LO 3.0 - Explain the working principles of two and four stroke petrol engine

Question 1

Question

Definition of an Engine.

3.1 - Working Principles of Engines

Answer 1

An engine is a piece of equipment made up of a number of components that converts fuel (potential energy) into working energy delivered via the crankshaft to produce kinetic energy.

3.1 - Working Principles of Engines

Question 2

Question

Name some Hort Machines.

ie, with engines harnessed. Try and name 10.

3.1 - Working Principles of Engines

Answer 2

Horticultural Machines with Engines harnessed.
* Lawnmower
* Strimmer
* Water pump
* Generator
* Tractor
* Leaf blower
* Consaw
* Mini digger
* Seeder
* Rotavator

3.1 - Working Principles of Engines

Question 3

Question

What is potential energy?

3.1 - Working Principles of Engines

Answer 3

• Potential energy is energy waiting to happen.

3.1 - Working Principles of Engines

Question 4

Question

What is kinetic energy?

3.1 - Working Principles of Engines

Answer 4

• Kinetic energy is energy in motion.

3.1 - Working Principles of Engines

Question 5

Question

How does the engine convert potential energy into kinetic energy?

3.1 - Working Principles of Engines

Answer 5

• The engine burning fuel in a metered and controlled way does this by the use of fire in a very confined space.

3.1 - Working Principles of Engines

Question 6

Question

OVERVIEW OF HOW THE ENGINE WORKS AND CREATES POWER

3.1 - Working Principles of Engines

Answer 6

• Fire needs air, We need air, Engines need air.
• Engines are just like us as – they need oxygen to work why? Because fire needs oxygen to burn.
• If you cover a fire, it goes out because you starved it of oxygen.
• If you have ever used a wood stove or fireplace, you know when you open the vent to allow more air to come in, the fire will burn more. The same principle applies to an engine. Think of an engine like a fire that will burn as hot and fast as you let it.

3.1 - Working Principles of Engines

Question 7

Question

How an engine works, step by step, 1 - 6.

3.1 - Working Principles of Engines

Answer 7

1. Engine takes in a mixture of fuel and oxygen.
2. The mixture is compressed into a very small volume via the piston.
3. When compressed & at the appropriate time a spark is introduced.
4. This causes an explosion.
5. This results in a loud bang and a rapid expansion of gases.
6. The force of this explosion will always expand in the path of least resistance.

3.1 - Working Principles of Engines

Question 8

Question

How an engine works, step by step, 7 - 11.

3.1 - Working Principles of Engines

Answer 8

7. The force of least resistance is the piston.
8. The piston which compressed the mixture (charge) in the first place is forced away (power) from the head of the engine and down into the block.
9. The piston is connected to the crankshaft.
10. This is where lateral movement is converted into circular motion.
11. This exhausted charge is expelled out.

3.1 - Working Principles of Engines

Question 9

Question

What’s the machine and type of engine?

3.1 - Working Principles of Engines

Answer 9

Brush Cutter
2 Stroke Petrol Engine

Lateral movement converted into circular motion.

3.1 - Working Principles of Engines

Question 10

Question

What’s the machine and type of engine?

3.1 - Working Principles of Engines

Answer 10

Plate Compactor
4 Stroke Diesel Engine

Lateral movement converted into circular motion.

3.1 - Working Principles of Engines

Question 11

Question

What’s the machine and type of engine?

3.1 - Working Principles of Engines

Answer 11

Rotary Mower
4 Stroke Horizontal Petrol Engine

Lateral movement converted into circular motion.

3.1 - Working Principles of Engines

Question 12

Question

What’s the machine and type of engine?

3.1 - Working Principles of Engines

Answer 12

Cylinder Mower
4 Stroke Vertical Petrol Engine

Lateral movement converted into circular motion.

