MECHANICAL TECHNOLOGY: AUTOMOTIVE
GRADE 12 
NSC EXAMS
PAST PAPERS AND MEMOS NOVEMBER 2018

MEMORANDUM 

QUESTION 1: MULTIPLE-CHOICE QUESTIONS (GENERIC) 
1.1 A ✔ (1)
1.2 C ✔ (1)
1.3 A ✔ (1)
1.4 B ✔ (1)
1.5 D ✔ (1)
1.6 A ✔ (1)

TOTAL QUESTION 1: [6]

QUESTION 2: SAFETY (GENERIC) 
2.1 Angle grinder: (Before using) 

• The safety guard must be in place before starting. ✔ 
• Protective shields must be placed around the object being grinded  to protect the people around. ✔ 
• Use the correct grinding disc for the job. ✔ 
• Make sure that there are no cracks in the disc before you start. ✔ 
• Protective clothing and eye protection are essential. ✔ 
• Check electrical outlets and cord/plugs for any damages. ✔
• Ensure that lockable switch is disengaged. ✔ 
• Ensure that the disc and the nut are well secured. ✔ 
• Ensure that the removable handle is secured. ✔ 
• Remove all flammable material from the area. ✔
• Secure the work piece. ✔ 
• (Any 2 x 1) (2) 

2.2 Welding goggles: 

• To protect your eyes against sparks ✔ 
• To protect your eyes against heat ✔ 
• To be able to see where to weld ✔ 
• To protect your eyes from UV rays / bright light ✔ 
• To protect your eyes from smoke ✔
• (Any 2 x 1) (2) 

2.3 PPE for Hydraulic press: 

• Overall ✔ 
• Safety shoes ✔ 
• Safety goggle ✔
• Leather gloves ✔ 
• Leather apron ✔
• Face shield ✔
• (Any 2 x 1) (2) 

2.4 Workshop layouts: 

• Process layout ✔ 
• Product layout ✔ (2) 

2.5 Employer’s responsibility regarding first-aid: 

• Provision of first-aid equipment ✔ 
• First aid training ✔ 
• First-aid services by qualified personnel ✔ 
• Any first aid procedures ✔ 
• Display first aid safety signs ✔ 
• First aid personnel must be identified by means of arm bands or  relevant personal signage ✔
• (Any 2 x 1) (2) 

TOTAL QUESTION 2: [10]

QUESTION 3: MATERIALS (GENERIC) 
3.1 Bending test:  

• Ductility ✔✔ 
• Malleability ✔✔ 
• Brittleness ✔✔ 
• Flexibility ✔✔
• (Any 1 x 2) (2) 

3.2 Heat-treatment:  
3.2.1 Annealing: 

• To relieve internal stresses ✔ 
• To soften the steel ✔ 
• To make the steel ductile ✔ 
• To refine the grain structure of the steel ✔ 
• To reduce the brittleness of the steel ✔
• (Any 2 x 1) (2) 

3.2.2 Case hardening: 

• To produce a wear resistant surface ✔ and it must be  tough enough internally ✔ at the core to withstand the  applied loads. 
• Hard case ✔ and tough core. ✔
• (Any 1 x 2) (2) 

3.3 Tempering process: 

• To reduce ✔ the brittleness ✔ caused by the hardening process. 
• Relieve ✔ strain ✔ caused during hardening process. 
• Increase ✔ the toughness ✔ of the steel. 
• (Any 1 x 2) (2) 

3.4 Factors for heat-treatment processes: 

• Heating temperature / Carbon content ✔
• Soaking (Time period at temperature) / Size of the work piece ✔
• Cooling rate / Quenching rate ✔ (3) 

3.5 Hardening of steel: 

• Steel is heated to 30 – 50°C above the higher critical temperature.  (AC3) ✔
• It is then kept at that temperature to ensure (soaking) that the whole  structure is Austenite. ✔ 
• The steel is then rapidly cooled by quenching it in clean water, brine  or oil. ✔ (3) 

TOTAL QUESTION 3: [14]

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

TOTAL QUESTION 4: [14]

