RBSE SS Voc Automotive cheat sheet

Four-stroke cycle order: intake, compression, power, exhaust; one power stroke per two crankshaft revolutions.

Compression ratio = (swept volume + clearance volume) / clearance volume; petrol engines typically 8:1 to 12:1, diesel 16:1 to 22:1.

Engine displacement = bore² × 0.7854 × stroke × number of cylinders.

Valve clearance is measured with a feeler gauge when the engine is cold unless the manufacturer specifies hot adjustment.

Torque sequence for cylinder heads runs from centre outward in two or three progressive stages to avoid head warpage.

Cylinder taper and out-of-round limits are checked with a bore gauge at three heights and two axes; exceeding the limit requires reboring or resleeving.

Piston ring end gap is measured by squaring the ring in the bore with a piston crown; too small a gap causes ring butting and breakage.

Diesel engines ignite by compression heat alone; glow plugs assist cold starting but are not the ignition source once running.

Overhaul verification includes valve seat concentricity, camshaft lobe lift, bearing oil clearance with Plastigauge, and correct timing mark alignment.

Manual gearbox ratio = driven gear teeth / driving gear teeth; overall ratio multiplies gearbox ratio by final drive ratio.

A clutch slips when pedal free play is too small or the release bearing preloads the diaphragm; free play is set per manufacturer spec.

Synchroniser rings block gear engagement until cone friction equalises shaft speeds; worn baulk rings cause grinding on downshift.

Automatic transmission fluid level is checked with the engine running and the selector in Park or Neutral at operating temperature, per dipstick marking.

Torque converter multiplication occurs when turbine speed is well below impeller speed; coupling occurs near 0.9 stall speed ratio.

CVT ratio range is set by pulley sheave diameter change on the belt or chain; belt slip shows as shudder under load.

Shift fork and rail wear shows as difficulty selecting one gear only; detent springs hold the selected gear against vibration.

Transmission oil seals and breathers must be clear; a blocked breather forces oil past seals and causes leaks mistaken for gasket failure.

Final drive ratio = ring gear teeth / pinion gear teeth; it converts gearbox output speed to wheel speed.

A universal joint operates through unequal angles; equal and opposite working angles at each end cancel speed fluctuation.

Driveshaft imbalance causes vibration that rises with road speed and is felt at a specific frequency band, not engine speed.

Differential allows wheel speed difference in turns; an open differential sends torque to the wheel with less traction.

Limited-slip differentials use clutch packs or viscous coupling; chatter on turns often means incorrect friction modifier or worn plates.

Half-shaft CV joints click on full lock when the outer joint is worn; a torn boot loses grease and admits grit.

Wheel bearing play is checked by rocking the wheel at 12 and 6 o'clock with the brake applied to isolate bearing from brake movement.

Driveline phasing: yokes at both ends of a shaft must be in the same plane to avoid torsional vibration.

Ackermann geometry gives the inner front wheel a larger steer angle than the outer wheel in a turn.

Caster is the steering axis tilt in side view; positive caster improves straight-line stability and self-centring.

Camber is wheel lean in front view; excessive negative camber wears the inner tyre shoulder.

Toe-in or toe-out is measured in mm or degrees and is set last after camber and caster because it is the most sensitive to adjustment.

Total toe = left toe + right toe; thrust angle is the angle between the rear axle centreline and the vehicle centreline.

Tyre wear patterns: centre wear means over-inflation, both shoulders mean under-inflation, one shoulder means camber or toe fault.

Power steering hydraulic pressure is tested with a gauge in the pressure line; low assist with normal pressure points to the rack or pump flow control.

Ball joint and tie-rod play is checked with the wheel loaded and unloaded; any perceptible axial play fails inspection.

Shock absorber condition is judged by bounce test, oil leakage, and damper dyno comparison; a weak damper causes cupped tyre wear.

Ohm's law: V = I × R; power P = V × I = I²R = V²/R.

Series circuit: resistances add and current is common; parallel circuit: voltage is common and 1/R total = sum of 1/R branches.

Battery capacity is rated in ampere-hours and cold cranking amps; specific gravity of a fully charged lead-acid cell is about 1.265 at 25 °C.

Alternator output test: measured voltage should be about 13.8 to 14.5 V at idle with loads off; below 13 V suggests a weak alternator or regulator.

Voltage drop testing is performed under load; more than 0.5 V across a cable or connection indicates excessive resistance.

CAN bus has two wires, CAN-High and CAN-Low, with about 2.5 V each at rest and differential signalling when active; 120 ohm termination at each end.

A relay coil is controlled by low current; the contact side switches the high-current load, protecting the switch and wiring.

LED and HID lamps require correct ballast or driver; fitting the wrong type causes flicker, fault codes, or fire risk.

Fuses are rated to protect wiring, not the device; replacing with a higher rating risks harness fire.

Diagnostic trouble codes are read from the ECU via OBD-II port pins 6 and 14 (CAN) with a scan tool; codes identify a circuit or system, not always the failed part.

Freeze frame data records engine conditions at the moment the fault set, which helps reproduce the fault.

Fuel trim: positive long-term trim above about +10 % indicates a lean condition (vacuum leak or low fuel pressure); negative trim indicates rich.

A vacuum gauge reading steady low at idle suggests intake leak; fluctuating needle suggests valve or ignition fault.

Compression test: cranking with throttle open and all plugs removed; a wet test rising pressure points to worn rings.

Cylinder leakage test identifies where air escapes: intake valve, exhaust valve, rings, or head gasket.

Scan tool live data must be compared with manufacturer specifications at specified rpm and temperature; guessing from codes alone causes misdiagnosis.

Intermittent faults are traced by wiggle testing harnesses and reading freeze frame or pending codes rather than clearing codes first.

