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ABS - Anti-lock Braking System. Uses sensors at each
wheel to sense when the wheels are about to lock, and releases the brakes to
prevent locking. This process occurs many times per second, and allows the
driver to maintain steering control under hard braking.
See article - What are anti-lock brakes.
Air-Con - Air
conditioning
AC - Air cooling, the
cooling of the cabin area of the vehicle with a cool air stream. Not to be
confused with Air Conditioning (air-con) or Climate Control.
Air Mass Meter - Also referred to as an
airflow meter. Will be located next to the airbox in the engine bay. It tells
the cars computer (ECU) the amount of airflow that is being delivered to the
engine so that the correct level of fuelling.
See article - what is an air mass meter
and see article - how to change an
air mass meter.
Alternator - A device that converts rotating mechanical energy into
electrical energy. As you are driving along, the alternator is turned by a belt
from the engine and sends an electrical charge back into the battery. If you did
not have an alternator then your battery would go flat.
See article - what is an alternator.
Anti-roll bar - A metal bar mounted across the underside of car,
it connects the two sides of the suspension, which counteracts the natural
tendency for the car to lean when cornering.
A-pillar - The vertical roof support between the windscreen and front edge of the front side
window.
Airflow meter - see air mass meter
Aquaplaning - A word to describe the cars tyres skating across
the surface of water. When there is a build up of water on the road, the tyres
will sit on the surface of the water and there will be no grip on the road. This
is a dangerous occurrence due to loss of braking and steering and should be
avoided by reducing your driving speed in bad weather.
See article - What is aquaplaning.
Aspect Ratio - The ratio between the width and height of a tyre. Lower aspect ratios
are usually found on sports models provide better handling
and a firmer ride. e.g - written on the side of your tyres might be
185 x 65 x 15 (185 is the width, 65 is the height and 15 is the wheel diameter).
ATF - Automatic Transmission Fluid.
Automatic transmission - A gearbox that selects the correct gear
automatically according to engine speed. These vehicles have no clutch pedal,
only a brake and accelerator. In the UK, if you pass your test in an Automatic
car, your license does not allow you to drive a manual gear driven vehicle.
Back Pressure - The pressure produced by restrictions in an exhaust system. Back pressure
affects the rate at which the exhaust gases are extracted from the engine cylinders.
This is an area where increases in engine performance can be achieved. Removing
the back pressure from the engine by fitting a more free flowing exhaust will
allow the engine to use its efforts to send power to the wheels instead of
wasting it pushing exhaust gases out down a restrictive exhaust.
BHP - Brake Horse Power, see Horsepower.
B-pillar - The vertical metal roof support between front and rear
side windows
Bio Diesel - It is an alternative to conventional
diesel. It can be produced from vegetable oil, animal oil/fats, and waste
cooking oil. These oils are converted Biodiesel using a process called
transesterification. It costs less than normal diesel and does not require any
modifications to your diesel engine. See our article on 'what is bio-diesel'.
Booster Seat (booster cushion) - A child-safety seat that is designed for children too large for a baby
seat, but not big enough to sit safely in the vehicle's seats. If a booster seat
is not used, then it is highly likely that the vehicles seat belts will not do
their proper job and also potentially harm the child. In the UK, there are
changes being implemented regarding children under a certain height. These
children must be seated onto a booster cushion in order that the seat belts
operate correctly and and restrain the child in the correct places as they would
if worn by an adult.
Booster cables -
See also, Jump Leads and Jump
Start. Heavy duty electric cables fitted with clips to enable a car's
battery to be connected to another battery for emergency jump starting.
See article - How to jump start your car.
Brake caliper - The part of a disc brake system, that houses the brake
pads and the hydraulically operated pistons.
Brake disc - A rotating metal disc which is clamped
between hydraulically operated brake pads in a disc brake system.
Brake fade - A temporary loss of braking efficiency due to overheating of
the brake friction material. This is usually overcome by fitting high
performance brake discs and pads. Performance pads will operate at higher
temperatures,, and performance discs typically have grooves and are
cross-drilled to remove gases and heat from the friction surfaces.
