Dictionary of Automotive Terms Abbreviations

DICTIONARY OF AUTOMOTIVE TERMS - "Ma"

M100: 100% (neat) Methanol

M85: 85% Methanol and 15% unleaded Gasoline by volume, used as a motor fuel in FFVs.

M+S: Acronym for mud and snow, as in M+S tire. A tire with a tread design (usually large lugs with wide spaces between them) which gives the maximum traction in mud and snow.

M+S tire: Mud and snow tire

Acronym for mud and snow tire, as in M+S tire. A tire with a tread design which gives the maximum traction in mud and snow.

MAC: Acronym for motor assisted bicycle -- usually an electric motor

Machine: See
Air-cooled Machine
Automatic Screw Machine
Automatic Screw Machine
Balancing Machine
Bolt-making Machine
Boring Machine
Injection molding machine
Milling machine
Perpetual motion machine
Picture Machine
Wheeling machine

Machineability

Relative ease or difficulty in forming.
The malleable characteristics of metal when cutting or forming on screw machines. Same as free machining

Machine drive: The direct process end use in which thermal or electric energy is converted into mechanical energy. Motors are found in almost every process in manufacturing. Therefore, when motors are found in equipment that is wholly contained in another end use: (such as process cooling and refrigeration), the energy is classified there rather than in machine drive.

Machined surface: A smooth surface of metal such as the top of a cylinder block.

Machine patch: A new layer of asphalt is placed on sections of the road, perhaps leaving some gaps depending on condition. First a layer of liquid asphalt or tack coat is sprayed on the road. Next, fabric may be placed on any badly broken areas for added strength. Finally hot asphaltic concrete is applied, raked and rolled to a prescribed density. Work moves quickly and you can drive on the new asphalt as soon as the rolling is complete. The work must be done when the ground is dry and reasonably warm.

Machine room: Area where commercial and industrial refrigeration machinery -- except evaporators -- is located.

Machinery cargo: See
Heavy Machinery cargo

Machinery spaces: See
Unmanned machinery spaces

Machine screw

A screw with thread running the length of the shank and available with a variety of different heads
A straight shank fastener for binding metal to metal by going through a pre-tapped hole or nut. Its head may be one of four common shapes:

Also see
Sems screw
Structure Machine Screws

Machining: An operation which shapes metal parts by carving away excess material as chips produced in a sequential process of turning, milling and grinding operations.

Machinists' caliper: A measuring tool with two curved arms for inside or outside measurement; the reading taken with the arms is transferred to a steel rule or micrometer to attain the exact value

Machinists' hammer: A Ball pien hammer

MacPherson strut: Click image to supersize

A Suspension piece which employs a Coil spring and Shock absorber attached to the lower A-arms and the top of the front body structure. Originally it had a Lateral link with an Anti-roll bar instead of the lower A-arm. It was first invented by a Ford of England engineer, Earle S. MacPherson.

MacPherson strut tower: A sheet metal panel surrounding the upper mount of the MacPherson strut at the side panels of the engine compartment; it may be a separate panel fitted by spot-welding or a deep-drawn section of the side panel shaped to take the upper strut end. Also called suspension leg turret

MacPherson suspension: A suspension layout incorporating Macpherson struts

Macromolecule: Any very large molecule, such as a synthetic polymer used in the manufacture of plastic

Macromolecular: With very large molecules

Made available: A vehicle is considered Made available if it is available for delivery to dealers or users, whether or not it was actually delivered to them. To be Made available, the vehicle must be completed and available for delivery; thus, any conversion to be performed by an OEM Vehicle Converter or Aftermarket Vehicle Converter must have been completed.

MAF: Acronym for Mass airflow meter. A sensor used to measure the amount of intake air entering the engine on some fuel injection systems

MAF RTN: Acronym for Mass Airflow Sensor Ground

MAFTS: Acronym for manifold air/fuel temperature sensor

MAG: Swiss engine makers, the initials stand for Motosacoche Acacias Geneva. The company also produced complete Motosacoche motorcycles

Mag

Abbreviation for Magneto.
Abbreviation for magnesium wheel, or Mag wheels

Mag alloy: Magnesium alloy, a strong lightweight metal used for many components, particularly wheels

Magnaflux

A special chemical process, used to check parts for cracks.
A magnetic method of determining surface and subsurface defects in metals.

Magnesium acetate: See
Calcium magnesium acetate

Magnesium chloride: A soluble compound in liquid form produced from magnesium carbonate and hydrogen chloride used to deice road or pre-wet salt before applying it to roads. It works like anti-freeze by lowering the freezing temperature of water, preventing ice from forming a strong bond to the road.

