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[ B ]
B-Pillar
A roof support between a car's front door window and rear
side window.
Balance Shaft
A shaft designed so that, as it rotates, its
vibrations reduce the vibration produced by an engine. They
are not essential parts but are fast becoming important for
engine refinement.
Ball Joint
A flexible joint consisting of a ball in a
socket, used in front suspensions.
Barrel (bbl)
For automotive barrel is same as carburetors.
"2bbl." means that the carburetor has 2 barrels or fuel
nozzles. A "4bbl." carburetor has 4 barrels, etc. The number
of venturi determine the amount of fuel that the carburetor
can supply. A 4bbl. carburetor can usually provide more fuel
than a similar 2bbl. unit.
Beam Axle
A rigid axle supporting the non-driven wheels.
Also called a dead axle.
Belt drive
A system where the final drive from gearbox to
wheels is by leather or rubber belts that are contained on
pulleys. Today many of the engine-driven auxiliaries use
belt drives.
Beltline
The line running around a car's body formed by the bottom
edges of its glass panels.
Belts
Belts are engine accessories that are used to run many
engine parts like power steering pump, water pump,
air-conditioning compressors, etc. Belts are used to drive
many engine accessories. Most overhead cam(OHC) engines use
cogged (toothed) belts to drive the camshaft(s). Belts drive
the.
Berline
From World War I, it described a closed luxury car with
small windows, which allowed the occupants to see out but to
be barely seen from the outside.
Bevel Gears
A gear set employing gears shaped like slices of
a cone, which allows the axes of the gears to be
nonparallel.
Boost Pressure
The increase above atmospheric pressure produced
inside the intake manifold by any supercharger. It is
commonly measured in psi, inches of mercury, or bar.
Bore
The diameter of a gasoline or steam reciprocating engine
cylinder.
Brake Bias
It is the front/rear distribution of a car's
braking power.
Brake Horsepower (bhp)
It is the measure of an engine's horsepower
without the loss in power. It is more than the actual
horsepower delivered to the driving wheels.
Brake Torquing
A procedure used in performance tests to improve
off-the-line acceleration of an automatic transmission car.
Brake torquing is effective with turbo charged cars to
overcome turbo lag.
Antilock Braking System
ABS eliminates wheel lockup during braking and
loss of steering control on slippery surfaces. Speed sensors
monitor each wheel and reduce brake pressure on any wheel
rotating significantly slower than the others.
Brakes, Calipers
Brake pads are mounted to calipers, which float
next to the brake disc. The caliper ensures that the brake
pads exert even pressure on the disc.
Brakes, Disc
A brake that uses a disc shaped rotor and
calipers that hold friction pads. The rotor is attached to
the wheel hub and spins with it. The calipers are
stationary. When the brake pedal is depressed, the calipers
press on the side of the side of the rotor. The friction
pads slow the rotor as needed. Most vehicles use disc brakes
on the front wheels. Disc brakes can shed heat and retain
their braking power better than drum brakes.
Brakes, Drum
A brake that uses an enclosed rotating drum or
can and stationary pads(shoes). When the brake pedal is
depressed, the brake shoes contact the sides of the can and
slow the wheel.
Breathing (engine)
A term used to describe an engine's ability to
fill its cylinders with air-fuel mixture and then discharge
the burnt exhaust gases.
Bushing
A simple suspension bearing that accommodates limited rotary
motion, typically made of two coaxial steel tubes bonded to
a sleeve of rubber between them. The compliance of the
bushing in different directions has a great effect on ride
harshness and handling.
By-pass Valve
A general term for a valve that lets liquid or
air circumvent a filter. For example, an oil bypass valve
allows oil to circulate when the oil filter is clogged.
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[ C ]
C-pillar
The roof support between a car's rearmost side window and
its rear window.
Cabriolet
Another term for a convertible. Also called a drophead coupé.
Cam
An eccentric (off-center) lobe or projection on a rotating
shaft; used to transmit a motion at a predetermined time
during the rotation of the shaft.
Cam Profile
The shape of each lobe on a camshaft. The profile
determines the amount, or "duration," of time the valve is
open; it also largely determines the valve's maximum
opening, or "lift" camber: the angle between the plane of a
wheel's circumference and a vertical line, measured in
degrees and minutes. The tops of a car's wheels tilt inward
when the camber is negative, outward when it is positive.