Brake pad - Part of the brake system which consists of friction material
on a metal back-plate.
Brake shoe - Part of a drum brake system (found at the rear of the
vehicle), that consists of friction material and a curved metal former.
Breather - A device that allows air into a system or allows, contaminated
air out e.g. oil breather, or crank case breather.
Bump stop - Hard rubber piece used in many suspension systems to
prevent moving parts from contacting the body during violent suspension
movements. Also, lowered vehicles may choose to have bump-stops fitted around
the shaft of the shock absorbers (shocks) so that the shocks do not bottom-out
or get damaged when under load.
Camber angle - The angle at which the front wheels are set from the
vertical (upright), when viewed from the front. Positive camber is the amount
that the wheels are tilted out at the top.
Cam follower
- A piece of metal used to transfer the rotary movement of the camshaft to the
up-and-down movement required for valve operation.
Camshaft - A rotating metal shaft driven from the engine crankshaft with lobes or cams
used to operate the engines inlet/exhaust valves.
Carburettor (carb) - A device that mixes air and fuel in the
proportions required for burning by the engine under all conditions of engine
running. Only found on older vehicles. Carbs
have now been replaced by fuel injection and engine management systems,
Catalytic converter - Part of the exhaust system that creates a
heat-producing chemical
reaction to convert potentially harmful combustion by-products into carbon
dioxide and water. All modern cars are now fitted with catalytic converters.
Central Locking (CL) - On a vehicle with powered door locks, the
system locks or unlocks all doors at one time e.g. put your key in to open the
drivers door and all the other doors will open at the same time. Remote Central
Locking is a further enhancement, meaning that you press a button on your key
fob instead of having to put your key in the door.
Charge cooler - See intercooler.
Choke - Usually found on older vehicles, it is a pull type lever found
around the steering column that is used to give extra fuelling on cold starting.
Later vehicles moved from having a manual choke to having it controlled
electronically.
Climate Control - The term for the heating, ventilation and air-conditioning
system (HVAC). Most current vehicles have all three - heating, defrost, and AC.
Clutch - A friction device that is found between the gearbox and the engine.
It acts as a coupling to be engaged or disengaged both parts smoothly during
gear changes, without the need for either to
stop moving.
Coil - A transformer used in the ignition system for increasing the voltage of the
electric current conducted through the spark plugs. This high level of
"electrical pressure" is what causes the current to jump the gap at the tip of
each spark plug and create the actual spark that ignites the fuel inside the
cylinder.
Coil spring - A spiral coil of spring steel used in many suspension
systems.
Combustion chamber - Area in the cylinder head into which the
fuel/air mixture is compressed by the piston and where the spark from the spark
plug ignites the mixture.
Compression ratio (CR) - A term used to describe the amount by which the
fuel/air mixture is compressed as a piston moves from the bottom to the top of
its travel, and expressed as a number.
The higher the ratio, the more compression during combustion and the more
powerful the engine.
Condenser (capacitor) - A device in a contact breaker point distributor,
which stores electrical energy and prevents excessive sparking at the contact
breaker points.
Connecting rod ('con-rod') - Metal rod in the engine connecting a piston
to the crankshaft.
CV Joint - see
constant velocity joint.
Constant velocity (CV) joint -
On front-wheel drive and all-wheel drive vehicles, a coupling that allows the
front axle to turn at a constant speed at various angles when the vehicle turns.
The CV joint is a shaft that transmits engine power from the transmission to the
wheel.
Contact breaker points - A device in the distributor, which consists of
two electrical points (or contacts), and a cam, which opens and closes them to
operate the HT electrical circuit, which provides the spark at the spark plugs.
Normally found on older vehicles.
Crankcase - The area of the cylinder block below the pistons, which houses the
crankshaft.
C-pillar - The vertical metal roof support between the side edge of the rear
screen and the rear edge of the rear window.
