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Glossary of Technical Terms
Ab
Ac
Ad
Ae
Af
Ai
Al
Am
An Ar
As
Au
Aw
Ax
A-2
tire A term used for tire sizes 16.00 and larger in
nominal cross section. Also called earthmover or off-the-road tire
A-Arm
See control
arm.
A-arm
suspension
See
double wishbone.
Abampere
A
unit of electric current in the CGS electromagnetic system of units. One
abampere equals 10A.
ABPV
Acronym for "air
bypass valve"
or anti-backfire valve
ABS Acronym
for "anti-lock
brakes.
A
system, usually electronically controlled, that senses incipient
wheel lockup during braking and relieves hydraulic pressure at wheels
that are about to skid.
ABS
override button A
button or switch which disengages the automatic anti-lock
braking system
so that the driver can operate the brakes himself.
ABV Acronym
for "air
bypass valve"
or anti-backfire valve
A/C
An abbreviation for air conditioning or air conditioner.
AC
[1]
Acronym for "alternating current."
Alternating
current or altitude compensator; also Ac, Actinium An element with
the atomic number of 89
[2]
Acronym for "air conditioning" or "air conditioner."
AC/TVS
Air cleaner/thermal vacuum switch
Accelerate
To increase the speed of a vehicle.
Accelerator
In automobiles, this is the "gas
pedal"
which is attached by linkage
to the throttle
in the carburetor
or to the fuel injection
system. It regulates the amount of fuel which is sent to the engine.
On
motorcycles, the accelerator is located on the right-hand twist grip
or an actuating lever.
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Accelerator
Pedal
The
accelerator,
gas pedal,
or throttle pedal.
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Accelerator
Pump A small cylinder
and piston
usually located inside the carburetor
that sprays an extra amount of fuel into the engine during
acceleration. It improves acceleration by giving more boost and
reducing a momentary lag in power. It is actuated by depressing the pedal.
Accord A
model of automobile manufactured by Honda
Ackermann
Steering
[1]
A double-pivoting steering system where the outer ends of the
steering arms are bent slightly inward so that when the vehicle is
making a turn, the inside wheel will turn more sharply than the outer
wheel. This is done to compensate for the greater distance the
outside wheel must travel. Notice 20 degrees on left wheel and 30
degrees on right wheel
[2]
Arrangement whereby a line extended from the track-arms, when the
wheels are set straight ahead, should meet on the chassis centerline
at 2/3 of the wheelbase from the front, allowing the inner stub-axle
to move through a greater angle than the outer.
Ackermann
angle
The
toe-out or toe-in of a vehicle with Ackermann
steering when the wheels are positioned straight ahead.
Ackermann
axle In a vehicle with Ackermann
steering (at the front of the vehicle), it is a
non-rotating axle that is steerable and has two pivot points (one on
each end of the axle) with vertical kingpins.
Acura A
vehicle brand from the Honda manufacturers
Adjusting
Screw
A
small screw usually found on carburetors,
brakes, or headlights
which change the way something operates, such as increasing or
decreasing the amount of fuel entering the engine;
or changing the idle speed;
or tightening up the brakes; or changing the setting on rocker arms;
or the level of the headlights.
Explore
The Carburetor
Aerodynamics
The study of the flow of air as it passes over and around a
moving object as well as the forces which the air makes on the
object. An airplane, for instance, needs positive lift to get it
airborne and negative lift to help it land. Thus the shape of a land
vehicle (car, bicycle, etc.) either promotes positive or negative
lift. Race cars may use spoilers and wings (air foils) to control
lift. In vehicle design, the airflow is monitored in a wind tunnel.
As well, aerodynamics also studies the most efficient shapes for
increased speed and fuel economy.
AF
Ratio
A/F
Ratio See
air-fuel ratio
Aftermarket
All products and services used in the repair and maintenance of
vehicles after the vehicle has been sold.
