(Labor)(General)
0.5 Glossary

A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

Additional Glossaries on the world wide web.
A
     
A   is the abbreviation for ampere, the unit of measurement of current.
     
ABDC   is the abbreviation for After Bottom Dead Center. It is any position of the piston between bottom dead center and top dead center when it is moving up in the cylinder.
     
Ability to Take A Charge   a test of a battery's condition allowing it to take and hold a charge.
     
Abrasive Wear   the result of particles of dirt, dust , and other contaminants grinding against any moving surface. It can be found an many systems of the automobile including the engine, transmission, brakes, steering and more. To minimize abrasive wear it is critical to perfrom routine maintenance such as the re-occuring 30,000 mile maintenance.
     
Abrasives   any substance that causes another substance to wear either through scratching or by increased friction between moving surfaces. Sandpaper is a common example of an abrasive.
     
Absolute Pressure   the pressure measured from the reference point of a perfect vacuum. Normal atmosphereic pressure on the absolute scale is about 14.7 psi or 1 bar at sea level.
     
Absolute Zero   1. the complete absence of heat or engergy in any object. This point is -460 degrees F or -273 degrees C. It is generally used only as a reference temperature as the point where any substance has only minimal energy; 2. the theoretical temperature at which substances possess no thermal energy, equal to −273.15°C, or −459.67°F; 3. he temperature at which an ideal gas would exert no pressure. The Kelvin scale of temperatures is defined in terms of the triple point of water, T3 = 273.16° (where the solid, liquid, and vapor phases coexist), and absolute zero. Temperature is measured most simply via the constant-volume ideal-gas thermometer, in which a small amount of gas is introduced (in order to limit the effect of interactions between molecules) and then sealed off, and the gas pressure P referenced to its value at the triple point P(T3) is measured. The ideal-gas law applies if the molecules in a gas exert no forces on one another and if they are not attracted to the walls. Absolute zero is the temperature at which the pressure of a truly ideal gas would vanish.

According to classical physics, all motion would cease at absolute zero; however, the quantum-mechanical uncertainty principle requires that there be a small amount of residual motion (zero-point motion) even at absolute zero.
     
AC   the abbreviation for alternating current. This flow of current changes direction, or polarity, in regualr cycles.
     
A-pillar   the roof support on either side of A car's windshield.
     
Acceleration   an increase in speed.
     
Acceleration Enrichement   the condition in which a higher ratio of fuel to air is present during acceleration becuase fuel condenses on the walls of the manifold.
     
Accelerator   a pedal for regulating the speed of an engine.
     
Accessories   anything in a vehicle that is not essential to its operation. This includes the radio, air conditioner, power windows, and other similar devices.
     
Acetylene or Oxy-Acetylene Welding   utilization of an acetylene flame to heat metal to fusion or melting point when uniting it.
     
Acid Rain   a corrosive rain formed when sulfur emissions for motor vehicles, industrial plants, or electric generating stations combine with hydrogen and oxygen in the atmosphere to form sulfuric acid (H2SO4). This is not only generally corrosive to anything it may come into contact with, it also raises the acidity of lakes and ponds, often to the point that fish and other aquatic life cannot survive.
     
Ackerman Principle   1. design having wheel spindles mounted on axle ends to permit spindles to be turned at an angle to axle for steering purposes; 2. the creation of toe-out when turning to minimize tire wear. To create the proper geometry, the steering arms are angled to turn the inside wheel at a sharper angle than the outside wheel. This allows the inside wheel to follow a smaller radius circle than the outside wheel.
     
Active Head Restraint  

SAAB Active Head Restraint (SAHR) is a mechanical system that is activated by human body weight using the placemnt of the body and collision force. It consists of an intergrated structure in the backrest which is connected to the head restraint. The system is activated in the event of collision form behind where the speed is relatively low, around 17 kmh.

In the event of a collison form behind, the car and front seats accelerate forwards, which means that the drive and passenger move backwards in relation to the seat. The lower part of the structure in the backrest is then pressed in by the the body wieght, which results in the upper part (together with the connected neck restraint) to slide forwards and upwards.

     
Active Material   1. in a storage battery, peroxide of lead (brown) in positive plastes and metallic lead (gray) in negative plates upoin which sulphuric acid acts; 2. the metals and acids used in a storage battery which are treated chemically and electrically to cause a chemical reaction to occur and voltage potential to be developed.
     
Active Suspension   an extremely sophisticated, computer controlled suspension system that uses powered actuators instead of conventional springs and shock absorbers. The actuators position a car's wheels in the best possible manner to deal with road disturbances and handling loads.
     
Acutator   an output device controlled by a computer.
     
Additive   1. in automotive oils, material added to oil to give it certain properties; 2. something added to coolant, gasoline or oil to allegedly improve or change its structure, characteristics, or the way it performs. Both SAAB and JGA do not recommend the use of additives.
     
Adhesive Sheer Strength   the property of a substance or component to hold two parts together and resist forces trying to pull them apart or separate them.
     
Adjust   1. to change the parts of a system or component so they correspond to some specified dimension, relationship, or standard; 2. to bring into proper relationship; 3. to bring the components of a multi-components system into a more effective or efficient calibration or state; 4. to change or move something to make it fit or to make it work correctly.
     
Adjustments   the changes in clearances, dimensions, or settings to bring a component or system in correct relationship with other or to bring it up to certain specifications.
     
Advance   a timing adjustment to cause the ignition spark to occur earlier in relation to the travel of the piston up in the cylinder. In older cars this was accomplished by centrifugal or vacuum mechanisms inside the distributor which reacted to changes in engine speed and load. Modern SAABs control timing through the use of an on-board computer.
     
Aerodynamic Drag the drag produced by a moving object as it displaces the air in its path. Aerodynamic drag is a force usually measured in pounds; it increases in proportion to the object's frontal area, its drag coefficient, and the square of its speed.
Aerodynamics 1. the branch of mechanics that deals with the motion of gases (especially air) and their effects on bodies in the flow. In car design the positive and negative lift of the airflow is studied in wind tunnels. Negative lift is preferred to press the vehicle closer to the ground; 2. the study or application of atmospheric interactions with moving objects.
Aftermarket all products and services used in the repair and maintenance of vehicles.
Air   1) a gas containing approximately 4/5 nitrogen, 1/5 oxygen and come carbonic gas 2) the combination of gases that makes up the earth's atmosphere.
     
Air Cleaner   a device for filtering, cleaning, and removing dust from intake air to an engine, air compressor, etc.
     
Air Conditioning   the process by which surrounding air is cooled and de-humidified.
     
Air-Dam   A front spoiler mounted beneath the bumper and shaped to reduce the airflow under the car. Air dams can increase the airflow to radiators, reduce aerodynamic drag, and/or reduce lift.
     
Air-Fuel Ratio   1. the ratio by weight of fuel compared to air; 2. the ratio of air to fuel in the mixture sent to the combustion chamber.
     
Air Gap   the space between spark plug electrodes, starting motor armatures, field shoes, etc.
     
Air Injection System   the means of injecting fresh air into hot exhaust gases to reduce HC and CO emissions
     
Air-Lock   a bubble of air trapped in a fluid circuit which interferes with normal circulation of fluid
     
Airflow Meter   a device that measures the rate at which air enters the engine
     
Alignment   an adjustment to bring related components into a line
     
All Wheel Drive   1. four wheel drive capability with automatic shifts; 2. (AWD) All four wheels are driven by the engine. AWD systems are superior to 4WD because (AWD) they can be used under any road conditions. AWD systems use a center differential to allow the front and rear wheels to rotate at different speeds. AWD provides better traction than front or rear-wheel drive
     
Allen Wrench   a hexagonal wrench which is "L" shaped and fits into a recessed hexagonal hole
     
Alloy   a mixture of different metals e.g. solder is an alloy of lead and tin
Alloy Wheels wheels usually made of aluminum alloy; installed to improve appearance. Alloy wheels are less prone to corrosion and can be significantly lighter than the equivalent steel wheels
Alternating Current an electric current alternating back and forth in direction and flow
Alternator a generator in which alternating current is changed to direct current by means of rectifiers (diodes)
Altitude 1) elevation measured in relationship to the Earth's surface at sea level 2) the distance of a point from sea level. It is important to automotive emission control because the higher the altitude, the fewer oxygen molecules per given volume of air, which alters the effective compression and air/fuel ratios.
     
Aluminum   a metal, noted for its lightness, often alloyed with small quantities of other metals
     
Ambient   surrounding on all sides
     
Ambient Temperature   the temperature of air (surrounding a vehicle).
     
American Wire Gauge (AWG)  

also known as the Brown & Sharpe wire gauge, is a standardized wire gauge system used in the United States and other countries, especially for nonferrous, electrically conducting wire. The steel industry uses a different numbering system for their wire thickness gauges (for example, W&M Wire Gauge or US Steel Wire Gauge or the different Music Wire Gauge) so data below does not apply to steel wire.

Increasing gauge numbers give decreasing wire diameters, which is similar to many other non-metric gauging systems. This seemingly-counterintuitive numbering is derived from the fact that the gauge number is related to the number of drawing operations that must be used to produce a given gauge of wire; very fine wire (for example, 30 gauge) requires far more passes through the drawing dies than does 0 gauge wire.

The AWG system is illogical and the metric system is a superior means of measuring the cross sectional diameter of the wire.

