Mechanical Technology Grade 12 NSC June 2024 Memo (English)

SENIOR CERTIFICATE EXAMINATIONS/ NATIONAL SENIOR CERTIFICATE EXAMINATIONS MECHANICAL TECHNOLOGY: AUTOMOTIVE MAY/JUNE 2024 MARKING GUIDELINES MARKS: 200 These marking guidelines consist of 19 pages. Copyright reserved Please turn over

Mechanical Technology: Automotive 2 DBE/May/June 2024 SC/NSC – Marking Guidelines QUESTION 1: MULTIPLE-CHOICE QUESTIONS (GENERIC) 1.1 A ✓ (1) 1.2 B ✓ (1) 1.3 A ✓ (1) 1.4 D ✓ (1) 1.5 C ✓ (1) 1.6 C ✓ (1) [6] Copyright reserved Please turn over

Mechanical Technology: Automotive 3 DBE/May/June 2024 SC/NSC – Marking Guidelines QUESTION 2: SAFETY (GENERIC) 2.1 First aid: • When illness occurs. ✓ • When an injury is sustained. ✓ • When an accident occurs. ✓ (Any 2 x 1) (2) 2.2 Bench grinder: A. A fire extinguisher should be readily available. ✓ B. Safety glasses must be worn. ✓ C. Maximum grinding wheel speed. ✓ D. Maximum distance between tool rest and grinding wheel. ✓ (4) 2.3 Drill press: • Never try to stop/hold the work piece by hand when the drill bit get stuck during drilling. ✓ • Don’t force a drill bit into the work piece. ✓ • Keep loose clothing and hair away from revolving parts. ✓ • Never leave the machine running if it is unattended. ✓ • Use a brush or wooden rod to remove chips from the drill. ✓ • Do not put hands near moving parts. ✓ • Never clean or adjust the machine while it is in motion. ✓ • Never try to stop the drill/chuck by hand. ✓ (Any 2 x 1) (2) 2.4 Surface grinder: • Never clean or adjust the machine while it is in motion. ✓ • Know how to stop the machine in an emergency. ✓ • Do not use excessive force when grinding the work piece. ✓ • Immediately report any dangerous defects of the machine. ✓ • Stop using defective machinery until it has been repaired by a qualified person. ✓ • Ensure that the grinding wheel is not submerged in coolant. ✓ • Never leave the machine running if it is unattended. ✓ • Do not put hands near moving parts. ✓ (Any 2 x 1) (2) [10] Copyright reserved Please turn over

Mechanical Technology: Automotive 4 DBE/May/June 2024 SC/NSC – Marking Guidelines QUESTION 3: MATERIALS (GENERIC) 3.1 Critical temperature: 3.1.1 Hardening: Above ✓ (1) 3.1.2 Tempering: Below ✓ (1) 3.1.3 Normalising: Above ✓ (1) 3.2 Machining test: • The chips heating colour ✓ • The chips curl ✓ (2) 3.3 Material tests: • Sound test ✓ • Bending test ✓ • Filing test ✓ • Hardness test ✓ • Density test ✓ • Weight measurement ✓ • Magnetic test ✓ • Visual inspection/observation ✓ • Scratch test ✓ (Any 3 x 1) (3) 3.4 Quenching methods: • Carburising ✓ • Nitriding ✓ • Cyaniding ✓ (Any 2 x 1) (2) 3.5 Heat treatment temperature: • Pyrometer ✓ • Crayons ✓ • Visually ✓ • Magnet ✓ (Any 1 x 1) (1) 3.6 Heat-treatment steps: • Heat the metal. ✓ • Soak the metal. ✓ • Cool the metal. ✓ (3) [14] Copyright reserved Please turn over

Mechanical Technology: Automotive 5 DBE/May/June 2024 SC/NSC – Marking Guidelines QUESTION 4: MULTIPLE-CHOICE QUESTIONS (SPECIFIC) 4.1 A✓ (1) 4.2 C✓ (1) 4.3 B✓ (1) 4.4 D✓ (1) 4.5 C✓ (1) 4.6 A✓ (1) 4.7 B✓ (1) 4.8 A✓ (1) 4.9 C✓ (1) 4.10 B✓ (1) 4.11 B✓ (1) 4.12 A✓ (1) 4.13 B✓ (1) 4.14 D✓ (1) [14] Copyright reserved Please turn over