Magnesium wheel: An alloy wheel.
Also see
Mag wheel

Magnet

A piece of magnetized steel that will attract all ferrous material. The Permanent magnet does not need electricity to function and will retain its magnetism over a period of years. Often shaped into the letter U.
The part of the electric actuating mechanism, which when energized is attracted to the armature, creating a controlled force to apply the brake(s).

Also See
Alnico® magnet
Ball-ended Magnet
Bar magnet
Blowout Magnet
Brake Magnet
Permanent magnet

Magnetic: See
Clutch Magnetic
Flux Magnetic
North Pole Magnetic
South Pole Magnetic

Magnetically controlled electronic ignition: See
Electronic ignition system.

Magnetic blowout: A device which extinguishes an electric arc. A magnetized coil moves one terminal to a cool surface or stretches out the arc.

Magnetic clutch

A coupling device used to turn the compressor off and on electrically.
Clutch built into automobile air conditioning compressor flywheel and is operated magnetically which allows the pulley to revolve without driving compressor when the refrigerating effect is not required.

Also See
Electromagnetic clutch

Magnetic core: Magnetic center of a magnetic field.

Magnetic drain plug: A plug or bolt fitted in the sump or oil pan to collect metal filings

Magnetic Electric Brake: See
Spot Magnetic Electric Brake

Magnetic field: The area encompassed by the magnetic lines of force surrounding either a bar Magnet or electromagnet. The flow of magnetic force between the opposite poles of a magnet.

Also See
Field
Primary magnetic field

Magnetic flux: Lines of force of a magnet.

Magnetic gasket: Door-sealing material which keeps door tightly closed with small magnets inserted in gasket.

Magnetic materials: An object made of certain pure metals (esp. iron and nickel) or an alloy of them such that when it encounters a magnetic field it is demonstrates an attraction or repulsion.

Magnetic north pole: End of magnet Out of which magnetic lines of force flow.

Magnetic permeability: A test that determines the level of magnetism.

Magnetic pick-up

A pulse generator consisting of a stator with a permanent magnet and a rotor, which induces an AC voltage in the inductive winding by the periodic change of the air gap between stator and rotor. Magnetic pick-ups attached to the distributor for ignition triggering have as many teeth on the pole piece (stator) and on the trigger wheel (rotor) as the engine has cylinders. Some magnetic pick-ups have a bowl-like rotor with ferrite rods inserted in the walls. Magnetic pick-ups on the crankshaft flywheel act as reference mark sensors.
A tool with flexible or rigid shaft and magnetic tip used to retrieve dropped nuts, bolts, and other metal parts from hard-to-reach places.

Also See
Pick-up tool
Transistorized ignition with magnetic pick-up

Magnetic pick-up assembly: A pulse generator consisting of a stator with a permanent magnet and a rotor, which induces an AC voltage in the inductive winding by the periodic change of the air gap between stator and rotor. Magnetic pick-ups attached to the distributor for ignition triggering have as many teeth on the pole piece (stator) and on the trigger wheel (rotor) as the engine has cylinders. Some magnetic pick-ups have a bowl-like rotor with ferrite rods inserted in the walls. Magnetic pick-ups on the crankshaft flywheel act as reference mark sensors

Magnetic pick-up tool: A tool with flexible or rigid shaft and magnetic tip used to retrieve dropped nuts, bolts, and other metal parts from hard-to-reach places.

Also See
Pick-up tool

Magnetic plug: A plug or bolt fitted in the sump or oil pan to collect metal filings

Magnetic screwdriver

A Screwdriver with a magnetized shank.
A screwdriver tool with hexagon socket end to accept and operate hex bits and hold them securely by magnetism. Some also have a hollow handle for storing the bits

Magnetic south pole: The part of a magnet into which magnetic flux lines flow.

Magnetism

A field of force which causes a magnet to attract materials made of iron, nickel-cobalt or other ferrous material.
As related to stainless fasteners, 300 series stainless is non-magnetic in its raw material condition. Cold working can sometimes induce traces of magnetism in 300 series, depending on the severity of cold working and chemical composition of the stainless. A rise in magnetism is related to an increase in tensile strength and work hardening caused by the heat and friction of cold forming and does not reduce corrosion resistance or cause any molecular change in austentic raw material. A higher portion of nickel can increase stability in stainless, thus decreasing work hardening and any possibilities of magnetism. Brass and silicon bronze are non-magnetic.

Also see
Induced Magnetism

Magnetization: See
Amperes Theory Of Magnetization

Magnetized: Made magnetic

Magneto: An electrical device which generates electrical Current when it is rotated by an outside source of power. It needs no outside source of power such as a Battery. It may produce either low or high tension Current.