Crankshaft - A cranked shaft that is driven by the pistons and provides
the engine output to the transmission.
Crossflow cylinder head - A cylinder head in which the inlet and exhaust
valves and manifolds are on opposite sides.
Cruise Control - A device that, when set by the driver, will hold the car at the chosen speed.
Crumple Zone - Portions of a vehicle's structure designed to buckle and fold in an impact,
absorbing crash force rather than transmitting it to vehicle occupants.
Cubic capacity - The total volume within the cylinders of an engine which
is swept by the movement of the pistons.
CVH - A term applied by the Ford Motor Company to their overhead camshaft
engines which incorporate a hemispherical combustion chamber. CVH means Compound
Valve angle, Hemispherical combustion chamber.
Cylinder - Close fitting metal tube in which a piston slides. In the case
of an engine, the cylinders may be bored directly into the cylinder block, or on
some engines, cylinder liners are used which rest in the cylinder block and can
be replaced when worn with matching pistons to avoid the requirement for
reboring the cylinder block.
Cylinder block -The main engine casting which contains the cylinders,
crankshaft and pistons.
Cylinder head - The casting at the top of the engine, which contains the
valves and associated operating components.
Dashpot - An oil-filled cylinder and piston used as a damping device in
SU and Zenith/Stromberg CD type carburettors.
Diesel engine - An engine that relies on the heat generated when
compressing air to ignite the fuel, and which therefore doesn't need an ignition
system. Diesel engines have much higher compression ratios than petrol engines,
normally around 20:1. They do not require spark plugs to ignite the air/fuel
mixture, only the compression from the engine cylinders.
Differential - A gearbox or fluid coupling that allows the wheels to rotate at
different speeds. They are usually located on an axle, allowing the outside wheels to
turn faster than the inside wheels during cornering. Four-wheel-drive and
all-wheel drive vehicles have two differentials, one for the rear axle and one
for the front.
Disc brakes - A brake assembly where a rotating disc is clamped between
hydraulically operated friction pads.
Distributor - Part of the ignition (electrical) system,
used to distribute the HT current from the ignition coil to the individual spark
plugs via the HT leads.
Distributor cap - Plastic cap which fits on top of the distributor and
contains electrodes, in which the rotor arm rotates to distribute the HT spark
voltage to the correct spark plug.
DOHC - Abbreviation for Double Overhead Camshaft (see 'Twin-cam').
Downpipe - The pipe that joins the entire exhaust system to the exhaust manifold.
Driveshaft - Term usually used to describe the shaft (normally
incorporating universal or constant velocity joints), that transmits drive from
a differential to one wheel. More commonly found in front-wheel-drive cars.
Drum brakes - A brake assembly with friction linings on 'shoes' running
inside a cylindrical drum attached to the wheel.
Dual circuit brakes - A hydraulic braking system consisting of two separate
fluid circuits, so that if one circuit becomes inoperative, braking power is
still available from the other circuit.
Dwell angle - A measurement that corresponds to the number of degrees of
distributor shaft rotation during which the contact breaker points are closed
during the ignition cycle of one cylinder. The angle is altered by adjusting the
contact breaker points gap.
Earth strap - A flexible electrical connection between the battery and a
car earth point, or between the engine/gearbox and the car body to provide a
return current path flow to the battery.
EBD - Electronic Brake Distribution is a component used with ABS and usually a brake
assist mechanism, for small powerful cars, like the new Mini of 1998.
ECU - Electronic Control Unit.
EFI - Abbreviation for Electronic Fuel Injection.
EGR - Exhaust Gas Recirculation. Part of the emissions system that recirculates exhaust gases into the intake
manifold, cooling the combustion chamber.
Electronic ignition - A system which uses an electronic unit as opposed to an older mechanical
style distributor with points (contacts) to control the timing and firing of
spark plugs.
Engine management system - Computerised control of the ignition an fuel
systems, making driving more economical, quieter, and power-effective.
EW - Electric windows.