     
Ammeter   an instrument for measuring flow of electric current
     
Ampere   a unit of measurement for flow of electric current
     
Ampere-Hour Capacity   a term used to indicate capacity of a storage battery. e.g. the delivery of a certain number of amperes for a certain number of hours
     
Annealing   a process of softening metal e.g. the heating and slow cooling of a piece of iron
     
Annular Ball Bearing   a ball bearing with a non-adjustable inner and outer race or races
     
Annulus   in a planetary gear system, an internal ring gear that operates in conjuction with a sun gear, pinion gears, and pinion carrier--also see Ring Gear
     
Anode   a positive pole of an electric current
     
Anti-Freeze   a material, such as ethylene glycol, addes to water to lower its freezing point
     
Anti-Friction Bearing   a bearing constructed with balls or rollers between journal and bearing surface to provide rolling instead of sliding friction
     
Anti-Lock Brake System   1. a system on an automobile that provides rapid and repeated brake applications and releases to bring a vehicle to a stop without brake lock up or skidding; 2. A braking system that senses when any of the wheels have locked up, or are about to, and automatically reduces the braking forces to keep the wheels rolling
     
Anti-Roll Bar   A suspension element (used at the front, the rear, or both ends of a car) that reduces body roll by resisting any unequal vertical motion between the pair of wheels to which it is connected. An anti-roll bar does not affect suspension stiffness when both wheels are deflected equally in the same direction
     
Aperture   an opening, hole or port
     
Arc Welding   a method of utilizing an electric current jumping an air gap to provide heat for welding metal
     
Arcing   electricity bridging a gap between to electrodes
     
Armature   a part of an electrical device which includes main, current-carrying winding
     
Articulated Mounting a term used where parts are connected by links and the links are anchored to provide a double hinging action
Asbestos a natural fibrous mineral with great heat resisting ability
Aspect Ratio 1. the ratio of tire section height to tire section width; 2. generally the ratio between two dimensions of an object. In tire terminology it applies to the unloaded sidewall height of the tire divided by its overall width. A lower aspect ratio implies a shorter, wider tire
Atmospheric Pressure the weight of air at sea level, about 14.7 psi
Atom the smallest distinct chemical unit of a substance, composed of elctrons, neutrons, and protons
Automobile four-wheeled passenger motor vehicle having a seating capacity for not more than 10 people including police cars and racing cars but not including ambulances or hearses
AWG is the abbreviation for American Wire Gauge. It is also known as the Brown & Sharpe wire gauge, is a standardized wire gauge system used in the United States and other countries, especially for nonferrous, electrically conducting wire. The steel industry uses a different numbering system for their wire thickness gauges (for example, W&M Wire Gauge or US Steel Wire Gauge or the different Music Wire Gauge) so data below does not apply to steel wire.

Increasing gauge numbers give decreasing wire diameters, which is similar to many other non-metric gauging systems. This seemingly-counterintuitive numbering is derived from the fact that the gauge number is related to the number of drawing operations that must be used to produce a given gauge of wire; very fine wire (for example, 30 gauge) requires far more passes through the drawing dies than does 0 gauge wire.

The AWG system is illogical and the metric system is a superior means of measuring the cross sectional diameter of the wire.

     
Axle 1. a shaft or shafts of a vehicle upon which wheels are mounted, also a simple machine; 2. a pin or shaft on or with which wheels revolve; with fixed wheels, one of the basic simple machines for amplifying force.
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
   
B
     
B&S Gauge   Brown and Sharpe gauge, which is a standard measure of wire size, which in America is the smaller the number the larger the wire
     
B-pillar   the roof support between a car's front door window and rear side window, if there is one
     
Backfire   1) the pre-mature ignition of fuel in the intake manifold resulting in a loud, premature explosion 2) an explosion in the exhaust system of a motor vehicle caused when unburnt air/fuel mixture is ignited 3) an explosion of the air/fuel mixture in the intake manifold and may be caused by improper ignition timing, crossed spark plug wires, and intake valve stuck open, etc.
     
Backlash   the clearance or "play" between the teeth of two gears
     
Back Pressure   1. a resistance to free flow, such as a restriction in the exhaust system; 2. resistance of an exhaust system to the passage of exhaust gases. This can have an adverse effect on performance, fuel economy, and emissions. Excessive back pressure may be caused by a clogged catalytic converter or a dented or crimped pipe.
     
Balance Shaft   A shaft designed so that, as it rotates, it vibrates in a way that reduces or cancels some of the vibration produced by an engine. Not essential to an engine's operation, balance shafts are nonetheless becoming increasingly common as a means of engine refinement. Balance-shafted four-cylinder engines use two shafts turning in opposite directions on either side of the engine's crankshaft. A single balance shaft is used when fitted to three-cylinder and V-6 engines
     
Balk Ring   a friction-regulated pawl or plunger used to facilitate engagement of gears
     
Ball Bearing   an anti-friction bearing consisting of a hardened inner and outer race with hardened steel balls interposed between the two races
     
Ball Joint   a flexible joint consisting of a ball in a socket, used primarily in front suspensions because it can accommodate a wide range of angular motion
     
Ball Peen Hammer   featuring a hardened head, it's used for striking cold chisels and punches for general metalwork. The ball peen was originally used to mushroom rivet heads. Sizes 8 to 32 oz
     
Barometric Pressure   the pressure exerted by the weight of the Earth's atmosphere, equal to one bar, 100 kilopascals, or 14.7 psi at sea level. Barometric pressure changes with the weather and with altitude. Since it affects the density of the air entering the engine and ultimately the air/fuel ratio, computerized fuel management systems such as SAAB's Trionic system account for air pressure changes
     
Battery   any number of complete electrical cells assembled in one housing or case, also called galvanic battery or voltaic battery, a combination of two or more cells elctrically connected to work together to produce electric energy
     
Battery Capacity   the amount of current a battery will deliver
     
Battery Plate   component made of special active materials contained in cast grids
     
Battery Ratings   the standards of power-delivering capability of batteries as established by the Battery Council International
     
Bead   the part of a tire shaped to the rim
     
Bell Housing   the covering around the f lywheel and clutch or torque converter
     
Bevel Gears   A gearset employing gears shaped like slices of a cone, which allows the axes of the gears to be nonparallel. Bevel gears are used to transmit motion through an angle
     
Bleed   the process of removing air from hydraulic circuits such as the brake or clutch systems
     
Blow-By   1. a leakage or loss of pressure, often used with reference to leakage of compression past piston rings between the piston and cylinder; 2. byproducts of combustion that leak out of the combustion chamber past the piston rings and into the crankcase. Mostly hydrocarbons, (HC) this represents approximately 20% of the air pollution a pre-emissions controlled engine produced. In modern vehicles, the blow by vapors are drawn into the intake stream through the positive crankcase ventilation system (PCV) to be burned in the cylinders. Problems with blow-by gasses have contributed to the sludge problem in certain SAAB engines; 3. a combination of oil mist, burned gases from the combustion chamber, water vapor, and small quantities of gasoline in the crankcase.
     
Boiling Point   the temperature at atmospheric pressure at which bubbles or vapors rise to the surface of a liquid
     
Booster   a mechanical or hyraulic device attached to the brake or steering systems to increase power or effectiveness
     
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 cylinder, also to enlarge a hole as distinquished from making a hole with a drill
     
Brake   an energy conversion mechanism used to retard, stop or hold a vehicle
     
Brake Bias   the front/rear distribution of a car's braking power. For the shortest stopping distance, brake bias should match the car's traction at each end during hard braking brake modulation: the process of varying pedal pressure to hold a car's brakes on the verge of lockup. Ideally, the brakes will unlock with only a slight reduction in the pressure needed to lock them. Typically, however, a considerable pressure reduction is required
     
Brake Bleeding   the process of removing air from the hyraulic brake system
     
Brake Caliper   the brake caliper is the assembly which houses the brake pads and pistons. The pistons are usually made of aluminum or chrome-plated iron. There are two types of calipers: floating or fixed. A fixed caliper does not move relative to the disc. It uses one or more pairs of pistons to clamp from each side of the disc, and is more complex and expensive than a floating caliper. A floating caliper (also called a "sliding caliper") moves with respect to the disc, along a line parallel to the axis of rotation of the disc; a piston on one side of the disc pushes the inner brake pad until it makes contact with the braking surface, then pulls the caliper body with the outer brake pad so pressure is applied to both sides of the disc.
     
Brake Cylnder   a cylinder in which a movalbe piston converts pressure to mechanical force to move brake shoes against the braking surface of the drum or the rotor
     
Brake Disc   a parallel-faced circular plate attached to the road wheel against which the brake lining is forced to retrad the vehicle, also called brake rotor
     
Brake Drum   a metal cylinder attached to the road wheel and acted upon by the brake lining which is forced to retard the vehicle
     
Brake Fade   a condition where repeated (and possible severe) applications of the brakes result in little effect upon the expected braking force resulting in impaired braking
     
Brake Fluid   A compounded liquid for use in hydraulic circuits such as brake or clutch systems which must meet standards as regarding to heat, freezing, thickening, bubbling, etc.
     
Brake Flushing   a process for removing fluid from a hydraulic circuit to remove debris and sediment.
     
Brake Horsepower   the actual horsepower delivered by the crankshaft delivered to the road wheels as measured by a dynanometer
     
Brake Hose   a flexible hose which used in hydraulic circuits that allows the conduction of brake fluid in a brake system
     
Brake Lining   a material have a suitable coefficent of friction which is attached to a brake pad or brake shoe
     
Brake Master Cylinder   The part of the hydraulic brake system which stores the brake fluid. As the brake pedal is applied pressure is forced against a small movable piston in the master cylinder to push hydraulic fluid through the lines to the brake pads against the disc.
     
Brake Pad   a carrier to which a brake lining is attached which is applied against a brake disc (also brake rotor) during braking operation to retard the vehicle
     
Brake Pedal   a foot pedal that moves a piston in the master brake cylinder
     
Brake Shoe   a carrier to which a brake lining is attached which is applied against a brake drum during braking opertion to retard the vehicle
     
Braze, Brazing   the process of joining two pieces of metal together usually with brass using a heat greater than 800 degrees F (as opposed to soldering which is a similar process of joinging metals together at temperatures between 400-700 degress F using solder)
     
Breaker Arm   the movable part of a pair of contact points in an ignition distributor (not used in SAABs since the 1970's)
     
Break-In   the process of wearing into a desirable fit between surfaces of two new or reconditioned parts
     
Breathing   a term used to describe an engine's ability to fill its cylinders with air-fuel mixture and then discharge the burnt exhaust gases. In general, the more air-fuel mixture an engine burns the more power it produces
     

Brinell Hardness

  a scale for designating the degree of hardness possessed by a substance
     
British Thermal Unit (Btu)   the amount of heat required to raise one pound of water one degree Fahrenheit. The heat value of various motor fuels are often compared in Btu's per gallon or per pound.
     