3.1 - Working Principles of Engines

Question 13

Question

Small Horticultural Engines differences

3.1 - Working Principles of Engines

Answer 13

• Two stroke or four stroke.
• They have very different constructions and operation.
• They use different fuel, ie Petrol, Petrol-oil, Diesel.
• The manufacturer specifies the fuel and no other fuel type may be used.

3.1 - Working Principles of Engines

Question 14

Question

What are the broad differences between Petrol and Diesel engines?

3.1 - Working Principles of Engines

Answer 14

• In the engine using petrol or petrol oil mix there is a spark introduced to ignite the fuel.
• In a diesel engine, a compression ignition system is used where an injector injects fuel so fuels cannot be substituted, as they will not ignite.

3.1 - Working Principles of Engines

Question 15

Question

Name some common Horticultural machines that use 4 stroke petrol engines.

list of 4

3.1 - Working Principles of Engines

Answer 15

Horticultural equipment that use four stroke petrol engines.
* Small garden tractor.
* Ride-on lawnmower.
* Pedestrian controlled lawnmower.
* Rotary cultivators.

3.1 - Working Principles of Engines

Question 16

Question

Name some common Horticultural machines that use 4 stroke petrol engines.

list of 5

3.1 - Working Principles of Engines

Answer 16

Horticultural equipment that use two stroke petrol engines.
* Hedge cutters.
* Chainsaws.
* Brush cutters.
* Strimmers.
* Leaf blowers/vacuums.

3.1 - Working Principles of Engines

Question 17

Question

4 stroke or 2 Stroke?

3.1 - Working Principles of Engines

Answer 17

Honda, have recently developed four stroke engines that will operate Strimmers & Flymo’s, that were generally regarded as 2 stroke engines.

3.1 - Working Principles of Engines

Question 18

Question

4 stroke or 2 Stroke?

3.1 - Working Principles of Engines

Answer 18

• Makita 4 stroke backpack petrol blower.
• Husqvarna 4 stroke strimmer, blower.
• Ryobi 4 stroke strimmer, blower.

3.1 - Working Principles of Engines

Question 19

Question

Why is it called an Internal Combustion Engine?

3.1 - Working Principles of Engines

Answer 19

The term internal combustion engine is so given because fuel is ignited and burned within a cylinder in a controlled and metered fashion.

3.1 - Working Principles of Engines

Question 20

Question

Why is it called an Internal Combustion Engine?

3.1 - Working Principles of Engines

Answer 20

• The term internal combustion engine is so given because fuel is ignited and burned within a cylinder in a controlled and metered fashion.
• A small explosion takes place and heat energy is transferred through the parts of the engine into mechanical energy.

3.1 - Working Principles of Engines

Question 21

Question

What is referred to as the Operating cycle in an Internal combustion engine?

3.1 - Working Principles of Engines

Answer 21

The operating cycle is a series of events that must occur in an Internal combustion engine to make it operate.

– Four stroke petrol operating cycle
– Four stroke diesel operating cycle
– Two stroke petrol operating cycle

3.1 - Working Principles of Engines

Question 22

Question

Can you name these engine components?

3.1 - Working Principles of Engines

Answer 22

Components of an engine
* Cylinder
* Piston
* Connecting Rod
* Timing Gears
* Cylinder Head
* Valves

3.1 - Working Principles of Engines

Question 23

Question

Can you name these engine components?

3.1 - Working Principles of Engines

Answer 23

Components of an engine
* Valves
* Cylinder head
* Piston
* Air filter
* Connecting rod (con rod)
* Crankshaft
* Cylinder
* Engine block

3.1 - Working Principles of Engines

Question 24

Question

What is the engine block?

3.1 - Working Principles of Engines

Answer 24

The engine block:
– is the main part of the engine. It houses the pistons, cylinders, crankshaft and other main parts of the engine.

3.1 - Working Principles of Engines

Question 25

Question

What is the Cylinder?

3.1 - Working Principles of Engines

Answer 25

Cylinder
– Basically a cylindrical pipe fitted in the block in which the piston runs.

