Soak the metal for a certain period to ensure a uniform temperature. ✓
Cool the metal at a certain rate to room temperature. ✓ (3)
3.2 Quenching mediums:
Water ✓
Brine✓
Liquid salts ✓
Oil ✓
Soluble oil and water ✓
Sand ✓
Molten lead ✓
Air ✓
Lime ✓ (Any 3 x 1) (3)
3.3 Annealing:
To relieve internal stresses of the steel ✓
Soften steel to make machining possible ✓
Make steel ductile ✓
Refine grain structure ✓
Reduce brittleness ✓ (Any 1 x 1) (1)
3.4 Carbon steels:
Low carbon steel ✓
Medium carbon steel ✓
High carbon steel ✓ (3)
3.5 Iron-carbon equilibrium diagram:
Percentage carbon / carbon content ✓
Temperature in °C ✓
AC3 line / Higher critical temperature ✓
AC1 line / Lower critical temperature ✓ (4)
[14]
QUESTION 4: MULTIPLE-CHOICE QUESTIONS (SPECIFIC) 4.1 C ✓(1) 4.2 C ✓(1) 4.3 D ✓(1) 4.4 B✓(1) 4.5 C ✓(1) 4.6 C✓(1) 4.7 B✓(1) 4.8 A ✓(1) 4.9 C ✓(1) 4.10 A ✓(1) 4.11 A ✓(1) 4.12 D✓(1) 4.13 C ✓(1) 4.14 D ✓(1) [14]
QUESTION 5: TOOLS AND EQUIPMENT (SPECIFIC) 5.1 Compression tester labels:
Pressure gauge/Pressure meter ✓
Pressure release valve ✓
Air hose/Pipe/Flexible pipe ✓
Spark plug connector/Adapter ✓(4)
5.2 Function of Cylinder Leakage Tester:
To check where the combustion chamber/cylinder leaks gases ✓ during compression stroke/power stroke. ✓
To determine the percentage ✓ pressure loss ✓ from the combustion chamber. (Any 1 x 2) (2)
5.3 Cylinder leakage test procedure:
Turn the crank shaft until both valves, on the cylinder to be tested, are closed. ✓
Remove the HT leads / spark plugs ✓
Connect the spark plug adaptor (tester) to the spark plug hole. ✓
Lock the crankshaft pulley so that it cannot turn. ✓
Couple the compressed air pipe to the tester and calibrate the tester. ✓
Couple the spark plug adapter hose to the cylinder leakage tester. ✓
Note the results and location of gas leakage occurring in the combustion chamber. ✓ (Any 6 x 1) (6)
5.4 Exhaust gas analyser:
Hydrocarbon (fuel and oil vapour) / HC ✓
Carbon dioxide / CO2 ✓
Sulphur dioxide / SO2 ✓ (Any 2 x 1) (2)
5.5 Exhaust gas analysis test precautions:
Always calibrate the exhaust gas analyser with the pick-up hose removed. ✓
The pick-up hose must not be stepped on or restricted in any way. ✓
The pick-up hose connections must be airtight. ✓
The vehicle being tested should have no leaks in the exhaust, manifolds or vacuum systems. ✓
Must be conducted in a well-ventilated area.✓
Take good care when handling the equipment. ✓ (Any 3 x 1) (3)
5.6 Function of Turn-tables: To make it possible ✓ to turn the front wheels in and out / side to side ✓ when checking the wheel alignment angles. (2) 5.7 Use of optical alignment gauge: To measure / check the toe-in and toe-out of the vehicle. ✓ (1) 5.8 Functions of OBD scanner:
Scan for faults (diagnostics). ✓
Programme the ECU. ✓
Reset fault codes. ✓
Programme the keys to vehicle's ignition system. ✓ (Any 3 x 1) (3)
By fitting balance mass pieces to the crank webs. ✓
By removing metal from the crank webs. ✓
By arranging the crank pins of the crankshaft. ✓ (Any 2 x 1) (2)
