Automotive Glossary
Automotive Glossary
Browse the glossary using this index
Special | A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z | ALL
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O RingsCircular rubber rings used to seal pipe and other connections. | |
O2Oxygen | |
O2 SensorOxygen sensor, lambda EGO or HEGO sensor to provide exhaust oxygen content signal to the ECM. | |
O2SOxygen Sensor | |
OBDOn board diagnostic. A connector for diagnostic analysis of a vehicle's electronic systems. | |
OBD IOnboard Diagnostics One | |
OBD IIOnboard Diagnostics Two | |
ObjectiveThe goal intended to be attained and which is believed to be attainable. | |
Objective InformationInformation that is unbiased and open minded. | |
ObligatoryCompulsory. | |
ObsceneOffensive, foul, disgusting. | |
OCOxidation Catalyst. | |
OccupationThe job that you do. For example, training to be a motor mechanic is training for an occupation. | |
ODOutside Diameter | |
OdometerInstrument that displays distance travelled by vehicle. | |
OEOriginal Equipment | |
OEMOriginal Equipment Manufacturer. | |
OffensiveTo attack somebody/something. | |
Office ApplicationsA package of programs including Word Processor (Word), Spreadsheet (Excel), Presentation (PowerPoint), Email and Organisation (Outlook). | |
OffsetAny point that is not on the axis of shaft or component. | |
OHCOverhead cam - type of valve operating gear. Camshaft in cylinder head above the valves. | |
OhmElectrical unit of resistance. | |
Ohm's LawThe electrical law, named after its originator, that shows the relationship between electrical pressure in volts, electrical current in amps and the electrical resistance in Ohms is proportional. Volts is equal to amps multiplied by Ohms. | |
OhmmeterA meter for measuring Ohms, the standard unit for electrical resistance. | |
OHVOverhead valve - type of valve operating gear. Camshaft in cylinder block connected to valves by push rods and rockers. | |
Oil CoolerA small heat exchanged (radiator), which has oil pumped through so that a flow of air will cool it. | |
Oil DilutionThe thinning of engine oil by fuel flowing down the cylinder walls into the oil pan. | |
Oil DrillingsHoles through various engine components, such as the crank, to allow oil to flow. | |
Oil PanSump that holds oil for lubricating the engine. | |
Oil PumpAn mechanically driven pump used to supply oil pressure. | |
Oil SealA seal that prevents oil loss. Usually described as a radial lip seal but other types are used. | |
Oil SeparatorPlates or baffles used to prevent oil being mixed with air or drawn through air pipes. | |
Oil StrainerThe mesh filter on the end of an oil pick up pipe. | |
Oil-Based PaintsPaints which dry by absorbing oxygen from the atmosphere. This 'uptake of oxygen' promotes a chemical reaction which is irreversible. | |
On Board Diagnostics (OBD)See OBD | |
One-way ClutchAn automatic mechanical clutch that permits drive from one shaft to another in one direction only. A drive transmitted to the outer hub of the clutch bypasses the inner hub and the clutch free wheels. This type of clutch allows drive to be transmitted by two alternative routes and at different rotational speeds. | |
OpacimeterSmoke meter used to measure the amount of smoke in diesel engine exhaust gases. | |
OpacityThe ability of a paint film to obliterate the colour or pattern of a surface. Opacity is measured by determining the minimum thickness at which a paint film will completely obscure a black and white pattern. | |
OpaqueImpervious to light transmission -non-transparent. | |
Open CircuitApplied to an electrical circuit when the switch is 'off' or the circuit is not continuous. | |
Open CoatA type of abrasive paper coating in which the abrasive particles are scattered in a low density to prevent it from clogging up. Typically found in Production Papers | |
Open Period(1) The number of degrees of distributor rotation during which the primary circuit remains open. (2) The number of degrees of crankshaft rotation during which an inlet or exhaust valve remains open. | |
Open-loopAn electronic control system using a comparison of sensor signals and a pre-programmed map. | |
Operational SafetySafety aspects that are operational during use of a vehicle. | |
Optical GaugeA measuring instrument that uses light/reflection to align steering (for example). | |
OPTLOne Person Test Lane. These are lanes authorised by VOSA to conduct testing where the tester has the option of not using an assistant if so desired. | |
Orange cablesThese indicate high voltages – take care. | |
Orange PeelAn irregularity in the surface of a paint film resulting from the inability of the wet film to "level out" after being applied, caused by a lack of flow. Orange peel appears as a characteristically uneven or dimpled surface to the eye, but usually feels smooth to the touch. | |