Excess - (car insurance) The amount you would have to pay in the
event of an insurance claim. See article - Car
Insurance Tips
Exhaust Manifold - A set of cast pipes that attach directly to the engine
and connect to the exhaust system via the downpipe and remainder of the system.
The exhaust gases exit the engine cylinders and are pushed out into the exhaust.
The exhaust manifolds are are made from cast metal materials because they need
to withstand extreme temperatures of the expelled gases
Expansion tank - A container used in many cooling systems to collect the
overflow from the car's cooling system as the coolant heats up and expands.
Float chamber - The part of a carburettor, which contains a float and
needle valve for controlling the fuel level in the reservoir.
Flywheel - A heavy rotating metal disc attached to the crankshaft and
used to smooth out the pulsing from the pistons. It can also be encircled by a
ring gear designed to mesh with the gear in a starter motor. The starter motor,
using power from the battery will turn the engine (via the flywheel) and to help
initiate the the ignition sequence (starting).
Forced Induction - When a gas is blown into the engine to increase speed, by a turbo or
supercharger.
Fuel injection - Injectors are used on fuel injection engines to inject fuel
directly or indirectly into the combustion chamber. Some fuel injection Systems
use a single fuel injector, while some systems use one fuel injector for each
cylinder of the engine. The fuel injection system has electronic control to time and
meter the fuel flow.
Gasket - Compressible material used between two surfaces to provide a
leakproof joint.
Gearbox - A group of gears and shafts installed in a housing, positioned
between the clutch and the differential, and used to keep the engine within its
safe operating speed range as the speed of the car changes.
Horsepower - A measurement of power. Brake Horsepower (BHP) is a measure
of the power required to stop a moving body.
HPI check - A HPI check is a check on the history of a vehicle. HPI
checks should be purchased before buying a vehicle. It will tell you whether it
has been stolen, written off, ringed, cloned, clocked etc.
See Article - What is a HPI check.
HT - High Tension (meaning high voltage) used to describe
the spark plug voltage in an ignition system.
Hydroplaning - see aquaplaning.
Idle Speed - The speed of the engine at minimum throttle and the engine in neutral.
Independent suspension - A suspension system where movement of one wheel
has no effect on the movement of the other, e.g. independent front suspension.
Ignition coil - An electrical coil, which forms part of the ignition
system and which, generates the HT voltage.
Ignition system - The electrical system which provides the spark to
ignite the air/fuel mixture in the engine. Normally the system consists of the
battery, ignition coil, distributor, ignition switch, spark plugs and wiring.
Ignition timing - The time in the cylinder firing cycle at which the
ignition spark (provided by the spark plug) occurs. The spark timing is normally
a few degrees of crankshaft rotation before the piston reaches the top of its
stroke, and is expressed as a number of degrees before top-dead-centre (BTDC).
Independent Suspension - A suspension design that lets each wheel
move up and down independently of the others. A vehicle can have two-wheel or
four-wheel independent suspension; sportier models have four-wheel independent
suspension.
Inlet Manifold - A set of cast metal pipes through which fuel or air is directed into
the engine cylinders.
Inlet Valves - Devices that open passageways within the engine for fuel vapor to enter the cylinders but which
also close them to maintain cylinder pressure during compression and combustion.
In-Line Engine - Cylinders are arranged side by side in a single row. Most
four-cylinder and some six-cylinder engines are in-line engines. In V-6, V-8 or
V-12 engines, the cylinders are divided into two rows angled
away from each other in a 'V' pattern (Hence the 'V' in V8, V12).
Immobiliser - An electronic security device that prevents a car from being
stolen. It usually disables the ignition system so that the engine may not be
started.
Induction kit - An upgrade to your manufacturers air filter. Usually
replacing the airbox and paper airfilter with a cone performance filter -
See article - What is an Induction Kit.
Intercooler - A device much like a radiator that cools air as it leaves a turbocharger or supercharger before the
air is blown into the engine air intake. Cooling makes the air denser and richer
in oxygen, which lets the engine produce more power.
See article - What is an intercooler.