Brushes   the bars of carbon or other conducting material which contact the commutator of an electric motor or generator
     
Burnish   to smooth or polish by using of a sliding tool under pressure
     
Bushing   1. a removable liner for a bearing, a removable rubber (or similar material) liner often used in pivot points; 2. 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
   
C
     
C-pillar   the roof support between a car's rearmost side window and its rear window. On a vehicle with four side pillars, the rearmost roof support may be called a D-pillar
     
Calibrate   to determine or adjust any graduation or scale of any instrument giving quanatative measuremenets
     
Calibration   a precise facgtory setting
     
Caliper   a non-rotational hydraulic component of a disc brake that stradles the disc
     
Calorie   the metric measurement of the amount of heat required to raise one gram of water from 0 degrees C to 1 degree C
     
Cam   an eccentric curved wheel mounted on a rotating shaft used to produce variable or reciprocating motion in another engaged or contacted part
     
Cam Angle   the number of degrees of rotaion of a distributor shaft during which contact points are closed
     
Cam Profile   1. 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; 2. 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
     
Camber   in wheel alignment, the outward or inward tilt of the wheel at top
     
Camshaft   1. a shaft containing cams which operate engine valves; 2. A shaft fitted with several cams, whose lobes push on valve lifters to convert rotary motion into linear motion. The opening and closing of the valves in all piston engines is regulated by one or more camshafts
     
Canister   a reservoir of the evaporative emission control system usually containing activated charcoal granules for absorbing fuel vapors
     
CARB   California Air Resources Board (CARB) a state agency responsible for regulations intended to reduce air pollution, especially created by motor vehicles
     
Carbon   a common, non-metallic element that is an excellent conductor of electricity
     
Carbon Dioxide   1. a colorless, odorless, incombustable gas formed during respiration, combustion, and organic decomposition, when compressed into solid form it is also known as dry ice and it remains at a temperature of -109 degrees F, at normal pressures and temperatures carbon dioxide does not phase from solid to liquid to gas--it goes from a solid state to a gas state by a process known as sublimation; 2. in automoitve science, carbon dioxide is the product of complete combustion.
     
Carbon Fiber   thread-like strands of pure carbon that are extremely strong in tension (that is, when pulled) and are reasonably flexible. Carbon fiber can be bound in a matrix of plastic resin by heat, vacuum, or pressure to form a composite that is strong, light: and very expensive
     
Carbon Monoxide   1. a colorless, odorless, poisonous gas which results from an incomplete oxidation of carbon in combustion; 2. carbon monoxide is a major air pollutant that is formed by the incomplete combustion of any fuel containing carbon (gasoline, diesel, fuel, alcohol, coal, wood, etc.).
     
Carcass   the tire structure except for the sidewall and tread
     
Catalyst   a substance that accelerates or enhances a chemical reaction without being changed itself. When used in a catalytic converter, the can reduce the level of harmful pollutants in the exhaust. Catalysts which are commonly used include platnum, palladium, and rhodium, all of which are expensive to refine and produce.
     
Caster   1. in wheel alignment, the backward or forward tilt of steering axis; 2. the angle between a vertical line and the car's steering axis when viewed from the side, measured in degrees and minutes
     
Catalytic Converter   1. a emission control device in the exhaust system that chemically treats exhaust gases after combustion to oxidize noxious emission; 2. an automotive exhaust sytem component containing a catalytic element to reduce NOx and/or HC and CO tailpipe emissions. When hot exhaust gases pass through the converter, the catalyst allows oxygen from the air pump or aspirator to "reburn" the pollutants lowering the concentrations of HC and CO to almost zero. This process is called an "oxidation" reaction. It creates a great deal of heat (1200-1600 degrees F) so the converter is made of stainless steel surrounded with a heat shield.
     
Cathode   the negative pole of an electric current
     
Cell   a unit of a battery containing a group of positive and negative plates along with electrolyte
     
Celsius   a scale of temperature measurement on which, under standard atmospheric pressure, water freezes at 0 degrees and boils at 100 degrees
     
Center of Gravity   the point of a body from which it could be suspended, or on which it could be supported, and be in balance
     
Centrifugal Force   a force which tends to move a body away from its center of rotation
     
Centrifugal Advance   a mechanical means of advancing spark timing with flyweights and springs. These devices are located inside the distributor and the size of the weights, the amount of spring tension, and the engine RPM rating determines the rate of advance.
     
Charcoal Canister   the basic component of evaporative emission control systems,this is a small cylindrical or rectangular container that holds activated charcoal particles. The charcoal traps gasoline vapors from a vehicle's sealed fuel system.
     
Charge Temperature Sensor   on computer-controlled engines, a sensor which sends a signal to the computer that varies with the temperature of the intake stream
     
Chase   to straighten or repair damaged threads
     
Chassis   1. the framework of a vehicle; 2. a general term that refers to all of the mechanical parts of a car attached to a structural frame. In cars with unitized construction, the chassis comprises everything but the body of the car
     
Check Valve   1. a gate or valve which allows the passage of a gas or a fluid in only one direction; 2. a valve which permits the passage of a gas or fluid in one direction, but not in the other.
     
Choke   a reduced passage
     
Chlorofluorocarbons (CFCs)   a family of chemicals that includes R-12 automotive air conditioning refrigerant. Research has shown that CFCs have a deleterious effect on the Earth's protective ozone layer. All SAABs from 1993 no longer use R-12 refrigerant and instead use a CFC free refrigerant known as R134a.
     
Chromium Steel   an alloy of steel with a small amount of chromium to produce a metal which is highly resistant to oxidation and corrosion
     
Circuit   the path of electric current, fluids, or gases
     
Clean Air Act   originally passed in 1970 by the US Congress, and updated in 1990, this legislation created today's automotive emissions laws and established the Environmental Protection Agency (EPA) as the watchdog over our nation's air quality.
     
Clearance   the space allowed between two parts
     
Closed Loop   the basic principle of electronic engine management in which input from an oxygen sensor allows the engine control computer to determine and maintain a nearly perfect air/fuel ratio.
     
Clutch   a friciton device used to connect and disconnect a driving force from a driven force i.e. the engine from the transaxle
     
Coefficient of Friction   the amount of friction developed between two surfaces pressesd together and moved one on the other
     
Coil Spring   1. a spiral-shaped, coiled steel or steel alloy compression device; 2. A bar of resilient metal wound into a spiral that may be compressed or extended without permanent deformation. Coil springs have many automotive applications but are particularly important as suspension springs
     
Combustion   the process of burning
     
Combustion Chamber   1. in an internal combustion engine, the volume of the cylinder above the piston with piston on top center; 2. the space within the cylinder when the piston is at the top of its travel. It is formed by the top of the piston and a cavity in the cylinder head. Since most of the air-fuel mixture's combustion takes place in this space, its design and shape can greatly affect the power, fuel efficiency, and emissions of the engine
     
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
     
Composite   any material that consists of two or more components, typically one or more of high strength and one an adhesive binder. The most common composite is fiberglass, which consists of thin glass fibers bonded together in a plastic matrix. The structural properties of composites can be altered by controlling the orientation and configuration of the high-strength components
     
Compound   a mixture of two or more ingredients
     
Compound Winding   two electric windings: one in series, the other in shunt or parallel wiht the other elctric units
     
Compression   the reduction in volume of a gas, also the condition when a coil spring is squeezed together, the opposite of tension
     
Compression Ratio   1. in an internal combustion engine, the ratio between the volume of a cylinder and combustion chamber with the piston at bottom center as compared with volume of the chamber at the end of the compression stroke; 2. 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; 3. the relationship between the piston cylinder volume from bottom dead center to top dead center.
     
Compressor   an engine driven unit that circulates and pressurizes refrigerant in the air-conditioning system, also in a turbo charger system the component that pumps air into the engine
     
Computerized Engine Controls   a microprocessor-based engine management system that use sensor inputs to regulate spark timing, fuel mixture, emissions, and other functions. Modern systems have self-diagnostic capability to generate and store fault codes.
     
Concentric   two circles have the same center but different diameters
     
Condensation   the process of a vapor becoming a liquid, the reverse of evaporation
     
Condenser   the device for turning refrigerant vapor into liquid causing heat to be discharged from the refrigerant, also a device for temporarily collecting and stroring a surge of elctrical current for later discharge
     
Conductance   the current-carrying ability of a wire or electrical component
     
Conductor   a material along or through which electricity will flow with slight resistance
     
Connecting Rod   1. in an internal combustion engine,a rod that connects the piston to the crankshaft; 2. The metal rod that connects a piston to a throw on a crankshaft
     
Constant Velocity Joint   1. a double universal joint that cancels out vibrations caused by driving power being transmitted at an angle; 2. a particular kind of universal joint designed so that there is no cyclic fluctuation between the speeds of its input and output shafts
     
Contraction   a reduction in mass or dimension, the opposite of expansion
     
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
     
Convection   a transfer of heat by circulating heated air
     
Coolant   a liquid circulated through the cooling system of a engine
     
Coolant Pump   a component in the cooling system used to circulate coolant between the water jackets in the engine and the radiator. Also called a water pump.
     
Coolant Sensor   a device that measures the temperature of engine coolant and transmits that measurement to the computer or instruments
     
Cornering Limit   the maximum speed at which a car can negotiate a given curve
     
Corrode   to eat away gradually as if by gnawing, to destroy a metal or alloy gradually especially by oxidation or chemical reaction
     
Countershaft   the intermediate shaft in a transmission that transfers motion from one shaft to another
     
Coupe   a closed car with two side doors and less than 33 cubic feet of rear interior volume, according to measurements based on SAE standard J1100. A two-door car is therefore not necessarily a coupe
     
Coupling   a means of connecting for transfering movement from one part to another, may be be mechanical, hydraulic, or electrical
     
Cowl   the portion of a car body between the engine compartment and the driver
     
Crankcase   the housing in which the crankshaft operates
     
Crankcase Dilution   the condition of the engine oil, when under certain circumstances the unburned portions of fuel get past the piston rings into the crankcase allowing the oil to be thinned
     
Cranking Circuit   the battery, starting motor, ignition switch and related electrical wiring
     
Crankshaft   the main shaft of an engine which, in conjunction the the connecting rods, changes the reciporcating motion of the pistons into rotary motion
     
Curb Weight   the weight of a vehicle (not including the driver or load) including fuel, oil, coolant, other fluids, and all standard equipment
     
Current   the flow of electricity
     
Cycle   a series of events which are repeated
     
Cylinder   in an internal combustion engine, a round hole having some depth bored to receive a piston
     
Cylinder Block   the largest single part of an engine containing the pistons, connecting rods, and related parts
     
Cylinder Head   1. a detachable part of the engine fastened securely to the cylinder block which contains valves, camshafts, and related parts; 2. the aluminum or iron casting that houses the combustion chambers, the intake and exhaust ports, and much or all of the valvetrain. The head (or heads, if an engine has more than one bank of cylinders) is always directly above the cylinders
     
Cylinder Head Gasket   the seal betwen the engine and the cylinder head
   
D
     
DBA   a unit of measure for decibels, the measure of sound intensity or pressure named after Alexander Graham Bell. It is a logarithmic measurement; every 3dB increase represents a doubling of the sound pressure. The ""A"" in dBA indicates that the measurement was taken with an A-weighted scale; sound pressure varies across the audible spectrum, and the A-weighted scale approximates the human ear's sensitivity to various frequencies
     
Dead-blow Hammer   strikes blows without damaging the work's surface. The tool's hollow head is partially filled with small metal shot, which reduces rebounding
     
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
     
Dealer Preperatoin Fee   a fee that dealers may charge for getting a car ready for purchase or lease
     
Detonation   a phenomenon of internal combustion wherein the compressed air/fuel charge explodes violently instead of burning smoothly, usually due to the creation of a second flame front in the chamber away from the spark plug, which collides with the spark-ignited flame front, causing a noise known as "pinging". This condition is potentially damaging and SAAB developed systems as early as 1982 to detect and control detonation.
     