Aftermarket
part Goods not for use as original equipment in the
production of light-duty vehicles or heavy-duty vehicles, i.e.,
products and services used in the repair and maintenance of these vehicles
Air
bag An inflatable bag hidden in the steering wheel
(driver's side) or the dash or glove box (passenger side). In a
head-on collision, the bags inflate, preventing the driver and front
passenger from being thrown forward into the steering wheel or windshield.
Air
Brake:
[1]
A system of braking which is usually found on large truck in which
compressed air pushes against a brake piston or diaphragm in order to
apply the brakes to stop or slow the vehicle.
[2]
A mechanical brake operated by air-pressure acting on a piston
Air
Bypass Valve
Air
By-pass Valve
(ABPV
or ABV) a backfire-suppressor valve used in air injection systems.
During high engine vacuum conditions such as deceleration, it vents
pressurized air from the air pump to the atmosphere in order to
prevent backfiring. At other times, it sends air to the exhaust
manifold. On vehicles with a three-way catalyst, it sends air to the
oxidation catalyst only when the engine warms up.
Also
called an anti-backfire valve, diverter valve, or gulp valve.
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Air
cleaner A metal or plastic housing, containing a filter
element,
whichremoves dust and dirt from the air being drawn into the engine.
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Air
Conditioner
(A/C)
or (Air)
[1]
A device used to control temperature, humidity, cleanliness, and
movement and sometimes the air purity, in an enclosed space
[2]
A system of devices which causes a reduction or control of the
temperature and humidity within the cab of a vehicle. It was first
offered on the 1941 Packard. Two types are used in vehicles:
Receiver-dryer type and accumulator type.
Air
Filter or Air filter ELEMENT
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The
actual filter in an air
cleaner system,
usually manufactured from pleated paper and requiring renewal at
regular intervals.
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Airflow
Sensor
A
device in an electronically controlled fuel injection system which
detects the amount of air entering the combustion chambers.
Continuous injection systems use an airflow sensor plate to measure
airflow volume; electronic systems use a vane or flap-type airflow sensor.
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The
Airflow Sensor or Mass Airflow Sensor (MAF) used to measure amount
of air entering the engine. Usually it's located in the intake after
the air filter, before the throttle. Based on MAF sensor readings,
the engine computer (ECM) calculates proper amount of injected fuel. |
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Air
Fuel (air-fuel, air/fuel)
See
air-fuel ratio
Air
Fuel Mixture (Air-Fuel Mixture) See rich
air-fuel mixture and
lean
air-fuel mixture
Air
Fuel Ratio (air-fuel
ratio, A/F ratio) The mass of air supplied to the engine
divided by the mass of fuel supplied in the same period of time. The
stoichiometric, or chemically correct, air-fuel ratio is the exact
ratio necessary to burn all the carbon and hydrogen in the fuel to
carbon dioxide and water with no oxygen remaining. The fuel-air
ratio is
the reciprocal of the air-fuel ratio.
Also
see
lean
air-fuel mixture
rich
air-fuel mixture
Air
Intake
The
opening through which air enters a component such as the carburetor (Vent
in a carburetor through which air is sucked to mix with the gasoline
vapor from the jet) , fuel
injection
system, radiator,
heating system, or ventilation system. See cold
air intake.
Air
Shock Absorber A
shock absorber or damper which has a rubber bladder filled with
compressed air. As the air pressure increases the vehicle is raised.
The system is used in automatic leveling suspensions.
Air
Suspension
A
suspension
system
using air rather than metal springs to support the vehicle and
control ride motions.
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Air
springing results in a smoother ride, because the natural frequency
of vibration of an air spring does not vary with loading as it does
with metal springs. Air springs can be made very soft for the lightly
loaded condition and the pressure automatically increased to match
any increase in load, thus maintaining a constant sprint vibration
period any load. |
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Alignment
When referring to wheel alignment, it is the proper adjustment of a
vehicle's front
or rear suspension
for camber,
toe-in,
toe-out,
kingpin inclination
or steering axis inclination, and turning radius or toe-out on turns,
caster, and ride height. Four-wheel alignment is necessary for front-wheel
drive vehicles.