Also See
Flywheel magneto

Magneto file: A tool for filing ignition points and other small objects

Magneto ignition: A compact assembly of a magneto generator, an ignition coil, and a distributor. Ignition voltage is induced within the magneto by the movement of a coil relative to the poles of a permanent magnet. Because it needs no battery, the system is particularly suited for small engines, e.g., motorcycles, outboard engines, etc.

Magnetomotive force (mmf): The magnetic energy supplied with the establishment of flux between the poles of a magnet

Magneto puller: A tool which screws into the center of the magneto to force the magneto away from the shaft on which it rides.

Magnet sensor: See
Hall vane switch

Mags: See
Mag wheel.

Mag wheel: Mag wheel

Lightweight, sporty wheels made of magnesium. The term mag is often applied to aluminum and aluminum and steel combination wheels. In some applications (e.g., wheelchair wheels) one-piece plastic wheels are called mag wheels to distinguish them from wire-spoke wheels.
Also See
Alloy wheels

Main: British term for household AC voltage.
See
Blast Main
Four Bolt Main
Two Bolt Main

Main bar: The bar on a convertible top which carries the main load when the top is raised and taut, and defines the hinge point for the folding motion. Also called main bow

Main beam: British term for High beam

Main beam indicator: British term for High beam indicator

Main bearings: The bearings in the engine block that support the Crankshaft.

Main bearings: See
Main bearing

Main bearing support: A steel plate that is installed over the main bearing caps to increase their strength for racing purposes.

Main bearing supports: See
Main bearing support.

Main bow: The bar on a convertible top which carries the main load when the top is raised and taut, and defines the hinge point for the folding motion. Also called main bar

Main burner: A device or group of devices essentially forming an integral unit for the final conveyance of fuel or a mixture of fuel and air to the combustion zone, and on which combustion takes place to accomplish the function for which the equipment is designed.
Also see
Individual Valve Main Burner

Main combustion chamber: With diesel engines, the fuel may be injected in three different locations in the prechamber, the swirl chamber, or the main combustion chamber (for direct injection engines), depending on the process used

Main deck: The continuous deck of a ship running from fore to aft. The freeboard is measured from this deck.

Main jet: The primary, large fuel orifice in a carburetor through which most of the fuel flows.

Mainline pressure: See
Line pressure

Main member: The primary chassis rail

Main metering circuit: The cruising circuit or the high speed circuit. It supplies the correct air/fuel mixture to the engine during cruising and high-speed conditions. Also called Main metering system

Main mixing well: Main well main nozzle Main delivery tube

Main mixture discharge nozzle: The jet through which the gasoline and air is fed into the carburetor barrel where it becomes the air/fuel mixture

Main petal: The primary petal of a dual-stage reed valve. The opposite is Subsidiary petal. In dual-stage reed valves, the subsidiary petal opens first

Main pressure: See
Line pressure

Main regulating system: The carburetor components are divided into the fuel intake control, the main regulating system, the idle system, and the staring aids. The main regulating system includes the main jet, jet needle, needle jet, and throttle valve, whose purpose it is to provide an appropriate amount of fuel and air to the carburetor

Mains: The caps which secure the crankshaft.
See
Bolt Mains
Four bolt mains

Main Seal Bearing: See
Split-lit-type Rear Main Seal Bearing

Main shaft: The transmission Output shaft

Main sun visor: In dual visor systems, the main visor is moved sideways and the secondary visor is flipped down, thus shielding the driver from the sun from both the front and side

Maintenance: The work undertaken by a car owner to keep his vehicle in good working order; typically checking the tires, lights, oil and coolant levels, windscreen wipers, and seat belts. Compare Service

Maintenance-free: Something that requiring no work in order to be kept operational

Maintenance-free battery: A battery with a permanently sealed top, thus requiring no topping-up

Maintenance manual: A book of instructions detailing routine maintenance

Maintenance Reporting Standards: See
Vehicle Maintenance Reporting Standards

Main triangle: See
Front triangle.

Main Valve Shutoff: See
Manual Main Valve Shutoff

Main venturi: Large venturi cast into the carburetor main body

Main well: The reservoir in which fuel for the main system is stored. The main well is located in the main body casting. It is connected to the venturi area by the discharge nozzle

Main-well tube: A perforated tube which extends from an air bleed in the top of the air horn down into the main well. Admits air from the air bleed into the main well to emulsify the fuel in the main well. Improves idle response and stability when the engine is hot and prevents fuel percolation and general hot-starting problems. Also improves response in the main metering circuit during part throttle conditions. Also called Emulsion tube

Major diameter

On a bolt or screw, the diameter measured from the crest of a thread to the corresponding crest on the opposite side of the bolt or screw
Largest or outside diameter of the screw threads.
On a straight thread, the diameter of the coaxial cylinder which would pass through the crests of an external thread or the roots of an internal thread.