Differential   a gear assembly that permits either side of an axle, or two separate driveshafts, to rotate at different speeds, which allows different wheels to rotate at different speeds as the vehicle turns
     
Diagnostic Trouble Code (DTC)   a number generated by a computer to indicate a failure in a sensor, circuit, or the computer itself. The number may be communicated to the technician through the use of a diagnostic can tool such as the Tech 2 used by SAAB and used at this shop.
     
Disc Brake   a brake system that slows a wheel’s rotation by squeezing an attached metal disc in a viselike hydraulic caliper
     
Displacement   the volume of an engine’s cylinders, a general indicator of its size and power
     
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; this transfer occurs because the car's center of gravity, through which all inertial forces pass, is higher than its contact patches, the points where the braking forces are exerted on the ground
     
Double-Wishbone Suspension   a suspension design borrowed from Formula One racecars that uses two wishbone-shaped, hinged control arms to guide each wheel’s up-and-down motion
     
Downforce   a vertical force directed downward, produced by airflow around an object: such as a car body
     
Drag Coefficient   1. a measure of a vehicle’s resistance to the air through which it passes; 2. a dimensionless measure of the aerodynamic sleekness of an object. A sleek car has a drag coefficient, or "Cd," of about 0.30; a square, flat plate's is 1.98. Also signified by Cx
     
Drivability   the general qualitative evaluation of a powertrain's operating qualities, including idle smoothness, cold and hot starting, throttle response, power delivery, and tolerance for altitude changes
     
Driveline   everything in the drivetrain, less the engine and the transmission
     
Drivetrain   1. all components that generate power and propel a vehicle; 2. all of a car's components that create power and transmit it to the wheels; i.e. the engine, the transmission, the differential(s), the hubs, and any interconnecting shafts
     
Drum Brake   a brake system that slows a wheel’s rotation by pressing curved brake shoes against the inside of an attached metal drum
     
Dry Sump   a type of engine lubrication system in which the oil supply is in a seperate tank instead of the oil pan. SAAB does not use a dry sump system.
     
Dynamometer   a machine used to simulate loaded driving conditions for emissions and diagnostic purposes. A vehicle's drive wheels are placed on a pair of rollers so the vehicle can be driven in place at various speeds while being subjected to changing loads.
   
E
     
EEPROM   Electronically Ereasable Program Read Only Memory, a special type of computer calibration chip that can be reprogrammed electronically by a service technician using the proper equipment, which at JGA is a Tech 2.
     
Electrochromatic Mirror   a rearview mirror that darkens automatically at night in response to headlights
     
Electronic Fuel Injection (EFI)   any type of fuel injection injection system that uses electronic (as opposed to mechanical) controls.
     
Electronic Stability Program   an anti-lock braking system (ABS) that uses computer control to keep a vehicle on the intended course
     
Emissions   unwanted, harmful chemicals and chemical compounds that are released into the atmosphere from a vehicle, especially from the tailpipe, crankcase, and fuel tank. These include unburned hydrocarbons (HC), carbon monoxide (CO), oxides of nitrogen NOx, particulates (soot), and sulfur.
     
Environmental Protection Agency (EPA)   a regulatory agency of the US federal government responsible for creating and enforcing regulations concerning the protection of the environment from various forms of pollution, including that which is generated by motor vehicles.
     
EPA Fuel Economy   laboratory fuel-economy tests administered by the Environmental Protection Agency using simulated weight and drag to re-create real driving conditions. The city fuel-economy test, also used to test emissions compliance, is based on a drive through typical Los Angeles urban traffic of about twenty years ago. Of course, such nostalgic conditions are purely nostalgic these days. The highway test uses a higher, steadier speed, averaging 49.4 mph
     
Evaporative Emissions   hydrocarbons (HC) from fuel which evaporate from a vehicle's fuel tank. They are eliminated by sealing the fuel system and using a charcoal canister to trap vapors from the fuel tank.
     
Exhaust Analyzer   an automotive diagnostic tool which uses a process involving infrared energy to determine and display the composition of an engine's exhaust gases. The two-gas type measures hydrocarbons (HC) and carbon monoxide (CO) content, while the four-gas type also measures oxygen and carbon dioxide content. A probe is inserted into the tailpipe of the vehicle so that samples of the exhaust gases can be drawn into the machine. HC is read in parts per million and CO is read in percent.
     
Exhaust Gas Oxygen(EGO)   the amount of oxygen present in the exhaust stream, as measured by the oxygen sensor and reported to the computer in closed-loop, feedback systems. The computer uses this information along with signals from other sensors to control the air/fuel mixture.
     
Exhaust Gas Recirculation   an emissions-control system which reduces an engine's production of oxides of nitrogen (NOx) by diluting the air/fuel mixture with exhaust gases so that peak combustion temperatures in the cylinders are lowered.
     
Exhaust Emissions   pollutants identified by clean air legislation as being harmful or undesirable. These include lead, unburned hydrocarbons (HC), carbon monoxide (CO), oxides of nitrogen (NOx). Permissble levels for these pollutants are specified in grams per mile or percent of volume.
     
Exhuast Manifold   the network of passages that gathers the exhaust gases from the various exhaust ports and routes them toward the catalysts and mufflers of the exhaust system. A manifold with free-flowing passages of a carefully designed configuration, called a ""header,"" can improve breathing
     
Exhaust Port   The passageway in the cylinder head leading from the exhaust valves to the exhaust manifold
   
F
     
Feedback Fuel-Air Ratio Control   1. a feature of a computer-controlled fuel system. By using a sensor to measure the oxygen content of the engine's exhaust, the system keeps the fuel-air ratio very close to the proportion for chemically perfect combustion. Such tight control of the fuel-air ratio is mandatory for the proper operation of three-way catalyst; 2. a principle of fuel system design wherein a signal from an oxygen sensor in the exhaust system is used to give a computer the input needed to properly regulate the fuel injection system in order to maintain a nearly perfect air/fuel ratio.
     
Fiberglass   a composite material that relies on small glass fibers for its strength
     
Final Drive Ratio   The reduction ratio, found in the gearset of a drivetrain, that is furthest removed from the engine. Typically, the differential ratio
     
Floorpan   the largest and most important stamped metal part in a car's body. Usually assembled from several smaller stampings, the floorpan forms the floor and fixes the dimensions for most of the car's external and structural panels. It is also the foundation for many of the car's mechanical parts
     
Fluid Coupling   any device that transfers power through a fluid between its inputs and outputs. A fluid coupling basically consists of two fans in a sealed, oil-filled housing. The input fan churns the oil, and the churning oil in turn twirls the output fan. Such a coupling allows some speed difference between its input and output shafts
     
Flywheel   a heavy disc attached to an engine's crankshaft to increase its rotary inertia, thereby smoothing its power flow
     
Fuel Injection   1. any system that meters fuel to an engine by measuring its needs and then regulating the fuel flow, by electronic or mechanical means, through a pump and injectors. Throttle-body injection locates the injector(s) centrally in the throttle-body housing, while port injection allocates at least one injector for each cylinder near its intake port; 2. a system that uses no carburetor but sprays fuel under pressure into the intake manifold or directly into the cylinder ports. The advantage of fuel injection over carburetion is that it allows more precise control of the air/fuel mixture for improved performance, fuel economy, and reduced emissions.
     
Fuel Sending Unit   a component of the fuel level indicating system which is located inside the fuel tank. It usually consists of a float-perated rheostat that sends varying voltage to the instrument unit.
   
G
     
g   the unit of measure for lateral acceleration, or "road-holding." One g is equivalent to 32.2 feet per second per second, the rate at which any object accelerates when dropped at sea level. If a car were cornering at 1.0 g: a figure that very few production cars are able to approach: the driver's body would be pushing equally hard against the side of the seat as against the bottom of it
     
Gearset   a group of two or more gears used to transmit power
     
Grams Per Mile (GPM)   a measurement of the amount of emissions a vehicle produces.
   
H
     
Half-Shaft   an articulating, rotating shaft used in independent-suspension systems to transmit power from a differential to a wheel
     
Hall Effect   a phenomenon in which voltage is generated by the action of a magnetic field acting on a thin conducting material, commonly used to control the primary circuit of an electronic ignition system. Named for the American scientist Edwin Hall (1855-1938).
     
Handling   a general term covering all the aspects of a car's behavior that are related to its directional control.
     
Harmonic Balancer  

A harmonic balancer (also called crank pulley damper, torsional damper or vibration damper) is a device connected to the crankshaft of an engine to reduce torsional vibration.

Every time the cylinders fire, torque is imparted to the crankshaft. The crankshaft deflects under this torque, which sets up vibrations when the torque is released. At certain engine speeds the torques imparted by the cylinders are in synch with the vibrations in the crankshaft, which results in a phenomenon called resonance. This resonance causes stress beyond what the crankshaft can withstand, resulting in crankshaft failure.

To prevent this vibration, a harmonic balancer is attached to the front part of the crankshaft. The damper is composed of two elements: a mass and an energy dissipating element. The mass resists the acceleration of the vibration and the energy dissipating (rubber/clutch/fluid) element absorbs the vibrations.
     
HC-CO meter   see exhaust analyzer above
     
Headlamp   A light with a reflector and lens mounted on the front of a locomotive, automobile, or other vehicle. Also called "headlight".
     
