| Magneto |
A
self-contained device used widely on race cars, dirt bikes and small
engines to generate power, step up voltage and fire spark plugs at
the correct time. A magneto does not require a battery to generate
voltage. A magneto contains wire windings and usually is installed
on the crankshaft or runs off a belt. It makes it's own power much
like an alternator does. The voltage is stepped up to high tension
voltage which is used to fire the spark plugs. As a motor's rpm increases
so does the high-tension voltage. The downside of a magneto is that
relatively high rpm's are required to get enough energy to produce
enough energy to create the spark required to start and run an engine.
Most vehicles still need a battery to operate a starter, lights and
accessories. |
|
|
| Mag
wheel |
See
Mag or Alloy wheel. |
|
|
| Main
bearing caps |
Removable
caps with a semicircular machined surface that bolt to the engine
and hold the lower crankshaft bearing and crankshaft in place. |
|
|
| Main
bearings |
The
bearings in an engine that support the crankshaft. The bearing are
flat and fit at very close tolerances to the crankshaft. Because of
oil pressure and the tight tolerances, the crankshaft essentially
rides on a thin film of oil. |
|
|
| Main
shaft |
The
principle shaft in a transmission where power is transmitted to the
differential. The main shaft consists of several gears that mesh with
countershaft gears to produce different output speeds and torque depending
on gear combination. |
|
|
| Manifold |
Strictly
speaking, a device, usually a metal object that accepts a single input
of air or fluid and distributes to numerous outputs, or, accepts inputs
from several sources and channels into one output. Automobile engines
use an intake manifold which air enters one port and is distributed
to one of several ports (intake runners) that lead to each cylinder.
Another manifold, the exhaust manifold works the opposite way, exhaust
gasses coming from several input sources (exhaust ports) get channeled
into a single output channel that hooks up to the exhaust pipe. |
|
|
| Manifold
heat |
Heat
from the exhaust manifold that is used to heat the air going into
the intake manifold to help a cold engine run smoother. See Heat
Control Valve.
Older
automobiles were fitted with a tube leading from the carburetor
to a heat stove on the exhaust manifold and used manifold heat to
disengage the choke.
|
|
|
| Manifold
pressure |
Positive
pressure in an intake manifold that occurs when the intake valves
are closed and the pistons are moving upward. The opposite of manifold
vacuum. Manifold pressure also occurs in turbo and supercharged motors.
|
|
|
| Manifold
vacuum |
Vacuum
created in an intake manifold as the pistons move downward and air
is drawn into the cylinders. Occurs during the intake stroke. |
|
|
| Manual
steering |
A
steering system that does not use hydraulic pressure to reduce steering
effort. |
|
|
| Manual
transmission |
A
transmission that requires shifting by the driver in order to make
gear changes. Does not shift automatically. Requires the use of a
clutch. |
|
|
| MAP
sensor |
Manifold
Absolute Pressure sensor. A sensor usually located in the intake of
fuel injected engines which measures pressure inside the intake manifold.
Sends an electrical signal to the electronic control module which
is used to create more precise fuel metering. |
|
|
| Map
light |
Individual
lamps usually positioned at a high point such as in an overhead console,
rear view mirror or top of dashboard that shines downward onto a passenger's
or driver's lap and allows that occupant to read without requiring
the dome light. Because the light shines on the reading zone of an
individual, other occupants are free to sleep undisturbed and the
driver can drive without the glare of the brighter dome light. |
|
|
| Map
pocket |
Small
pockets in the lower sides of doors or behind seats used for convenient
stowage of newspapers, magazines, tissues and, of course, maps. |
|
|
| Marine-style
alternator |
Commonly
referred to as a "One-wire" alternator. The alternator has
one positive output which the current can be used to charge the battery
and operate accessories. Popular among racers and street rodders for
it's ease of wiring. |
|
|
| Mass
airflow sensor |
A
sensor used in an engine's fuel injection system. It measures the
amount of airflow through the intake manifold. A signal from the airflow
sensor is sent to the vehicle's computer to determine the amount of
fuel necessary. Also called Airflow sensor. |
|
|
| Master
cylinder |
A
key brake component which converts and multiplies foot pressure into
high hydraulic pressures used to activate a vehicle's brakes. The
master cylinder is located in the engine compartment behind the brake
pedal. When the pedal is pushed, brake fluid is compressed and pressure
is sent through steel brake lines to wheel cylinders at each wheel.