Orbital SanderType of sander that uses a circular motion to accomplish the sanding of different materials. | |
Organic MaterialsCompounds composed of carbon, hydrogen, and other elements with chain or ring structures. | |
OrificeA hole, usually with a precise drilling diameter to control a fluid flow or spray. | |
OSOxygen Sensor | |
OscillateTo move or swing from one place to another (e.g. side to side). | |
OscillatorAn electronic circuit that produces as signal of a set frequency. | |
OscilloscopeAlso shortened to ‘scope'. An instrument that draws an image to represent changes in voltage over a set time period. | |
Otto CycleAn alternative term for the four stroke engine cycle using the name of its inventor. | |
Out-of-roundA term used to describe a component that should be perfectly round or cylindrical but is not. Usually caused by wear but can be from faulty machining. | |
Outdoor ExposureThe most realistic way to measure the behaviour of a paint film. Manufacturers paint sample panels and leave them exposed to the elements for long periods of time, and inspect them at intervals to measure the effects of the exposure. | |
Outer RacesThe outside rings of ball or roller bearings. | |
Outgoing Telephone CallTo make a telephone call to somebody. | |
Outlet PortsUsed to describe any port that allows a gas or liquid to leave. Exhaust ports are a good example. | |
OutputPower or data that comes out from a mechanical unit or electronic control module. Usually adapted or modified by the unit or module to suit a particular purpose. | |
Output CircuitThe battery charging circuit for the electrical current from a generator. | |
Output DeviceA device that allows information from the computer to be displayed. Egg, monitor, printer. | |
Output ShaftShaft that outputs drive from a gearbox to a propshaft or final drive. | |
OvenEquipment used to bake paint finishes. Originally developed by vehicle manufacturers, whose applied finishes may require temperatures as high as 180°C to cure. In the refinishing industry, ovens are used to bake sprayed coatings at varying temperatures up to 80°C, producing fully-cured finishes in as little as 20 minutes. | |
Over-thinTo add more thinner or reducer to a paint than is normally necessary for application. This is sometimes done in order to lower the paint viscosity, to aid in blending, or to achieve a special colour effect with metallics or pearlescents | |
Overall PaintingA type of refinish task in which the entire car is completely repainted. | |
Overall RatioThe term used to describe the output ratio of a series of mechanical components such as gears or levers. | |
OverbakeThe result of curing a paint film at too high temperature, or for longer than the specified time. The film often becomes too hard and brittle. | |
Overdrive GearA gear drive that increases the rotational speed of the output shaft above that of the input shaft. | |
Overdrive UnitA separate unit that at one time was fitted on the output shaft of a gearbox. It produces a higher gear ratio. | |
OverlapThe area of coverage in which one spray pass is extended over and partly covered by the next pass. | |
Overlap (Valve)The term used to describe the angle of crankshaft rotation when the inlet and exhaust valves are both open. | |
OverrunMovement of vehicle when engine is not under power. Engine braking. | |
Overrun Clutch(1) A clutch on a starter drive pinion that prevents the engine from driving the starter motor after the engine has started. (2) A one-way clutch in an automatic transmission. | |
OversprayAn overlap of dry spray particles landing on areas that were not meant to be painted, or on previously painted areas where they do not blend in. | |
OversteerSteering condition of a turning vehicle when the vehicle attempts to turn by a greater degree than the steered position taken by the driver. A difficult driving condition requiring opposite lock to control. | |
OxidationThe chemical combination of oxygen and the binder of synthetic-enamel type paints which leads to drying. Also refers to the destructive combination of oxygen with a dry paint film leading to age degradation, or the destructive combination of oxygen and metal commonly known as Corrosion. | |
Oxygenated SolventAn organic solvent containing oxygen as part of the molecular structure. Alcohols and ketones are oxygenated compounds often used as paint solvents. | |
OzoneA colourless gas (O3) soluble in alkalis and cold water; a strong oxidizing agent; can be produced by electric discharge in oxygen or by the action of ultraviolet radiation on oxygen in the stratosphere (where it acts as a screen for ultraviolet radiation). | |