6.2 Crankshaft balancing: 6.2.1 Dynamic balancing: Balancing in all directions✓ while crankshaft is rotating. ✓ (2) 6.2.2 Reciprocating mass: The mass of the pistons, gudgeon pins ✓ and the upper third of the connecting rod. ✓(2) 6.3 Features to improve engine balance:
Connecting rods and pistons are kept as light as possible / static balanced. ✓
Flywheel is carefully balanced. ✓
Counterweights on the crankshaft. ✓
The firing order is reconfigured. ✓ (4)
6.4 Types of vibration dampers:
Friction face-type ✓
Combined rubber and friction disc ✓
Rubber type ✓
Inertia ring type ✓ (Any 2 x 1) (2)
6.5 Different types of cylinder arrangements:
Inline type / Straight arrangement ✓
V-type ✓
W-type / double-V type ✓(3)
6.6 Three-cylinder inline engine: Marking: Labelling power impulse angle 120°. ✓ Drawing position of crankpins. ✓ Numbering of crankpins. ✓ (3) 6.7 Types of superchargers:
Roots ✓
Twin-screw ✓
Centrifugal and ✓
Vane ✓ (Any 3 x 1) (3)
6.8 Advantages of using a turbocharger:
More power is obtained from an engine with the same engine capacity. ✓
A turbocharger is driven by the exhaust gases of the engine and therefore there is no power loss✓
It gives improved fuel consumption in proportion to engine capacity. ✓
The effect of height above sea level on power is eliminated.✓
Improve volumetric efficiency. ✓ (Any 3 x 1) (3)
6.9 Turbocharger:
Intercooler/air cooler ✓
Compressed air flow ✓
Turbine/Turbine housing/Turbocharger ✓
Exhaust gas flow/exhaust system/exhaust manifold✓ (4)
[28]
QUESTION 7: FORCES (SPECIFIC) 7.1 Terms: 7.1.1 Power: Power is the rate ✓ at which work is done. ✓ 7.1.2 Compression Ratio: It is the ratio between the total volume of a cylinder when the piston is at bottom dead centre (BDC) ✓ to the volume in a cylinder when the piston is at top dead centre (TDC).✓ (2) 7.2 Calculation of compression ratio: 7.2.1 Swept volume:= πD2 x L 4 π72 x 7.5 4 SV = 288,63 cm
7.2.3 New bore diameter: Compression ratio = SV +CV CV = SV + 1 CV SV = CV(CR 1) = 33,96(10 - 1) SV = 305,64 cm3 SV =πD2 x L 4 Diameter =√SV x 4 π x L D = 305,64 4 π x 7,5 D = 7,203 cm D = 72,03 mm (6)
7.3 Power calculations: 7.3.1 Torque: Torque = Force x Radius = (25 x 10) x 420 1000 = 250 x 0,42 = 105 N.m
7.3.2 Indicated power: P = 900kPa = 900 x 103Pa L = 86mm = 86 = 0.086m 1000 D = 84mm = 84 = 0,084m 1000 A = π x D2 4 = π x 0.0842 4 = 5,54 x 10-3 m2
OR A = π x D2 4 = π x 842 4 = 5541,77mm2 =5541,77 x 10-6m2
N = 2000r/min = 2000 = 16,667 power stroke/sec 60 x 2 n = 4 cylinders
IP = PLANn = (900 x 103) x 0,086 x 5541,77 x 10-6 x 16,667 x 4 = 28596W = 28,60 kW
OR N = 2000r/min =2000= 33,333 r/sec 60 n = 4/2 = 2 power strokes IP = PLANn = (900 x 103) x 0,086 x 5541,77 x 10-6 x 33.333 x 2 = 28600W = 28,60 kW (8)
7.3.3 Brake power: Brake Power = 2πNT = 2 x π x 2000 x 105 60 = 21991,149 W = 21,99 kW (3)
7.3.4 Mechanical efficiency: Mechanical efficiency = BP x 100 IP = 21.99 x 100 28.60 = 76.89% (NO UNIT, NO MARK FOR FINAL ANSWER) (2) [32]