Mechanical Technology: Automotive 6 DBE/May/June 2024 SC/NSC – Marking Guidelines QUESTION 5: TOOLS AND EQUIPMENT (SPECIFIC) 5.1 Compression tester: 5.1.1 Functions: A. To indicate the compression pressure. ✓ B. To reset the pressure gauge./Release the pressure from the tester. ✓ C. To fit the tester into the spark plug hole. ✓ (3) 5.1.2 Test battery voltage: • To ensure that the engine is able to swing ✓ at the correct speed. ✓ • To ensure maximum compression pressure ✓ is developed. ✓ • It is to ensure that the correct reading ✓ is obtained. ✓ (Any 1 x 2) (2) 5.1.3 Perform the wet test: • To check if the compression rings are worn. ✓ • To check for excessive wear between the piston/piston rings and cylinder wall. ✓ (2) 5.2 Cylinder leakage test: 5.2.1 Calibrate (zero): To obtain accurate readings. ✓ (1) 5.2.2 Piston at TDC: The cylinder should have minimal leaks on the compression stroke. ✓ (1) 5.2.3 Crankshaft is locked: Prevent the engine from turning during the test. ✓ (1) 5.3 Exhaust gasses: • Carbon monoxide (CO) ✓ • Carbon dioxide (CO2) ✓ • Oxygen (O2) ✓ • Hydrocarbon (HC) ✓ • Sulphur dioxide (SO2) ✓ (Any 4 x 1) (4) Copyright reserved Please turn over

Mechanical Technology: Automotive 7 DBE/May/June 2024 SC/NSC – Marking Guidelines 5.4 OBD-II scanner: 5.4.1 Specifications: • VIN ✓ • Make of the vehicle ✓ • Model of the vehicle ✓ • Engine type ✓ • System to be scanned ✓ (Any 2 x 1) (2) 5.4.2 Functions of OBD-II scanner: • Scan diagnostic trouble codes ✓ • Clear the trouble codes ✓ • Programme ✓ • Retrieve information ✓ (Any 2 x 1) (2) 5.5 Correcting dynamic wheel balancing: Place the weights indicated on the balancer ✓ at the place indicated on the wheel. ✓ (2) 5.6 Wheel alignment equipment: 5.6.1 Identify the equipment: • Periscope optical alignment gauge ✓ • Optical alignment gauge ✓ (Any 1 x 1) (1) 5.6.2 Function: To check toe. ✓ To check toe-out. ✓ To check toe-in. ✓ (Any 1 x 1) (1) 5.6.3 Unit of measurement: • Degrees ✓ • Millimetres ✓ (Any 1 x 1) (1) [23] Copyright reserved Please turn over

Mechanical Technology: Automotive 8 DBE/May/June 2024 SC/NSC – Marking Guidelines QUESTION 6: ENGINES (SPECIFIC) 6.1 Crankshaft: 6.1.1 Vibration damper ✓ (1) 6.1.2 • Mass pieces are added to the crankshaft counterweights/webs. ✓ • Holes are drilled in the crankshaft counterweights/webs. ✓ (2) 6.1.3 Connecting rod ✓ (1) 6.1.4 Causes of the crankshaft twist: • The torque or turning movement of the crankshaft. ✓ • The torque produced alternates between high and low value. ✓ • The shaft alternately winds up and releases as it rotates. ✓ • Natural frequency of crankshaft vibrations. ✓ • Resonance on crankshaft. ✓ • Imbalanced crankshaft. ✓ • Faulty vibration damper. ✓ • Imbalanced flywheel. ✓ (Any 3 x 1) (3) 6.2 Rotating mass: • Crank pin ✓ • Big-end bearing ✓ • The lower two-thirds of the connecting rod ✓ (3) 6.3 Engine cylinder layouts: 6.3.1 A. V-engine ✓ B. Inline ✓ C. W-engine/double V engine ✓ (3) 6.3.2 Advantages of V- engine over inline-engine: • Shorter in length ✓ • Can be mounted in smaller engine compartments ✓ • Lighter in weight ✓ • Better power to weight ratio ✓ (Any 2 x 1) (2) 6.4 Degrees of crankshaft rotation: 6.4.1 180° ✓ (1) 6.4.2 120° ✓ (1) 6.4.3 90° ✓ (1) Copyright reserved Please turn over