QUESTION 5: TOOLS AND EQUIPMENT (SPECIFIC) 
5.1 Equipment: 
5.1.1 Compression tester ✔ (1) 
5.1.2

• A – Flexible piping / hose / tubing ✔
• B – Adaptor screw / Fitting / Attachment / Connector ✔
• C – Gauge ✔
• D – Pressure release valve ✔ (4) 

5.1.3 Compression Tester: 

• It measures the pressure created, ✔ when the piston is at top  dead centre on power stroke. ✔ (2) 

5.2 Cylinder leakage: 

• To check whether the engine leaks gases ✔ from the cylinder during the  compression stroke. ✔ (2) 

5.3 Gas Analyser: 

• To ensure ✔ an accurate reading. ✔ 
• o prevent ✔ a lean reading. ✔
• (Any 1 x 2 ) (2) 

5.4 Function of a computerized diagnostic scanner: 

• Scans all systems ✔ on the vehicle.
• Informs what adjustments can be made after diagnosis ✔
• (Any 1 x 1 ) (1) 

5.5 Bubble gauge camber procedure: 

• Mount the bubble gauge on to the straightened wheel ✔ 
• Zero the bubble gauge at the gauge zero scale ✔ 
• Take the reading on the camber scale ✔ 
• Do the same for the other wheel ✔ (4) 

5.6 Dynamic balance on wheels: 

• The plane of imbalance ✔ 
• The extent of the unbalancing forces ✔ 
• The sense of direction of these forces (clockwise or counter clockwise) ✔ 
• Determine the location of weight placement ✔ 
• Magnitude of the weights ✔ 
• The run-out of the tyre and wheel assembly ✔
• (Any 3 x 1 ) (3) 

5.7 Purpose of turn tables: 

• To make it possible to turn ✔ the front wheels in or out ✔ to check ✔ the  wheel angles. ✔ (4) 

TOTAL QUESTION 5: [23]

QUESTION 6: ENGINES (SPECIFIC) 
6.1 Static balancing of the crankshaft: 

• The crankshaft is in static when the mass in all directions ✔ from the centre  of rotation is equal while it is at rest. ✔ (2) 

6.2 Cylinder layouts: 
6.2.1 V - engine layout ✔ (1)
6.2.2 In line (straight) engine layout ✔ (1) 
6.3 Firing order in an engine:  

• By removing the tappet cover and determining which are intake  valves and which are exhaust valves ✔ 
• Rotating the engine in the direction in which it turns. ✔ 
• Watch the order in which one set of valves, inlet or exhaust  operates ✔ 
• This will give the order in which the inlet stroke or exhaust stroke  occurs ✔ 
• The power strokes occur in the same order ✔
  OR 
• Cylinder 1 must be at TDC on power stroke ✔ 
• Remove the distributor cap ✔ 
• Ensure to turn the engine in the correct direction of rotation ✔ 
• Determine the direction of rotation of the rotor ✔ 
• Trace the firing order by the HT leads ✔
• (Any 1 x 5 ) (5) 

6.4 Firing order of engines: 
6.4.1 Four cylinder in-line engine: 

• 1,3,4,2; or ✔ 
• 1,2,4,3 ✔
• (Any 1 x 1 ) (1) 

6.4.2 V6-cylinder engine: 

• 1,4,2,5,3,6 ✔ 
• 1,2,3,4,5,6 ✔ 
• 1,6,5,4,3,2 ✔ 
• 1,4,5,6,3,2 ✔
• (Any 1 x 1 ) (1)

6.5 Turbo charger: 
6.5.1 Turbocharger: 

• A – Compressor air inlet ✔
• B – Turbine housing ✔
• C – Turbine exhaust gas outlet ✔
• D – Turbine wheel ✔
• E – Turbine exhaust gas inlet ✔
• F – Compressed air outlet ✔
• G – Compressor wheel ✔ (7) 

6.5.2 Turbocharger advantages: 

• More power / speed / boost is obtained from an engine  with the same capacity ✔ 
• There is no power loss as the turbocharger is driven by  exhaust gasses ✔ 
• Improved fuel consumption ✔ 
• The effect of height above sea level is eliminated ✔ 
• Generally, cheaper than superchargers ✔
• Any ( 2 x 1) (2) 