3.1 - Working Principles of Engines

Question 26

Question

What is the Cylinder Head?

3.1 - Working Principles of Engines

Answer 26

Cylinder Head
– Is a cover which fits on top of the block and is bolted down to it. It forms a top to the cylinder and is sealed with the aid of a gasket.

3.1 - Working Principles of Engines

Question 27

Question

What is the Gudgeon Pin?

3.1 - Working Principles of Engines

Answer 27

Gudgeon pin
– This connects the piston to the con rod. It acts as a bearing for the con rod and pivots as the piston moves.

3.1 - Working Principles of Engines

Question 28

Question

What is the Connecting rod?

3.1 - Working Principles of Engines

Answer 28

Connecting Rod (Con Rod)
– This is sometimes referred to as the con rod for short; it connects the piston to the crankshaft via the small end and the big end bearings.

3.1 - Working Principles of Engines

Question 29

Question

Can you name these Engine crankshaft and Con Rod components?

3.1 - Working Principles of Engines

Answer 29

Engine crankshaft and Con Rod components
* Weight for balance to carry the engine through it’s cycle.
* Crank shaft
* Big End
* Con Rod
* Small End

3.1 - Working Principles of Engines

Question 30

Question

Can you name these Piston Assembly parts?

3.1 - Working Principles of Engines

Answer 30

Piston Assembly
* Piston Rings
* ID Mark
* Retaining Ring
* Connecting Rod Bolt
* Cap
* Self-locking nut
* Washer
* Matching marks
* Connecting Rod
* Piston pin
* Piston

3.1 - Working Principles of Engines

Question 31

Question

Can you name these Valve parts?

3.1 - Working Principles of Engines

Answer 31

Valve Parts
* Head
* Spring
* Rotator
* Retainer
* Pin
* Stem
* Seat

• Pin
• Slotted Disc
• Split Collar
• Combination Retainer & Lock

3.1 - Working Principles of Engines

Question 32

Question

What is the Crankshaft?

3.1 - Working Principles of Engines

Answer 32

Crankshaft
– This is the main shaft of the engine and is fitted in the block. It is by the crankshaft that power is transferred to whatever is being driven. The crankshaft, owing to its name, is cranked and it is here that linear movement of the piston is turned into circular movement, which is why we say the engine is turning over.

3.1 - Working Principles of Engines

Question 33

Question

What is the Camshaft?

3.1 - Working Principles of Engines

Answer 33

Camshaft
– This is the mechanism, which opens the valves at the correct time in the engine cycle, and itself is driven from the crankshaft. It is also mounted in the cylinder head of larger engines and in the block of smaller engines. Both valves will be in the same position in an engine, a given engine that is in either the head or the block not one in the head and one in the block.

3.1 - Working Principles of Engines

Question 34

Info graphic

Example of a Camshaft at work within an Internal Combustion Engine

3.1 - Working Principles of Engines

Answer 34

3.1 - Working Principles of Engines

Question 35

Question

What is the Inlet Valve?

3.1 - Working Principles of Engines

Answer 35

Inlet valve
– What is a valve? A valve is an assembly or a mechanism, which controls the flow of a fluid or a liquid. Because a fluid is defined as something that flows, valves can control both liquids and gases. The inlet valve in an engine is housed in the cylinder head of larger engines and in the block of smaller engines. It opens at the correct time of the engine cycle to allow a new charge of air and fuel mix into the cylinder to support combustion.

3.1 - Working Principles of Engines

Question 36

Question

What is the Exhaust Valve?

3.1 - Working Principles of Engines

Answer 36

Exhaust Valve
– The exhaust valve is also housed in the head of larger engines and in the block of smaller engines. It too opens at the correct time of the engine cycle to allow the engine to expel a charge of exhausted gases.

3.1 - Working Principles of Engines

Question 37

Question

Name these Valve Gear parts.

