the carcreate power to move the car

the intake valve opensthe intake valve opens the piston moves downthe piston moves down

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Intake Stroke Continued…Intake Stroke Continued…

As the piston moves down the cylinder…As the piston moves down the cylinder…

a mixture of gas and air enters the cylindera mixture of gas and air enters the cylinder this mixture is 15 parts air to 1 part gas (15:1 air – fuel ratio)this mixture is 15 parts air to 1 part gas (15:1 air – fuel ratio) the air & fuel is mixed & delivered by the fuel system – either a the air & fuel is mixed & delivered by the fuel system – either a carburetor or fuel injection systemcarburetor or fuel injection system

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22ndnd Stroke: Compression Stroke Stroke: Compression Stroke

Intake valve closesIntake valve closes Piston moves up the cylinderPiston moves up the cylinder When the piston reaches the top When the piston reaches the top of the cylinder, the air & fuel has of the cylinder, the air & fuel has been squeezed to 150psibeen squeezed to 150psi

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33rdrd Stroke: Power Stroke Stroke: Power Stroke

a spark created by the ignition system, jumps the gap at the spark a spark created by the ignition system, jumps the gap at the spark plug & ignites the air/fuel mixtureplug & ignites the air/fuel mixtureThis causes the burning gases to expand and drive the piston down This causes the burning gases to expand and drive the piston down the cylinderthe cylinder

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44thth Stroke: Exhaust Stroke Stroke: Exhaust Stroke

Once the piston reaches the bottom of the cylinder from the Once the piston reaches the bottom of the cylinder from the power stroke…power stroke…

The exhaust valve opensThe exhaust valve opens The piston moves upThe piston moves up The burnt gases are pushed out of the cylinderThe burnt gases are pushed out of the cylinder

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Then what happens?Then what happens?After the exhaust stroke, the piston begins moving down on After the exhaust stroke, the piston begins moving down on another intake stroke, continually repeating the 4 strokes another intake stroke, continually repeating the 4 strokes

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Interesting FactsInteresting Facts

the burning air-fuel mixture can reach ≈1200the burning air-fuel mixture can reach ≈1200°C or more°C or more

the crankshaft spins the crankshaft spins ≈≈750 times per minute at idle750 times per minute at idle

it spins it spins ≈3000 times per minute at freeway speeds≈3000 times per minute at freeway speeds

this equals 50 times this equals 50 times per secondper second!!

the force on the piston during the power stroke is ≈1700kgsthe force on the piston during the power stroke is ≈1700kgs

a well maintained engine can last 300,000 km or more!a well maintained engine can last 300,000 km or more!

the design of a 4 stroke engine hasn’t changed very much the design of a 4 stroke engine hasn’t changed very much over the last 100 years over the last 100 years