6.6 Terminology: 
6.6.1 Boost: 

• Refers to the increase in manifold pressure ✔ that is generated  by the turbocharger in the intake that exceeds the normal  atmospheric pressure. ✔ (2) 

6.6.2 Turbo lag: 

• It is a delay ✔ between pushing on the accelerator and  feeling turbo kick in. ✔ or
• The time ✔ it takes the turbo charger to reach operating  speed. ✔
• (Any 1 x 2) (2) 

6.7 Purpose of waste gate: 

• It diverts exhaust gases ✔ away from the turbine wheel to regulate the  turbine speed ✔ and consequently boost pressure. (2) 

6.8 Oil cooler: 

• To cool (prevent overheating) the oil ✔ that lubricates the turbocharger  bearings and shaft. ✔ (2) 

TOTAL QUESTION 6: [28]

QUESTION 7: FORCES (SPECIFIC) 
7.1 Torque: 

• Torque is the twisting effort ✔ transmitted by a rotating shaft or  wheel. ✔ 
• Turning force applied ✔ over a centre of a round object. ✔
• (Any 1 x 2) (2) 

7.2 Clearance volume: 

• This is the volume of the space ✔ above the crown of the piston at TDC. ✔ (2) 

7.3 Method to increase compression ratio: 
Remove shims between the cylinder block and cylinder head. ✔ 

• Fit thinner cylinder head gasket. ✔ 
• Machine metal from cylinder head. ✔ 
• Skim metal from cylinder block. ✔ 
• Fit a piston with a higher crown. ✔ 
• Fit a crankshaft with a longer stroke. ✔ 
• Increase the bore of the cylinders. / bigger pistons. ✔
• (Any 2 x 1) (2) 

7.4 Calculation of compression ratio: 
7.4.1 

• Swept Volume = πD²  × L ✔ 
                               4
  =  π (7,5)²  8,0 ✔ 
           4 
  353,43 cm³ ✔  (3) 

7.4.2 

• Compression Ratio  = SV + CV
                                         CV 
  CV =   SV     
           CR - 1
  =  353,43
       8,5 1
  = 353,43
       7,5
  = 47,12 cm  ✔ (3) 

7.4.3 New compression ratio: 

• Sweptvolume  =  πD²  × L
                               4
  =  π7,8²  × 8  
         4
  = 382,27 cm  ✔
• New compression Ratio = SV + 1 
                                            CV
  = 382,27  + 1 
      47,12
  = 8,11 + 1:1
  = 9.11:1
  OR
• New compression Ratio  = SV + CV 
                                                 CV
  = 382.27 +  47.12
         47.12
  = 9.11:1 ✔(6) 

7.5 Calculations: Power: 
7.5.1 IndicatedPower = P × L × A  × N  × n 

• P = 1400 kPa
  L =  110  
       1000
  = 0,11 m 
• A =  πD²
           4   
  =  π0,10²
          4
  = 7,85 x 10^-3m² ✔ ✔
•  N = 3600 
         60 × 2
  = 30 r/s  ✔ ✔
  n 4 cylinders 
• IndicatedPower  = P × L  × A × N ×  n
  = [1400 × 10³] × 0,11 × [7,85 × 10^-3] × 30 × 4
  = 145068 W
  = 145,07 kW  (8)

7.5.2 T = F × r

• (75 × 10) × 0,45
  = 337,5N.m ✔
• Brake power = 2π × N × T
  = 2π × 60 × 337,5 ✔
  = 127234,5 W
  = 127,23 kW ✔ (4) 

7.5.3 Mechanicalefficiency  = BP 100%
                                               IP 

• = 127,23  × 100%
     145,07 00 %
  = 87,70%  ✔ (2) 

TOTAL QUESTION 7: [32] 

QUESTION 8: MAINTENANCE (SPECIFIC) 
8.1 Gas analyser: 

• Exhaust gasses ✔ 
• CO gasses ✔ 
• CO2 gasses ✔ 
• SO2 gasses ✔ 
• NOx gasses ✔ 
• HC gasses ✔ 
• O2 gasses ✔
• (Any 1 x 1) (1) 

