MARKING GUIDELINES

QUESTION 1: MULTIPLE-CHOICE QUESTIONS (GENERIC)
1.1 .B (1)
1.2 A (1)
1.3 D (1)
1.4 A / C (1)
1.5 A (1)
1.6 C (1) [6]

QUESTION 2: SAFETY (GENERIC)
2.1 First-aid applications to an open wound:

• Use surgical gloves.
• Do not remove anything that is stuck to the wound.
• Never use sticky plaster on the wound.
• Cover the wound with a clean, lint-free cloth.
• Avoid using any oily substances or lotions on wounds.
• If necessary, cool wounds with cold water.
• Apply pressure to prevent blood loss if necessary.
• Avoid contact with blood from patient.
• If the wound is on your arm, raise the arm above your head to stop the bleeding.
  (Any 2 x 1) (2)

2.2 Surface grinder: (Already switched on)

• Never leave the grinder unattended.
• Switch off the machine when leaving.
• Don’t try to stop revolving emery wheel with your hand.
• Don’t adjust the machine while working.
• Don’t open any guard while the machine is on.
• Do not force the grinding wheel on to the work piece.
• Approach the work piece slowly and evenly.
• Don’t clean the machine while working.
• Do not put hands near the work piece when grinder is in motion.
• Don’t clean or adjust the machine while working.
• Check for oil on the floor while working (spilling of cutting fluid on floor while working)
• Check that the grinding wheel is running evenly.
  (Any 2 x 1) (2)

2.3 Gauges calibrated:

• To ensure accurate readings.
• To prevent overloading.
  (Any 1 x 1) (1)

2.4 Finger protectors’ hazards on power driven guillotines:

• The finger protector prevents the hazards of getting the fingers cut by the blades.
• To be crushed by the hold-downs. (2)

2.5 Welding or flame cutting operation safety:

• An operator has been instructed on how to use the equipment safely.
• A workplace is effectively partitioned off.
• An operator uses protective equipment.
• Ensure that all equipment is in safe working condition.
• Ensure that here are no flammable materials around the welding area.
• Weld area must be well ventilated.
• Fire extinguisher must be in close proximity.
  (Any 2 x 1) (2)

2.6 Workshop layout:

• Product layout. (1)

[10]

QUESTION 3: MATERIALS (GENERIC)
3.1 File test:
3.1.1 Difficult (1)
3.1.2 Easy (1)
3.1.3 Difficult (1)
3.2 Heat treatment:

• A. – Grain growth.
• B. – Recrystallisation.
• C. – Recovery.
  (3)

3.3 Bending test:

• Bend the test piece through a specific angle or around a mandrel or bar, having a defined radius, until a rupture in the metal occurs.
• Place the material in a vice and bend it then observe the ductility of the material.
  (Any 1 x 3) (3)

3.4 Purpose of case hardening:

• Creates a hard surface with a tough core. (2)

3.5 Quenching media for hardening:

• Water
• Brine (saltwater)
• Oil
• Soluble oil and water
• Nitrogen air-infused air 
  (Any 3 x 1) (3)

[14]

QUESTION 4: MULTIPLE-CHOICE QUESTIONS (SPECIFIC)
4.1 C (1)
4.2 B (1)
4.3 C (1)
4.4 A (1)
4.5 B (1)
4.6 D (1)
4.7 B (1)
4.8 D (1)
4.9 A (1)
4.10 C (1)
4.11 A (1)
4.12 D (1)
4.13 D (1)
4.14 B (1)
[14]

QUESTION 5: TOOLS AND EQUIPMENT (SPECIFIC)
5.1 Compression test: (Please note that if one step is missing and others still follow the sequence, marks can still be allocated accordingly) 5.1.1 – 5.1.4

• Completely open the throttle valve. (1)
• Crank the engine until maximum pressure is reached (normally 4 to 10 revolutions)/needle stops moving. (1)
• Read the pressure that the piston created, off the gauge. (1)
• Move on to the next cylinders/Compare the readings of all the cylinders to the manufacturer’s specification’s readings/Compare readings with each other. (1)