Mechanical Technology: Automotive 9 DBE/May/June 2024 SC/NSC – Marking Guidelines 6.5 Turbocharger on an internal combustion engine: 6.5.1 A. Air/Air intake ✓ B. Exhaust gas/Exhaust gas inlet ✓ C. Turbine housing ✓ D. Turbine wheel ✓ (4) 6.5.2 Vanes ✓ (1) 6.6 Types of superchargers: • Roots ✓ • Twin-screw ✓ • Centrifugal ✓ • Sliding-vane/Eccentric ✓ (Any 3 x 1) (3) 6.7 Disadvantages of superchargers: • Superchargers are less effective at increasing engine power at high revolutions. ✓ • Superchargers use engine power to drive it (parasitic). ✓ • Higher fuel consumption if generated power is not fully used. ✓ • More space required to mount the Roots supercharger. ✓ • Roots and twin-screw superchargers deliver air in bursts. ✓ • It is more expensive than a turbocharger. ✓ (Any 2 x 1) (2) [28] Copyright reserved Please turn over

Mechanical Technology: Automotive 10 DBE/May/June 2024 SC/NSC – Marking Guidelines QUESTION 7: FORCES (SPECIFIC) 7.1 Definition: 7.1.1 Torque: It is the twisting effort/force ✓ transmitted by a rotating shaft or wheel. ✓ (2) 7.1.2 Brake power: • The useable power ✓ developed at the flywheel or the wheels. ✓ • The actual output power ✓ of an engine measured at the flywheel or the wheels. ✓ (Any 1 x 2) (2) 7.2 Increase swept volume: • Fit crankshaft with longer stroke (with suitable connecting rods). ✓ • Increase bore of cylinders. ✓ (Any 1 x 1) (1) 7.3 Calculations: 7.3.1 Swept volume: π  d2 Swept volume = L 4 ✓ π  7,4 2 =  7,7 ✓ 4 = 331,16 cm 3 ✓ (3) 7.3.2 Compression ratio: 42 ml = 42 cm3 ✓ SV Compression ratio = +1 CV 331,16 ✓ = +1 42 ✓ = 8,88 :1 ✓ OR SV + CV Compression ratio = CV 331,16 + 42 ✓ = 42 ✓ = 8,88 :1 ✓ (4) Copyright reserved Please turn over

Mechanical Technology: Automotive 11 DBE/May/June 2024 SC/NSC – Marking Guidelines 7.3.3 Stroke length: SV CV = CR - 1 SV = CV (CR − 1) ✓ SV = 42 (10 − 1) ✓ = 378 cm3 ✓ π  d2 SV =  length 4 SV  4 length = ✓ π  d2 378  4 = ✓ π  7 , 42 = 8,789 cm = 87,89 mm ✓ (6) 7.4 Calculations: 7.4.1 Indicated power: IP = PLANn P = 950  103 70 L= = 0,07 m ✓ 1000 π  0,065 2 Area = ✓ = 3,318307  10 −3 m2 ✓ 4 2500 N= = 20,833 ✓power strokes/ sec 60  2 ✓ n=4 ( ) ( ) IP = 950  103  (0,07 )  3,318307  10 −3  (20,833 )  (4 ) ✓ = 18388,95 W = 18,39 kW ✓ (7) Copyright reserved Please turn over

Mechanical Technology: Automotive 12 DBE/May/June 2024 SC/NSC – Marking Guidelines 7.4.2 Torque: Torque = Force  radius = 142,5  0,4 ✓ = 57 Nm ✓ (2) 7.4.3 Brake power : Brake power = 2π N T  2500 ✓ = 2 π    57 ✓  60  = 14922,565 W = 14,92 kW ✓ (3) 7.4.4 Mechanical efficiency: BP Mechanical efficiency =  100 IP 14,92 = ✓  100 18 ,39 = 81,13 % ✓ (2) [32] Copyright reserved Please turn over