Jet - A calibrated nozzle or orifice in a carburettor through which fuel
is drawn for mixing with air.
Jump leads - See also, Booster Cables and
Jump Start. Heavy duty electric cables fitted with clips to enable a car's
battery to be connected to another battery for emergency jump starting.
Jump start - To transfer electrical power from one car battery to another to enable the
cars ignition system to startup, using jump leads. See
article - How to jump start your car.
Kerb weight - The weight of a car, unladen but ready to be driven, i.e.
with enough fuel, oil, etc, to travel an arbitrary distance.
KPH - Kilometers Per Hour, used as a measure of speed especially
in europe. Multiply by 0.621 to convert to miles per hour.
Lag - see turbo lag
Leaf spring - A spring commonly used on cars with a live axle, consisting
of several thin, curved steel plates clamped together at the ends to the
underside of the vehicle. Usually found on older cars such as the Ford Escort
mk2.
Limited slip differential (LSD) - A device that helps prevent the drive wheels from skidding or losing traction
by diverting power from the slipping wheel to the opposite wheel on the same
axle.
Often used on high-performance cars.
Live axle - A solid axle allowing movement of the wheel on one end to affect the opposite
wheel. Found on older rear-drive cars and trucks. Also called a rigid axle.
Lock-to-lock - The amount of turns needed to move the steering wheel from
one full lock position to the other. Full lock being the point at which you
cannot turn the steering wheel any further.
Loom - A complete car wiring system or section of a wiring system
consisting of all the wires of correct length, etc, to wire up the various
circuits.
LPG - liquid petroleum gas. A natural hydrocarbon fuel made up of
propane and butane, cheaper than petrol to run your
car on.
LT - Abbreviation of Low Tension (meaning low voltage) used to describe
battery voltage in the ignition system.
Manifold - A device used for ducting the air/fuel mixture to the engine
(inlet manifold), or the exhaust gases from the engine (exhaust manifold).
MAP Sensor - Manifold Absolute Pressure Sensor. It detects engine
load by measuring air pressure or vacuum in the inlet
manifold.
Mass Airflow Sensor - Also known as an air-mass meter. A device that measures the flow of air entering the throttle housing.
Master cylinder - A cylinder containing a piston and hydraulic fluid,
directly coupled to a foot pedal (e.g. brake or clutch master cylinder). Used
for transmitting pressure to the brake or clutch operating mechanism.
MOT - Ministry of Transport annual test of vehicle road safety
see article - what is an MOT
MPG - Miles Per Gallon. Fuel economy measurement. Generally, a vehicle maker may offer mpg ratings
for city (urban) driving, motorway driving, and combined driving.
MPH - Miles Per Hours
MPV - Multi-person vehicle. e.g. Renault espace, Ford Galaxy. VW Sharan
(7 seater) Toyota Previa etc.
Multi-Link Suspension - Independent suspension controlled with several link arms that restrict
undesired motion of the suspension for a smoother ride and more precise
handling.
Needle valve - A component of the carburettor, which restricts the flow of
fuel or fuel/air mixture according to the position of the valve in an orifice or
jet.
Negative earth - Electrical system (almost universally adopted) in which
the negative terminal of the car battery is connected to the car body. The
polarity of all the electrical equipment is determined by this.
Octane - The hydrocarbon substance in fuel that reduces engine knock or pinking,
which is a noise caused by premature ignition of fuel in the cylinder combustion
chamber. The higher the octane number, the less chance of premature ignition.
Typically, higher octane fuels will give
improved engine power/performance. Petrol in the UK has a higher octane rating
that that in the US.
Octane rating - A scale rating for grading petrol.
OHC (overhead cam) - Describes an engine in which the camshaft is
situated above the Cylinder head, and operates the valve gear directly.
Single overhead-cam (SOHC) engines have a single cam above the cylinder head.
Double
overhead-cam (DOHC) engines have two cams above the cylinder head.
OHV (overhead valve) - Describes an engine, which has its valves in the
cylinder head, but with the valve gear, operated by pushrods from a camshaft
situated lower in the engine.
