Small Engines Modified by John Templeton Objectives n

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Small Engines Modified by: John Templeton

Small Engines Modified by: John Templeton

Objectives n Describe the operation of small gas engine ignition systems n Describe the

Objectives n Describe the operation of small gas engine ignition systems n Describe the fundamental scientific principles of engine operation n Distinguish between the operating of two and four stroke engines n Identify common two and four stroke engine parts and systems

Objectives n Discuss the function of common engine parts and systems n Explain the

Objectives n Discuss the function of common engine parts and systems n Explain the procedure used to measure engine output

Types of Engines _________________ n 4 Stroke n Flat Head n. V n Hemi

Types of Engines _________________ n 4 Stroke n Flat Head n. V n Hemi n Flat n n Rotary

_____________ n Used in ¨ Cars ¨ Small engines (lawn mowers, snow blowers, ect)

_____________ n Used in ¨ Cars ¨ Small engines (lawn mowers, snow blowers, ect) ¨ Motorcycles ¨ 4 Wheelers

Cylinder n n ______________________. The piston moves up and down inside the cylinder. The

Cylinder n n ______________________. The piston moves up and down inside the cylinder. The engine described here has one cylinder. That is typical of most lawn mowers, but most cars have more than one cylinder (four, six and eight cylinders are common). In a multi-cylinder engine the cylinders usually are arranged in one of three ways: inline, V or flat (also known as horizontally opposed or boxer), as shown in the following figures.

Spark Plug n _________________ that ignites the air/fuel mixture so that combustion can occur.

Spark Plug n _________________ that ignites the air/fuel mixture so that combustion can occur. The spark must happen at just the right moment for things to work properly.

Valves n ____________________ to let in air and fuel and to let out exhaust.

Valves n ____________________ to let in air and fuel and to let out exhaust. Note that both valves are closed during compression and combustion so that the combustion chamber is sealed.

Valve Failure

Valve Failure

Piston Rings n ________________________ between the outer edge of the piston and the inner

Piston Rings n ________________________ between the outer edge of the piston and the inner edge of the cylinder. The rings serve two purposes: n They prevent the fuel/air mixture and exhaust in the combustion chamber from leaking into the sump during compression and combustion. n They keep oil in the sump from leaking into the combustion area, where it would be burned

Combustion Chamber n n The combustion chamber is the area where compression and combustion

Combustion Chamber n n The combustion chamber is the area where compression and combustion take place. As the piston moves up and down, you can see that the size of the combustion chamber changes. It has some maximum volume as well as a minimum volume. The difference between the maximum and minimum is called the displacement and is measured in liters or CCs (Cubic Centimeters, where 1, 000 cubic centimeters equals a liter).

Connecting Rod n _________________ to the crankshaft. It can rotate at both ends so

Connecting Rod n _________________ to the crankshaft. It can rotate at both ends so that its angle can change as the piston moves and the crankshaft rotates.

Crank Shaft n __________________________________ motion into circular motion just like a crank on a

Crank Shaft n __________________________________ motion into circular motion just like a crank on a jack-in-the-box does.

Sump n _________________. It contains some amount of oil, which collects in the bottom

Sump n _________________. It contains some amount of oil, which collects in the bottom of the sump (the oil pan).

Why do they call it a four stroke engine?

Why do they call it a four stroke engine?

Intake Stroke n ____________, the intake valve opens, and the piston moves down to

Intake Stroke n ____________, the intake valve opens, and the piston moves down to let the engine take in a cylinder-full of air and gasoline. This is the intake stroke. Only the tiniest drop of gasoline needs to be mixed into the air for this to work.

Compression n _________________ to compress this fuel/air mixture. Compression makes the explosion more powerful.

Compression n _________________ to compress this fuel/air mixture. Compression makes the explosion more powerful.

Combustion n ______________________, the spark plug emits a spark to ignite the gasoline. The

Combustion n ______________________, the spark plug emits a spark to ignite the gasoline. The gasoline charge in the cylinder explodes, driving the piston down.

Exhaust n Once the piston hits the bottom of its stroke, the exhaust valve

Exhaust n Once the piston hits the bottom of its stroke, the exhaust valve opens and the exhaust leaves the cylinder to go out the tail pipe.

The four stokes of an engine

The four stokes of an engine

What are rpm’s? n How do we calculate rpm’s?

What are rpm’s? n How do we calculate rpm’s?

How does the spark know when to let out a spark?

How does the spark know when to let out a spark?

Fuel System

Fuel System

Review n What are the four strokes of an engine and what happens on

Review n What are the four strokes of an engine and what happens on each stroke? n What are the parts of a valve and what purpose do they serve?