The pressure at each wheel assembly is used to force brake pads against
brake components (rotors & drums) attached to the wheel. This,
in turn, slows the vehicle down. |
|
|
| Maximum
power/ torque |
The
maximum amount of power and torque an engine or vehicle can produce
as measured on a chassis or engine dynamometer. Engine torque and
power differ. Torque is the amount of twisting force (not necessarily
motion), and power is the rate at which work is done. An engine's
power and torque vary with engine speed. Maximum power occurs near
the top of an engine's rpm range and maximum torque generally near
the middle of the rpm range. |
|
|
| Mean
Effective Pressure (MEP) |
The
steady pressure that if applied to each piston's power stroke would
produce the power an engine is capable of. MEP is a theoretical quantity
that is used to compare engines. During normal operation, however,
during the power stroke the pressures in each of an engine's cylinders
varies greatly. |
|
|
| Mechanical
brake |
A
brake system that uses cable or levers to operate the brakes. Vintage
automobiles widely used mechanical brakes until hydraulic brake systems
were widely adopted. The parking brake on nearly all vehicles is still
a mechanical brake separate from the hydraulic brake system. See Emergency
Brake. |
|
|
| Mechanical
efficiency |
A
ratio of the actual power output at an engine's crankshaft divided
by the power produced on the pistons. Crankshaft power is always less
because of power lost through friction and heat and power required
to operate the valve train and oil pump. |
|
|
| Mechanical
valve lifter |
A
solid metal valve lifter that rides between the camshaft and the valves.
Not hydraulic. Solid lifters are used in racing to achieve increased
engine responsiveness, but not in production automobiles because they
are typically noisier and require frequent adjusting. |
|
|
| Memory |
A
place where information is stored on computers, a type of computer
chip. There are two different kinds of computer memory, ROM and RAM.
Read Only Memory (ROM) is the type used in automobiles. It is preprogrammed
and permanent and cannot be changed. RAM memory can be changed but
disappears when power is removed. New EPROM chips (Erasable, Programmable
Read Only Memory) are special ROM memory chips in which certain parts
of the memory can be altered. Such technology is used for such automotive
accessories such as power seat memory. |
|
|
| MEP |
See
Mean Effective Pressure. |
|
|
| Metering
rod |
A
thin rod that is tapered or stepped on it's end that is used to vary
the orifice size of a carburetor's fuel jet's to regulate the amount
of fuel flowing into an engine. The rod moves up or down in the metering
jets and the taper or steps in effect change the orifice size and
vary fuel flow into the engine. |
|
|
| Methanol |
Methyl
alcohol produced from wood products or natural gas. An alternative
fuel to gasoline. Frequently used as a fuel in race cars. It contains
more energy than gasoline and produces more power, but fuel consumption
is higher. Can also be mixed with gasoline and has been looked at
as a way to stretch gasoline resources. Also called Wood alcohol. |
|
|
| Methyl
alcohol |
Same
as Methanol (above). |
|
|
| Metric
rating system |
A
tire rating system that uses metric measurements, used widely in Europe
and throughout the world. Similar to the P-Metric system used in the
U.S. that includes tire sidewall marking such as P195/75/R14. The
metric rating system used in Europe does not require the use of a
P (passenger) but does require a speed rating designation. |
|
|
| Microchip |
A
tiny silicon wafer that can contain thousands, even millions of transistors.
Used throughout modern automobiles in radios, the ignition system,
and engine computer systems. Microchips replaced bulky tubes and transistors
in radios and other functions. Besides being very compact (a single
microchip the size of a nickel can carryout dozens of functions),
they also consume much less power, produce less heat and last longer
than traditional transistors and tubes. |
|
|
| Micrometer |
A
precision C-shaped instrument used by engineers and engine builders
that can make precise measurements down to the one hundred thousandths
of an inch. Used to measure critical surfaces such as crankshaft bearing
journals and pistons diameters. More accurate than a veneer caliper
but not as quick to use. Newer micrometers which have digital scales
are particularly accurate. |
|
|
| Microprocessor |
A
semiconductor that is made of a silicon wafer and contains millions
of transistors. The main component of a computer. |
|
|
| Mid-engine |
A
vehicle with it's engine positioned within it's wheelbase (between
front and rear wheels). In most mid-engine vehicles, the engine is
usually located just ahead of the rear axle but behind the passenger
compartment, but can also be located ahead of the passenger compartment
but slightly behind the centerline of the front wheels. Many sports
cars utilize the mid-engine design because it promotes even weight
distribution which translates into improved handling and cornering. |
|
|
| Miles
per hour (mph) |
A
measure of speed or velocity in miles. Based on the English measuring
system. Used in the United States and England. |