Camshaft
A rotating shaft with a number of cams or eccentric lobes
used to open and close the engine cylinder valves. The
crankshaft drives the camshaft through gears and belts.
Captive Import
An imported motor vehicle or part manufactured by
another automaker usually for sale under the brand name of
the importer.
Carburetor
A device through which air and fuel are atomized and drawn
into the engine. It meters the proper proportions of fuel
and air to form a combustible mixture and varies the ratio
according to the engine operation. Air blowing over the fuel
nozzles (jets) results in an air-fuel mixture burned in the
cylinders. Carburetors were common on most vehicles before
1985. Currently, most vehicles use some form of fuel
injection instead.
Caster
The angle between a vertical line and the car's steering
axis when viewed from the side, measured in degrees and
minutes. Casting technology that delivers a liquid molten
metal into a purpose-built mould. After cooling, the solid
metal surface has the shape of the mould cavity.
Catalytic Converter
Often simply called a catalyst, it is a
stainless-steel canister fitted to a car's exhaust system.
The material used is some combination of platinum, rhodium,
and palladium; it induces chemical reactions that convert an
engine's exhaust emissions into less harmful products.
So-called three-way catalysts are particularly efficient;
their operation, however, demands very precise combustion
control, which can be produced only by a feedback
fuel-air-ratio control system.
Center Differential
A differential used in four-wheel-drive systems
to distribute power to the front and rear differentials.
Chain Drive
The driving of one shaft by another by toothed
wheel on each shaft. The toothed wheels are connected with
an endless chain having links corresponding to the teeth.
Chassis
A term that refers to all of the mechanical parts of a car
attached to a structural frame. The chassis comprises
everything but the body of the car.
Choke
A temporary restriction in a carburetor throat that reduces
the flow of air and enriches the fuel-air mixture to aid in
starting the engine.
Clutch
A mechanism that uses plates coated with a high-friction
material to transfer power from the engine to the drive
train. Used when changing gear ratios during acceleration
Clutches isolate rotating and non-rotating components.
Coachwork (French Carrosserie, German Karosserie, Italian
Carrozzeria)
The automobile body especially the comfort and
luxury appointments as distinguished from the operational
chassis.
Coil Spring
Used to isolate a vehicle from the road, coil
springs are preferred over leaf springs. They have many
automotive applications but are particularly important as
suspension springs.
Combustion Chamber
Where the fuel-air mixture begins to burn. It is
the space at the top of the cylinder when the piston is at
top center.
Compliance
A slight resiliency, or "give," designed into suspension
bushings to help absorb bumps. Good compliance allows the
wheels to move rearward a bit as they hit bumps but doesn't
allow them to move laterally during cornering. Component a
raw material, ingredient, part or subassembly that goes into
a higher level assembly, compound, or other item.
Component
Assembly a combination of two or more parts or
sub-components to form an assembly.
Compression
In internal-combustion reciprocating engines, the squeezing
of the fuel-air mixture in the cylinder of a spark-ignition
engine or the squeezing of the air in a diesel engine.
Compression makes combustion more effective and increases
engine efficiency.
Compression ratio
The ratio between the combined volume of a
cylinder and a combustion chamber when the piston is at the
bottom of its stroke, and the volume when the piston is at
the top of its stroke. The higher the compression ratio, the
more mechanical energy an engine can squeeze from its
air-fuel mixture. Higher compression ratios, however, also
make detonation more likely.
Concept Vehicle
A current production vehicle modified for
installation of new design concepts for evaluation of
environmental functional feasibility.
Connecting Rod
The arm that connects the piston to the
crankshaft and converts the reciprocating motion into rotary
motion. Connecting rod The metal rod that connects a piston
to a throw on a crankshaft.
Constant Velocity Joint (CV Joint, Halfshaft)
A shaft that transmits engine power from the
transmission to the wheel. CV joints allow the wheel to
steer and follow suspension motion while receiving power.
Control arm
A suspension element that has one joint at one
end and two joints at the other end, typically the chassis
side. Also known as a wishbone or an A-arm.
Convertible
Any car with a folding roof. Term used in U.S. since the
1930s. In the 1950s, the "hardtop convertible" was developed
to look like a convertible but had a fixed roof that did not
fold. Also called a drophead coupé.
Cornering limit
The maximum speed at which a car can handle a
given curve.
Cowl
A protective cover for mechanical components.