Allen
key A hexagonal wrench which fits into a recessed
hexagonal hole.
Allen
Wrench
A
rod with six sides and often L-shaped. Used to remove certain screws
and fastenings, especially set screws. Sometimes called "hex
wrenches" or "Allen
key."
Alligator
clip A spring-loaded metal clip with meshing teeth. Used
to make temporary electrical connections. As you squeeze the two "legs"
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of
the clip, the other two jaws (usually serrated) open. Used to
make temporary electrical connections. Larger ones are used at the
ends of jumper
cables. |
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Alloy
Wheel A generic term used to describe any non-steel road
wheel. The usual alloys are either aluminum or magnesium; the latter
material led to the common usage of the term "mag wheel,"
often referring to any non-steel wheel.
All
Terrain Tire A
tire which has a number of lugs or knobs used to propel the vehicle
over rough surfaces.
All
Terrain Vehicle A
vehicle used in rough surface conditions. Also called off-road vehicle
All-Weather
Tire A
tire that can be used on roads that is bare or covered with rain,
snow, or ice.
All-Wheel
Drive (AWD) A variation of four-wheel
drive (4WD)
designed to improve on-road traction in unfavorable road conditions
or for ultra high performance driving. All-Wheel Drive ( WD) reduces
wheel slippage and provides greater driver control over the vehicle.
AWD usually does not require the driver to actively engage the system
and does not have a low range. AWD automatically splits engine torque
between the front and rear wheels as needed. All-Wheel Drive is
generally an on-road system and is not designed for off-road use.
Alternator The
chief source of power of the electrical system is the
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alternating-current
generator, or alternator. Its shaft is driven by the same belt that
spins the fan and it keeps the engine running and
also recharges the battery when the engine is running.
It converts mechanical energy into alternating-current electricity,
which is then channeled through diodes that alter it to direct
current for the electrical system and for recharging the battery. |
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If
the alternator fails, the engine will continue to run using the
battery power, but the car will eventually stop as soon as the
battery will be completely discharged. When the alternator fails,
there is a warning light on the instrument panel that comes on with
the engine running. Usually it's something like 
or "charge"
warning light. If you see that sign on your instrument panel while
driving, have your vehicle inspected before it dies on you.
Ammeter
The device is used to determine whether the electrical system is
charging, discharging, or staying "level". The gauge should
dip when the engine is started, then go up as the alternator re-
charges the battery. After a few minutes, it should go to its middle position.
Ampere
(amp) A unit of measurement for the flow of electric current.
One amp is the amount of current produced by one volt acting through
a resistance of one ohm.
Anaerobic
sealer A substance used to prevent bolts and screws from
loosening. Anaerobic means that it does not require oxygen for
activation. The Loctite brand is widely used.
Anode
In an electrical circuit it is the positive pole. It is that part of
an electrical circuit to which electrons are flowing.
Antenna
A
device which pulls in radio reception. A power antenna automatically
rises when the radio is turned on and lowers when it is shut off.
Some cars had the antenna wires imbedded in the windshield.
Anti-Backfire
Valve
Valve used in air injection reaction (exhaust
emission control)
system to prevent backfiring during the period immediately following
sudden deceleration by diverting the air coming from the air pump
away from the exhaust ports. Otherwise the exhaust gases which
contain unburned gasoline could mix with fresh air and cause unwanted backfiring.
Also
see air
bypass valve
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Antifreeze
A substance (usually ethylene glycol) mixed with water, and
added to a vehicle's cooling system, to prevent freezing of the
coolant in winter.
Antifreeze
also contains chemicals to inhibit corrosion |
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and
the formation of rust and other deposits that would tend to clog the
radiator and coolant passages and reduce cooling efficiency.