Make: Brand name of a car or truck (i.e., Chevrolet, Ford, Dodge, Honda).

Make-and-break Switch: See
Quick Make-and-break Switch

Maker: See
Automatic Ice Cube Maker
Solid-state Controlled Ice Maker

Male end: A plug, pin, or protrusion which fits into a receptacle (female end).

Make the trip?: Trucker slang for cb signal reception as in "Did my signal make the trip?"

Male thread: Something with external threads like a bolt or screw. Female threads are found in nuts.

Malfunction: Problem in system that affects normal operation

Malfunction indicator light: (MIL) an electric circuit between the computer and the check engine or service engine soon light on the dash panel of a computer equipped vehicle

Malibu Hybrid: A Chevrolet midsize Hybrid sedan similar to the Saturn Aura Green Line that uses a Belt Alternator Starter hybrid system.

Malleable castings

Cast forms of metal which have been heat-treated to reduce their brittleness.
A casting which has been toughened by annealing

Mallet: See
Bossing mallet
Rubber mallet
Wood mallet

Man: Short form for Manual transmission

Management: See
Bureau Of Land Management
Thermal Management
Total Energy Management
Total Quality Management

Management Control System: See
Energy Management Control System

Management District: See
Air Quality Management District

Management system: See
Engine management system

Mandrel: A round shaft used to mount a stone, cutter, saw, etc.

Maneuver: To drive or steer a vehicle around obstacles, change direction, or moving in a confined space.

Maneuverability: The ease with which a vehicle can be steered around objects

Manganese: A non-magnetic metal which improves strength and hardness to steel and bronze
See
Methylcyclopentadienyl Manganese Tricarbonyl

Manganese bronze: An alloy of copper, zinc, and manganese

Manganese phosphate coating: A phosphate coating with added manganese to increase resistance to wear and fatigue

Manganese Tricarbonyl: See
Methylcyclopentadienyl Manganese Tricarbonyl

Manhattan: See
Frazer.

Manhole: A hole or opening in a street, with a removable cover, through which an underground structure, such as a sewer or conduit, can be entered for repair or inspection.

Manifold

A pipe or number of pipes connecting a series of holes or outlets to a common opening.
A device which controls refrigerant flow for system test purposes by means of hand valves which can open or close various passageways connected together inside the manifold. Used in conjunction with manifold gauges and service hoses
The conduit of an Appliance that supplies gas to the individual burner.

Also See
Air injection manifold
Dry Manifold
Exhaust manifold
Gauge Manifold
High-rise manifold
Inlet manifold
Intake manifold
Log manifold
Ram intake manifold
Service Manifold
Split manifold
Variable intake manifold
Wet Manifold

Manifold absolute pressure: (MAP) manifold pressure measured on the absolute pressure scale, an indication of engine load. At sea level, MAP = 1 bar (14.5 psi)

Manifold absolute pressure sensor

(MAP)

A sensor which monitors the engine's intake manifold pressure and transmits the data to the engine controller. A pressure-sensitive disk capacitor used to measure air pressure inside the intake manifold. The Map sensor sends a signal to the computer which uses this information to determine load conditions so it can adjust spark timing and fuel mixture. Also called Manifold pressure sensor or Pressure differential sensor
A sensor that measures absolute air pressure in the intake manifold.

Also see
Barometric And Manifold Absolute Pressure Sensor

Manifold air temperature sensor: (MAT sensor) sensor that monitors the temperature of the air entering the intake manifold

Manifold charge temperature sensor: (MCT) same as the air charge temperature sensor (ACT)

Manifold control valve: (MCV) a thermostatically operated valve in the exhaust manifold for varying heat to the intake manifold with respect to the engine temp. Also called exhaust heat control valve

Manifold gauge set: A complete, testing assembly consisting of a high side gauge, a low side gauge and a high side gauge, a test manifold, and a set of service or charging hoses. Also, can be used to discharge refrigerant, evacuate air and moisture, and charge air conditioning system with refrigerant

Manifold heat control valve: A valve placed in the Exhaust manifold, or in the Exhaust pipe, that deflects a certain amount of hot gas around the base of the Carburetor to aid in warmup.

Manifold heater: A system used to improve the cold start behavior of an engine, consisting of heating ducts incorporated into the intake manifold that are connected to the water cooling system of the engine; alternatively, an electric heater may be used.