QUESTION 8: MAINTENANCE (SPECIFIC) 8.1 Cooling system pressure test: 8.1.1 Repair or replace water hose or clamp. ✓(1) 8.1.2 Cylinder head gasket blown. / Cylinder head warped. ✓(1) 8.1.3 Replace Welch or core plug. ✓(1) 8.1.4 Replace radiator cap with suitable replacement. ✓(1) 8.2 Function of the radiator cap:
Regulates the pressure in the cooling system. ✓
Allows coolant to return to the radiator from the expansion tank. ✓
The radiator cap seals / close the cooling system. ✓ (Any 2 x 1) (2)
8.3 Exhaust gas readings causes: 8.3.1 Possible causes of high carbon monoxide (CO) reading:
Too rich mixture ✓
Ignition misfire✓
Dirty or restricted air filter ✓
Improper operation of the fuel delivery system. ✓
Faulty thermostat / stuck in open position or coolant sensor ✓
Non-functioning PCV valve system ✓
Catalytic converter not working ✓ (Any 2 x 1) (2)
8.3.2 Possible causes high nitrogen oxide (NOx) reading:
Lean fuel mixture ✓
Improper spark advance ✓
Malfunctioning EGR valve ✓
Malfunctioning catalytic converter ✓ (Any 2 x 1) (2)
8.3.3 Possible causes high oxygen (O2) reading:
Too lean air-fuel ratio ✓
Ignition problems ✓
Vacuum leaks✓
Malfunctioning catalytic converter ✓ (Any 2 x 1) (2)
8.4 Safety requirements when setting up the oil tester:
Ensure the tester can read the expected pressures of the engine. ✓
Clean the sender unit area before fitting the tester. ✓
Ensure that the rubber hoses of the tester are not perished.✓
Keep the tester away from moving engine parts when conducting the test.✓ (Any 3 x 1) (3)
Manual – Gears selected manually with gear lever. ✓ Automatic – Gears selected automatically by the gearbox. ✓ (Any 1 x 2) (2)
9.2 Function of torque converter:
Multiplies engine torque automatically according to road and engine speeds✓
Transfers drive from the engine to the transmission. ✓
Acts as a Flywheel to keep the engine turning during the idle strokes.✓
Slips during initial acceleration and while stopping to prevent stalling.✓
Dampens torsional vibrations of the engine✓
Drives the Transmission oil pump.✓ (Any 2 x 1) (2)
9.3 Lockup clutch: To overcome slip✓ that occurs inside the torque converter. ✓ (2) 9.4 Stall speed:
The condition when the impeller of a torque converter rotates at maximum speed ✓ and the turbine is almost stationary.✓
When the pump has reached the highest velocity ✓ and the turbine is at stall (standing still). ✓
When the vehicle is stationary✓ just before it starts moving / while the engine is idling. ✓ (Any 1 x 2) (2)
9.5 Single epicyclic gear system: 9.5.1 Epicyclic gear train:
Sun gear✓
Annulus / Ring gear ✓
Planet gear ✓
Planet carrier ✓ (4)
9.5.2 Advantages of an epicyclic gear train:
The input shaft and output shaft have the same axis of rotation. ✓
Load is distributed to several planetary gears.✓
Many transmission-ratio options from ONE or a combination of several gear trains.✓
Longer service life compared to traditional gearboxes for similar load. ✓
Epicyclic gearbox has the ability to transmit higher torque. ✓
It has less inertia. ✓
Used to obtain higher gear ratios.✓
Compact in size.