|
|
| Military-style
gas cans |
Durable
fuel cans typically made of steel used by the military. Also known
as a jerry can. |
|
|
| Military
wrap |
A
leaf spring treatment used on military vehicles and some off-road
trucks in which the ends of the second leaf are wrapped around, or
partially wrapped around the primary leaf's eyelet. If the primary
leaf spring were to break, the second leaf would remain attached to
the spring perch and support the vehicle. Normal leaf springs are
attached by eyelets at the ends of the primary leaf spring only. If
the primary spring breaks, the vehicle can become disabled. |
|
|
| Miller
cycle |
A
refined four-stroke process where air is pumped into a cylinder of
a small engine to enhance it's combustion process. By pumping in about
twice as much air/fuel mix as an engine would normally take on it's
own, a more powerful combustion process occurs. Under normal circumstances
detonation would occur and prevent such combustion process. To overcome
this condition, Ralph Miller (the inventor of the idea) produced an
engine where the compression stroke is shortened. How it works is,
during the compression stroke, the intake valve is held open for a
short amount of time allowing some of the air to be pushed back through
the intake valve. That prevents overheating the air (which would lead
to detonation) but still leaves about twice as much air in the cylinder
than would normally have entered. The result is an engine that produces
significantly more power. Used primarily on small engines. |
|
|
| Minivan |
Small
vans that are typically more car-like in ride and driveability and
typically seat seven passengers. Popularized by Chrysler. Minivans
became extremely popular through the 1980's and 90's, having taken
the place of full-sized cars and station wagons as the defacto family
hauling car. Most manufacturers produce a minivan. |
|
|
| Misfire |
When
the air/fuel mixture in a cylinder doesn't ignite properly or at the
right time. Common causes are faulty spark plugs or plug wires, mixed-up
wires (wrong firing order), faulty distributor cap, bad coil, vacuum
leak, incorrect air/fuel mix or valve problems. The end result is
a rough-running motor and a vehicle with reduced power. |
|
|
| Miss |
A
shortened term for Misfire (above). |
|
|
| Mixture |
Same
as Air/Fuel mixture. A blend of air and fuel supplied to an engine
which is used for combustion. As an engine draws in air, a fine spray
of fuel is sprayed from the carburetor or fuel injectors into the
passing airstream. The air/fuel mixture is then drawn into the combustion
chambers (cylinders) where it is ignited by a spark plug. |
|
|
| Mobil
auto club. |
An
auto club maintained by the Mobil Oil company. |
|
|
| Model
T |
A popular first mass-produced automobile designed and produced by
the Ford Motor Company from 1908 to 1927 of which more than 20 million
were sold. It's popularity is considered responsible for the development
of large-scale motoring than was any other vehicle in automotive history.
It also spurred the building of roads and streets in the United States.
It was nicknamed the "fliver" and the "Tin lizzie." Also see Ford
Motor Company. |
|
|
| Modesty
panel |
See
Valance panel. |
|
|
| Modesty
skirt |
See
Valance panel. |
|
|
| Modular
wheel |
An
exotic type of wheel often used in racing where the wheel center and
outer rim are detachable. Allows rims of different widths and offset
to be quickly bolted to the wheel center. Generally such wheels use
magnesium centers that bolt to lightweight rims. |
|
|
| Modulation |
Used
to describe applying the brakes in a slow, controlled fashion so as
not to lock up the wheels. May involve controlled pumping. Antilock
braking systems essentially do the same thing only faster and better.
Sensors at each sense wheel lockup and automatically modulate
hydraulic pressure to the affected wheel, which is better than driver
modulation because a driver can modulate a brake system, but not control
a single brake at a particular wheel. |
|
|
| Modulator |
A
pressure regulating device used in older automatic transmissions
to control shift timing. The modulator was generally operated off
engine vacuum and was used to vary internal oil pressure in the
transmission which would affect shift timing. Under hard acceleration
the modulator would cause the transmission gears to "hold"
longer than normal for greater power and delayed shifting.
Also,
a modulator is used in an antilock braking system to reduce hydraulic
pressure in a slipping wheel to prevent wheel lockup.
|
|
|
| Molding |
A
piece of metal or plastic trim used for decoration or protective purposes.
On the outside of a car, a rubber molding is typically fastened to
the side of the vehicle to protect against dings. Chrome moldings,
or moldings painted black or body color are often used on bumpers
and as trim on the interior. |
|
|
| Moment
of inertia |
Rotational
inertia of an automobile that has a major impact on it's cornering
and handling abilities. Rotational inertia is the tendency of an object
to resist rotational acceleration. Imagine a vertical pole through
the center of an automobile (sticking out the top of it's roof). If
the car were to be rotated on the vertical pole it would resist rotation.
