Thursday, 28 March 2024, 6:05 PM
Site: IMI eLearning
Course: IMI eLearning (IMI eLearning)
Glossary: Automotive Glossary
M
M.O.TMinistry of Transport. Colloquial for the annual inspection test for vehicles. |
MAFMass Air Flow Meter. |
MagnetAny material with the naturally occurring phenomenon that has the ability to attract iron. |
Magnetic fieldMagnetic fields surround magnetic materials and electric currents and are detected by the force they exert on other magnetic materials and moving electric charges. The magnetic field at any given point is specified by both a direction and a magnitude (or strength). |
Magnetic FluxThe force contained in a magnetic field. |
Magnetic PoleThe ends of a magnet where the lines of force originate. The north and south poles. |
Magnetic Pulse GeneratorA sensor that uses an iron core and electrical winding to induce an electrical current when passed by a toothed wheel or rotor. Also known as an inductive generator. |
Magnetic StandA holding device for measuring equipment such as a dial test indicator. |
MagnetismA natural force found in iron and some other materials. |
MagnitudeThe height of a wave. The maximum voltage in an AC wave pattern. |
Main BeamThe upper of the two headlamp beams. Also driving beam and upper beam. |
Main BearingsCentral journals and bearings on a crankshaft axis mounted in the engine crankcase. The crankshaft rotates in these bearings. |
Main GalleryA tube shaped section cast in to the engine block where other oil feeds are taken from. |
Mainline PressureThe regulated hydraulic pressure in an automatic transmission. |
Makeup AirA system that brings and heats air from the outside to a desired air flow and temperature. |
MalleableDescribes a material that means it can be easily shaped. |
MAMMaximum Authorised Mass – The maximum gross weight permissible in GB. |
MandrelsBars used to locate a component. |
ManifoldPipes or ducting to route air in or burnt gases out of an engine. Attached to the ports. |
Manifold Absolute PressureThe mean gas absolute static pressure in an engine induction manifold. Absolute pressure is equal to gauge pressure plus atmospheric pressure. |
Manifold VacuumThe depression or low pressure that occurs in the inlet manifold due to the increasing volume above the pistons when they are moving downwards in the cylinders. The airflow into a naturally aspirated engine cannot move quickly enough to fill the additional volume and therefore loses pressure and density. |
Manual TransmissionTransmission system where the driver makes the gear shifts by means of a control (gear) lever and linkages to the gearbox. |
Manual ValveThe gear selector valve in an automatic transmission operated by the driver. |
MAPManifold Absolute Pressure Sensor. The mean gas absolute static pressure in an engine induction manifold. |
Map LightSmall light used in a vehicle for illuminating a map! |
MAP SensorA pressure sensor used to measure manifold absolute pressure in an engine induction system. |
MappingUsed to identify opportunities for developing and assessing key skills within the curriculum. |
Mapping (Contouring)Edge of a repaired area under a paint film that shows up after a surface has been repainted. |
MaskingApplication of paper or other material and adhesive tape to cover an object that must be protected from overspray. |
Masking PaperPaper designed to prevent paint from bleeding through. |
MassThe total theoretical weight of matter based on its atomic structure. The weight of matter without gravitational pull. |
Mass Air Flow MeterA sensing device in the air intake duct of a fuel injection engine that provides data for control of the quantity of fuel that is injected. |
Master CylinderThe pump on a brake hydraulic system. |
MATManifold Air Temperature |
MatchingIn painting, to make refinishing colours look the same as the original finish. |
MattA surface with minimal reflection. |
MatterA term used to describe any substance as a 'quantity of atoms'. |
Matting agentAn additive used to lower the gloss of topcoat, single-stage colours and clearcoats. |
MbMegabyte. Used to measure computer memory. 1 Mb = 1,000,000 bytes or 1024 Kb (kilobytes). |
MCMMotor control module |
McPherson StrutTelescopic independently sprung suspension member incorporating a damper, and fixed at its upper end to the body. The lower end is located by linkages which counteract transverse and fore and aft movement. The original system used a track control arm for transverse forces and an anti-roll bar for longitudinal (fore and aft) location. Usually incorporated in a steered front suspension system. |
MCSMixture Control Solenoid |
MCTManifold Charge Temperature |
MeanThe average value (the sum divided by the number of items). |
Mechanical AdvantageThe effectiveness of a simple machine, such as a lever, inclined plane, wedge, pulley system or a screw at amplifying a force. |
Mechanical EfficiencyThe ratio between the actual total output of a machine and the theoretical maximum output. |
MechatronicsA combination of a mechanical and electronic control system |
MedianThe middle number of a series when the data is arranged in ascending order. |
MelamineUsed in 1K OEM finishes, a hard resin used to modify alkyd resins and other films formed used in baking finishes. |