Heated Exhuast Gas Oxygen Sensor (HEGO)   an oxygen sensor whichis heated electrically as well as by engine exhaust so that it warms up to normal operating temperature more quickly, thus allowing the engine to enter closed-loop operation sooner than with a non-heated sensor.
     
Helical Gear   a type of gear in which the teeth are cut at a slanting angle to the gear's circumference. A helical design produces an even, constant tooth loading in a gearset, thereby reducing noise
     
Horsepower   the common unit of measurement of an engine's power. One horsepower equals 550 foot-pounds per second, the power needed to lift 550 pounds one foot off the ground in one second: or one pound 550 feet up in the same time
     
Humidity   the amount of water vapor in the air. The amount of water air can hold before it becomes saturated depends on temperature. Warm air can hold more moisture than cold air. At 100 percent humidity, the air is completely saturated with moisture. Humidity affects engine performance because it tends to boost the effective octane rating of the air/fuel mixture. Engines can therefore tolerate more spark advance during humid weather than during dry weather.
     
Hydraulic Lifter   a valve lifter that, using simple valving and the engine's oil pressure, can adjust its length slightly: thereby maintaining zero clearance in the valvetrain. Hydraulic lifters reduce valvetrain noise and are maintenance-free
     
Hydrocarbon (HC)   any chemical compound composed chiefly of hydrogen and carbon, especially petroleum. As an automotive pollutant, HC is simply unburned fuel and lubricating oil, and may be found in the crankcase as blowby, evaporating from the gas tank, and escaping from the tailpipe.
   
I
     
Inches of mercury (in. Hg.)   a measurment of vacuum related to the height towhich atmospheric pressure can push a column of mercury within a tube.
     
Independent Suspension   any suspension in which the camber of a wheel is not directly affected by the vertical motion of the opposite wheel
     
Inspection/Maintenance (I/M)   the periodic inspection and maintenance of a vehicle's ignition, fuel and emission control systems. By maintaining the engine's various subsystems, emissions are kept to a minimum while fuel economy and performance are enhanced. A well maintained engine is an efficent running, clean engine.
     
Internal Combustion Engine    
     
Intake Charge   the mixture of fuel and air that flows into the engine
     
Intake Manifold   the network of passages that direct air or air-fuel mixture from the throttle body to the intake ports in the cylinder head. The flow typically proceeds from the throttle body into a chamber called the plenum, which in turn feeds individual tubes, called runners, leading to each intake port. Engine breathing is enhanced if the intake manifold is configured to optimize the pressure pulses in the intake system
     
Intake Port   the passageway in a cylinder head leading from the intake manifold to the intake valve(s)
     
Integrated Circuit   a miniaturized electronic circuit having all necessary components, such as transistors, resistors, capacitors, etc., integrated into a silicon chip.
     
Intercooler   a heat exchanger that cools the air (or, in some installations, the intake charge) that has been heated by compression in any type of supercharger. An intercooler resembles a radiator; it houses large passages for the intake flow, and uses either outside air or water directed over it to lower the temperature of the intake flow inside
   
J
     
Joule   a unit of energy; approximately 4.2 Joules (J) equal one calorie. One kilogoule (KJ) equals 1000 J and is the amount of heat required to raise the temperature of 239g of water by 1 degree Celcius (C); and one megajoule (MJ) equals 1000 KJ.
     
Jounce   the motion of a wheel that compresses its suspension
     
Jounce Bumper   an elastic cushion used to stiffen the suspension gradually as it approaches the end of its jounce travel
   
K
     
K-Jetronic   A Robert Bosch mechanical port fuel injection system which injects gasoline continuously. Also known as CIS (Continuous Injection System), late model variations include KE-Jetronic, and K-Jetronic with Lambda, both of which employ oxygen and other sensors to keep the air/fuel mixture within a stricter range.
     
Kickdown   a downshift in an automatic transmission caused by depressing the throttle
     
Knock Sensor  

1. a sensor mounted on the engine that is designed to detect the high-frequency vibrations caused by detonation. By employing a knock sensor, a computerized engine-control system allows an engine to operate very near its detonation limit: thereby improving power and efficienc; 2. a sensor that signals the engine control computer when detonation is detected. When the computer receives a knock signal from the knock sensor, it momentarily retards ignition timing until detonation ceases. Knock sensors react to engine vibrations in a specific frequency band, and are sometimes fooled by other engine sounds suchs as those produced by worn rod bearings or a knocking transmission torque converter.

   
L
     
Lambda   the 11th letter of the Greek alphbet which is used by engineers to represent the air/fuel ratio. The oxygen sensor is often also refered to as the lambda sensor.
     
Lambda Sond   the first closed loop fuel injection system to appear in production, developed jointly by Robert Bosch and SAAB.
     
Lateral Link   a suspension link that is aligned to resist sideways motions in a wheel
     
Leading Link   a suspension link that is aligned to resist longitudinal motions in a wheel; it is mounted to the chassis behind the wheel
     
Leaf Spring   a long, flat, thin, flexible piece of spring steel or various composite materials that deflects by bending when forces act upon it. Leaf springs are used primarily in suspensions
     
Leaner and Later   refers to early calibration strategies for air/fuel mixture and ignition timing that reduced HC and CO formation
     
Lean Misfire   a condition caused by an air/fuel mixture that is too lean to sustain combustion. Lean misfire causes one or more cylinder to pass unburned fuel into the exhaust system resulting in a large increase in HC emissions.
     
Lift   a vertical force directed upward, produced by the airflow around a moving object: such as a car body
     
Limited-Slip Differential  

A differential fitted with a mechanism that limits the speed and torque differences between its two outputs. Limited slip ensures that some torque is always distributed to both wheels, even when one is on very slippery pavement.
     
Link   a suspension member that has a single joint at each end
     
Live Axle   a rigid axle incorporating a differential and axle shafts to power the two wheels it is supporting
     
L-Jetronic   a Robert Bosch port EFI system which uses input on the volume of intake air to calculate fuel delivery. Later LH versions appeared on the Classic 900.
     
Lockup Differential  

a differential whose two outputs can be locked together, eliminating any differential action but maximizing traction under slippery conditions
     
Lubrication Cycle   the process of oil movement through an engine that begins when oil is picked up from the oil pan, forced under pressure through galleries to the moving parts, then allowed to drip back into the oil pan to continue the cycle.
   
M
     
Machine   1. a device consisting of fixed and moving parts that modifies mechanical energy and transmits it in a more useful form; 2. a simple device, such as a lever, a pulley, or an inclined plane, that alters the magnitude or direction, or both, of an applied force; a simple machine; 3. a system or device for doing work, as an automobile or a jackhammer, together with its power source and auxiliary equipment.
     
Main Bearings   the bearings in an engine block that support the crankshaft
     
Manifold Vacuum   the vacuum available at an engine's intake manifold generated by the engine's pumping action, measured in inches of mercury or millimeters of mercury
     
McPherson Strut   1. a suspension component combining a shock absorber and spring in one unit; 2. the MacPherson strut is a type of car suspension system widely used in modern vehicles, named after Earl S. MacPherson who developed the design. Though named for him, it was actually invented by an engineer named Fornaca at FIAT in the mid-1920s. It consists of a wishbone or a substantial compression link stabilized by a secondary link which provides a bottom mounting point for the hub or axle of the wheel. This lower arm system provides both lateral and longitudinal location of the wheel. The upper part of the hub is rigidly fixed to the inner part of the strut proper, the outer part of which extends upwards directly to a mounting in the body shell of the vehicle. To be really successful, the MacPherson strut required the introduction of unibody (or monocoque) construction, because it needs a substantial vertical space and a strong top mount, which unibodies can provide, while benefiting them by distributing stresses. The strut will usually carry both the coil spring on which the body is suspended and the shock absorber, which is usually in the form of a cartridge mounted within the strut.
     
Millimeters of mercury (mm of Hg)   a unit of measurement for pressure, also called a torr; 760 mm Hg = 760 torr = 101,325 Pa = 1 standard atmosphere 
     
Monocoque   a type of body structure that derives its strength and rigidity from the use of thin, carefully shaped and joined panels, rather than from a framework of thick members. Also called "unit" or unitized construction
     
Multileaf Spring   a leaf spring with several leaves bundled together by steel bands
     
Multilink Suspension  

a rear suspension consisting of at least four links, or "arms," and no struts. Because multilink suspensions assign specific wheel-locating duties to each element, they provide great flexibility for optimizing both ride and handling.
   
N
     
Naturally Aspirated   a non-turbocharged engine. Air is taken in naturally, not forced in by action of a turbocharger or supercharger
     
Negative   usually used to refer to the potential of a power source. It is the point in a circuit with an excess of electrons having the potential to move to a point with a deficiency of electrons.
     
Negative Charge   the electrical characteristics of a substance with an excess of electrons in the outer ring of its atoms.
     
Negative Plate   the sponge lead plate of a lead-acid storage battery
     
Negative Potential   the point in a circuit with an excess of electrons having the potential to move to a point with a deficiency of electrons.
     
Negative Temperature Coefficient   the property of any substance in which the elctrical resistance increases as the temperature of the substance decreases.
     
Negative Terminal   the battery terminal closest to the negative potential in the battery.
     
Neutron   a particle with no electrical charge in the nucleus of an atom
     
Nitrogen (N)   a colorless, tasteless, odorless gas making up about 78 percent of the volume of the Earth's atmosphere.
     
NOx   harmful gaseous emissions of an engine composed of compounds of nitrogen and varying amounts of oxygen which are formed at the highest temperatures of combustion. With other gases and int he presence of sunlight, an ingredient of the photochemical smog; see also oxides of nitrogen
     
Nucleus   the center of an atom around which elctrons orbit. The nucleus contains protons giving it a postive charge.
     
   
O
     
Octane   refers to gasoline's ability to resist detonation. The higher the octane number, the greater the fuel's resistance to detonation (spark knock or pinging under load).
     
Onboard Diagnostics OBD   a term for special diagnostic software and hardware that detects performance problems that adversely affect eimissions. OBD rules require a standardized diagnsotic connector and fault codes for emissions troubleshooting.
     
OnStar   a telematic service available in North America.
     
Open Loop   in engines with a computer management system with an oxygen sensor, a mode of operation during which the computer ignores the singal from the oxygen sensor, typically before the engine reaches normal operating temperature.
     
