ENGINEERING
GLOSSARY

 

 
Automotive
 
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                                           AUTOMOTIVE GLOSSARY
 
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[ A ]

A-pillar
The roof support on either side of A car's windshield.


Active Suspension

A computerized suspension system that uses powered actuators. The actuators position a car's wheels in the best possible manner to deal with road and load.


Aerodynamic Drag

The drag produced by a moving object as it displaces the air in its path.

 

Aerodynamics
A branch of mechanics that deals with the motion of gases (especially air) and their effects on bodies in the flow.


Aftermarket
(Replacement Market) all products and services used in the repair and maintenance of vehicles.


Air Dam

A front spoiler mounted beneath the bumper and shaped to reduce the airflow under the car.


All Wheel Drive (AWD)

All four wheels are driven by the engine. AWD systems are superior to 4WD as AWD can be used under any road conditions.


Alloy wheels

Wheels are usually made of aluminum alloy. These wheels improve appearance and are less prone to corrosion. They are lighter than similar steel wheels.


Alternator
A device that converts rotational energy to AC current. Alternators provide energy for the vehicle electrical system and recharge the battery.


Anti-Dive
A front suspension characteristic that reduces dive under braking.


Anti-Lock-Braking System

A braking system that senses when any of the wheels have locked up, or are about to and automatically reduces the braking forces.


Anti-Roll Bar

A suspension element that reduces body roll by resisting any unequal vertical motion between wheels that it is connected to. An anti-roll bar improves vehicle handling by increasing stability during sudden maneuvers.

Anti-Squat
Similar to anti-dive, this suspension characteristic uses acceleration-induced forces in the rear suspension to reduce squat.


Apex
The point(s) or region on the line through a corner that touches the corner's inner radius.


Automated Guided Vehicle System (AGVS)

Vehicles equipped with automatic guidance equipment which follow a prescribed path, stopping at each machining or assembly station for manual loading and unloading of parts.



Automatic Transmission

A transmission that shifts its own gears according to the speed. It is also called automatic gearbox.


Automobile
Four-wheeled passenger motor vehicle having a seating capacity for not more than 10 people.


Axle Ratios

The gear ratio of the differential gearbox. The differential gearbox distributes the engine's power (via the transmission input shaft or propellor shaft) to the wheels. The axle ratio of the differential reduces the revolutions of the transmission input shaft before it reaches the wheels. Typical automotive axle ratios are in the range of 2.71 up to 4.31. The higher the ratio, the faster the engine will rev at a particular vehicle speed. Axle Tramp A form of wheel hop that occurs on cars with live axle caused by the axle repeatedly rotating slightly with the wheels and then springing back.

 

Axle, Live or Rigid

A solid or straight axle that allows the movement of one wheel to affect the opposite wheel. A live axle is inexpensive to manufacture and is useful for heavy duty applications.

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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 reduced.


Runabout
It is an open, lightweight sporting-type vehicle with two seats and simple bodywork.


Running Board

It is the long flat board under the doors of a car which acts as a footstep for the passengers.

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[ S ]

 

Safety Restraint Systems

The devices like safety belts, airbags which are used to provide some protections from injury in case of an accident.


Scrub radius

Commonly called "steering offset", it refers to the gap from the point where the steering axis meets the ground to the longitudinal line which runs through the centre of the tire's contact patch.


Sealed Beam

It is a sealed airtight headlight in which the filament is a crucial part of the unit and the lens itself is the bulb.


Selective Transmission

It is sort of the conventional manual transmission in which any gear may be selected at will without any specific order.


Semi-elliptic leaf spring

It is a slightly curved leaf spring joined to a car's body at its ends and to a suspension component near its middle.

Semi-trailing-arm suspension

It is an independent rear-suspension system where each wheel hub is located by a large, roughly triangular arm which pivots at two points.


Shift Gate

It is the mechanism in a transmission linkage that regulates the motion of the gearshift lever. It is usually an internal mechanism except in some exceptional cases.


Shock absorber

It is an instrument to convert motion into heat especially by forcing oil through small internal passages in a tubular housing. The majority of shock absorbers are hydraulic. Their basic function is to dampen suspension oscillation and respond to motion.


Single-rate spring

It is a spring with a constant spring rate. If a 100-pound force deflects the spring by one inch, an additional 100 pounds will deflect it one inch more, and so on until the spring either gets to the bottom or fails.

Skidpad
It is usually a large area of smooth, flat pavement used to test various handlings.


Sleeve Valve

This valve remains in between the piston and the cylinder wall. It consists of metal sleeves. Holes in the sleeves, when moved up and down, provide passage for the gases at the right time.

Slip angle

It suggests the difference in angle between the direction in which a tire is moving and the plane of its wheel. It is usually created by deflections in the tire's sidewall and tread during cornering.

Slushbox
It is an informal term for an automatic transmission.


SOHC
An acronym for single overhead cam, this engine uses one camshaft in each cylinder head to operate both the exhaust and the intake valves.


