MITO Light Auto L4 key terms

The sequence of intake, compression, power and exhaust strokes that a piston completes in two crankshaft revolutions. Almost all light vehicle petrol and diesel engines operate on this principle.

The ratio of the cylinder volume when the piston is at bottom dead centre to the volume when it is at top dead centre. Higher ratios improve efficiency but demand higher-octane petrol.

A shaft carrying egg-shaped lobes that push valves open and let them close in step with the crankshaft. It is driven by a timing belt, chain or gears.

A toothed belt that keeps the camshaft and crankshaft rotating in sync. On interference engines, a snapped belt lets pistons hit valves, causing expensive damage.

A turbine turned by exhaust gas drives a compressor that pushes extra air into the engine, raising power. Boost is limited by a wastegate or variable vanes.

A system that sends a measured portion of exhaust gas back into the intake. This lowers combustion temperature and reduces oxides of nitrogen, but can cause carbon build-up.

A filter in the exhaust of a diesel that traps soot. It periodically burns off the collected carbon at high temperature, a process called regeneration, often triggered automatically by the engine management system.

A friction assembly between the engine and a manual gearbox. Pressing the pedal releases clamping force so the driver can change gear or pull away smoothly.

A fluid coupling used in automatic transmissions. It multiplies engine torque at low road speed and slips enough to let the car stop in gear without stalling.

A gear set that divides drive between two wheels while allowing them to turn at different speeds, which is essential when the vehicle corners.

A joint at each end of a driveshaft that keeps transmitting power smoothly while the shaft moves through changing angles, typical of front-wheel-drive cars.

A rechargeable lead-acid or absorbed glass mat unit that stores electrical energy, supplies current for starting and powers electronics when the engine is off.

A belt-driven generator that produces alternating current, rectifies it to direct current, and charges the battery while running the vehicle's electrical loads.

A heavy-duty electric motor that engages the flywheel ring gear and cranks the engine until it starts and runs under its own power.

A twisted-pair network that lets electronic control units exchange data quickly. It reduces wiring and allows scan tools to read multiple systems.

The computer that reads sensor inputs and controls fuel delivery, ignition timing and emissions devices so the engine runs efficiently and stays within legal limits.

A measurement of the voltage lost across a cable, connector or switch while current is flowing. More than about 0.5 V on a main circuit indicates excessive resistance.

The traction circuit in a hybrid or electric vehicle, often 200 to 800 volts DC. It requires insulated tools, rated gloves and specific training before any work.

A steering layout in which a small gear on the steering column turns a toothed rack, moving the track rods left or right.

Steering assistance provided by an electric motor controlled by sensors and a module. It removes the hydraulic pump, hoses and fluid, saving weight and fuel.

Adjusting camber, caster and toe so the wheels sit correctly relative to the vehicle and road. Correct alignment prevents rapid tyre wear and improves handling.

The tilt of a wheel from vertical when viewed from the front. Negative camber leans the top inward; too much either way wears the tyre unevenly.

How much the front of a pair of wheels points in or out compared with the rear. Wrong toe scrubs the tyres and can make the steering feel vague.

A suspension unit that combines a coil spring and damper in one assembly. The strut also forms an upper locating link for the wheel.

A system that releases and reapplies brake pressure many times a second to stop wheels locking, so the driver can still steer while braking hard.

A glycol-based or silicone hydraulic fluid that carries pedal pressure to the brakes. It absorbs moisture over time and must be replaced at the specified interval.

A wrench that signals, by click, beep or display, when the set tightening torque is reached. It must be stored at its lowest setting and calibrated regularly.

A precision tool with a calibrated screw that measures thickness or diameter, usually to 0.01 mm. It is used for brake discs, shafts and bearing journals.

A sliding measuring tool that reads outside, inside and depth dimensions, typically to 0.02 mm. It is checked against zero before use.

A set of thin metal blades of known thickness used to measure small gaps, such as valve clearances, spark plug gaps and piston ring end gaps.

A device that connects to the diagnostic socket to read fault codes, display live sensor data and command actuators on electronic control systems.

An instrument that measures voltage, resistance and current. It is used to check batteries, circuits, sensors and continuity during diagnosis.

Safety glasses, gloves, hearing protection, boots and other items worn to reduce injury. Both employer and worker are responsible for making sure it is used.

An isolation procedure where energy sources are switched off, locked and tagged so equipment cannot be started while someone is working on it.

The process of spotting anything that could cause harm, judging how serious the risk is, and putting controls in place before work starts.

An adjustable rigid support placed under the vehicle after it is lifted. It holds the load safely and must never be replaced by a hydraulic jack alone.

A document listing a chemical's hazards, safe handling, first aid and disposal. It must be available to anyone using the product at work.