Mechanical Technology: Automotive 13 DBE/May/June 2024 SC/NSC – Marking Guidelines QUESTION 8: MAINTENANCE (SPECIFIC) 8.1 Exhaust gas analysis: 8.1.1 Gas analysis results: • High oxygen (O2) ✓ • High nitrogen oxide (NOx) ✓ (2) 8.1.2 High nitrogen oxide (NOx): • Improper spark advance ✓ • Malfunctioning exhaust gas regulator (EGR) ✓ • Malfunctioning catalytic converter ✓ • Lean fuel mixture ✓ • Lower octane fuel ✓ • Vacuum leaks ✓ (Any 3 x 1) (3) 8.2 Compression test: 8.2.1 Possible causes: • Piston rings are worn. ✓ • Piston is damaged. ✓ • Valves leaking. ✓ • Cracked cylinder head. ✓ • Blown head gasket. ✓ • Cylinder walls are worn. ✓ (Any 1 x 1) (1) 8.2.2 Corrective measures: • Fit new rings. ✓ • Fit new pistons. ✓ • Replace/Re-seat valves. ✓ • Stitch weld/Replace the cylinder head. ✓ • Replace the cylinder head gaskets. ✓ • Re-bore cylinders. ✓ (Any 1 x 1) (1) 8.2.3 Fault: Low to no compression pressure readings. ✓ (1) 8.2.4 Corrective measures: • Replace the bent valves. ✓ • Correct the cambelt tension. ✓ • Fit a new cambelt. ✓ • Reset valve timing. ✓ (Any 1 x 1) (1) Copyright reserved Please turn over

Mechanical Technology: Automotive 14 DBE/May/June 2024 SC/NSC – Marking Guidelines 8.3 Place of hissing sounds: 8.3.1 • Dipstick ✓ • Oil filler cap hole ✓ • Breather pipe ✓ (Any 1 x 1) (1) 8.3.2 Intake manifold ✓ (1) 8.3.3 Exhaust pipe ✓ (1) 8.4 Oil pressure test: • Oil pressure when idling. ✓ • Oil pressure when engine is cold. ✓ • Oil pressure when engine is hot. ✓ • Oil pressure on high revolutions. ✓ (Any 3 x 1) (3) 8.5 Low fuel pressure: NOTE: The cause and the corrective measure must match each other. CAUSES CORRECTIVE MEASURES Faulty fuel pump. ✓ • Replace fuel pump. ✓ • Replace fuel filter. ✓ Blocked or restricted fuel filter. ✓ Cracked or restricted fuel line. ✓• Renew or repair fuel line. ✓ • Blow out fuel lines. ✓ (Any 1 x 1) Clogged pump inlet strainer. ✓ • Clean the strainer. ✓ Low voltage to the fuel pump. ✓ • Repair faulty wiring and connections. ✓ • Recharge or replace battery. ✓ (Any 1 x 1) Faulty or failed fuel pressure • Replace fuel pressure regulator. ✓ regulator. ✓ Defective fuel pump relay. ✓ • Replace relay. ✓ Empty fuel tank. ✓ • Refuel. ✓ (Any 2 causes x Any 2 matching corrective measures) (4) 8.6 Test the cooling system: • Fit radiator pressure tester to the radiator. ✓ • Pressurize the cooling system according to manufacturer’s specification. ✓ • Watch the pressure for a while, ✓ if it drops there is a leak. • Conduct a visual check for leaks. ✓ (4) [23] Copyright reserved Please turn over

Mechanical Technology: Automotive 15 DBE/May/June 2024 SC/NSC – Marking Guidelines QUESTION 9: SYSTEMS AND CONTROL (AUTOMATIC GEARBOX) (SPECIFIC) 9.1 Advantages of an 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/no clutch pedal pressing). ✓ (Any 3 x 1) (3) 9.2 Torque converter: 9.2.1 Labelling: A. Turbine ✓ B. Impeller/Pump ✓ C. Stator ✓ D. Output shaft/Turbine shaft ✓ (4) 9.2.2 Stall speed: • When the impeller 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 ✓ and just before it starts moving. ✓ (Any 1 x 2) (2) 9.2.3 Converter stops multiplying torque: • When the turbine turns at almost the same speed ✓ as the pump. ✓ • When the speed of the oil leaving the pump ✓ is almost the same as the pump speed. ✓ (Any 1 x 2) (2) 9.3 Advantages of transmission control unit: • Better fuel economy ✓ • Reduced engine emissions ✓ • Greater shift system reliability ✓ • Improved shift feel ✓ • Improved shift speed ✓ • Improved vehicle handling ✓ (Any 2 x 1) (2) Copyright reserved Please turn over