Crankcase
A pan or box that encloses the bottom of the engine,
supports the crankshaft, and contains the oil for the
engine.
Crankshaft
The shaft that converts the linear motion of the pistons
into rotation.
Cubic Capacity
The volume of the cylinder between the piston top
dead center and bottom dead center. Expressed in cubic
centimeters or cubic inches.
Custom Car
a restyled vehicle or a new body fitted on an
existing chassis.
Cylinder head
The aluminum or iron casting that has the
combustion chambers, the intake and exhaust ports of the
engine.
Cylinder liner
The circular housing that the piston moves in
when the cylinder is not an integral part of the block. Also
known as a "sleeve."
Cylinder
The hollow tubular cavity in the cylinder block in which the
piston travels and in which combustion takes place.
Typically made of cast iron and formed as a part of the
block.
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[ D ]
Dead Pedal
A footrest found to the left of the leftmost
pedal. It provides a place for the driver to brace his left
leg during hard cornering.
Detonation
Also called knock, it is a condition in which, after the
spark plug fires, some of the unburned air-fuel mixture in
the combustion chamber explodes. It increases the mechanical
and thermal stresses on the engine.
Diesel Engine
An internal-combustion engine in which the fuel
is injected into the cylinder near the end of the
compression stroke and is ignited by the heat of the
compressed air in the cylinder. No spark plug or carburetor
is needed.
Differential
A differential allows the right and left wheels to rotate at
different RPM. The differential allows the outside wheel to
spin faster to compensate for the greater distance.
Differential Gears
The gears that convey engine power to the driving
axles. They allow the rear wheels to turn at different
speeds as required when the vehicle is negotiating a turn.
Disc brakesA type of brake in which two friction pads grip a
steel disc attached to the wheel. They are also called
caliper disc brakes.
Distributor
A device that transfers voltage to the spark plug. A rotor
in the distributor spins and touches contacts that are
connected to spark plug wires. The wires then conduct the
voltage to the spark plug.
Dive
The dipping of a car's nose that occurs when the brakes are
applied. Dive is caused by a load transfer from the rear to
the front suspension.
Downforce
A vertical force directed downward, produced by airflow
around an object: such as a car body.
Drag Coefficient
A dimensionless measure of the aerodynamic
sleekness of an object.
Drivability
A general evaluation of the driving qualities of a vehicle
that includes smoothness, cold and hot starting throttle
power etc.
Drive Train
That combination of a car's components like the
engine, transmission, differential(s), any interconnecting
shafts, gears etc that transmits the engine power to the
wheels.
Driveline
Everything in the drive train, less the engine and the
transmission.
Driveshaft
A rotating shaft that transfers power from the transmission
to the rear wheels.
Drum brakes
A type of brake that has an iron casting shaped
like a shallow drum that rotates with the wheel. Curved
brake shoes are forced into contact with the inner periphery
of this drum to provide braking.
Dry Sump
Type of internal-combustion engine in which the
lubricating oil is stored either in a separate tank or
cooling radiator instead of in the crankcase pan. The oil is
pumped to and taken from the engine by separate pumps.
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[ E ]
Electric Vehicle
Vehicles using dedicated or hybrid electric systems as the
source of their power.
Electrical System
It refers to a certain configuration of
components such as generator or alternator, Points,
condenser, coil, distributor, spark plugs and wiring which
convert the electricity produced by the generator into a
high-voltage spark for the plugs.
Engine Overhaul
Major engine work that requires the removal of
the engine from the vehicle, and rebuilding or replacing
internal components like pistons, connecting rods, valves
and so on.
Engine Types
F-Head It has side exhaust valve and overhead inlet
valve.
L-Head In this type of engine both the valves are
located on one side of the cylinder.
T-Head In such an engine the exhaust-valve is kept on
one side and inlet valve on the other side of the cylinder.
I-Head Popularly known as valve--in-head or overhead
valve engine, it has both valves remaining directly over the
piston.
Engine, Inline
It involves a sort of engine arrangement where
all cylinders are in one plane.
Engine, V (e.g. V-8)
It has two banks of cylinders arranged in a
V-like shape and an included angle of around 30-90 degrees
that separates the individual banks. V-8 engines are
shorter, wider and more compact than inline-8 engines.
Engine-control system
It is just like a computerized brain that
controls an engine's operation by monitoring certain engine
characteristics such as rpm, coolant temperature, intake
airflow, etc. through a network of sensors. It then
regulates key variables like fuel metering, spark timing,
EGR, etc. according to the pre-programmed schedules.