All the gears are constantly in mesh. ✓ (Any 2 x 1) (2)
9.6 Function of the valve body:
It detects the load ✓ and adjust the gear ratio according to the torque requirements.✓
It directs the oil pressure ✓ to the correct hydraulic actuator. ✓ (Any 1 x 2) (2)
9.7 Methods of cooling the automatic transmission oil:
By using a special oil cooler alongside the engine cooling radiator ✓ and circulating transmission fluid through it. ✓
Circulating transmission fluid ✓ through a radiator✓
The transmission oil sump ✓ is designed with fins to assist with cooling. ✓ (Any 1 x 2) (2)
[18]
QUESTION 10:SYSTEMS AND CONTROL (AXLES, STEERING GEOMETRY AND ELECTRICITY) (SPECIFIC) 10.1 Requirements of a well-planned steering mechanism: It must be …
light and easy to control. ✓
free from vibration and road shocks.✓
as direct as possible without needing too much driver attention or effort.✓
self-centring. ✓
able to operate without being unduly affected by the action of the suspension or braking systems.✓ (Any 3 x 1) (3)
10.2 Wheel alignment angles: 10.2.1 Function of Positive camber:
Less steering effort ✓
The vehicle mass being carried by the larger inner front wheel bearing. ✓ (Any 1 x 1) (1)
10.2.2 Function of Ackermann's angle: It allows for variable toe-out to the front wheels on turns. ✓(1) 10.3 Caster: 10.3.1 Wheel alignment angle: C Negative ✓ caster ✓angle (2) 10.3.2 Negative caster angle purpose: Negative caster ensures easier turning ✓ and provides better cornering to the vehicle. ✓ (2) 10.3.3 Caster angle labels: A. King pin / Steering axis ✓ B. Perpendicular line ✓ D. Centre line of kingpin / Steering axis ✓ (3) 10.4 Engine management system: 10.4.1 Function of sensor:
It detects the engine operating conditions. ✓✓
It gives the input information to the ECU. ✓✓ (Any 1 x 2) (2)
10.4.2 Function of actuators:
It gets the output information / signal from the ECU.✓✓
It makes the necessary adjustments. ✓✓ (Any 1 x 2) (2)
10.5 Requirements to make the catalytic convertor function effectively:
The convertor working temperature must not exceed 600 °C. ✓
Unleaded petrol must be used. ✓
Prevent persistent misfire. ✓
Prevent burnt engine oil from melting the ceramic monolith. ✓
The lambda sensor must function properly. ✓ (Any 2 x 1) (2)
10.6 Lambda sensor: The lambda sensor is fitted on the exhaust system. (1) 10.7 Adaptive speed control:
Maintain a speed as set by the driver.✓
Adapt the speed to maintain a safe distance from the vehicle in front. ✓
Provide a warning if there is a risk of a collision. ✓
Prevent driver fatigue. ✓
Improve fuel economy. ✓
A constant controlled speed setting prevents speeding fines. ✓ (Any 3 x 1) (3)
10.8 Diode: 10.8.1 Diode ✓ (1) 10.8.2 Function of the diode:
The function of the diode is used to change alternating current ✓ into direct current. ✓
It allows the current flow in the circuit in one direction only ✓ and blocks it from flowing in the opposite direction. ✓ (Any 1 x 2) (2)
10.9 Function of components in the alternator: 10.9.1 Rectifier: Converts alternating current (AC) to direct current (DC). ✓ (1) 10.9.2 Stator:
To provide a core ✓that concentrates the magnetic lines of force onto the stator windings. ✓
To provide a coil ✓ into which a voltage is induced which is used to charge the battery.✓
Converts the rotating magnetic field ✓ to electric current to charge the battery.✓ (Any 1 x 2) (2)
10.9.3 Rotor:
Provides a rotating ✓ electro-magnet. ✓
Induces an electric voltage ✓ into the stator windings. ✓
Fitted with slip rings ✓ to allow for a moving electrical connection. ✓ (Any 1 x 2) (2)
10.10 Functions of the check valve in the electric fuel pump:
It ensures the pressure in the fuel line is maintained. ✓
It allows the fuel to flow in one direction only from the fuel tank.✓ (2)