Space frame

A sort of tube frame consisting of relatively short, small-diameter tubes, these are welded together in aa arrangement that loads them mainly in tension and compression.


Spark Plug

It is instrumental in converting high voltage energy into an arc that passes between its electrodes. This arc allows the gasoline-air mixture in the cylinder to ignite and expand, fetching power by pressing down the piston.]


Spoiler
AnIt is a device that helps alter the direction of airflow in order to reduce lift or aerodynamic drag and better engine cooling.


Sports Car

It refers to a car which accelerates briskly, brakes positively, handles well, steers precisely and is easily maneuverable.Unlike a conventional car, it springs tightly and does not wallow and heave.


Spyder
Known as Spider in the early 1900s, it is just a light two-seater car. Some Italian manufacturers used this term for an open two seater sports car in 1950.


Squat
It is the dipping of a car's rear end which occurs during hard acceleration. It is caused by a transfer of load from the front to the rear suspension.


Starter
It is a motor driven by the battery which rotates the crankshaft before the engine starts.


Steering Axis

It is the line which crosses the upper and lower steering pivots on a steered wheel. The steering axis in a car with a strut suspension can be described as the line through the strut mount at the top and the ball joint on the bottom.


Steering Feel

It is referred to describe the relationship between forces at the steering wheel and the handling. Ideally, as the wheel is rotating away from the center, the steering effort should be enhanced smoothly. It should also build with the increase in the cornering forces at the steered wheels. Moreover, the friction in the steering mechanism should be small in comparison with the handling-related steering forces.


Steering gain

It indicates a certain relationship between the yaw and the steering wheel's position and effort. These three things should be proportional and they should increase smoothly.


Steering Geometry

It refers to a set of design variables outside the steering mechanism which virtually affect steering behavior, including camber, caster, linkage arrangement, ride steer, scrub radius, toe-in and trail.


Steering, Power

It is usually used to reduce the steering effort. Power steering is crucial in managing large, heavy vehicles.

Steering, Rack and Pinion

A In such a mechanism the steering wheel is connected to a pinion gear which meshes with a rack, or linear gear. With the rotation of the pinion, the rack moves side to side allowing the steering linkage to move and causing the wheels to pivot left or right.


Steering Response

It generally refers to the combination of steering feel and steering gain.


Straight-line Tracking

It indicates the ability of a car to run in a straight line without any modifications in steering and to resist road irregularities.


Stroke
It signifies the back-and-forth motion of the piston.


Strut
It suggests a suspension element where a reinforced shock absorber is used as one of the wheel's locating members by fastening the wheel hub with the bottom end of the strut.


Sump
It is the space in the engine block under the crankshaft into which the oil drains.


Supercharger (Blower)

It is an air compressor for forcing more air into an engine than it can inhale on its own.


Suspension
The arrangement of springs, shock absorbers, torsion bars, joints, arms, etc. which reduces the shock of bumps on the road. It keeps the wheels in constant contact with the road and improves control and traction.

Swing Axle

It describes a sort of independent rear suspension with the use of half shafts which have universal joints at their inboard ends on both sides of the differential. This creates up-and-down movements of the wheel with a camber angle change.

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[ T ]

 

Tachometer
It is an indicator of the number of revolutions per minute at which the engine is turning.


Targa
It refers to a fixed, roll-bar-like structure stretching from one side to the other behind the front seats. However, its removable-roof body style popularized by Porsche is quite similar to a convertible.


Throttle-body
It is located between the air cleaner and the intake plenum. It contains a valve which regulate the airflow through the intake manifold.


Throttle-body fuel injection

It is a fuel injection mechanism in which the injectors remain at the engine's throttle-body and feed fuel to more than one cylinder. Though it saves money by using fewer injectors, it eliminates some of the tuning possibilities offered by port fuel injection as it routes both fuel and air through the intake manifold.


Tires, All Season

These types of tires allow acceptable traction for snow in winter and slush driving conditions. It hardly compromises on dry and wet traction.


Tires, Aspect Ratio (e.g. 60-series tires)

It is the ratio between the tread (section) width and the sidewall. A 205/50-15 tire would have a sidewall height of 0.50 x 205 or 102.5 mm. Lower aspect ratios provide superior handling at the cost of increased ride harshness. Tires with M+S rating are designed to perform well in mud and snow and are superior to all-season tires under these conditions.


Toe Steer

It refers to the changes that occur in the wheel direction without the steering input of the driver. It can be caused either by the deflections in suspension components, accelerating or braking.


Toe-Control Link

It is just like a lateral link that is located in a multi link suspension to regulate a wheel's direction when the suspension moves up and down.


Tool
It is a device to use for either the production of machinery or the assembling of materials or the working of materials by turning, milling, grinding, polishing, drilling, punching, boring, shaping, shearing, pressing or planing.

Tooling
It refers to a set of special tools required to produce a particular part. It includes jigs, fixtures, gages and cutting tools but not machined tools.