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Most commercially available antifreeze contains ethylene glycol, a
chemical that helps to control the temperature of the water in a
vehicle’s radiator. During its life in a vehicle, antifreeze may
become contaminated with fuel or heavy metal particles and grit. If
the levels of dissolved metals, such as lead or cadmium, are high
enough, used antifreeze may be a hazardous waste.
Do not dispose of antifreeze down the drain, in sewers, or into
streams. Never drain the antifreeze from your car onto the street.
The sweet smell of antifreeze is appealing to dogs and cats, who may
drink it. Antifreeze is poisonous to animals — even a small
amount can kill them.
CHEMICAL CONSTITUENTS: Ethylene glycol, Lead, Toluene
Here are some waste reduction tips:
Reduce the amount of antifreeze you use by routinely checking the
radiator, reservoir, and hoses for leaks and repairing them immediately.
Avoid overfilling the radiator or reservoir.
Extend preventive maintenance (PM) cycle. As long as a chemical
analysis or an antifreeze tester reveals that your antifreeze is
doing its job, don’t drain and replace it.
Do not drain antifreeze into the street, into storm drains, or onto
the ground.
Use dedicated equipment and containers to collect and store used
antifreeze to avoid contamination.
Recycle used antifreeze by sending it off-site for recycling, or
contracting with an on-site recycling service. Specify a totally
enclosed system. |
Anti-Knock
Agent A
substance like tetraethyl lead which is added to gasoline to raise
the octane number and reduce the gasoline's tendency to detonate,
knock, or ping. In unleaded gasoline, tetraethyl lead is not used
because of its environmental danger.
Anti-Lock
Brake System (ABS) Sometimes called "anti-skid
brakes." A device which senses that one or more of the wheels
are locking up during braking. It monitors the rotational speeds of
the wheels and reduces hydraulic pressure to any wheel it senses
locking up.It is controlled by both mechanical and electronic
components. When you apply the brakes, the ABS
will regulate the flow of brake fluid being delivered to the brake calipers.
It must be remembered that a wheel cannot be steered unless it is
rolling; so if the wheel is locked up, there is no steering control.
By the use of electronic computers, the brakes rapidly alternate (at
a rate of 30 times per second) from full pressure to full
release. This process will also alternate from the left-front wheel
and the right-rear wheel and switch to the right-front wheel and
left-rear wheel. In this way both maximum braking and maximum
steering control is allowed during braking. Before the advent of ABS,
drivers were advised to pump the brakes to maintain the same effect.
However, the human foot cannot pump the brakes faster than the
computer control. Also, steady application of the brakes without ABS
may cause brake failure (brake fade) because of the excess heat.
Never pump the brakes if you have ABS. When you firmly apply the
brakes with ABS, you may feel a pulsing sensation and hear a banging
noise. The abbreviation ABS comes from the German anti blockier system.
Anti-Roll
Bar Sometimes
called the "anti-sway bar," "stabilizer bar," or
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even
(incorrectly) "roll-bar." It is usually a round bar
which connects the left wheel suspension assembly with the right
side. It may be found at the front and/or rear. Its main function is
to keep both wheels rolling at the same rate when meeting bumps; but
it also affects handling. A front anti-roll bar increases understeer
and a rear bar increases oversteer. |
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Anti-seize
compound A coating that reduces the risk of seizing on
fasteners that are subjected to high temperatures, such as exhaust
manifold bolts and nuts.
Anti-Skid (
ASBS) A computer controlled automotive device which senses when one
or more of the wheels are locking up during braking. It eases up on
the amount of hydraulic pressure to that wheel. It must be remembered
that a wheel cannot be steered unless it is rolling; so if the wheel
is locked up, there is no steering control. By the use of electronic
computers, the brakes rapidly alternate from full power to none so
that both maximum braking and maximum steering control is allowed. If
you jam on the brakes, you will feel a pulsing sensation. Sometimes
called "anti-lock
brakes."