Otto cycle   the basic principle of operation of the common four-stroke piston engine, involving intake, compression, ignition/power, and exhaust. Named for the German inventor, Nikolaus Otto (1832-1891).
     
Overdrive   any gearset in which the output shaft turns faster than the input shaft. Overdrive gears are used in most modern transmissions because they reduce engine rpm and improve fuel economy. Occasionally, a separate gearbox with an overdrive gearset is coupled to a conventional transmission
     
Overhead Cam   the type of valvetrain arrangement in which the engine's camshaft(s) is in its cylinder head(s). When the camshaft(s) is placed close to the valves, the valvetrain components can be stiffer and lighter, allowing the valves to open and close more rapidly and the engine to run at higher rpm. In a single-overhead-cam (SOHC) layout, one camshaft actuates all of the valves in a cylinder head. In a double-overhead-camshaft (DOHC) layout, one camshaft actuates the intake valves, and one camshaft operates the exhaust valves
     
Oversteer   a handling condition in which the slip angles of the rear tires are greater than the slip angles of the front tires. An oversteering car is sometimes said to be "loose," because its tail tends to swing wide
     
Oxidation   any reaction in which a chemical joins with oxygen, as rusting or combustion.
     
Oxidation Catalyst   a two-way catalytic converter which promotes the oxidation of HC and CO in an engine's exhaust stream, as distinquished from a three-way or reduction catalyst.
     
Oxides of Nitrogen   harmful gaseous emissions of an engine composed of compounds of nitrogen and varying amounts of oxygen which are formed at the highest temperatures of combustion. With other gases and int he presence of sunlight, an ingredient of the photochemical smog; see also NOx
Oxygen (O)   a gaseous element given the chemical symbol O, and ocurring as O2, which makes up approximately 20 percent of the Earth's atmosphere.
     
Oxygen Sensor   a device, usually threaded into the exhaust manifold, which uses platinum inner and outer electrodes and a zirconium electrolyte to generate a small voltage, the strength of which is dependent upon the amount of oxygen present in the engine's exhaust stream. This voltage is used as a signal to the engine control computer, which takes the signal into consideration when determing the amount of fuel necessary to maintain a proper air/fuel ratio.
     
Ozone   a molecule of oxygen chemically represented as O3 which is formed by exposure of O2 to an electrical discharge, and has pungent odor and a strong oxidizing effect.
     
   
P
     
Panhard Rod   a long lateral link that provides lateral location of a rigid axle. It usually sits roughly parallel to the axle, with one end attached to the body and the other attached to theaxle
     
Particulate Emission   solid particles, such as carbon and lead, found in vehicle exhaust; soot. A problem especially in diesels.
     
Parts per Million   a measurement of the emissions of a motor vehicle given as the number of parts of a patricular chemical within one million parts of exhaust gas.
     
Photochemical Smog   a noxious, unhealthful gaseous compound in the atmosphere formed by the ineraction of various chemicals such as the pollutants hydrocarbons and oxides of nitrogen in the presence of sunlight
     
Piezoelectricity   voltage generated by a dielectric crystal under mechanical stress. The principle is used in knock sensors.
     
Pitch   the rotation of a car about a horizontal axis, which causes its nose or tail to bob up and down. Dive and squat are pitching motions
     
Planetary Gears   a gearset in which all of the gears are in one plane, grouped around each other like the planets around the sun. The central gear is called the sun gear. In mesh with it is a circular grouping of gears, called planet gears, mounted on a rotating carrier. The planet gears also engage teeth on the inner periphery of the ring gear. By holding any one of the three gear elements motionless, different ratios can be produced between the other two. Planetary gearsets are common in automatic transmissions
     
Platinum (Pt)   a rare, valuable metallic element given the symbol Pt, which is highly resistant to corrosion, and is used as a catalytic agent in automotive catalytic converters of the oxidzing type.
     
Plenum Chamber   a chamber, located between the throttle body and the runners of an intake manifold, used to distribute the intake charge evenly and to enhance engine breathing
     
Ported Vacuum   engine vacuum as available forward of the throttle body, as used to advance igntion timing when the throttle is opened above its idle position.
     
Positive Crankcase Ventilation (PCV)   an engine emission control system which picks up crankcase gases such as blowby and meters them into the intake stream to be burned. Clogging of the PCV system typically causes oil leaks as blowby increases crankcase pressure. It can also lead to rapid sludge build up in the crankcase and possible engine damage.
     
Pound-feet   the unit of measurement for torque. One pound-foot is equal to the twisting force produced when a one-pound force is applied to the end of a one-foot-long lever
     
Power   the rate at which work is performed. Power is proportional to torque and rpm and is measured in horsepower
     
Power Brakes   an energy conversion mechanism used to retard, stop or hold a vehicle that is assited by an external force beyond the basic hyudraulic circuit.
     
Powertrain   an engine and transmission combination
     
Preignition   the igntion of the air/fuel mixture in the combustion chamber by means other than the spark plug; the same as dieseling. It is usually caused by hot spots in the combustion chamber (sharp edges, carbon accumulation or spark plugs with too hot a heat range). Preigntion can burn holes in pistons and contribute to detonation.
     
Programmed Read Only Memory (PROM)   a computer component which contains values and programming which is not lost when the power supply to the computer is shut off or interrupted, its memory being non-volatile. Used to determine the basic paramenters of operation in an engine control computer system.
     
Progressive-rate Spring   a spring with an increasing spring constant. For example, if the first inch of spring motion requires 100 pounds of force, the second inch would require more than an additional 100 pounds, and the third inch would require still more. Progressive-rate springs become stiffer as they are compressed, unlike single-rate springs, which have a fixed spring rate
     
psi   pounds per square inch, the common unit of measurement for pressure. Normal atmospheric pressure at sea level is 14.7 psi
     
Pulse Width   in EFI systems, the length of time the injectors are energized and held open ("on" time), which determines the amount of fuel injected. It is measured in milliseconds.
     
Pushrod   a general term for any rod that transfers force in compression. In a valvetrain, pushrods are used to transfer reciprocating motion from the cam followers to a more distant part of a valvetrain, typically the rocker arms
   
Q
     
Quench Area   any internal portion of a combustion chamber which causes combustion to cease because of the temperature drop in the air/fuel charge where it meets this area
   
R
     
R-12   a type of refrigerant used in automotive air conditioning systems that contains ozone-damaging chlorofluorocarbons (CFCs). R-12 has been phased out and replaced with R-134a. Professional technicians are required by law to recover and recycle R-12 when performing any type of AC service or repair work.
     
R-134a   an ozone safe refrigerant that is used on most 1993 and later vehicles. It is not a direct drop-in replacement for R-12, although conversion kits are available to change R-12 systems to R-134a systems.
     
Rack and Pinion   a steering mechanism that consists of a gear in mesh with a toothed bar, called a rack. The ends of the rack are linked to the steered wheels with tie rods. When the gear is rotated by the steering shaft, it moves the rack from side to side: turning the wheels
     
Rebound   the motion of a wheel that extends the suspension. The opposite of jounce
     
Reduction Catalyst   the section of a three-way catalytic converter that breaks NOx down into harmless nitrogen and oxygen through a reduction reaction.
     
Reference Voltage   in computerized engine management systems, a five volt signal sent out from the ECU to a variable resistance sensor such as a TPS. The computer then reads the voltage value of the return signal.
     
Resistance   the quality of reducing the flow of electrons in a circuit
     
Retard   to cause ignition sparkto occur later in an engine's cycle.
     
Rich Mixture   an air/fuel mixture with insufficent air or excessive fuel. The ideal mixture for gasoline and air is 14.7:1 by weight.
     
Rigid Axle   a simple non-independent suspension, consisting of a rigid transverse member with wheel hubs solidly bolted to it. The axle can be attached to the body by leaf springs, or by a combination of suspension arms and links
     
Ring and Pinion Gear   any gearset consisting of a small gear (the pinion gear) which turns a large-diameter annular gear (the ring gear).
   
S
     
Sensor   an electrical device used to provide a computer with input as to temperature, rpm, vacuum, etc.
     
Sequential Fuel Injection (SFI)   a type of multiport injection system where the individual fuel injectors are pulsed sequentially one after another in the same firing order as the spark plugs rather than being pulsed simultaneously. This allows for more precise fuel control for lower emissions and better performance, but also requires more complex controls.
     
Smog   a general term for air pollution, especially the photochemcal variety. Smog forms when sunlight causes chemical reactions in air polluntants resulting in the formation of ozone and other compounds.
     
Spark Advance Curve   the rate at which ignition timing advances. If plotted on a graph, the line resembles a curve. It rises from some initial amount of advance and levels off at the maximum advance. On older ignition systems with mechanical and vacuum advance controls, the curve depended on engine RPM and intake vacuum. On later ignition systems with electronic spark advance, various sensor inputs are used to calculate the amount of advance needed.
     
Specific Gravity   the wieght of a substance compared to the wieght of water. Any substance with a specific gravity less than 1.00 is lighter than water; more than 1.00 is heavier than water. The amount of another substance (such as battery acid or coolant) in water can be determined by measuring the specific gravity of the mixture.
     
Speed   the unit of measurment for motion indicated in miles or kilometers per hour.
     
Stoichiometric   referring to the ideal air/fuel ratio, 14.7:1 by weight, in which all the oxygen is consumed in the burning of all the fuel.
     
Stoichiometry   the state of having a stoichiometric air/fuel mixture.
   
T
     
Tach Dwell Meter   a diagnostic tool that combines in one unit an instrument to measure engine speed (tachometer) and one to measure how long igntion points remain closed (dwell meter. This tool has not been used on SAABs since the 1970's as SAAB has long used electronics to control ignition as well as fuel management.
     
Tachometer   a device used to measure engine speed, usually indicated in revolutions per minute (RPM). A tachometer is found on the left side of the Main Instrument Unit (MIU) of all modern SAABs.
     
Tank   a reservoir or container for any liquid, usually the storage place for fuel in a vehicle.
     
Taper   a gradual reduction in the diamter of a shaft or hole
     
Taper Charge   the process of charging a storage battery at a constant voltage. The rate of current flow decreases as the battery becomes charged.
     
TDC   an abbreviation for Top Dead Center which is the position of the piston when it has reached the upper limit of its travel in the cylinder. In automotive terms, the relevant cylinder is the designated #1 cylinder.
     