3.1 - Working Principles of Engines

Answer 37

Valve Gear parts
* Rocker Arm
* Valve Spring
* Valve
* Pushrod
* Tappet
* Cam

Two to four valves per cylinder.
Cams which operate the rocker arm which causes the valves to open are mounted on the camshaft.

3.1 - Working Principles of Engines

Question 38

Question

Two different Valve Gear types. What are they called.

3.1 - Working Principles of Engines

Answer 38

• Push Rod Valve Gear
• Overhead Camshaft

3.1 - Working Principles of Engines

Question 39

Question

What is the Flywheel?

3.1 - Working Principles of Engines

Answer 39

Flywheel
– This is connected to the crankshaft and is used for balance of the engine and also for weight to carry the engine through it’s strokes until it fires again. If the engine has electric start the ring gear is fitted on the flywheel so the starter motor can start the engine.

3.1 - Working Principles of Engines

Question 40

Question

What is the Spark Plug?

3.1 - Working Principles of Engines

Answer 40

Spark Plug
– This is an electrode which is highly insulated and is screwed into the cylinder head. It is connected to a power source in the engine via a highly insulated lead or cable. The engine generates an extremely high voltage in this power supply unit at the correct time in the cycle, which causes a spark to jump across the electrode causing the petrol and air mix to explode in the cylinder.

3.1 - Working Principles of Engines

Question 41

Question

What is the Injector?

3.1 - Working Principles of Engines

Answer 41

Injector
– This is used in a diesel engine and also screws into the cylinder head in place of the spark plug. It vaporises the liquid flowing through it at high pressure (2500 psi).

3.1 - Working Principles of Engines

Question 42

Question

What is the Sump?

3.1 - Working Principles of Engines

Answer 42

Sump
– This is usually at the base of the engine and is where the oil for lubricating the engine is stored.

3.1 - Working Principles of Engines

Question 43

Question

What is the Air Filter?

3.1 - Working Principles of Engines

Answer 43

Air Filter
– This is where the air being drawn into the engine to support combustion is filtered to remove all impurities.

3.1 - Working Principles of Engines

Question 44

Question

What is the Fuel Tank?

3.1 - Working Principles of Engines

Answer 44

Fuel Tank
– The fuel tank is usually mounted on the machine close to the engine or indeed in a lot of cases directly on the engine itself. The tank is usually manufactured from steel or PVC and in some cases has a tap fitted on to it so the fuel supply can be switched off.

3.1 - Working Principles of Engines

Question 45

Question

What is the Injection Pump?

3.1 - Working Principles of Engines

Answer 45

Injection Pump
– Fitted to a diesel engine to pressurise the diesel to approximately 2500psi for the purpose of combustion.

3.1 - Working Principles of Engines

Question 46

Question

What is the Throttle?

3.1 - Working Principles of Engines

Answer 46

Throttle
– The throttle is connected to either the injector pump on a diesel engine or the carburettor on a petrol engine to control the speed of the engine.

3.1 - Working Principles of Engines

Question 47

Question

What is the Choke?

3.1 - Working Principles of Engines

Answer 47

Choke
– Fitted to a petrol engine to aid starting from cold by letting a much richer fuel/air mix be drawn into the engine by the piston.

3.1 - Working Principles of Engines

Question 48

Question

What is the Governor?

3.1 - Working Principles of Engines

Answer 48

Governor
– This helps to regulate the speed of the engine at a pre set speed when it comes under load by allowing in more fuel and similarly as the engine speeds up when the load is shed it cuts the amount of fuel allowed into the engine.

3.1 - Working Principles of Engines

Question 49

Question

What is the Carburettor?

3.1 - Working Principles of Engines

Answer 49

Carburettor
– This unit is fitted to a petrol engine and is where the petrol and air to support combustion are mixed in the venturi (narrowing tube or passage) before being drawn into the engine.

3.1 - Working Principles of Engines