Torque
It suggests the measurement of the twisting force. It is measured in lb.-ft.(pound-foot) or N-m(Newton-meters).

Torque Converter

It is a fluid coupling in automatic transmission which transmits power from the engine to the wheels. The torque converter engages the transmission to be engaged while the vehicle is stopped. The transmission fluid absorbs power and prevents engine stalling.


Torque steer

It reflects the tendency of a car to turn in a particular direction with the application of power. Torque steer is common in front-drive cars as generation of uneven steering forces in the front tires is created by the reaction forces in the half-shafts.


Torsion Bar

It is a kind of simple or rugged spring used in the suspension system which twists when compressed or stretched.

Traction Control

It refers to the limiting of wheel slip under acceleration. When the wheel slip is detected this system usually applies brakes and reduce throttle.

Trail braking

It is used to indicate a driving technique in which the driver applies the brake before approaching a turn and then continues it till he eases into the corner.


Trailing arm

It is basically a suspension element having a longitudinal member which pivots from the body at its forward end with a wheel hub being joined to its trailing end. A rigid trailing arm provides all the locations of a wheel.


Trailing link

It is a type of suspension link attached to the chassis ahead of the wheel to resist the longitudinal motions in a wheel.


Transaxle
It suggests the combination of a transmission and a differential in one integrated assembly.


Transmission
It indicates the gear-changing or gear-shifting system through which the power of an engine is transferred to the wheels.


Tread
Otherwise known as track, it suggests the measurement of the width of a car the from the center line of the wheels.


Tread squirm

It is indicative of the flexibility between the surface of the tread and the tire carcass in the tire tread . While snow tires have a large amount of tread squirm, Slick racing tires without the tread pattern, have very little squirm.

Trim Level

It suggests the designation of a vehicle representing specific equipment packages that is assigned by its manufacturer.

Tube Frame

It is a sort of car frame made by welding together the rigid tubing.


Tumblehome
It is a technical term to describe the convex curvature on the side of a car body.


Tuned intake and exhaust systems

It refers to the intake and exhaust systems which are instrumental in enhancing the flow of intake charge into and out of the combustion chambers.


Turbocharger
It is a supercharging device run by the exhaust gases from the engine.


Turn-in
It is suggestive of the moment of transition between driving ahead straight and cornering.


Turning Circle

It is the diameter of the circular path created by the wheel that remains furthest from the center of the turn. The path created by the right front wheel while turning left defines the turning circle and the vice versa.

Twist Beam Axle

It is a semi-independent axle used on rear suspensions of front-wheel drive vehicles. The beam can twist to reduce the effect of the motion of one wheel on the other wheel. A horizontal beam connects the two rear wheels together. A twist-beam axle is less expensive and more compact than an independent suspension.

Two-Stroke Cycle

Hardly used in automobile, it is just an internal-combustion engine which needs two piston strokes and only one revolution per cylinder to achieve a power stroke.

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[ U ]

 

Understeer
Understeer is a condition where the front wheels provide less steering than desired in a given direction.


Unitized Construction

It is a vehicle body make that does not require a support frame.


Universal joint

A joint that transmits rotary motion between two shafts not in a straight line. Depending on its design, a universal joint can accommodate a large angular variation between its inputs and outputs.

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[ V ]


Value analysis (VA)

Valve that opens and closes the combustion chamber of an internal-combustion for fuel-air mixture or exhaust the gases.


Valve Lifter

Also called a "valve follower" it is a cylindrical component that presses against the lobe of a camshaft and moves up and down as the cam lobe rotates.


Valves
Signifies the total intake and exhaust valves in an engine


Valve Train

The collection of parts that make the valves operate. It includes the camshaft, various parts that convert the camshaft's rotary motion into reciprocating motion at the valves.


VEE Engine

An engine with cylinders arranged in two rows at an angle to the common crankshaft. Has a "V" shape when viewed from the front.


Viscous Coupling

A particular kind of fluid coupling in which the input and output shafts mate with thin, alternately spaced discs in a cylindrical chamber.

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[ W ]

 

Waste gate

A valve used to limit the boost developed in a turbocharger


Water Pump

A pump that circulates coolant within the engine It is driven by the engine crankshaft.


Wheel Hop

A suspension characteristic in which the wheel moves up and down so violently that it actually leaves the ground. The situation indicates suspension problem.


Wheel Size (e.g. 15 X 7)

Wheel size is defined by the diameter and width of the wheel. A 15 X 7 wheel has a 15-inch diameter and a 7-inch width.


Wheelbase
The distance between the centers of the front and rear wheel axles as viewed from the side of the car.

Wishbone Suspension

An independent suspension that uses curved members to control suspension travel. A wishbone suspension offers good axle control

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[ X ]

 

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[ Y ]

 

Yaw
The rotation about a vertical axis that passes through the car's center of gravity.

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[ Z ]

 

Zero-offset steering

A steering system that minimizes the steering effects produced during acceleration or braking.                

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Relevant topics
 

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