Epicyclic Gearbox
This form of gear used by Benz has small pinions
revolving around a central or sun gear and meshing with an
outer ring gear called the annulus. These are also referred
to as planetary gears, sun-and-planet gears.
Exhaust
It is the process of releasing the burned gases from an
internal-combustion engine consisting of piping or tubing,
silencers, and, at times, resonators.
Exhaust-gas Recirculation (EGR)
A method of reducing the exhaust emissions of
Nitrogen oxides by recalculating some of the engines'
exhaust gas into the intake manifold.
Exhaust Manifold
It is a network of passages that gathers the
exhaust gases from various exhaust ports and directs them
towards the catalysts and mufflers of the exhaust system.
Exhaust Port
It is the passageway in the cylinder head
stretching from the exhaust valves to the exhaust manifold.
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[ F ]
Fastback
It refers to a certain design of a car that has an unbroken
curved line from the top of the roof to the rear bumper. The
rear window slope follows the unbroken roofline and often
remains at less than a 45-degree angle.
Feedback Fuel-Air-Ratio Control
It is a computer-controlled fuel system which
keeps the fuel-air ratio very close to the proportion for
chemically suitable combustion using a sensor.
Fiberglass
It is a plastic material with fibers running through the
plastic used for race cars and sports cars.
Final-Drive Ratio
It is the reduction ratio located in the gear set
of a drive train which is furthest removed from the engine.
Floorpan
It is the largest and most important stamped metal part
which forms the floor and fixes the dimensions for most of
the car's external and structural panels. It also acts as
the foundation for the mechanical parts of many cars.
Fluid Coupling
It is a device to transfer power through a fluid
between its inputs and outputs. It consists of two fans in a
sealed, oil-filled housing. The input fan churns the oil,
which, in turn, twirls the output fan. Such a coupling
enables some speed difference between its input and output
shafts.
Flywheel
It is the large, heavy iron or steel disc attached to the
rear of an engine crankshaft. Its function is to provide
sufficient centrifugal force and smoothen its power flow.
Four Valves per Cylinder
It is a valve train with four valves including
two intakes and two exhausts in the combustion chamber.
Four Wheel Drive (4WD)
It is a system which transfers engine power to
all four wheels of the vehicle. It provides superior
traction.
Four Wheel Steering (4WS)
It signifies a mechanism that steers the rear as
well as the front wheels.
Four-Stroke Cycle
Otherwise known as Otto cycle, it indicates an
internal-combustion engine that needs two revolutions per
cylinder or four piston strokes. The purpose is to achieve
power stroke, internal stroke, compression stroke, exhaust
stroke.
Four-Wheel Drift
It is a term to describe a cornering situation in
which all four tires are operating at large slip angles.
Frame
It is a bridge like structural base of a car that supports
and positions the body and other major mechanical items.
Front Wheel Drive (FWD)
In such a system the front wheels receive engine
power. More weight is concentrated over the drive wheels and
all drivetrain components are concentrated in the front of
the car.
Fuel Injection
It refers to a system in internal -combustion
engines, which injects a precisely measured amount of fuel
into the cylinder at the right moment. It enhances engine
efficiency and provides better metering of fuel and air than
carburetors.
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[ G ]
Gas Turbine - It is an internal-combustion-rotating
engine with one main moving part with some blades attached.
Gears - Made of hard steel, these are basically
wheels with meshing teeth to transmit power between rotating
shafts. These are instrumental in affecting the speed ratio
of the vehicle.
Gearset - It consists of a set of two or more gears
to transmit power.
Generator - Used in older cars to provide electrical
energy for the vehicle, it is just a device to provide
electrical energy to the vehicle.
Greenhouse - It refers to a part of a car's body that
rises above its beltline.
Gross Vehicle Weight (GVW) - It indicates the maximum
legal weight at which a vehicle can be operated.
Ground Effect - It suggests a creation of downforce
because of the airflow between a moving object and the
ground.
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[ H ]
Half Shaft
It is a rotating shaft used in
independent-suspension systems which functions as a power
transmitter between the final drive unit to the power wheel.
Handling
It is a common term for all aspects of a car's function
relating to its directional control.
Heavy-duty Vehicle
These are vehicles, especially trucks, weighing
from 26,001 to 33,001 lbs.