Also See
Intake manifold heater

Manifold pressure controlled: (MPC) a fuel injection system which determines engine load based on intake man pressure

Manifold pressure sensor: A sensor that reads pressure changes in the intake manifold in relation to barometric pressure. Also known as Manifold vacuum sensor, Manifold absolute pressure sensor, Pressure differential sensor, or Vacuum sensor

Manifold runners: Single passage in a manifold from one cylinder to the major manifold opening

Manifold, service: Chamber equipped with gauges and manual valves, used by service technicians to service refrigerating systems.

Manifold surface temperature sensor: A sensor that provides information on the surface temperature of the intake manifold

Manifold vacuum: As the Pistons move down on the Intake stroke, they create a suction or Vacuum in the Intake manifold. This vacuum reading can be used to determine how well the engine is running.

Manifold vacuum sensor: (MVS) A sensor that reads pressure changes in the intake manifold in relation to barometric pressure. Also known as Manifold pressure sensor, Pressure differential sensor, or Vacuum sensor

Manifold vacuum zone switch: A type of manifold vacuum sensor (MVS) that dramatically changes the sensor output signal level upon reaching a preselected level or zone of manifold vacuum.

Manoeuvrability: British spelling of Maneuverability

Manoeuvre: British spelling of Maneuver

Manometer

A device for measuring a vacuum, consisting of a U shaped tube partially filled with fluid. One end of tube is open to air, the other is connected to a chamber in which vacuum is to be measured. A column of mercury 30 in. high equals 14.7 psi, which is atmospheric pressure at sea level. Readings are given in inches of mercury (Hg)
Instrument for measuring pressure of gases and vapors. Gas pressure is balanced against column of liquid, such as mercury, in U-shaped tube.

Manual

Originally something done by hand, but later has come to mean something that is done without power assistance. For instance, manual brakes on a car are operated by the driver's foot, not hand; but if the brakes are power assisted, they are no longer manual brakes.
A colloquial term for a vehicle with manual transmission.
A book of instruction.

Also See
Flat rate manual
Maintenance manual
Manual choke
Manual steering
Manual transmission
Owner's manual
Repair manual
Service manual

Manual adjuster: A type of brake adjuster that must be adjusted from time-to-time, with the use of a hand tool

Manual bleeding: A technique for bleeding hydraulic brakes that requires two people. One pumps the brakes, and the other opens and closes the bleeder screw.

Manual choke: A Linkage system which begins with a knob on the Dash which can be pulled to activate and pushed to de-activate. The knob is attached to a cable and the other end of the cable is attached to a the Butterfly valve on the Carburetor. Because many Drivers had difficulty knowing when to use the choke knob, manufacturers developed the Automatic choke system which decides this information for the Driver.

Manual-crank window: See
Manually operated window

Manual frost control: Manual control used to change operation of refrigerating system to produce defrosting conditions.

Manual gearbox: See
Manual transmission

Manual hydraulic brake system: A hydraulic-type brake system that uses unassisted driver effort.

Manual Main valve shutoff: A manually operated valve in the fuel line for the purpose of completely turning on or shutting off the fuel supply to fuel utilization equipment, except to a pilot provided with independent shutoff valves.

Manually operated window: A window (usually a side windo) operated by turning a lever by hand. Compare Electric window

Manual panel cutter: Cutting tool drawn manually across a panel surface to cut to the desired shape

Manual steering: A Steering system that does not have a Power booster to reduce the effort of steering changes especially during slow movements such as parallel parking.

Manual transmission: Click image to supersize

(MT or M/T) A Transmission system in which gears are selected by the Driver by means of a hand-operated Gearshift and a foot-operated Clutch. In a Motorcycle the Clutch is hand-operated and the gearshift is foot-operated. Contrasts with an Automatic transmission. Also called a standard transmission.

Manual valve: (MV) A control in an automatic transmission which distributes Line pressure to the various control valves and pistons which operate the multi-plate or band brakes or the clutches; operated by the driver via the selector lever

Manual valve shutoff: A manually operated valve in a fuel line for the purpose of completely turning on or shutting off the fuel supply to fuel utilization equipment.

Manual version: A passenger car with a manual transmission

Manufactured gas: A gas obtained by destructive distillation of coal or by the thermal decomposition of oil, or by the reaction of steam passing through a bed of heated coal or coke. Examples are coal gases, coke oven gases, producer gas, blast furnace gas, blue: (water) gas, carbureted water gas. Btu content varies widely.