Oil cooler - Small radiator fitted in the oil circuit and positioned in a
cooling airflow to cool the oil. Used mainly on high-performance engines.
Oversteer - A tendency for a car to turn more tightly into a corner than
intended. Occurs when the rear tyres lose adhesion, and can lead to a
spin if the driver doesn't reduce acceleration. See also Understeer.
Oxygen Sensor - An emissions related device which senses the presence of oxygen in the
exhaust. The voltage it puts out is interpreted by the main computer (ECU) along
with other sensor input to determine automatic adjustment of the air/fuel
mixture.
Piston - A cylindrically shaped part which compresses fuel vapour
within a cylinder (compression stroke) and is thrust downward by the force of the explosion that results when the vapour
is ignited.
Piston ring - Hardened metal rings that fit in a groove
around the outside of the piston to ensure a gas-tight seal between the piston and
cylinder wall.
Positive earth - The opposite of negative earth.
Power steering - A steering system that uses hydraulic fluid pressure (provided
by an engine-driven pump) to reduce the effort required to steer the car.
Power-to-Weight Ratio - The power output of a vehicle
in comparison to its weight, usually described in number of bhp per ton. For
example, if a car has a powerful engine but is also very heavy it may not be as
fast as a lighter car with less power, there is less weight for the engine to
move.
Projector-Beam Headlights - A headlight that uses a spherical reflector to control the light
beam. The bulb directs the light inward, toward the reflector which then projects it forward.
These lights are more powerful, accurate and expensive than standard sealed-beam
and halogen headlights.
Pressure Plate - Holds the clutch disc against the flywheel.
Propeller shaft (prop-shaft)- The shaft, which transmits the drive from the gearbox
to the rear axle in a front-engine rear-wheel-drive car (i.e. BMW)
PSI - Pounds per square inch. A measurement of air pressure, i.e.
when inflating a tyre.
Pushrod - A rod that is moved up and down by the rotary motion of the
camshaft and operates the rocker arms in an OHV engine.
Quarter light - A triangular window mounted in front or behind the main
front or rear windows, usually in the front door, or behind the rear door.
Radiator - Cooling device through which the engine coolant is passed,
situated in an airflow and consisting of a system of fine tubes and fins for
rapid heat dissipation. Usually has a fan situated behind it that will start
when the coolant reaches a certain temperature. This will pull more air across
the fins of the radiator to aid cooling.
Redline - The point on the engine rev counter that indicates the maximum RPM the engine
can safely withstand.
Rev counter - See Tachometer.
Rolling Radius - This is
the radius of your wheels and tyres. If you change your wheels for bigger or
smaller diameter items, it is important to try and keep the same rolling radius
as the wheels originally fitted to the car. The reason is that if the rolling
radius changes greatly, the gearing, 0-60 speed and top end speed can be
affected.
Rocker arm - A lever that rocks on a central pivot, with one end moved up
and down by the camshaft, and the other end operating an inlet or exhaust valve.
Rotary engine - See 'Wankel engine'.
Rotor arm - A rotating arm in the distributor, which distributes the HT spark
voltage to the correct spark plug.
RPM - Revolutions per Minute. This shows the speed at which the engine is
turning.
Running on - A tendency for an engine to keep on running after the
ignition has been switched off. Often caused by a badly maintained engine or the
use of an incorrect grade of fuel.
Sat-nav - Satelite Navigation. A System that shows you on a small
screen where your car is
and normally gives you directions to where you want to go.
Sealed beam - A sealed headlamp unit where the filament is an integral
part and cannot be renewed separately.
Semi-trailing arm - A common form of
independent rear suspension.
Servo - A device for increasing the normal effort applied to a control,
i.e. servo assisted braking.
Shock absorber - A device for damping (smoothing) the up-and-down movement of the
suspension when the car hits a bump in the road.