Heel-and-Toe
It refers to a performance-oriented system of down-shifting
while braking.
Heim Joint
Popularly known as "spherical rod-end", it is an
extremely rigid articulating joint used mainly in the
suspension links of race cars as they locate wheels quite
precisely.
Helical Gear
In such type of gear the teeth are cut at an
angle to the shaft and two teeth are always meshing. It
reduces noise.
Hemi
It is an engine having hemispherical combustion chambers in
its cylinder head. It is used in many sports and racing cars
and it offers sound breathing characteristics.
Hemi-Head
It is a hemisphere shaped combustion chamber at the top of
the engine cylinder in which the forces of the explosion are
directed to the piston by the curved surface of the
combustion chamber. It provides better efficiency.
Hood
It is that removable or lift-up part of an auto body which
covers the engine and allows access to it.
Horsepower (BHP)
It is the unit for measuring the power output of
an engine.One horsepower is almost equal to the power needed
to lift 550 pounds one foot off the ground in one second.
Higher horsepower increases the top speed of the vehicle.
Vehicles with more horsepower consume more air and fuel.
Hot Rod
It refers to a sort of production auto in which
significant changes have been made to the engine, chasis and
body by the owner of the vehicle to acquire outstanding
speed and acceleration.
Hotchkiss Suspension
It is a sort of live-axle rear suspension in
which leaf springs handle both the axle's springing and
location.
Hydraulic
It is a mechanical operation involving the incompressibility
of liquids which offers resistance when being forced into a
cylinder or through an orifice. It then transmits an
increase in applied force. This principle is followed by
hydraulic brakes and clutches.
Hydraulic Valve Lifter
It uses hydraulic oil pressure to operate and is
capable of maintaining zero clearance between metal parts.
It reduces noise, wear and periodic valve adjustments.
Hypoid Gears
It is responsible for a lower floor in the car.It
is a sort of differential final drive which uses a spiral
bevel gear on the drive shaft and allows it to be located
below the center of the ring gear on the axle.
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[ I ]
Ignition system
It is an electrical system which consists of a
battery, induction coil, capacitor, distributor, spark
plugs, relevant switches and wiring to produce timed sparks
from engine spark plugs.
Independent Suspension
It is a sort of suspension which prevents any
effect on a wheel even if the opposite wheel gets disturbed
as each wheel is sprung individually.
Inline Engine
Otherwise known as "straight" engine, it has
cylinders arranged one after the other in a straight line.
Intake Charge
It is the blending of fuel and air, which flows
into the engine.
Intake Manifold
It refers to a network of passages which direct
air or air-fuel mixture from the throttle body to the intake
ports in the cylinder head.
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[ J ]
Jounce
It refers to the motion of the wheel of the vehicle thath
compresses its suspension.
Jounce Bumper
It is a sort of elastic cushion which stiffens
the suspension as it approaches the end of its jounce
travel.
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[ K ]
Kickdown
It is a downshift in an automatic transmission caused by
depressing the throttle.
Knock Sensor
It is an instrument located on the engine which
detects the high-frequency vibrations caused by detonation.
With the use of a knock sensor, a computerized
engine-control system can improve power and efficiency by
allowing an engine to operate very near to its detonation
limit.
Knock-Off
Usually struck with a mallet on the wings, it is just a wing
nut for fastening a wheel to the hub which can easily be
removed.
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[ L ]
Lacquer
It is a sort of pyroxylin paint used primarily to finish
automobile bodies which can dry fast.
Laminated Windshield
It is a type of windshield that has a thin layer
of rubbery plastic compressed between two sheets of glass.
In case of an accident it bows out without puncturing
allowing the plastic to hold the glass to prevent it from
splintering.
Lateral Link
It refers to a kind of suspension link that is
placed in a line to prevent sideways motions in a wheel.
Leading Link
It is a suspension link which is mounted to the
chassis behind the wheel. It prevents longitudinal motions
in a wheel.
Leaf Spring
Primarily used in suspension, it is made of
spring steel or various materials, which deflects by bending
when some force is put on it. It consists of a number of
slightly curved, flexible steel plates of different lengths,
mounted one on the other.
Lease
It is a form of contract to transfer the use of a vehicle
after considering the payment.
Lift
It is just like a vertical force produced by the airflow
around a moving object like a car body.
Lift
Throttle OversteerIn times of hard cornering when the
throttle is released, it acts as a handling characteristic
that causes the rear tires to lose some of their cornering
grip.
