MOTOR EXERCISE: QUESTIONS ONE NAME:

1. List the four essential operations which occur over and over in any internal combustion engine.

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2. State the difference in the way the fuel/ air mixture is ignited in a diesel and petrol engine.’

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3. In a four stroke there is one power stroke for every cycle or _______ revolutions of the crankshaft.

4. If the camshaft timing gear has twice as many teeth on it as the crankshaft timing gear, how many turns would the crankshaft have to do, to open the exhaust valve once?

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5. From your answer to question 4 above, can you work out if the engine is a two-stroke or four-stroke design? Explain your answer!

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6. Work is the use of _____________ to overcome resistance.

7. Explain the meaning of power:

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8. Name the two most common types of chambers in an indirect injection system:

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9. Direct injection gives higher thermal efficiency with lower fuel consumption. (Circle the correct answer)

TRUE or FALSE

10. In timing a fuel injection pump, the principle is that fuel injection commences on the _____________ stroke just before _____________.

11. What is the main advantage of a turbo charger?

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Check your answers on the next page

MOTORS ANSWERS ONE

1. List the four essential operations which occur over and over in any internal combustion engine.
Induction
Compression
Combustion or Power
Exhaust

2. State the difference in the way the fuel/ air mixture is ignited in a diesel and petrol engine.
In a diesel the fuel/air is ignited at injection by the heat of the highly compressed air in the cylinder. In a petrol engine the fuel/air mix is ignited by an electrical spark from the ignition system and spark plug.

3. Two

4. If the camshaft timing gear has twice as many teeth on it as the crankshaft timing gear, how many turns would the crankshaft have to do, to open the exhaust valve once?
Two complete turns

5. From your answer to question 3 above, can you work out if the engine is a two-stroke or four-stroke design? Explain your answer!
The engine is a four-stroke, because in a two-stroke, the exhaust valve would have to open for every turn of the crankshaft.

6. Energy

7. The amount of work done or energy expanded in a given time.

8. Turbulence, pre-combustion.

9. True

10. Compression, Top Dead Centre

11. Fuel consumption is lower than a normally aspirated engine of the same power output.

MOTORS QUESTIONS TWO

1. Briefly describe what happens in each of the four strokes of a four-stroke cycle diesel engine:

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2. What keeps the engine turning between power strokes?

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3. How is the opening and closing of the valves timed with respect to the position and movement of the piston?

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4. What ignites the fuel at the beginning of the power stroke of a diesel engine?

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5. How is this ignition timed, in relation to the position of the piston?

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6. Name 6 components of a fuel system:

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7. Name 2 causes of fuel contamination:

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MOTORS ANSWERS TWO

1. Briefly describe what happens in each of the four strokes of a four-stroke cycle diesel engine

Induction: With the inlet valve open and the piston going down, fresh air is drawn into the cylinder.
Compression: With both valves shut and the piston rising, the fresh air charge is compressed in the cylinder.
Combustion or power: With both valves shut and the air compressed in the cylinder, diesel fuel is injected as a mist into the hot compressed air. It ignites and expands, driving the piston down.
Exhaust: With the exhaust valve open and the piston rising, the burnt gas is driven from the cylinder.

2. What keeps the engine turning between power strokes?
The mass of the rotating engine and flywheel.

3. How is the opening and closing of the valves timed with respect to the position and movement of the piston?
By means of gears or sprockets and chain between the crankshaft and camshaft.

4. What ignites the fuel at the beginning of the power stroke of a diesel engine?
The heat from the highly compressed air in the cylinder

5. How is this ignition timed, in relation to the position of the piston?
Injection is timed by the injector pump which is normally driven from the camshaft. This is driven by the timing gears from the crankshaft.

6. Tank, supply line, return line, fuel filters, lift pump, fuel pump, water separators, injectors

7. Condensation, bacterial action

MOTOR QUESTIONS THREE

1. Describe the operation of a diesel two-stroke engine. Pay particular attention to the four essential operations for an internal combustion engine and the movement of the piston.

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2. Complete the statement. “In a two-stroke diesel engine, standard valves, operated by____________________________ are used for the exhaust, but the air inlet is through ports around the bottom of the cylinder wall. Inlet ports are opened by _________________________

3. A diesel engine, operating at high speed with a turbo-charger running at close to 100 000 rpm, is quickly shut down:

(a) When the engine stops, will the turbo stop instantly? YES / NO

(b) The turbo is supplied with oil from the engine oil system. What happens to the oil feed to the turbo during this time?

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What will happen to the glowing exhaust heat in the turbo vanes, and what will happen to the bearings and oil after the engine has stopped? (Hint: Heat-Soaking!)

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(d) Suggest a better way of shutting down the engine.

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MOTOR ANSWERS THREE

1. Describe the operation of a diesel two-stroke engine. Pay particular attention to the four essential operations for an internal combustion engine and the movement of the piston.

Induction: With the exhaust valve open and the piston at bdc, the inlet ports at the bottom of the cylinder are uncovered. Air is forced into the cylinder by the blower, and it pushes the burnt gas past the exhaust valve into the exhaust.
Compression: With the exhaust valve closed, the piston rises from bdc, and covers the inlet ports. The piston continues to rise and compresses the air in the cylinder.
Combustion: Fuel is injected into the hot air and ignites, driving the piston down.
Exhaust: Before the piston reaches bdc, the exhaust valve opens and releases the burnt gas into the exhaust. A moment later the inlet ports are uncovered by the piston, and incoming air continues to drive burnt gas out on the next induction stroke.

2. Complete the statement. “In a two-stroke diesel engine, standard valves operated by the camshaft and cams are used for the exhaust, but the air inlet is through ports around the bottom of the cylinder wall. Inlet ports are opened by the movement of the piston down toward bdc.”

3.         A diesel engine, operating at high speed with a turbo-charger running at close to 100 000 rpm, is quickly shut down:

(a) When the engine stops, will the turbo stop instantly?            NO

(b) The turbo is supplied with oil from the engine oil system. What happens to the oil feed to the turbo during this time?

The oil feed will stop.

(c) What will happen to the glowing exhaust heat in the turbo vanes, and what will happen to the bearings and oil after the engine has stopped? (Hint: Heat-Soaking!) The heat in the glowing turbo will spread into the bearings, oil and oil seals, causing burning and bearing damage.

(d) Suggest a better way of shutting down the engine.
Reduce the engine speed to idle and allow the turbo to reduce speed and cool down slowly for some time. After a reasonable cool down time, the engine can be shut-down.