Teflon   a trademark name used for a waxy, opaque material, polytetrafluoroethylene, employed as a coating on cooking utensils and in industrial applications to prevent sticking. It's automotive uses include coating some fuel injectors to resist the accumulation of carbon deposits.
     
Temperature   the measure of how hot or cold something is (in terms of the human experience). Temperature is indicated in degrees on Fahrenheit (F), Celcius (C), or Kelvin (K)
     
Temperature Gauge   an instrument on the dash that is used to indicate the temperature of any given sub-system such as the coolant or engine oil.
     
Temperature Sending Unit   a component used to sense the temperature of engine sub-system such as coolant. The electrical resistance of the sending unit (sensor) changes in proportion to changes in temperature and this signal is sent to the appropriate gauge, computer, or module. Ultimately, the gauge (either directly or through a computer) processes the signal on an instrument for the driver.
     
Temperature Sensor   a component used to sense the temperature of engine sub-system such as coolant. The electrical resistance of the sending unit (sensor) changes in proportion to changes in temperature and this signal is sent to the appropriate gauge, computer, or module. Ultimately, the gauge (either directly or through a computer) processes the signal on an instrument for the driver.
     
Temperature Stability   the ability of a cooling system to maintain engine temperature at a constant, generally around 195 degrees F (90 C).
     
Temperature Stick   a pencil-like device with a wax material containing certain chemicals that melt at a given temperature. It is rubbed on a metal surface and melts when a specified temperature is reached. With the advent of non-contact infrared thermometers, temperature sticks no longer needed for diagnostics.
     
Terminal   a part of the battery to which the cables are connected. This completes the DC circuit.
     
Thermal   pertaining to, or caused by heat.
     
Thermal Cycling   the continual expanding and contracting of a metal from exposure to a range of temperatures.
     
Thermal Efficiency   a ratio of the energy output of an engine to the energy in the fuel required to produce that output.
     
Thermal Fatigue   the failure of a metal part caused by exposures to extremes of heat or cold.
     
Thermistor   1. a resistor the value of which changes according to its temperature. Used as a sensor for a gauge or computer system; 2. a heat-sensitive electrical component in which electrical resistance decreases as its temperature increases.
     
Thermo-time Switch   a control switch that operates on both temperature and time.
     
Thermostat   a device to automatically regulate the flow of air, gas, or a liquid according to temperature. A temperature sensitive element expands or contracts with temperature changes to close or open a passageway.
     
Thermoswitch   an electrical switch that responds to changes in temperature by opening or closing a circuit.
     
Three-phase Current   a combination of three alternating current cycles, each starting one-third of a cycle apart so each of the cycles in the resulting combined wave is 120 degrees out of phase from the others. Three-phase current provides a smoother direct current flow when rectified because voltages of each alternating cycle are not allowed to decay completely before the next cycle begins to rise.
     
Three-way Catalyst (TWC)   a catalytic converter that oxidizes HC and CO, and also reduces NOx emissions. Usually, it has separate chambers. The one upstream handling reductions, and the one downstream handling oxidation. The noble metals used as the catalytic agents are plantinum, palladium, and, for reduction, rhodium.
     
Throttle   a disc valve in the throttle body that pivots in response to accelerator position. Whether the throttle is mechanical or electronic (throttle-by-wire), the throttle allows the driver to control engine speed (by pressing the accerator pedal) to regulate the amount of air/fuel mixture entering the intake manifold.
     
Throttle Body   A housing containing a valve to regulate the airflow through the intake manifold. The throttle-body is usually located between the air cleaner and the intake plenum.
     
Throttle Position Sensor (TPS)   1. in comuterized engine control systems, the variable resistor-type sensor which informs the ECU of throttle position. A strip of carbon provides resistance, and a brush or wiper moves along its face as the throttle is opened. It is a three-wire device with terminals for reference voltage, output back to the ECU, and ground; 2. a device used to signal the position of the throttle (to the computer) in a electronic fuel injection system.
     
Thrust   1. the force exerted on or by an object in the lengthwise or end-to-end direction; 2. to push or drive quickly and forcibly.
     
Thrust Bearing   a main bearing in the engine used to prevent excessive forward backward movement of the crankshaft.
     
Timing Belt   a belt that is driven by a gear on the crankshaft that connects to gear(s) on the camshaft in order to synchronize the turning of the crankshaft to the camshaft(s) for the proper valve timing.
     
Timing Chain   a chain that is driven by a gear on the crankshaft that connects to gear(s) on the camshaft in order to synchronize the turning of the crankshaft to the camshaft(s) for the proper valve timing.
     
Timing Cover   a cover made of metal or plastic that encloses the parts of the valve timing system.
     
Timing, Ignition   the delivery of the spark from the coil to the spark plug at the precise time it is needed for the power stroke
     
Timing Light   1. a diagnostic tool that is a light connected to the ignition system. It inductively picks up the ignition signal in the number #1 spark plug wire and causes a light to flash accordingly. By shining this flashing light onto the timing marks located on the flywheel (or flexplate) it is used to adjust ignition timing. This tool is not used on modern SAABs as ignition is entirely computer controlled; 2. On older engines it is common to set the timing using a timing light, which flashes in time with the ignition system (and hence engine rotation), so when shone on the timing marks makes them appear stationary due to the stroboscopic effect. The ignition timing can then be adjusted to fire at the correct point in the engine's rotation, typically a few degrees before top dead centre and advancing with increasing engine speed. The timing can be adjusted by loosening and slightly rotating the distributor in its seat.
     
Timing Marks   A timing mark is an indicator used for setting the timing of the ignition system of an engine, typically found on the crankshaft pulley (as pictured) or the flywheel, being the largest radius rotating at crankshaft speed and therefore the place where marks at one degree intervals will be furthest apart.
     
Timing, Valve   the control of the opening and closing of the valves in relation to the position and speed of piston travel.
     
Top Dead Center   the position of the piston when it has reached the upper limit of its travel in the cylinder. In automotive terms, the relevant cylinder is the designated #1 cylinder.
     
Torque   the turning or twisting effort that is usually measured in in foot-pounds or newton-meters. To torque means to tighten a connection to a specific value of applied pressure.
     
Torque Converter   a fluid coupling device in an automatic transmission used to increase and transmit the torque of the crankshaft to the transmission.
     
Torque Wrench   a tool used to indicate the amount of turning or twisting effort being applied to tighten a threaded part or move some other component.
     
Torsional Vibration   a rotary vibration that casues a twisting and untwisting action on a rotating shaft causing part of the shaft to move ahead or lag behind the remainder of the shaft.
     
Transistor   an electronic component using a semiconductor to amplify or switch current.
     
Transaxle   1. a combination transmission and differential; 2. an automotive part that combines the transmission and the differential and is used on vehicles with front-wheel drive.
     
Transducer   a device used to convert an input signal of one form to an output signal of another form.
     
Transformer   1. a device used to change alternating current from one voltage to another. It consists of two coils, one with more windings that the other, that induce voltage in one coil when current flows to the other. It can increase or decrease voltage; 2. a device used to transfer electric energy from one circuit to another, especially a pair of multiply wound, inductively coupled wire coils that effect such a transfer with a change in voltage, current, phase, or other electric characteristic.
     
Transmission   an assembly of gears used to provide the different gear ratios to overcome the inertia of the vehicle and to transmit engine power to the differential causing the wheels to turn.
     
Transmission Oil Cooler   a small radiator used to cool the transmission fluid of an automatic transmission.
     
Transverse   in automotive terms, a means of describing engine placement in an engine bay. A transverse engine has the crankshaft across the width of the vehicle.
     
Trickle Charge   a low rate of charge give to a storage battery over a long period of time.
     
Turbocharger   a device in the intake system of an engine used to pressurize the incoming air/fuel mixture. A turbo charger is driven by exhaust gases.
     
Tune Up   an archaic term used to describe the process of inspection, testing, and adjusment of electrical and fuel system components to produce ideal performance and low emissions. In modern cars, this process is called "maintenance" as the mechanical components that were previously adjusted are no longer present on computer controlled fuel management systems. The most critical maintenance in modern automobiles is the re-occurring 30,000 maintenance.
     
Tungsten (W)   a hard, brittle, corrosion-resistant, gray to white metallic element extracted from wolframite, scheelite, and other minerals, having the highest melting point and lowest vapor pressure of any metal. Tungsten and its alloys are used in high-temperature structural materials; in electrical elements, notably lamp filaments; and in instruments requiring thermally compatible glass-to-metal seals. Atomic number 74; atomic weight 183.84; melting point 3,410°C; boiling point 5,900°C; specific gravity 19.3 (20°C); valence 2, 3, 4, 5, 6. Also called wolfram.
     
Tungsten Steel   an alloy of steel and tungsten providing a hard-tempered steel and retains this property when heated to high temperature.
     
Two-way Catalyst   a catalytic converter that oxidizes HC and CO, but has little effecton NOx.
     
Two-stroke Cycle   two strokes of the piston during which intake, compression, combustion, and exhaust take place. In this engine, there is a power stroke for every revolution of the crankshaft. SAAB has not used a two-stroke engine since 1967.
   
U
     
Underhood Decal   a notice placed under the hood or on the engine of all vehicles produced since 1972 giving the exact specifications for a particular production run engine and emission control system.
     
Undersize Bearing   a bearing made thicker with a smaller inside diameter to fit a crankshaft that had been machined or worn away.
     
Unleaded Fuel   gasoline to which no lead compounds have been intentionally added. Must contain less than 0.05 gram of tetraethyl lead per gallon. It is required by law to be used in vehicles made since 1975 equipped with catalytic converters.
     
Upshift   to shift to a higher gear (to a lower numerical gear ratio).
   
V
     
V   abbreviation for volt, a unit of measurement for electrical potential
     
V-4 Engine   an engine with two rows of two cylinders each set on an angle to form a V. Of the entire SAAB line-up only the 1968-1980 (1968-1974 in the US) SAAB 95 and 96 had Ford supplied V-4 engines.
     
V-6 Engine   an engine with two rows of three cylinders each set on an angle to form a V. Of the entire SAAB line-up, a V-6 engine has been available since 1994 in the N900, 9000, 9-3 (second generation 9440) 9-5 (1999-2003), and 9-7 vehicles.
     
V-8 Engine   an engine with two rows of four cylinders each set on an angle to form a V. Of the entire SAAB line-up, only the rebadged GM SUV based on the GMT platform is available with a V-8 engine. The SAAB 9-7x (aka the Trollblazer) is available with either a V-6 or V-8 GM Vortec engine.
     