Arm
A suspension linkage formed in the shape of an "A" or
"V" found commonly on the front suspension. The sides of
the two legs of the A-arm
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are
connected to the chassis by rubber bushings and the peak of the
A-arm is attached to the wheel assembly. In this way, the wheel can
freely move up and down. Sometimes there is an upper A-arm, a lower
A-arm, or both upper and lower A-arms. The British call it a "wishbone." |
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Asbestos
A natural fibrous mineral with great heat resistance, commonly used
in the composition of brake friction materials. Asbestos is a health
hazard and the dust created by brake systems should never be inhaled
or ingested.
Asymmetrical
Tread The
tread of a tire which has different shapes/patterns and sizes of
grooves in the same tire. Often they are divided into three distinct
patterns: The outside shoulder, the center zone, and the inside
shoulder. The outside shoulder tread will have larger shoulder
elements with very few sipes to provide increased cornering stability.
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The
center tread zone enhances steering control. The inside shoulder
tread zone provides additional traction because the shape of the
tread elements, sipes and larger shoulder slots help disperse water
and slush. |
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Obviously
these tires must be mounted only one way so that the outside pattern
is actually on the outside of the wheel.
Automatic
Choke A device attached to the carburetor
that automatically reduces the amount of air entering the carburetor
by sensing changes in engine temperature. It is usually controlled by
a coil spring which changes length as the engine is warmed or cooled.
Automatic
Transmission A
transmission that shifts its own gears according to the prevailing
speed, load, and road condition. Also called automatic gearbox.
Operation can be electrical or hydraulic
An
Automatic Transmission a mechanism of the drivetrain which takes the
power from the engine and transfers it to the driveshaft or wheels.
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Without
using a clutch, it uses a torque converter and fluid coupler to
change the gear ratio. It automatically effects gear changes to meet
varying road and load conditions. |
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Gear
changing is done through a series of oil operated clutches and bands.
Automatic
transmission has made driving a lot easier to drive and than manual
transmission. The best part is that you don't have to use a clutch
pedal or gearshift lever. An automatic transmission manages all of
this on its own. Automatic transmissions automatically change to
higher and lower gears with changes in the car's speed and the load
on the engine. These transmissions are also aware of how far down you
have pushed the gas pedal, and shift accordingly.
The
output shaft turns the governor. The rolling of the governor is
directly proportional to the speed of the car. The centrifugal force
from the governor sends the oil is sent from the pump to the shift
valves. The shift valves then move out sending the transmission fluid
to the gear shifting mechanisms in the transmission. When the car
slows down, the valves move in and send the transmission fluid in the
opposite direction, thus changing the gears. The different gears are
selected by routing the pressure to the clutches and brake bands
Automatic
Transmission Fluid (
ATF) A very thin viscosity liquid designed for use in automatic
transmissions to transfer the movement of the torque converter to the driveshaft.
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However
it is also recommended for use in the forks of motorcycles. When
poured into the throat of an automobile carburetor, it helps to
remove a build-up of carbon on the cylinder head and the domes of pistons
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Automatic
Voltage Regulator
A
voltage regulator which automatically holds the voltage of a
distribution circuit or an alternator constant within certain limits,
or causes it to vary in a predetermined manner.
AWD
Acronym for All
Wheel Drive
Axle
A shaft on which a wheel revolves, or which revolves with a wheel.
Also, a solid beam that connects the two wheels at one end of the
vehicle. An axle which also transmits power to the wheels is known as
a live axle.
Axle
Housing The large metal container for a rear-wheel-drive
vehicle's axles, differential and ring and pinion gear. (Four-wheel-drive
vehicles have a similar setup at the front, as well.) The bottom of
the differential, often called a pumpkin, is usually the lowest point
on a vehicle.
Axleshaft
A single rotating shaft, on either side of the differential, which
delivers power from the final drive assembly to the drive wheels.
Also called a driveshaft or a halfshaft.
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