Light Truck
This refers to the vehicle weighing less than
14,000 lbs.
Lights, Driving
Having a narrower beam than the headlights, these
are the auxiliary lights which enhance the reach of standard
headlights.
Lights, Foglights
These are complementary lights usually mounted
lower than the headlights to illuminate in times of fog and
reduce reflected glare. It has a wider beam pattern than
standard headlights.
Lights, Halogen
Such types of Lights acquire some acceptability
because of their brighter, longer lasting illumination than
other standard incandescent lights. Halogen bulbs are filled
with a gas like iodine that reduces the gradual evaporation
of the tungsten filament and enhances its life.
Lights, Projector Beam
This type of light has a spherical reflector to
control the light beam. That's why projector beams are
relatively more expensive than other standard headlights.
Limousine
It indicates a closed, chauffeur-driven automobile in which
the driver and the passengers are separated by a glass
partition.
Link
It is a part of the suspension system which has a single
joint at each end.
Live Axle
It is an axle, which, unlike a dead axle,
transmits power either by separate half shafts or by side
chains.
Lockup Converter
It refers to an automatic transmission having a
mechanical clutch that bypasses the fluid coupling of the
torque converter.
Lockup
It is the juncture at which a tire starts skidding during
braking.
Lockup Torque Converter
It is a torque converter fitted with a lock-up
clutch to eliminate the slip between the torque converter's
input and output. In this process it improves fuel
efficiency and performance.
Loose
It is an informal term to describe oversteer.
Louver
It is an air outlet or air intake consisting of some slats
which are used to capture and control the airflow.
Low Emission Vehicle (LEV)
It is applied to vehicles that fulfills the
emission standards which are far more stringent than the EPA
minimum. Some automobile giants like Honda manufactures LEV
compliant gasoline powered cars.
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[ M ]
Mac-Pherson strut
It is a shock absorber and spring unit that
allows relatively long springs to increase suspension travel
and bump absorption capability.
Main Bearings
It refers to the bearings in an engine block that
support the crankshaft.
Make
-It is a term to describe the brand name of a car or truck
belonging to Chevrolet, Ford, Dodge, Honda etc.
Manual Transmission
It is a mechanism consisting of a lever that the
driver operates along with the clutch to change gear. It has
gears located in the drive train to vary the power and
torque delivered to the driven wheels.
Manufacturer's Suggested Retail Price (MSRP)
It is the margin or the return an intermediary
achieves on the selling price of the article.
Market Share
-It indicates the percentage of total sales
represented by an individual manufacturer or importer.
Mechanic Installed Market (MIL)
It is the maintenance and repair of vehicles done
by a mechanic or professional at a service outlet.
Medium-duty Truck
It refers to the vehicle weighing between 14,001
to 26,000 lbs.
Metal Forming
It signifies the solid or molten metal process
such as casting, forging, stamping and machining.
Methylcyclopentadienyl Manganese Tricarbonyl (MML)
It is an organic manganese compound used as a
fuel supplement to enhance octane levels in gasoline.
Mid-engine
It is a sort of chassis configuration that positions the
engine ahead of the rear axle but behind the passenger
compartment.
Mock-Up
It is a full size replica of a car made of wood and clay. It
is primarily used for design studies.
Monocoque
It is a type of body structure which allows the use of thin,
carefully shaped and joined panels instead of a thick
framework.
Motor
Rally
Motor Rallying is a sport that need no
introduction to those who love to drive to their extremes.
To know more you can consult this site.
Multi-link suspension
It suggests independent suspensions which are
regulated with several link arms to restrict the undesired
motion of the suspension. Though it is more expensive to
manufacture, it also facilitates better handling and ride
control than other simpler types.
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[ N ]
Neutral Steer
It projects a cornering condition in which the
rear and front slip angles are almost the same.
Normally Aspirated
It is a sort of engine which can receive air or
"breathes" without the help of a supercharger or
turbocharger.
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[ O ]
Octane
It is a type of numeric rating to suggest the resistance of
gasoline to detonation. Octane is actually a hydrocarbon.
High octane number indicates less chance of detonation.
Octane is actually a hydrocarbon (C8H18).
Off-Highway Vehicle
It is the vehicle designed for operation on
unmade surfaces or rough terrain and used especially for
construction or agriculture purposes.