Manufacturer: See
Automobile manufacturer
Original Equipment Manufacturer

Manufacturers And Traders: See
Society Of Motor Manufacturers And Traders

Manufacturers Association: See
National Electrical Manufacturers Association

Manufacturer discounts: In some leases, particularly subvented leases, the manufacturer reduces the MSRP which lowers the purchase price of the vehicle, which the lease is based on. This is a form of capitalized cost reduction.

Manufacturer's performance ratings: The performance data as specified by the car manufacturer

Manufacturer's suggested retail price: (MSRP) The suggested retail price the dealer is asking. Generally the same as the sticker price. Dealers typically sell at a discount to this price.

Manufacturer Vehicle: See
Original Equipment Manufacturer Vehicle

Manufacturing

Process technology (i.e., metal forming, machining, injection molding, blow molding, die casting, forgings, electronics/electrical, assembly, coating/plating); capacity utilization (in percent); production volumes; strategic alliances (e.g., joint ventures, technology agreements).
An energy-consuming subsector of the industrial sector that consists of all facilities and equipment engaged in the mechanical, physical, chemical, or electronic transformation of materials, substances, or components into new products. Assembly of component parts of products is included, except for that which is included in construction.

Manufacturing division: One of ten fields of economic activity defined by the Standard Industrial Classification Manual. The manufacturing division includes all establishments engaged in the mechanical or chemical transformation of materials or substances into new products. The other divisions of the U.S. economy are agriculture, forestry, fishing, hunting, and trapping; mining; construction; transportation, communications, electric, gas, and sanitary services; wholesale trade; retail trade; finance, insurance, and real estate; personal, business, professional, repair, recreation, and other services; and public administration. The establishments in the manufacturing division constitute the universe for the MECS: (an EIA survey).

Manufacturing establishment: An economic unit at a single physical location where mechanical or chemical transformation of materials or substances into new products are performed.

MAP

Acronym for Manifold absolute pressure
Acronym for manifold air pressure sensor

Map: A pictorial representation of a series of data points stored in the memory of the control unit of system with complete engine management. The control unit refers to the map to control variables such as fuel injection pulse width and ignition timing

Also See
Characteristic map
Dwell-angle map
Engine map
Ignition map

Map-controlled ignition: A microprocessor-controlled ignition system with electronic ignition timing by means of an ignition map stored in the control unit memory. The engine speed is sensed by Hall generators at the distributor or magnetic pick-ups on the crankshaft, the load signal being given by pressure sensors which measure the air mass or air per unit of time

Map light: An interior light to facilitate, for example, map reading.

Also See
Gooseneck map light

MAPP: A stabilized methyl acetylene-propadiene fuel gas. It is a Dow Chemical Co. product.

Mapped ignition: A microprocessor-controlled ignition system with electronic ignition timing by means of an ignition map stored in the control unit memory. The engine speed is sensed by Hall generators at the distributor or magnetic pick-ups on the crankshaft, the load signal being given by pressure sensors which measure the air mass or air per unit of time

Mapping: See
Characteristic map

MAP sensor: Manifold absolute pressure system sensor tells computer how much pressure is in the intake manifold

Maquila: Mexican assembly plant located near the U.S.-Mexican border where most production is exported to the United States.

Maquiladora: Mexican assembly plant located near the U.S.-Mexican border where most production is exported to the United States.

Marbling: A special decorative painting effect with rotating brushes

Margin: The return an intermediary achieves on the selling price of the article. That is, if the intermediary buys a product for $1 and sells it for $1.50, the margin is calculated. For example, .50 (i.e., $1.50 - $1) divided by $1.50, or 33%.
Also See
Gross margin
Valve margin

Margin bracket: A bracket connecting a side frame to the margin plate at the bilge

Margin line: A line, not less than 3 inches below the top of the bulkhead deck at side, defining the highest permissible waterplane in the final condition of sinkage, trim and heel

Marine Diesel Oil: (MDO) Marine Diesel oil is a middle distillate fuel oil which can contain traces often percent: (10%) or more residual fuel oil from transportation contamination and/or heavy fuel oil blending. The MDO does not require heated storage.

Marine freight: Freight transported over rivers, canals, the Great Lakes, and domestic ocean waterways.

Mark: See
Beach Marks
Burn Mark
Draft marks
Jaguar Mark
Reference mark sensor
Skid mark
Swirl marks
Timing mark
Tracking mark
Witness mark

Marker: See
Mile Markers
Pavement markers
Spark Plug Cable Marker
Spark Plug Wire Marker

Marker lamp: A light which is mounted on the extreme edges of the roof of a truck to show the maximum height and width of a vehicle. Also called clearance lamp.
Also see
Side marker light

Marker light: A Side marker light

Market: See
Aftermarket
Do-it-yourself market
Grey market
Mechanic installed market
Replacement market
Gray Market Vehicles

Market share: The percentage of total sales represented by an individual manufacturer/importer, make or nameplate.