MemoryThe stored data in a microcomputer or electronic control module. |
Memory ChipA chip that stores data. |
Memory KeeperA battery or secondary power source used to preserve ECU memories when the main battery is disconnected. It can often be plugged in to the cigar lighter socket. |
Memory SaverA battery or secondary power source used to preserve ECU memories when the main battery is disconnected. It can often be plugged in to the cigar lighter socket. |
MeshCriss-cross fibres to produce a material with very small holes. Used to make filter elements. |
Mesh (Gears)Gear teeth in contact. |
Metal ConditionerAn acid-type cleaner which removes small amounts of rust and corrosion left from mechanical metal cleaning. Usually based on Phosphoric Acid solutions. |
Metallic PaintTopcoat which contains metallic pigments, usually in the form of tiny flakes of aluminium. Custom finishes may use other non-ferrous metal flakes such as copper or bronze. |
MetamerismA term used to describe colours that match under a specific light source, but do not match under all light sources. It is primarily caused by the use of pigments that are different to those used in the original formulation. |
MeterMeasuring the flow rate of a gas or liquid. |
MeteringWhen applied to fuel systems a control device for achieving the correct air/fuel mixture strength for specific engine running conditions. |
Metering NeedleSee metering rod. |
Metering PortsPorts designed to a set size to allow accurate flow of fuel or air. |
Metering RodA tapered needle in a jet in a carburettor. The taper allows a varied or metered supply dependent on the position of the taper in the jet. |
MethanolMethyl-alcohol used as a fuel or fuel additive. |
MethodThe way in which a task is carried out. |
Methyl Ethyl Ketone (MEK)A fast-evaporating solvent. |
MetricEuropean standards of measurement based on the metre. |
Metric MeasurementA system designed to regulate measurement. Each quantity has a single unit. These include; metre, kilogram, ampere. |
MFIMultiport fuel injection. Usually known a port fuel injection or multipoint fuel injection (MPI). |
MHMetal hydride |
Micro ProcessorA processor on a single integrated circuit or chip. The calculator in a microcomputer or electronic control module. |
Micro SwitchA small switch usually operated by a moving mechanism. |
Micro-checkingA condition which appears as severe dulling of a paint film, but when viewed under magnification, is actually very fine cracking of the painted surface . |
Micro-porousContaining lots of very small holes. |
MicroelectronicsRefers to integrated circuit electronics usually involving some form of processor. |
MicrometerMeasuring device based on an accurate screw thread. Measurements can be taken to 0.01mm/0.001''. |
MicronA measure of paint film thickness, equal to one one-thousandth of a millimetre. |
MicrophoneA device that converts sound waves to audio signals. |
Microsoft OfficeA package of programs including Word Processor (Word), Spreadsheet (Excel), Presentation (PowerPoint), Email and Organisation (Outlook). |
Microwave1. Essential equipment for use when a technician is hungry...2. High frequency radio waves. |
Middle SolventA solvent that evaporates at a medium rate, leaving the paint primarily during flash-off. |
MILMalfunction indicator lamp. Dashboard warning light from an electronic control module to signal a system or component failure. |
MillingA machining process that uses a rotating blade to cut through the surface of materials. |
MinibusA motor vehicle constructed or adapted to carry more than eight but no more than sixteen seated passengers (see also Bus). |
Ministry PlateDisplays the maximum authorised weights at which a vehicle may be operated. This information supersedes the maximum weights displayed on the Manufacturer’s plate. |
MiscibilityThe property of materials that mix easily. |
MiscibleCapable of being mixed with or dissolved in other components of a paint, etc. |
MisfireUneven running of an engine due to one or more cylinders not working properly. |
MisrepresentationRepresent wrongly with false account (legal). |
Mist CoatingA light sprayed coat of a paint material to assist in blending and/or gloss enhancement and metallic control in single-stage colours. |
Mixing (Ratio) StickInstrument used to gauge the correct ratio of paint material being mixed for ready-to-spray configuration. |
Mixing RatioThe proportion of ingredients to be mixed together to make a ready-to-spray paint. |
mmMillimetres |
ModeThe most common number in a series. |
ModemModulator-demodulator. Used to convert computer signals so that they can be sent over telephone lines. |
Modulating ValveA valve that can be switched on and off rapidly such as to control its partially open position. |
Modulator AssemblyReleases and re-applies fluid pressure to brake units. (ABS). Adjusts and regulates. |
Modulator ValveFlow control valve in power steering pump. In an automatic transmission a valve that responds to manifold vacuum to create hydraulic pressure feedback to the main control assembly. |
ModuleAn electronic control unit for a vehicle system. |
MolMethod of Inspection |
MolecularRelating to atoms formed into molecules. |
Molecular MassTerm used to describe the mass of molecules - usually relating to the mass of the protons and neutrons. |