Mechanical Technology: Automotive 16 DBE/May/June 2024 SC/NSC – Marking Guidelines 9.4 Cooling oil in the automatic transmission: • Use a separate oil cooler. ✓ • Circulating fluid through the bottom radiator tank. ✓ • Air flowing over the transmission housing and oil sump. ✓ (Any 2 x 1) (2) 9.5 Forward overdrive: 1. Input shaft drives the sun gear. ✓ 2. Annulus 2/Ring gear 2 is held stationery. ✓ 3. Planet carrier rotates faster than the input shaft. ✓ (3) [18] Copyright reserved Please turn over

Mechanical Technology: Automotive 17 DBE/May/June 2024 SC/NSC – Marking Guidelines QUESTION 10: SYSTEMS AND CONTROL (AXLES, STEERING GEOMETRY AND ELECTRONICS) (SPECIFIC) 10.1 Features wheel alignment • Desirable steering ✓ • Good wheel tracking ✓ • Better road-holding ✓ • Improved fuel economy ✓ • Even tyre wear ✓ • Reduced wear on the suspension ✓ (Any 2 x 1) (2) 10.2 Positive camber: 10.2.1 Labels: A. Centre line of wheel ✓ B. Positive camber angle/Camber angle ✓ C. Strut ✓ D. Lower control arm ✓ (4) 10.2.2 Camber adjustment: • Cam on the suspension ✓ • Wedge plates on the suspension ✓ • Offset screw ✓ • Upper strut mounting ✓ (Any 1 x 1) (1) 10.2.3 Excessive positive camber: • Hard steering ✓ • Rapid tyre wear ✓ • Increased chance of vehicle rolling when cornering ✓ (Any 2 x 1) (2) 10.3 Wheel pre-checks: • Tyre pressure ✓ • Tyre wear ✓ • Tyre for bruises, cracks ✓ • Damaged side walls of tyre ✓ • Wheel rim for damaged beads ✓ • Foreign matter on the rim and tyre ✓ • Tyre expiry date ✓ (Any 3 x 1) (3) Copyright reserved Please turn over

Mechanical Technology: Automotive 18 DBE/May/June 2024 SC/NSC – Marking Guidelines 10.4 Fuel-delivery system: 10.4.1 Pressure regulator: The fuel pressure is kept constant ✓ in relation to the manifold pressure. ✓ (2) 10.4.2 Fuel pump: The fuel pump transfers the fuel ✓ from fuel tank to the engine through fuel lines. ✓ (2) 10.5 Ignition timing: • Engine speed ✓ • Engine load ✓ • Engine temperature ✓ • Throttle position ✓ • Engine knocking ✓ • Altitude ✓ (Any 2 x 1) (2) 10.6 Common rail direct injection (CRDI) system: A. Common rail ✓ B. Fuel injector ✓ C. Fuel line ✓ D. Fuel filter ✓ (4) 10.7 Requirements for the catalytic converter to function: • A temperature of at least 250°C. ✓ • Unleaded petrol must be used. ✓ • Accurate ignition timing. ✓ • No misfiring. ✓ • No burnt engine oil in the exhaust gases. ✓ • Functioning oxygen/lambda sensor. ✓ (Any 2 x 1) (2) 10.8 Alternator: 10.8.1 Labels: A. Rotor ✓ B. Stator ✓ C. Battery ✓ (3) 10.8.2 Diodes: Six ✓ (1) 10.8.3 Function of the diodes: • Allows the current to flow in one direction ✓ only. ✓ • It blocks the current ✓ from flowing in the opposite direction. ✓ (Any 1 x 2) (2) Copyright reserved Please turn over

Mechanical Technology: Automotive 19 DBE/May/June 2024 SC/NSC – Marking Guidelines 10.9 Deactivate speed control: • Switch it off. ✓ • Apply brakes. ✓ • Press the clutch pedal/change gears. ✓ • ECU mapping. ✓ (Any 2 x 1) (2) [32] TOTAL: 200 Copyright reserved