Oil, Synthetic
This type of oil is not derived from raw
petroleum. Though it is 3-5 times costlier than conventional
mineral oil, it has superior engine protection properties.
Oil Pump
It is an engine-driven pump, which delivers oil
to the engine's moving parts under pressure.
Oil Ring
It is the lowermost piston ring that discards
excess oil from the cylinder walls and returns it to the oil
pan through vents in the ring and piston.
On Board Diagnostics (OBD)
- During normal vehicle operations it monitors
the Electric Control Unit and system responses for errors.
When the vehicle is open for service, this information on
the errors can be down loaded and displayed to the service
personnel to facilitate the trouble shooting process.
On-Center Feel
-It is the response or feel of the steering when
the wheel is approximately centered. In a vehicle having
good on-center feel, the steering wheel returns to center
when slightly deflected and maintains straight-line
stability.
Opposite Lock
It is used to control a car when it is
oversteering and its back is swinging wide. It offers a
system in which the steering wheel is turned in the
direction away from where the car is turning.
Overcapacity
It is used to describe a situation where the global
production of automobiles exceeds the total global demand
for them.
Overdrive
It is the secondary gearbox which provides an additional
gear ratio. It allows the drive shaft to turn faster than
the engine crankshaft. Overdrive gears reduce engine rpm and
improve fuel economy at highway speeds.
Overhead Cam
It is a type of valvetrain configuration in which
the camshaft of the engine is in its cylinder head. When the
camshaft is located close to the valves, the engine runs at
higher rpm. In a single-overhead-cam (SOHC) layout, one
camshaft activates all the valves in a cylinder head while
in a double-overhead-camshaft (DOHC) layout, one camshaft
actuates the intake valves, and the other operates the
exhaust valves.
Overhead Valve (OHV)
It suggests that the intake and exhaust valves
are above the cylinder head. All OHC, SOHC, and DOHC engines
are also OHV.
Oversquare
It is used to describe an engine whose bore is larger than
its stroke.
Oversteer
This phenomenon occurs when the rear wheels help steering
the vehicle more in a given direction. It usually happens
under hard braking while turning. The rear of the vehicle
loses adhesion and starts to rotate in the direction of
steering. Most cars are designed not to oversteer under
normal conditions because it is difficult to control and can
result in a disastrous spin.
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[ P ]
Panhard Rod
-It is a long link which provides lateral
location of a rigid axle. It usually remains roughly
parallel to the axle, with one end joined with the body and
the other attached to the axle.
Passenger Vehicle
A four-wheeler that includes mini-vans as well as
sports utility vehicles.
Pent-roof
It is a combustion chamber usually used with four valves per
cylinder which resembles a shallow peaked roof.
Phaeton
It is a sleekly styled car, usually having two doors, with a
convertible top.It generally refers to the convertibles
built in the 1930's and earlier. The four-seater was known
as a double phaeton and the six- or seven- seater a triple
phaeton.
Pinion
It is a small diameter gear with a number of teeth designed
to engage with a much larger gear wheel or a toothed rod. It
is usually used for reduction in speed and increase in power
in rack-and-pinion steering.
Piston
It is a partially hollow cylindrical metal engine part with
a closed end which fits into the engine cylinder. It is
usually joined to the crankshaft through the connecting rod
and fitted with rings to seal it in the cylinder.
Pitch
It refers to the rotation of a car around a horizontal axis,
which causes its nose or back to move up and down. Dive and
squat are pitching motions.
Planetary Gears
It is a sort of gearset in which all the gears
are set around each other like the planets around the sun
and also in one planeThe planet gears also have teeth on the
inner area of the "ring gear." Planetary gearsets are
usually found in automatic transmissions.
Platform
It is a structural base which supports the driveline and
links the suspension components of a motor vehicle.It bears
the structural assembly of a motor vehicle and determines
its basic size.
Plenum chamber
Located between the throttle body and the runners
of an intake manifold, it is just like a chamber to
distribute the intake charge and improve engine breathing.
Pneumatic Tire
It is a circular tube, usually of rubber or
synthetic rubber, fabric or steel, attached to the rim of
the car's wheel having resilience.
Pneumatic Tire Flexible
It is a sort of hollow rubber inflated by air
pressure that forms the outer part of the vehicle wheel.
Polar moment of inertia
It indicates the resistance of an object to
rotational acceleration. When the mass of an object remains
far from its axis of rotation, the object has a high polar
moment of inertia, and when it is close to the axis of
rotation, its polar moment of inertia remains usually low.
