Four-Stroke Engine Basics

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Four-Stroke Engine Basics

• Cars
• Trucks
• Semis
• Tractors
• Airplanes
• Motorcycles
• Lawnmowers

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The Basics

• A four-stroke engine
• Is an internal combustion engine
• Converts gasoline into motion
• Is the most common car engine type
• Is relatively efficient 20
• 4 piston strokes per cycle
• 2 crankshaft revolutions per cycle

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Basic Components
Camshaft
Intake Valve
Exhaust Valve
Valve Cover
Spark Plug
Intake Port
Exhaust Port
Head
Piston
Connecting Rod
Coolant
Rod Bearings
Engine Block
Crankshaft
Oil Pan
Oil Sump
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The 4-Stroke Cycle

• 1.
• 2.
• 3.
• 4.

Intake
Compression
Combustion
Exhaust
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• Intake
• process of filling the cylinder with the proper
  air-fuel mixture through the intake valve.

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• Compression
• the process of compressing the air-fuel mixture
  in the cylinder to make it more combustible

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• Combustion
• the process of igniting the compressed air-fuel
  mixture to create motion and the over all power
  of the engine.

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• Exhaust
• the process of releasing the exhaust out of the
  cylinder through the exhaust valve.

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How Stuff Works Animation

• http//auto.howstuffworks.com/engine1.htm

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• Engine Block- cast in one piece. The basis for
  most of the parts of the engine.

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• Valve Cover- Protects the valves and the valve
  springs. Keeps dirt out and lubricating oil in.

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• Head- a platform containing most of the parts of
  the combustion chamber.

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• Intake Valve- opens at the proper time to let in
  air and fuel.
• Intake Port- the passageway in a cylinder head
  for the fuel and air to pass through.

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• Exhaust Valve- open at the proper time to
  release the exhaust
• Exhaust Port- the passageway in a cylinder head,
  for the exhaust to pass through

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Valve Guide

• Controls the position of the valves

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Lubrication

• Oil Pan where the oil is collected and
  recirculated primarily for lubricating the
  crankshaft and rod bearing
• Oil Sump where the oil is stored for lubrication

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• Camshaft- a round shaft with lobes, that rotates
  to open and close the fuel and exhaust valves.
• Aligned with crankshaft gear for proper timing

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• Spark Plug
• a device, inserted into the combustion chamber
  for firing an electrical spark to ignite air-fuel
  mixture

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Cylinder

• Three types
• Cast aluminum
• Cast aluminum with cast iron sleeve
• Cast iron
• Usually use a cross-hatch finish to improves ring
  lubrication

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• Piston
• the part of the engine that moves up and down in
  the cylinder converting the gasoline into motion

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• Piston Rings-Keep tight seal against cylinder
  wall

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Ring Grooves

• Ring grooves are machined grooves in the piston
  designed to hold the rings.
• Ring lands are the areas of the piston between
  the ring grooves.
• The clearance between the rings and the ring
  lands is critical.

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• Connecting Rod- links the piston to the
  crankshaft.
• Rod Bearing- used to reduce friction to the rod
  and crankshaft

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• Crankshaft- converts the up and down (linear)
  motion of the piston into a turning, or rotating
  motion

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Crankcase Breather

• Maintains pressure in the crankcase at less than
  ambient pressure to assist in the control of oil
  consumption.
• Excessive blow by renders the breather useless.
• Old engines vent to the atmosphere.
• New engines vent to the carburetor.

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Application

• Now that you understand the basics of four-stroke
  engines, how can you use this information in the
  real world?

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Quiz
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• Lets take a quiz to see what you have learned!

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Quiz
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• 1. The ____ controls the amount of intake and
  the release of exhaust.
• a. head
• b. valves
• c. coolant
• d. connecting rod

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• The _____ Cycle is the ignition of the compressed
  fuel-air mixture.
• a. Exhaust
• b. Combustion
• c. Compression
• d. Intake

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• The most common type of engine?
• a. diesel engines
• b. 2-stroke engines
• c. rotary engines
• d. 4-stroke engines

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• What part of the engine converts up and down
  motion into a rotation motion?
• a. crankshaft
• b. piston
• c. valve cover
• d. camshaft

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• What is the name of the part listed?
• a. intake valve
• b. piston
• c. oil pan
• d. spark plug

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• Congratulations! That is the end of your quiz,
  and the end of your lesson on four-stroke engines.

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Four Stroke Chart
Stroke Piston Movement Intake Valve Exhaust Valve



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Compare Contrast 2 4 Cycle Engines