Market Vehicles: See
Gray Market Vehicles

Marking: See
Hatched marking
Pavement markings
Size marking
Tire Size Markings
Water marking
Wheel marking

Mark sensor: See
Reference mark sensor

Mark-up: The return an intermediary achieves on the cost price of an article. Using the same example described above, mark-up is .50 divided by $1, or 50%.

Marles steering: A form of cam-and-roller steering

Marmon

A vehicle brand of which the following models are classic cars:

all 16-cyl. models
1925 model 74
1926 model 74
1927 model 75
1928 model E75
1930 model Big 8
1931 model 88 and Big 8

Marque: A particular brand name of a vehicle. Also spelled marquee

Marquee: A particular brand name of a vehicle. Also spelled marque

Martensitic: Named for Robert Martens, a German metallurgist, martensitic grades of stainless steel (types 410, 416, and 420) have a high carbon content which reduces corrosion resistance, but allows a sharp increase in tensile strength after heat treatment. Because of its high tensile strength, martensitic stainless is used for highly stressed parts such as control rod mechanisms, valves, shafts, pump parts under high stress. Martensitic stainless is magnetic, contains no nickel, loses toughness in very cold temperatures, and may have tendency to become brittle. Used in approximately 5% of stainless fasteners. Its corrosion resistance is not as good as austentic or ferritic stainless, so martensitic fasteners are used in mild atmospheres.

Martin: See
Aston Martin.

MAS: Acronym for mixture adjust screw

Mascot: See
Emily

Maserati: Click image for books on
Maserati

A vehicle brand of which the 1925-1948 models with required application are classic cars. The 1957-64 3500/3700 GT models are milestone cars.

Masher: A cyclist who habitually pedals hard in a high gear, at a slow cadence. The opposite of a spinner.

Mask: To cover the surrounding area when paint spraying to protect it from splashes

Masking: See
Aural Masking

Masking tape: An adhesive tape used to cover surfaces that border an area to be painted, so as to protect them

Mass: The quantity of matter a body contains. Mass is measured in kilograms (and often incorrectly called weight). The mass of a body does not change if, for example, it is moved to the Moon where the force of gravity is less.

Also See
Relative Atomic Mass
Sprung weight
Unsprung weight
Weight

Mass airflow meter: (MAF) device for measuring the mass flow of air into an engine.

Also See
Air flow sensor
Hot-wire airflow meter

Mass damper: A device which reduces or prevents vibrations or oscillations, usually a weight which counteracts (balances) undesirable motions; used on drive shafts of some FWD cars

Mass Flow: See
Air Mass Flow

Mass Meter: See
Air Mass Meter

Mass-produced car: A car which is manufactured in great numbers to a standard pattern and with extensive mechanization

Mass Sensor: See
Air Mass Sensor

Mass tone: The tone of a paint as it appears from the color of the paint in the can; this is required for formulating the ingredients of a paint tone.

Also See
Tint tone

Mass transit system: A system designed to transport large numbers of people or goods

Mast: A tall vertical or raked structure, usually of circular section, located on the centerline of a ship and used to carry navigation lights, radio antennas and cargo booms

Master: The primary or controlling device. A secondary or dependent device is called a slave.

Also See
Brake master cylinder
Tandem master cylinder
Master link

Master brake cylinder: See
Brake master cylinder.

Master con rod: In a two-stroke dual piston engines, the connecting rod that is articulated directly on the crankshaft.

Also See
Slave con rod

Master cylinder

The primary component for pressurizing fluid in a hydraulic system. Used in the braking system, it supports a reservoir for holding brake fluid and is activated each time the driver depresses the brake pedal.
The device that converts mechanical pressure from the brake pedal into hydraulic pressure that is routed to the wheels to operate the friction assemblies.

Also See
Brake master cylinder
Dual Master Cylinder
Single Master Cylinder
Slave cylinder
Tandem master cylinder
Vacuum-powered Master Cylinder

Master cylinder pushrod: The rod that transmits the movement and force of the driver from the brake pedal lever to the master cylinder piston.

Master Gauge: A thread-plug gauge which represents the physical dimensions of the nominal or basic size of the part. It clearly establishes the minimum size of the threaded hole and the maximum size of the screw at the point at which interference between mating parts begin.