5.2 Cylinder leakage tester:
5.2.1 Labelling:

• A - Leakage meter / gauge
• B - Control valve
• C - Flexible hose / pipe / tube
• D - Spark plug connector / adaptor (4)

5.2.2 Unit of measure:

• Percentage or % (1)

5.3 Exhaust gas analyser:

• Water trap
• Paper filter
• Condenser
  (Any 2 x 1) (2)

5.4 Set up of the on-board diagnostics (OBD) scanner:

• Plug the on-board diagnostics (OBD) scanner into the connector.
• Turn on the ignition but do not start the car.
• Enter the vehicle information as required by the scanner.
• Select correct system to scan (diagnostics)
  (Any 3 x 1) (3)

5.5 Wheel balancer:
5.5.1 Wheel balancer (1)
5.5.2 Function of the wheel balancer:

• To balance wheels / statically / dynamically. (1)

5.5.3 Safety feature:

• Wheel safety cover / guard / hood (1)

5.6 Wheel alignment angles:

• Caster
• Camber
• King pin inclination (KPI) / steering axis (3)

5.7 Wheel alignment precautions:

• Ensure the wheels are in a straight-ahead position
• Ensure the steering box is on its high spot.
• Centralise the steering wheel.
• Lock the steering wheel in place.
• Lock the brake pedal.
• Check tire and rim condition.
• Check tyre pressure and size.
• Calibrate / zero the equipment before it is fitted to the wheels.
  (Any 3 x 1) (3)

[23]

QUESTION 6: ENGINES (SPECIFIC)
6.1 Crankshaft firing order:

• To overcome the twisting effect of the power stroke on the crankshaft.
• To reduce vibrations on the crankshaft.
• Increase the lifespan of the crankshaft.
• To improve engine cooling evenly throughout the engine.
  (Any 3 x 1) (3)

6.2 Crankshaft dynamic imbalance:

• Fit balance mass pieces to the crank webs.
• Remove metal from the crank webs.
• Arrange the crank webs on opposite sides of the crank pins.
• Add a vibration damper.
  (Any 2 x 1)  (2)

6.3 Engine vibration:

• The varying quantity of torque / low compression produced on power strokes.
• The crankshaft alternately winding up and releasing as it rotates.
• The crankshaft also has its own natural frequency of vibration.
• The coinciding of different dynamic imbalances could produce excessive vibration called resonance.
• The torsional/twisting effect of the power strokes upon the crankshaft.
• The crankshaft is not statically balanced.
• The crankshaft is not dynamically balanced.
• The flywheel is not statically balanced.
•  The flywheel is not dynamically balanced.
• The reciprocating mass is not balanced.
• Faulty vibration damper.
• Engine misfire.
• Incorrect air/fuel ratio.
• Improper tightened / loose engine components.
• Worn parts.
  (Any 4 x 1)(4)

6.4 Power Impulses:
6.4.1 180° (1)
6.4.2 144° (1)
6.4.3 120° (1)
6.4.4 90° (1)
6.5 Roots supercharger:
6.5.1 Labels:

• A – Casing / housing
• B – Air inlet / fill side
• C – Rotor  (3)

6.5.2 Operation of the Roots supercharger:

• The engine drives the rotors by means of gears, belt or a chain.
• Two symmetrical rotors spin.
• Trapped air, between the rotors and casing, is pushed from the inlet side to the discharge side.
• Large quantities of air move into the intake manifold.
• This creates increased pressure in the cylinder. (5)

6.6 Variable geometry turbocharger:
6.6.1 Function of intercooler:

• Intercooler is used to cool air that has been compressed by a turbocharger
• It reduces the volume and increases the density of the air.
• Improving volumetric efficiency.
  (Any 1 x 2) (2)

6.6.2 Function of vanes:

• Vanes alter the air flow path of the exhaust gases to optimize the turbine speed. (2)

6.7 Advantages of a supercharger over a turbocharger:

• Does not suffer lag.
• It is more efficient at lower r/min.
• Simpler installation.
• Cheaper to service and maintain.
• Does not always need an intercooler.
• No special lubrication required.
  (Any 3 x 1) (3)

[28]

QUESTION 7: FORCES (SPECIFIC)
7.1 Definitions:
7.1.1 Brake power:

• Brake power is the useable power / actual power / output power developed at the flywheel or at the drive wheels. (2)

7.1.2 Torque:

• Torque is the twisting effort / force on a shaft or wheel.
• Torque is the twisting effort / force measured over the applied radius.
  (Any 1 x 2) (2)

7.2 Indicated power diagram:

• Compression stroke - pressure rise / increase.
• Power stroke - pressure drop / decrease. (2)

7.3 Calculations:
7.3.1 V1 - Clearance volume (1)
7.3.2 V2 - Swept volume (1)
7.3.3 Cylinder volume:
330 ml = 330 cm³
Total cylinder volume = V1 + V2
= 39 + 330
= 369 cm³ (3)

7.3.4 Bore diameter in mm:

(5)
7.3.5 Compression ratio:

• CR = Total cylinder volume/Clearancevolume
  = 369/39
  = 9.46
  = 9,5 : 1 (2)

7.4 Methods to lower the compression ratio:

• Fit thicker gasket between cylinder block and cylinder head.
• Fit pistons with suitable lower crowns.
• Fit crankshaft with shorter stroke.
• Fit suitable shorter connecting rods.
• Re-sleeve to a smaller bore size.
• Fit a shim between the cylinder head and engine block.
  (Any 2 x 1) (2)

7.5 Calculations:
7.5.1 Torque:

• BP = 2πNT/60
  T = BP/2π N
  =   48 000x 60   
    2 x π x 6 500
  = 70,52 N.m  (4)

7.5.2 Indicated power in kW:

• Lx A = Volume
  = 580,7 cm³
  = 580,7x10^-6 m³
  N = 6 500/60x1
  = 108,33 power stroke/sec
• IP = PLANn
  = 450 x10³ x 580,7x10^-6 x 108,33 x 2
  = 56 618,25 W
  = 56,62 kW (6)

7.5.3 Mechanical efficiency:

• Mechanical Efficiency (η ) = BP/IP x100
  = 48/56,62 x 100
  = 84,78 % (2)

[32]

QUESTION 8: MAINTENANCE (SPECIFIC)
8.1 Low CO₂ exhaust gas reading:
8.1.1 Possible causes:

• Too rich air/fuel mixture.
• Ignition misfire / Blown cylinder head or block.
• Dirty or restricted air filter.
• Improper operation of the fuel delivery system / Excessive fuel delivery pressure.
• Faulty thermostat or coolant sensor.
• Faulty PCV valve system.
• Catalytic converter not working.
• Exhaust system leaks
  (Any 2 x 1) (2)

8.1.2 Corrective measures:
Note: The answer for 8.1.2 must correspond with the causes mentioned in 8.1.1.

• Reset fuel mixture
• Correct cause of misfire / Replace cylinder head or block.
• Replace air filter.
• Correct fuel delivery system pressure.
• Repair or replace thermostat or coolant sensor.
• Repair PCV system.
• Repair or replace catalytic converter.
• Repair exhaust system.
  (Any 2 x 1) (2)

8.2 Indicate lean air/fuel mixture:

• High oxygen (O₂).
• High carbon dioxide (CO₂).
• High nitrogen oxide (NO_x).
  (Any 2 x 1) (2)

8.3 Cylinder leakage test:
8.3.1 Hissing sound at the exhaust pipe:

(2)
8.3.2 Bubbles in the radiator water:

(2)

8.4 Engine temperature:

• To allow the expansion of the components to obtain accurate readings. (2)

8.5 Fuel pressure test:
8.5.1 Replace fuel filter (1)
8.5.2

• Cracked fuel line
• Restricted / blocked fuel line
  (Any 1 x 1) (1)

8.5.3

• Clean the strainer
• Replace the strainer
  (Any 1 x 1) (1)

8.5.4

• Incorrect / Low voltage to the fuel pump
• Pump speed is slow
• Pump is not operational
  (Any 1 x 1)   (1)

8.6 Oil pressure test:

• Oil pressure when engine is idling.
• Oil pressure when engine is cold.
• Oil pressure when engine is hot.
• Oil pressure when engine is at high revolutions.
  (Any 3 x 1) (3)