MoleculeThe smallest possible unit or amount of any substance which retains the characteristics of that substance. |
MomentumForce that keeps a body moving. |
MonitorThe screen that displays information produced on a computer. An output device. |
MonolithThe honeycomb catalyst support element in a catalytic converter. |
MonopointA petrol fuel injection system using a single point (or monopoint) injector in a throttle body in the inlet air supply and positioned on top of the inlet manifold. Also throttle body injection (TBI). |
MoonroofSee also Sunroof... A sunroof that has a clear glass panel, rather than being opaque, so that light can enter the vehicle even when the roof is closed. Some vehicle have a sunroof at the front and a moonroof at the back. |
MopedThree wheeled vehicle with max speed of 45km/h, not over 50cc for a petrol engine or 4KW for any other engine or electric motor, not more than 450kg ULW. |
MOSTMedia Oriented Systems Transport. This protocol defines a multimedia fibre-optic point-to-point network implemented in a ring, star or daisy-chain topology over Plastic optical fibres. The MOST bus specifications define the Physical Layer as well as the Application Layer, Network Layer, and Medium Access Control. The MOST bus provides an optical solution for automotive media networks. |
MOTMinistry of transport (UK) |
Motor Reverse CircuitAn electrical circuit that reverses polarity supplied to a motor. |
Motor tricycleThree wheeled vehicle with wheels symmetrically arranged, a max speed over 45km/h, or engine size over 50cc. |
MottlingA film defect appearing as blotches or surface imperfections, normally due to metallic or pearlescent pigments not being properly orientated in the paint film. |
Mould-Release AgentsChemical compounds applied to manufacturing moulds which must be removed by a pre-treatment prior to refinishing plastic parts to insure adhesion. |
MountingGeneral term for the part of a component, or a separate component, which fits one thing to another. |
Mounting StudsThreaded fixings for an exhaust flange or similar. |
MountingsInsulated or solid attachments for components/units on the vehicle. Insulated versions absorb vibration and provide some protection from shock loads. |
MouseAn input device that allows the user to move the pointer around the screen and click on different items to operate computer applications. |
Moving ConductorThe armature in a motor or dynamo. |
MPFIMulti Point Fuel Injection |
MPGMiles Per Gallon |
MPHMiles Per Hour |
MPIMultipoint Fuel Injection. |
MPVMulti-Purpose Vehicle |
msMillisecond |
MSDSMaterial Safety Data Sheets. |
Muffler (Silencer)A component in the exhaust system to absorb the gas shock waves and noise in order to reduce the emitted noise from a vehicle engine. Also known as a silencer. |
Multi-Plate BrakeA brake that uses several clutch-type plates. |
Multi-plate ClutchA clutch mechanism having a series of friction and steel plates in a clutch drum assembly. One set of plates is splined to the drum and the other to a centre shaft so that drive through the clutch is via the drum, friction faces and the centre shaft. |
Multi-vee BeltA flat drive belt with several ridges or vee shapes running circumferentially (the long way round). |
Multigrade OilClassification for lubricating oils that change viscosity grades during temperature change. The lower number is the cold temperature grade and the higher number the hot temperature grade. These oils do not thin at the same rate as single grade viscosity oils as the temperature rises. Also known as multiviscosity oils. |
MultimeterAn electrical measuring tool with functions for volts, amps and ohms. |
MultiplateA clutch mechanism having a series of friction and steel plates in a clutch drum assembly. One set of plates is splined to the drum and the other to a centre shaft so that drive through the clutch is via the drum, friction faces and the centre shaft. |
MultiplexedIn signal transmission where each set of signal pulses is given a certain time or frequency slot. This allows a great number of individual signals to be carried by a common conductor. |
MultiplexerA unit used for signal transmission where each set of signal pulses is given a certain time or frequency slot. This allows a great number of individual signals to be carried by a common conductor. |
MultiplexingA common conductor system for digital signal transmission where each set of signal pulses carries its own unique identity. This allows a great number of individual signals to be carried by the common conductor. |
MultiplugA connector with more than one electrical terminal inside. |
Multipoint Fuel InjectionGasoline electronic fuel injection system with injectors in each inlet manifold spraying fuel in towards the inlet valves in the ports of each cylinder. Also known as port injection. |
MultisocketsSockets with many positions for fitting over a bolt or nut head. Sometimes described as multihex. |
Mutual InductionThe electrical current induced in one conductor because of the electrical current flow and magnetic field produced around another conductor nearby. Used in transformers to induce a current in one winding from the electrical flow of another when both are wound around an iron core to create a magnet field. |
mVMillivolts |