Vacuum   1. a condtion of pressure which is less than that of the atmosphere; negative pressure; 2. any pressure less than atmospheric pressure. Vacuum is usually measured in inches of mercury, millimeters of mercury, or kiloPascals or bar in the metric system
     
Vacuum Advance   the principle of using the vacuum generated by an engine to advance igntion timing, accomplished with a mechansim attached to the distributor which moves the breaker point or pickup coil plate when it receives vacuum.
     
Vacuum Dashpot   a chamber containg a vacuum diaphragm used to create movement in a component, such as a heated air intake blend door, when engine vacuum is routed to the chamber.
     
Vacuum Diaphragm   a thin, flexible wall separating two spces. It is used in mechanical fuel pumps, vacuum advance units, vacuum assisted power brake units, and other control devices.
     
Vacuum Gauge   an instrument used to measure the amount of vacuum, or to indicate how much lower the pressure is compared to atmospheric pressure. Part of a SAAB turbo gauge is a vacuum gauge and part is a pressure gauge.
     
Valence Ring   the outermost ring of electrons orbiting the nucleus of an atom.
     
Valve   a device used to control the flow of a gas or liquid by opening or closing a passeway or bore.
     
Valve Clearance   the space or distance between the rocker arm and the valve stem tip in an overhead engine. Modern SAABs do not have pushrods or rocker arms but instead have hydraulic valve lifters and overhead camshafts.
     
Valve Cover   a unit that fits on the engine to cover the valves. It also keeps lubrcation (engine oil) from splashing out and keeping contaminates from coming in.
     
Valve Face   the beveled part of the valve head that contacts the valve seat.
     
Valve Float   a condition in which the valves do not close completely or do not close at the proper time.
     
Valve Flutter   a condition that exits when the valve does not seat tightly and is pushed open against the spring pressure.
     
Valve Grinding   the process of refacing a valve with a special power tool.
     
Valve Guide   a cylindrical bore or hole in the cylinder block or head in which a valve moves up and down.
     
Valve Head   the top poriton of a valve, also called the crown.
     
Valve Lash   is the amount of free motion in the valve.
     
Valve Lift   the amount of lift at the valve depending on the camshaft lobe.
     
Valve Lifter   a cylindrical part of the vlave train that opens and closes the valve in response to movement from the camshaft lobe.
     
Valve Overlap   the time the intake and exhaust valves are open together, measured in degress of crankshaft rotation.
     
Valve Seat   the surface in the cylinder head for a valve to come to rest and provide a seal against leaks.
     
Valve Seat Insert   an insert of cast iron in an aluminum head used as the place where a valve come to rest because the aluminum is too soft to take the constant impact of opening and closing of the valve.
     
Valve Seat Recession   the tendency for valves to contact the seat in such a way the seat wears away and forms a recess in the cylinder head.
     
Valve Spring   one or two coiled springs used to return the valve to position after being lifted by valve lifter.
     
Valve Spring Retainer   a device on the valve stem to hold the valve spring in place.
     
Valve Spring Seat   that part of the cylinder head on which an exhaust or intake valve spring rests.
     
Valve Stem   a long, thin rod-shaped part of the valve that fits in the valve guide.
     
Valve Stem Seal   a device on or around the valve stem to reduce the amount of oil that can pass to the guide.
     
Valve Timing   the control of the opening and closing of the valves in relation to the position and speed of piston travel.
     
Valve Train   the valve operating mechanism including all components from the camshaft to the valve seat.
     
Vapor   a gas. Any substance existing as a fine mist suspended in air as distinguished from that same substance in the liquid or solid state.
     
Vapor Lock   a fuel system condition in which gasoline vaporizes in the fuel line or fuel pump restricting or preventing flow.
     
Vapor Recovery System   an evaporative emission control system designed to recover gasoline vapor from the fuel tank before it escapes into and pollutes the atmosphere.
     
Vaporize   the change of state from a liquid to a vapor or mist by evaporation, heating, or exposure to lower pressure.
     
Varnish   an undesirable deposit formed by the oxidation of fuel and motor oil
     
Variable Resistor   an elctrical component which reduces the flow of current in a circuit variably according to its postion, such as a TPS. Also called a "potentiometer".
     
Velocity   1. a measurement of motion, usually the speed of air or vapor passing through an opening; 2. the time rate of change of position of a body in a particular direction. Linear velocity is velocity along a straight line, and its magnitude is commonly measured in such units as meters per second (m/s), feet per second (ft/s), and miles per hour (mi/h). Since both a magnitude and a direction are implied in a measurement of velocity, velocity is a directed or vector quantity, and to specify a velocity completely, the direction must always be given. The magnitude only is called the speed.
     
Vent   an opening for air to pass from an enclosed chamber.
     
Ventilation   the circulation of fresh air through any space to remove and replace impure air
     
VIN (Vehicle Identification Number)   the number assigned to each vehicle by its manufacturer, primary for registration and identificaiton, but also sometimes required for repair shops when ordering replacement parts.
     
Viscosity   the resistance of a liquid to flow. A thicker oil has a greater viscosity than a thinner oil .
     
Viscosity Index   a rating of lubricating oil according to standards set by the Society of Automotive Engineers (SAE) indicating the resistance of the oil to flow.
     
Viscous   a term used to describe a fluid that is thick and that tends to resist flowing.
     
Viscous Friction   the friction between layers of a liquid.
     
Volt (V)   a unit of measurement for amount of elctrical force.
     
Voltage   the force causing electrons to flow in a conductor. The difference in potential between two points in a circuit.
     
Voltage Drop   the reduction in voltage across an electrical device or circuit because of the resistance to current flow of that device or circuit.
     
Voltage Leak   the loss of charge in a capacitor because of the imperfect insulating characteristics of the dielectric, allowing voltage to "leak" across, neutralizing the electrical charge.
     
Voltage Regulator   a device used to control the amount voltage and current flowing through a circuit.
     
Voltmeter   an instrument used to measure electrical potential (voltage) of a circuit.
   
W
     
W   the abbreviation for watt, a unit of measurment for power. It is determined by multipying the potential in volts by the current in amperes.
     
Warm-up   the period of time it takes for an engine to reach normal operating temperature.
     
Warning Light   a light that illuminates to alert the driver to some condition in the vehicle that is outside of nomial values.
     
Wastegate   a device used to limit the amount of boost form the turbocharger at higher engine RPM and loads. It consists of a valve that opens to the divert the exhaust gas away from the turbine when the desired boost pressure is reached.
     
Water Injection   a system in which a small amount of water vapor is sprayed into the air inlet to be drawn into the cylinder to help cool the heat of combustion when burning lean mixtures.
     
Water Jacket   the space between the inner and outer shells of the cylinder block or head for coolant to circulate.
     
Water Pump   a component in the cooling system used to circulate coolant between the water jackets in the engine and the radiator. Also called a coolant pump.
     
Watt   a unit of measurement of electric power. It is determined by multipying the potential in volts by the current in amperes.
     
Wax Pellet   a device used in thermal control devices (thermostats) in which metal particles are embedded in a sealed wax base for controlled movement when the metal expands with heat.
     
Wear   also known as "abrasive wear". It is the result of particles of dirt, dust , and other contaminants grinding against any moving surface. It can be found an many systems of the automobile including the engine, transmission, brakes, steering and more. To minimize abrasive wear it is critical to perfrom routine maintenance such as the re-occuring 30,000 mile maintenance.
     
Wet Sump   an engine in which oil drains into the crankcase after circulating to lubricate engine parts to provide a reservoir for delivery throught the lubrication system. As opposed to a dry sump (see above); SAAB uses wet sump engines.
     
Wheel   a solid disk or a rigid circular ring connected by spokes to a hub, designed to turn around an axle passed through the center.
     
Wire Feeler Gauge   a set of round wires of known diameters used to check the distance or gap between electircal contacts such as distributor points or spark plug electrodes. Mechanical distributors have not been used in SAABs since the 1970's and aftermarket companies such as Pertronix make conversion kits to electronic distributors. JGA does not used wire feeler gauges to adjust spark plug gap and instead JGA uses standard flat feeler gauges for a more accurate gap.
     
Wire Gauge   the size of current carrying conductors based on the cross section area of the conductor. In American Wire Guage (AWG) smaller wires have larger gauge numbers; 2. wire gauge is a measurement of how large a wire is, either in diameter or cross sectional area. This determines the amount of electrical current a wire can safely carry, as well as its electrical resistance and weight per unit of length. Wire gauge is therefore applicable to both electrical and non-electrical wires, thus it is important to electrical wiring and to structural cable; 3. a gauge for measuring the diameter of wire, usually consisting of a disk having variously sized slots in its periphery or a long graduated plate with similar slots along its edge; 4. an instrument for measuring the thickness of wire or sheet metal; usually consists of a steel plate having a series of notches, of standard opening sizes, around the edge. Note that SAAB uses the metric system to determine cross-sectional wire size and that these measurments are in millimeters.
     
Work   1. the changing of the position of an object against an opposing force; 2. the transfer of energy from one physical system to another, especially the transfer of energy to a body by the application of a force that moves the body in the direction of the force. It is calculated as the product of the force and the distance through which the body moves and is expressed in joules, ergs, and foot-pounds.
     
Worm   a type of gear in which the teeth resemble threads on a bolt or screw.
     
Wrist Pin   a metal rod used to hold the piston to the connecting rod.
   
X
     
Xenon   a colorless, odorless, highly unreactive gaseous element found in minute quantities in the atmosphere, extracted commercially from liquefied air and used in stroboscopic, bactericidal, and laser-pumping lamps. Atomic number 54; atomic weight 131.29; melting point −111.9°C; boiling point −107.1°C; density (gas) 5.887 grams per liter; specific gravity (liquid) 3.52 (−109°C).
   
Y
     
Yaw Angle   1. the amount something is turned on its axis. The yaw angle of a vehicle refers to the direction ofthe wind in relation to a direct headwind coming at the vehicle; 2. To turn about the vertical axis. Used of an aircraft, spacecraft, or projectile.
   
Z
     
Zener Diode   a semiconductor made so it will allow reverse current flow without damage at a voltage above a specific value.
     
Zero-lash Adjuster   another term used to descdribe a hydraulic lifter. Also a device used to remove all free motoin from the valve train.