SOHC - Single Overhead Cam. An engine with a single cam generally has one intake and one exhaust
valve per cylinder; the single cam opens and closes both valves. See also
Overhead Cam and Double Overhead Cam.
Spark plug - A device with two electrodes insulated from each other by a
ceramic material, which screws into an engine combustion chamber. When the HT
voltage is applied to the plug terminal, a spark jumps across the electrodes and
ignites the fuel/air mixture.
Starter motor - A powerful electric motor used to start the movement of engine so that
combustion can begin. Activating the starter by turning the ignition key, causes the solenoid to thrust the
pinion gear in the starter against the engine flywheel ring gear and begin
turning it.
Steering rack - See Rack and pinion.
Stroke - The total distance travelled by a single piston in its cylinder.
Stub axle - A short axle that carries one wheel.
Strut - A single, self contained pivoting suspension unit that integrates a coil
spring with a shock absorber. Struts are used on front wheel drive automobiles.
A suspension element in which a reinforced shock absorber is used as one of the
wheel's locating members, typically by solidly bolting the wheel hub to the
bottom end of the strut.
Strut brace - An
aftermarket item (commonly used in rallying) that fits inside the engine bay
with each end bolted to the top of the left and right suspension tops or
turrets. Its purpose is to increase the rigidity of the car by stiffening the
front end suspension set-up.
Subframe - A small frame that is mounted on the car's body, and carries
the suspension and/or the drivetrain assemblies.
Sump - The main reservoir for the engine oil, found at the bottom of the
engine. Usually has a drain plug built into it for draining oil during and oil
change or engine work.
Supercharger - Has the same function as a turbo but has no lag
time because it runs off an engine-driven pump. The
supercharger usually driven by a belt or gears from the crankshaft, drives a
compressor which forces air into the engine, providing increased fuel/air
mixture flow, and therefore increased engine performance and efficiency.
Suppressor - A device that is used to reduce or eliminate electrical
interference caused by the ignition system or other electrical components. i.e.
you would fit a supressor onto your radio if you were getting radio interference
when the car was turned on.
Suspension - A general term used to describe the components which suspend
the car body on its wheels.
Swing axle - A suspension arm, which is pivoted near the front-to-rear
centreline of the car, and which, allows the wheel to swing vertically about
that pivot point.
Synchromesh - A device in a gearbox, which synchronises the speed of one
gear, shaft with another to produce smooth, noiseless engagement of the gears.
Synthetic oil - Engine lubricant not derived from raw petroleum. It has superior
engine-protection properties but costs as much as five times more than petroleum
oil.
Tachometer - Also known as a rev counter, indicates engine speed in
revolutions per minute (rpm).
Tappet - A term often used to refer to the component which transmits the
rotary camshaft movement to the up-and-down movement required for valve
operation.
TC - Traction control
Thermostat - A device which is sensitive to changes in engine coolant
temperature, and opens up an additional path for coolant to flow through the
radiator (to increase the cooling) when the engine has warmed up.
Tie-rod - A rod which connects the steering arms to the steering gear.
Timing belt - On overhead cam equipped engines, a
fabric or rubber belt engaged on sprocket wheels and
driving the camshaft from the crankshaft. It synchronises the
operation of intake/exhaust valves with the compression/ignition process
occurring in the cylinder head and engine block.
Timing chain - Metal flexible link chain engaging on sprocket wheels and
driving the camshaft from the crankshaft.
Timing marks - Marks normally found on the crankshaft pulley or the
flywheel and used for setting the ignition firing point with respect to a
particular piston.
Toe-in/toe-out - The amount by which the leading edge of the front wheels
point inwards or outwards from the straight-ahead position. Front-drive
cars are often aligned with slight toe-in to compensate for the effects of
torque steer, or the tendency of the front wheels to pull to the side under hard
acceleration.
Top Dead Centre (TDC) - The point at which a piston is at the top of its
stroke.