8.2 Specification for gas analysis: 

•  % Hydrocarbon / HC ✔
• % Carbon monoxide / CO ✔
• % Carbon dioxide / CO2 ✔ 
• % Nitrogen oxide / NOx ✔ 
• % Sulphur dioxide / SO2 ✔
• (Any 3 x 1) (3) 

8.3 Cylinder leakage test: (Results) 

• Hissing noise at air intake ✔ 
• Hissing noise at exhaust pipe ✔ 
• Hissing noise in dipstick hole ✔ 
• Hissing noise under tappet cover ✔ 
• Bubbles in radiator water ✔ 
• Hissing noise at adjacent cylinders ✔
• (Any 2 x 1) (2) 

8.4 Cylinder Leakage test: (Causes) 

• Worn cylinders ✔ 
• Worn piston ✔ 
• Worn piston rings ✔ 
• Leaking inlet valve ✔ 
• Leaking exhaust valve ✔ 
• Leaking cylinder head gasket ✔ 
• Cracked cylinder head / block ✔
• (Any 2 x 1) (2) 

8.5 Compression test procedures: 

• Get the engine to normal operating temperature. ✔ 
• Disconnect the fuel supply and ignition system. ✔ 
• Remove spark plugs. ✔ 
• Fit the compression tester ✔ 
• Depress the throttle and crank the engine a few revolutions. ✔ 
• Record and compare the pressure reading for each cylinder with  manufacturers specifications. ✔ (6)

8.6 Reasons for low oil pressure: 

• Worn oil pump ✔ 
• Blocked oil pump screen/filter/strainer in the sump ✔ 
• Worn main, big-end and camshaft bearings ✔ 
• Blocked or restricted oil filter ✔ 
• Dirty or contaminated oil ✔ 
• Oil leaks ✔ 
• Too little oil in engine ✔
• Incorrect grade (viscosity) of oil ✔ 
• Pressure relief valve spring too weak or damaged ✔
• Plunger / Ball stuck in open position ✔ 
• Dirt stuck between ball and seat ✔
• (Any 2 x 1) (2) 

8.7 Cooling system pressure test: 

• Start engine and allow to heat up. Fit radiator pressure tester to  radiator. ✔ 
• Pressurize the cooling system according to manufacture’s  specification. ✔ 
• Watch the pressure for a while, if it drops there is a leak. ✔ 
• Make a visual check for leaks. ✔ 
• Install radiator cap to tester and pump tester, the cap should release  air at its rated pressure. ✔ 
• Check the rubber seal for cracks and damage. ✔ 
• Check the vacuum valve for free movement and operation. ✔ (7)

TOTAL QUESTION 8: [23]

QUESTION 9: SYSTEMS AND CONTROL (AUTOMATIC GEARBOX) (SPECIFIC) 
9.1 Differences between an automatic and manual gearbox: 

• There is no clutch pedal in a motor vehicle with an automatic gearbox. / There is a clutch pedal in a motor vehicle with a manual gearbox. ✔ 
• There is no need to change gears, the shifting of the gears happens  automatically. ✔ 
• Automatic transmission uses thin oil while manual gearbox uses  thicker oil. ✔ 
• Automatic transmission uses torque converter while manual gearbox  uses clutch assembly. ✔
• (Any 2 x 1) (2) 

9.2 Advantages of automatic gearbox: 

•  It reduces driver fatigue ✔ 
• It ensures great reduction of wheel spin under bad road conditions ✔
• The vehicle can be stopped suddenly without the engine stalling ✔ 
• The system dampens all engine torsional vibrations ✔ 
• Easier to drive (e.g. Disabled person with one leg) ✔ 
• (Any 2 x 1) (2) 

9.3 Torque converter: 
9.3.1 Torque converter function: 

•  Transfers engine torque to the transmission. ✔ 
• It multiplies the engine torque to the transmission. ✔ 
• Provides a direct-drive, or mechanical link from the  engine to the transmission. ✔ 
• The torque converter dampens all engine torsional  vibrations. ✔ 
• The torque converter acts as a flywheel. ✔ 
• (Any 2 x 1) (2) 