Port fuel injection
In this type of fuel injection system at least
one injector is located on the air intake manifold close to
the port of each cylinder. Port fuel injection improves
engine breathing because of good fuel distribution and
greater flexibility in intake-manifold design.
Power
It suggests the rate at which work is performed. It is
proportional to torque and rpm and is measured in
horsepower.
Power Band
It refers to the rpm range over which an engine
delivers a substantial fraction of its peak power. It
usually extends from below the engine's torque peak to above
its power peak.
Powertrain
It is just a combination of the engine and transmission.
Pre-selector Gearbox
It indicates a configuration that enables the
driver to select the speed of a gear before he needs it and
then depress the clutch pedal when he wishes to use the
selected gear.
Product Design
It refers to the process of planning the
specifications of the product.
Production Engineering
It suggests the Planning and control of the
mechanical means of changing the shape and condition of
materials for greater effectiveness and value.
Product Planning
A process whereby an enterprise is accountable
for the efficiency, planning, scheduling and coordination of
production activities.
Product Testing
It refers to the methods which measure a
product's quality and durability.
Productivity
In common parlance it suggests the relative
measurement of output per labour and/or that of the machine.
Push
It is an informal term for understeer.
Pushrod
It is a term for any rod that transfers force in
compression. Pushrods are used by non-overhead cam engines
to open and close valves.
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[ Q ]
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[ R ]
Rack-and-pinion Steering
It is a type of steering system in which the
pinion gear is at the lower end of the steering column. It
has a rack or a toothed rod that connects to the wheel
steering arms. The ends of the rack are joined to the
steered wheels with tie rods. When the gear is rotated by
the steering shaft, it moves the rack from side to side and
turns the wheels.
Radial Ply
It is a tire in which the fabric cords move
radially in a line from the wheel hub or straight out from
the bead or around the tubular shape of the tire. In such
kind of design, flexibility in side walls with a relatively
stiff tread area and a larger and more consistent footprint
on the road under all driving conditions are achieved.
Rear Wheel Drive
In such a system the rear wheels receive all the
engine power. RWD provides less traction than FWD in poor
road conditions and is appreciated for its superior handling
and acceleration capabilities.
Rebound
It refers to the motion of a wheel which extends the
suspension.
Reciprocating Motion
It is the motion of an object between two
limiting positions. It is applied to the piston engines
because of the limited up and down motion of the pistons.
Redline
It is the maximum desirable revolutions per minute for an
engine.
Registration
It is the motor vehicle ownership that is filed with a
certain province or state.
Ride Height
It is a measurement between some fixed reference
point on a car's body which varies with the vehicles and the
ground. This dimension can be used to measure the deflection
of suspension or the height of the body from the ground.
Ride Steer
Otherwise known as the "bump steer", it refers to
a condition in which a wheel steers slightly as its
suspension compresses or extends.
Rigid Axle
It is a simple suspension which consists of a
rigid transverse member with wheel hubs firmly bolted to it.
The axle can be joined to the body by a combination of
suspension arms and links or by leaf springs.
Ring Gear
It refers to the gear in the rear axle which
transmits power to the differential from the drive shaft.
Ring-and-Pinion Gear
It consists of a small gear like the pinion gear
which turns the ring gear.
Road-load horsepower
It signifies the amount of power required to move
a car down the road at a steady speed. The power varies
according to the speed of the car, aerodynamic drag,
mechanical friction, and the tires' rolling resistance.
However, it is quite different from the engine power.
Roadster
It generally refers to a two-seater open car with sporty
appearance and having side curtains instead of roll-up
windows.
Rocker Arm
It is a pivoted lever which transmits the action
of the pushrod to the valve stem.
Roadholding
It indicates the ability of a car to grip the pavement and
is measured in gs. Since cornering marks a deviation from a
straight path, roadholding is technically described as"
lateral acceleration".
Roll
Sometimes called "sway" or "lean", though less accurately,
it signifies the rotation of a car's body about a
longitudinal axis.
RPM
It is an acronym for Revolutions per minute. It indicates
the frequency of the rotation of the engine crankshaft per
minute.
Rubber-isolated crossmember
It is a laterally aligned structural member
attached to the body through vibration-absorbing rubber
isolators. By bolting suspension to crossmembers, the
transmission of noise can be redu | 