8.7 Radiator cap pressure test:

• Obtain the radiator cap's opening pressure specifications (stamped on the cap).
• Install the cap onto the adapter of the cooling system pressure tester.
• Pump up the tester while watching the pressure gauge.
• Note the reading when the pressure is released. (4)

[23]

QUESTION 9: SYSTEMS AND CONTROL (AUTOMATIC GEARBOX) (SPECIFIC)
9.1 Torque converters:
9.1.1 Torque converter labels:

1. Turbine
2. Casing / housing
3. Pump / Impeller
4. Turbine shaft / output shaft
5. Stator (5)

9.1.2 Functions of torque converters:

• 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.
• Wheel spin is greatly reduced.
• Drive the transmission oil pump.
• Contributes toward smooth gear changing.
  (Any 3 x 1) (3)

9.1.3 Maximum torque multiplication:

• When there is the largest speed difference between the impeller and turbine.
• Maximum torque multiplication occurs at rest, as the vehicle just starts to move.
  (Any 1 x 2) (2)

9.2 Epicyclic gear train: (forward overdrive)

• The sun gear is locked with the planet carrier as driving member and the annulus as driven component.
• The annulus is locked with the planet carrier as driving member and the sun gear is the driven component.
  (Any 1 x 3) (3)

9.3 Gearshift lever positions:
9.3.1 P – park (1)
9.3.2 R – reverse (1)
9.3.3 D – drive (1)
9.4

• P
• N (2)

[18]

QUESTION 10: SYSTEMS AND CONTROL (AXLES, STEERING GEOMETRY AND ELECTRONICS) (SPECIFIC)
10.1 Reasons for wheel alignment:
To achieve:

• desirable steering / Drive with least resistance.
• easier steering control.
• better tracking.
• minimal vibrations.
• even road-holding.
• increase tyre life.
• Checking of the camber angle.
• Checking of the kingpin inclination.
• Checking of the castor angle.
• Checking of the toe-out / toe-in.
• Less fuel consumption.
  (Any 3 x 1) (3)

10.2 Camber:
10.2.1 Camber wear causes:

• Suspension misalignment.
• A bent strut.
• Dislocated strut tower.
• A weak or broken spring.
• A bent stub axle.
• Collapsed or damaged control arm bushings.
• Worn upper strut bearing.
• Bent control arms.
• Improper wheel alignment setting.
• Damaged / worn ball joints.
  (Any 4 x 1) (4)

10.2.2 Positive camber angle:

• Positive camber angle refers to the outward tilt of the top of the wheel. (2)

10.2.3 Camber adjustment:

• Camber is adjusted by means of a cam / wedge bolts or wedge plates (shims) on the suspension. (2)

10.3 Toe-in:

(3)
10.4 Effects of wheel imbalances:

• Wheel shimmy (wobble).
• Wheel bounce (hop).
• Uneven tyre wear.
• Premature wheel bearing failure.
• Rapid tyre wear.
• Increased friction between road surface and the tyre.
  (Any 2 x 1) (2)

10.5 Types of injectors:

• Solenoid injector
• Piezo injector (2)

10.6 Purpose of the diesel particulate filter:

• It is a filter that converts particulate matter or soot into ash. (2)

10.7 The headway sensor:

• The headway sensor detects an obstruction ahead of a vehicle.
• The headway sensor will send a signal to the ECU. (2)

10.8 The alternator:
10.8.1 Component:

• Stator (1)

10.8.2 Stator function:

• It provides a coil into which a voltage is induced,
• Converts the rotating magnetic field to electric current.
  (Any 1 x 2) (2)

10.8.3 Stator windings:

• Delta connected stator windings (2)

10.8.4 Stator windings:

• Star or Y connected stator windings (2)

10.9 Advantages of an electric fuel pump:

• Immediate/quicker supply of fuel when the ignition switch is turned on.
• Low sound during operation.
• Less discharge pulsation of fuel.
• Compact and light design.
• Able to prevent internal fuel leaks and vapour lock.
• Can be fitted within any location on the fuel line.
  (Any 3 x 1) (3)

[32]
TOTAL: 200