9.3.2 Parts: 

• A – One-way clutch / Turbine ✔
• B – Turbine / Impeller ✔
• C – Pump ✔
• D – Turbine shaft ✔
• E – Gearbox housing ✔ (5) 

9.4 Single epicyclic gear train: 

• Overdrive forward ✔ 
• Overdrive reverse ✔ 
• Gear reduction forward ✔ 
• Gear reduction reverse ✔ 
•  Direct drive ✔ 
• Neutral ✔ 
• (Any 5 x 1) (5)

9.5 Purpose of gear ratio in the gearbox: 

•  It is used in order to utilise the usable torque ✔ developed in a  relatively limited speed range of the engine over a greater road  speed range. ✔ 
•  Allows different speeds ✔ depending on the different loads. ✔
• (Any 1 x 2) (2) 

TOTAL QUESTION 9: [18]

QUESTION 10: SYSTEMS AND CONTROL (AXLES, STEERING GEOMETRY  AND ELECTRONICS) (SPECIFIC) 
10.1 Preliminary wheel alignment checks: 

• Kerb mass (tank full of petrol, spare wheel and tools) against the  manufacturer’s specifications. ✔ 
• Uneven wear on the tyre. ✔ 
• Tyre pressure. ✔ 
• Run-out on the wheels; check wheel nuts with torque wrench. ✔ 
• Correct preload on the wheel (hub) bearings. ✔ 
• Kingpins and bushes. ✔ 
• Suspension ball joints for wear, locking and lifting. ✔ 
• Suspension bushes for excessive free movement. ✔ 
• Steering box play and whether secure on chassis. ✔ 
• Tie-rod ends. ✔ 
• Sagged springs, this includes riding height. ✔ 
• Ineffective shock absorbers. ✔
• Spring U-bolts. ✔ 
• Chassis for possible cracks and loose cross-members. ✔ 
• Wheels must be balanced ✔ 
• Wheel alignment specifications ✔ 
• Drive shafts / CV-joints ✔
• (Any 5 x 1) (5) 

10.2 Caster 
10.2.1 Negative ✔ Caster ✔ (2) 
10.2.2 Parts: 

• A – Contact point of king pin centre line ✔ 
• B – King pin ✔
• C – Perpendicular line / vertical line / normal line ✔
• D – Negative caster angle ✔
• E – Centre line of king pin ✔
• F – Front of vehicle / Direction of wheel motion ✔
• G – Point of wheel contact / Wheel ✔ (7) 

10.2.3 Negative caster angle is the forward tilt ✔ of the kingpin at the  top, ✔ viewed from the side. ✔ (3) 
10.3 Toe-out: 
(3)
10.4 Purpose of the king pin inclination: 

• To bring the front wheels back to the straight-ahead position ✔ after  rounding a corner without any driver effort. ✔ 
• Reduce ✔ the scrub radius. ✔ 
• (Any 1 x 2) (2) 

10.5 Catalytic converter: 

•  Oxidation ✔ 
• Reduction ✔
• (Any 1 x 1) (1) 

10.6 Purpose of the speed control system: 

• The purpose of the speed control system is to control the throttle  opening ✔ and to keep the vehicle speed constant. ✔ (2) 

10.7 Advantage of speed control: 

•  Driver fatigue is reduced. ✔
• The set speed is controlled constantly. ✔
• Improved fuel consumption. ✔ 
• A consistently controlled speed helps to prevent speeding fines. ✔
• (Any 2 x 1) (2) 

10.8 Fuel pressure regulator: 

•  Fuel pressure regulator regulates the fuel pressure in relation to the  manifold pressure. ✔ (1) 

10.9 Output frequency of an alternator: 

•  Increase the turns of wire on the stationary coil. ✔ 
• Increase the magnetic fields. ✔ 
• Increase the rotational frequency at which the magnet rotates. ✔
• (Any 2 x 1) (2) 

10.10 Stator and stator windings: 

•  To provide a core which 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. ✔ 
• (Any 1 x 1) (1) 

10.11 Function of rotor assembly: 

•  Is to provide a rotating electro-magnet. ✔ (1)

TOTAL QUESTION 10: [32] 
TOTAL: 200d