Master link: A special link on a Chain that can be opened by flexing a plate, removing a screw, or some other means besides driving out a Rivet. The retaining spring clip is shaped like a fish with a round head and twin tails. This illustration helps to determine the position of the clip because the fish moves in the direction of Chain movement. When installed in reverse, the clip may come off.

Master model: The first precision model of an automobile based on a clay model or CAD-data; essential for the manufacture of prototypes

Master pattern: The first precision model of an automobile based on a clay model or CAD-data; essential for the manufacture of prototypes

Master switch: See
Battery master switch

Master vac: See
Vacuum brake booster

Master vac servo unit: See
Vacuum brake booster

Masthead light: A white light situated on the fore and aft centerline of a ship

Mastic: Any heavy-bodied adhesive of such a consistency that it must be applied by notched trowel, gob, or by buttering methods

Mastication: The reduction of rubber to a pulp preparatory to making tires

Mastic seam sealant: Soft waterproof sealant for joints

Mat

A dull, not shiny, paint finish. Also spelled matt.
A covering.
Acronym for Manifold Air Temperature

Also See
Bead seat mat
Fiberglass mat
Floormat

Matador: Click image for books on
Matador

An automobile manufactured by AMC

Matching: See
Paint color matching

Mate: To fit together

Material: See
Active Material
American Society For Testing Materials
Base material
Bearing material
Bridges And Materials
Friction Material
Metallic Friction Material
Molding material
Moulding Material
Noncombustible Materials
Organic Friction Material
Performance characteristics of materials
Piston material
Soundproofing material
Viscoelastic materials
Waste Materials

Material safety data sheets: Sheets that contain information on the handling of hazardous wastes, the use of protective equipment and the procedures to follow in case of an accident

Mating: Fitting together; matching

Mating gears: Gears which mesh together

Mating surface: A surface which interacts perfectly with another

Mating thread: A thread which engages with a corresponding thread, such as the male and female threads of a nut and bolt

MAT sensor: Acronym for Manifold air temperature sensor

Matter: See
Particulate matter
Polycyclic Organic Matter
Total Particulate Matter
Volatile Matter

Matrix: That portion of the mold which surrounds the tire transferring heat to the uncured rubber and forming the tread pattern.

Matt: A dull, not shiny, paint finish. Also spelled mat

Maxima: Click image for books on
Maxima

A model of automobile manufactured by Nissan in Japan

Maximum brake power: The maximum power of an engine as measured by a dynamometer

Maximum diameter brake drum: The largest diameter to which a brake drum can be machined or worn before it becomes unsafe. This dimension is usually stamped or cast into the drum near the hub. Typically, this is 0.060" over original diameter.

Maximum ignition Time: The maximum allowable time for the specified function of any device.

Maximum Material Limit: The maximum limit of size of an external dimension or the minimum limit of size of an internal dimension.

Maximum operating pressure: (MOP) The steady-state or transient gauge pressure at which a part or system operates. It shall not exceed the allowable working pressure, and it is usually kept at a suitable level below the setting of pressure-limiting/relieving devices to prevent their frequent functioning.

Maximum power: The maximum power of an engine as measured by a dynamometer

Maximum regulation capacity: The high limit of flow below which is found acceptable regulating characteristics.

Maximum trailer weight: Also known as towing capacity; the heaviest trailer the vehicle is rated to tow. Towing capacity is typically based on the vehicle plus a driver of 150 pounds. The weight of additional passengers and/or cargo should be deducted from the maximum trailer weight.

Maybach: A vehicle brand of which the 1925-1948 models are classic cars.

Mays: See
Raymond-Mays

Mazda: Click image for books on
Mazda

A model of automobile manufactured in Japan by the Mazda Motor Corporation. It includes 323 (1980-94), 626 (1983-2002), 929 (1981-95), B2200 (19__-93), B2300 (1994-2007), B2500 (1998-2001), B2600 (19__-93), B3000 (1994-2007), B4000 (1994-2007), CX-7 (2007), CX-9 (2007), MAZDA3 (2004-08), MAZDA5 (2006-07), MAZDA6 (2003-08), Mazdaspeed3 (2007), MAZDASPEED6 (2006-07), Miata MX-5 (1990-2008), Millenia (1995-2002), MPV (1989-2006), MX-3 (1992-95), MX-6 (1988-97), Navajo (1991-94), Protege (1990-2003), Protege5 (2002-03), RX-7 (1993-95), RX-8 (2004-07), and Tribute (2001-06)

Mazda RX: Click image for books on
Mazda RX

A model of automobile with a Rotary engine manufactured in Japan by the Mazda Motor Corporation. It began with the R100 and included the RX2, RX3, RX4, RX5, RX7, and RX8.