Engine oil is specified by viscosity grade (e.g. 5W-30) and API or ACEA service category; both must meet the manufacturer requirement.

Oil change interval is set by mileage or time, whichever comes first; severe duty shortens the interval.

Brake fluid is hygroscopic; moisture above about 3 % by volume lowers boiling point and requires replacement.

Coolant concentration is checked with a refractometer; a 50/50 mix gives protection to about −37 °C and raises boiling point.

Tyre pressure is checked cold; pressure rises about 0.1 bar per 10 °C temperature increase.

Tread depth minimum is 1.6 mm in the EU and many other markets; wear indicators sit at that depth.

Service schedule items include filters, belts, plugs, fluids, and inspection of brakes, suspension, and steering at defined intervals.

Battery terminal cleaning and torque, plus charging system check, belong to every periodic service.

Wheel nut torque is applied with a calibrated torque wrench in a star pattern; retorque after the specified distance for new wheels.

Steel strength rises with carbon content; above about 2 % carbon it becomes cast iron rather than steel.

Aluminium alloy is used for cylinder heads and blocks because of low weight and good heat conduction, but it requires torque-to-yield bolts and careful hot torque sequences.

Cast iron has high wear resistance and damping; it is used for liners and some blocks.

Thermoplastic and thermoset plastics differ: thermoplastics soften on heating and can be recycled, thermosets cannot be remelted.

Galvanic corrosion occurs when dissimilar metals contact in the presence of electrolyte; the less noble metal corrodes.

Composite body panels reduce weight but require different repair methods and adhesives from steel panels.

Elastomers such as EPDM resist ozone and coolant; natural rubber is not suitable for fuel contact.

Material identification by spark test, magnet test, and hardness test guides welding and repair decisions.

Vernier calliper resolution is typically 0.02 mm; micrometer resolution is typically 0.01 mm and requires zero check before use.

Torque wrench accuracy must be within the manufacturer's tolerance; it is stored at the lowest setting to protect the spring.

Dial bore gauge and telescopic gauge are used with a micrometer to measure cylinder bore taper and clearance.

Feeler gauge measures valve clearance and gap; blade thickness is marked in mm or inches.

Plastigauge measures bearing oil clearance by crushing a plastic strip and comparing its width to a scale.

Torque angle gauge is used for torque-to-yield fasteners after the initial torque stage.

Micrometer reading = main scale + thimble scale × least count; always read at eye level to avoid parallax error.

Compression gauge, vacuum gauge, and pressure gauge must be calibrated and checked for leaks before trusting results.

Hand tool safety: sockets must match fastener size; using an extension bar as a breaker bar damages tools and risks injury.

Surface preparation order: strip, clean, straighten, prime, sand, seal, base coat, clear coat.

Primer promotes adhesion and corrosion protection; sealer prevents solvent penetration and gives uniform colour holdout.

Paint film thickness is measured with an ultrasonic or magnetic gauge; excessive thickness causes cracking and poor adhesion.

Base coat colour match is checked under a colour-match light or in daylight before clear coat application.

Clear coat provides UV protection and gloss; insufficient film thickness causes premature fading and peeling.

Spray gun settings: fluid, fan, and air pressure are adjusted per product data sheet; distance is typically 15 to 20 cm.

Masking must cover glass, trim, and gaps; overspray on rubber and plastic is difficult to remove.

Body filler must be applied over bare metal or properly prepared primer, never over paint or rust, to avoid lifting.

Baking or infrared curing accelerates drying but must follow the product's temperature and time limits.

A vehicle on a lift must be supported at manufacturer jacking points with locks engaged before working underneath.

Battery charging releases hydrogen; no sparks or open flame near the battery, and ventilation is required.

Brake fluid and coolant are toxic and must be collected in labelled containers for recycling, never poured to drain.

Used oil, filters, and solvents are hazardous waste and require licensed disposal; mixing waste streams increases cost and risk.

Airbag and pretensioner handling: wait the specified time after disconnecting the battery before removing an airbag.

PPE for refinishing includes respirator with correct cartridge, gloves, and eye protection; solvent vapours are harmful.

Fire extinguisher classes: A for solids, B for flammable liquids, C for gases, and electrical fires need CO2 or dry powder.

Lockout/tagout applies to workshop equipment during maintenance; never remove another worker's tag.

Noise above 85 dB requires hearing protection; hand-arm vibration exposure from impact tools must be limited.

Invoice must show parts, labour hours, rate, taxes, and total; a written estimate protects both customer and workshop.

Job card records vehicle details, complaint, work done, parts used, and technician signature for traceability.

Vehicle registration certificate, insurance, and periodic inspection certificate are the core legal documents a vehicle must carry.

A purchase agreement should state price, payment terms, delivery date, warranty, and dispute resolution.

Warranty terms must be disclosed in writing; implied statutory rights may exceed the written warranty in many jurisdictions.

Break-even point = fixed costs / (selling price per unit − variable cost per unit).

Gross profit margin = (revenue − cost of goods sold) / revenue × 100 %.

A CV should list verifiable qualifications, training certificates, and practical experience relevant to the vacancy.

Customer complaint handling: listen, record, verify, correct, and confirm resolution in writing.

Service history records prove maintenance and support resale value and warranty claims.

A pre-delivery inspection checklist must be signed before handing a vehicle to a customer.

Vehicle identification number is a 17-character code; it identifies manufacturer, model year, plant, and serial number.

Odometer disclosure statements are legally required in many jurisdictions at transfer of ownership.

Repair order must be signed by the customer to authorise work beyond the original estimate.

Insurance certificate states policy number, coverage type, and validity dates; an expired policy makes driving illegal.

Periodic technical inspection certificate has a validity date and must be renewed before expiry.

Records of hazardous waste disposal must be retained for the period required by local regulations.