Torque - The measure of turning force generated by a rotating component,
given in foot-pounds (lb.-ft.). In vehicle terms it is the twisting force the
engine exerts on the crankshaft. Vehicle specifications often include the
maximum torque an engine produces at a specific RPM. An engine producing 200
lb.-ft. of torque at 3,000 RPM or 200 lb.-ft.@ 3,000 RPM accelerates better at
low speeds than an engine that provides 200 lb.-ft.@5,000 RPM.
Torque steer - The tendency of the front wheels on a front-drive vehicle to pull to the side
under hard acceleration. Normally compensated for
with toe-in.
Torsion bar - A metal bar, which twists as it is compressed or
stretched. Peugeots and Citroens typically have torsion bars as part of their
rear suspension set-up.
Traction Control - A system that limits wheel spin under acceleration.
It maintains each
wheel's contact with the road surface. Traction-control systems generally use
the anti-lock braking system to stop wheel spin and reduce power from one or
more engine cylinders when an electronic sensor detects wheel spin.
Trailing arm - A form of independent suspension where the wheel is
attached to a swinging arm, and is mounted to the rear of the arm pivot.
Turbocharger - A device which uses a turbine driven by the engine exhaust
gases to drive a compressor which forces air into the engine, providing
increased fuel/air mixture flow, and therefore increased engine efficiency.
Commonly used on high-performance engines.
Turbo lag - The time taken for the turbocharger to kick in
upon acceleration. The lag occurs because a turbocharger compressor is
spun by exhaust gases in the exhaust manifold and it takes time for it to spin
up to speed. Larger turbos have more turbo lag but give more more further up the
rev range, whereas smaller turbos spin up faster but are less powerful. Many
performance cars now incorporate 2 turbos, a smaller one for low down response
and then a larger one that takes over as the engine speed increases.
Twin-cam - Abbreviation for twin overhead camshafts (see 'OHC'). Used on
engines with a crossflow cylinder head, usually with one camshaft operating the
inlet valves and the other operating the exhaust valves. Gives improved engine
efficiency due to improved fuel/air mixture and exhaust gas flow in the
combustion chambers.
Understeer - A tendency for a car to go straight on when turned into a
corner. It happens when the front wheels have lost adhesion or the driver is turning the
steering wheel too sharply for the vehicle's speed. In understeer, the front
wheels do not follow the steering wheel angle, and the car refuses to turn and
goes straight ahead.
Universal joint - A joint that can swivel in any direction whilst at the
same time transmitting torque. This type of joint is commonly used in propeller
shafts and some driveshafts, but is not suitable for some applications because
the input and output shaft speeds are not the same at all positions of angular
rotation. The type in common use is known as a HardySpicer, Hooke's or Cardan
joint.
Unsprung weight - The part of the car, which is not supported by the
springs.
Vacuum advance - System of ignition advance and retard used in some
distributors where the vacuum in the engine inlet manifold is used to act or a
diaphragm which alters the ignition timing as the vacuum changes due to the
throttle position.
VIN - Vehicle Identification Number A number that is unique to
each vehicle. This number is stamped onto the car so
that it can be identified. Different manufacturers put VIN numbers in different
places.
Vented Discs - A brake disc that has cooling passages between the friction surfaces.
When looked at, the disc looks like it is made up of 2 sections sandwiched
together with vanes in between. These vane pull in air to keep the friction
surfaces cooler and therefore aid braking.
Wankel engine - A rotary engine which has a triangular shaped rotor which
performs the function of the pistons in a conventional engine, and rotates in a
housing shaped approximately like a broad-waisted figure of eight. Very few cars
use this type of engine.
Waste gate - A device used to limit the boost developed in a turbocharger. A waste gate
operates by allowing some of the engine's exhaust flow to bypass the
turbocharger's turbine section under certain conditions. Normally controlled by
the 'waste-gate actuator'.
Wheel balancing - Adding small weights to the rim of a wheel so that
there are no out-ofbalance forces when the wheel rotates.
Wishbone - An 'A'-shaped suspension component, pivoted at the base of the
'A' and carrying a wheel at the apex. Normally mounted close to the horizontal.
VGC - Very good condition
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