The more weight at it's outer ends (front/rear) the greater it's resistance
to rotation which affects how well the car can corner. Shorter cars
and mid-engine designs which have a lower moment of inertia are desirable
for road courses which contain many corners. Such vehicles are typically
very nimble. |
|
|
| MON |
Stands
for Motor Octane Number. See Octane Number. |
|
|
| Monitor |
A
TV-like display used on diagnostic equipment to display vehicle information. |
|
|
| Monobeam
suspension |
A
solid axle suspension scheme used on the front of vintage automobiles
and on the rear of many front-wheel drive cars. On vintage automobiles,
a heavy-duty solid beam connected both wheels and was suspended by
leaf springs. Newer front wheel drive vehicles sometimes use a monobeam
axle in the rear. It is usually made of specially bent sheet steel
for reduced weight. |
|
|
| Monobloc |
An
engine where the block and crankcase are one complete unit. Not commonly
used on modern production automobile engines, but found widely on
other engines such as commercial truck motors and small engines such
as lawnmowers. |
|
|
| Monocoque |
A
type of vehicle design (primarily used in some racing events) where
the body and body panels become a load-bearing shell. The benefit
of such designs are a tremendous strength-to -weight ratio. |
|
|
| Monoposto |
Italian
for single-seat [vehicle]. |
|
|
| Moonroof |
A
term used interchangeably these days with sunroof to describe an opening
in the roof above the passengers. Technically, though, a sunroof is
a opening which can be covered by a piece of canvas or a retractable
or tiltable metal shield. A moonroof is a piece of glass or plastic
which allows light in both during the day and at night, hence the
term Moonroof. Also see Sunroof. |
| MOSFET |
|
| Motor |
Used
interchangeably with 'engine' to describe a vehicle's power plant.
Technically speaking, however, a motor is a machine that converts
electrical energy into mechanical energy. An engine converts heat
energy into mechanical energy. The heat energy comes from fuel - gasoline,
diesel, propane or alcohol. |
|
|
| Motor
mounts |
Special
rubber and metal parts which attach the engine and transmission to
the vehicle's frame. Rubber is used in a motor mount's construction
to reduce engine and transmission vibration from being transmitted
to the passenger compartment. Engine mounts also are designed to flex
due to engine torque. Also called Engine Mounts. |
|
|
| Motor
Octane Number (MON) |
See
Octane. |
|
|
| mph |
See
Miles Per Hour (above). |
|
|
| Mudflaps |
Rubber
shields which can be mounted behind a vehicle's wheels to prevent
mud, rocks and other road debris from being thrown behind the wheels.
Protects drivers behind the vehicle. Mudflaps are also frequently
mounted behind a vehicle's front wheels to prevent rocks from chipping
the paint on the vehicle's door, rocker panels and fenders. |
|
|
| Mudhogs |
Special
off-road tires with particularly large lugs for traction in deep mud
and snow. |
|
|
| Muffler |
A
barrel-shaped device fitted to a vehicle's exhaust system that contains
chambers and baffles to muffle and reduce engine noise. |
|
|
| Multi-grade
oil |
Oil
that is formulated with additives (viscosity index improvers) to flow
more easily at low (colder) temperatures. Single grade oils become
rather thick in cold temperatures reducing a motor's ability to properly
pump it through small chambers and lubricate moving parts. Multi-grade
oils allow good lubricating at a much wider range of temperatures,
especially in the cold. Nearly all motor oils used today are multi-grade
oils. |
|
|
| Multi-leaf
spring |
A
leaf spring comprised of several wide, flat, spring-steel leaves stacked
on top of each other and clamped together. Nearly all leaf springs
used on automobiles are multi-leaf springs. The advantage of using
multiple leaves is to fine tune spring rates which create a smoother
ride yet become stiffer after a certain amount of compression to allow
greater loads, and more passengers to be carried. |
|
|
| Multi-link
suspension |
Where
several suspension arms are used to locate a vehicle wheel or axle.
Using several arms allows fine tuning of the suspension to maintain
correct suspension and wheel geometry which translates into excellent
steering, braking and ride characteristics. |
|
|
| Multiple
disc |
A
clutch mechanism that uses two or more clutch discs. Found on high
output engines or where clutch discs must be smaller than a given
torque would require. An automatic transmission, for example, uses
multiple discs because it allows a more compact design. |
|
|
| Multi-port
injection |
See
Fuel injection. |
|
|
| Multi-valve
engine |
An
engine that uses more than one intake or exhaust valve per cylinder.
Many new vehicles use three or four valves per cylinder because it
allows air to enter and exit with less resistance thereby improving
performance. |
|
|
| Multi-valve
head |
Same
as Multi-valve engine (above). |
|
|
| Multi-viscosity
oil |
Same
as Multi-grade oil (above). |
