Glossary Of Auto Repair Terms

• ABS (Antilock Brake System)
  This is a safety arrangement that enables wheels to brake rapidly without locking and therefore causing a skid and loss of control. Computerized sensors monitor wheel speeds; and during sudden decelerations, will alter brake pressure rapidly by means of an electro-hydraulic system so that the vehicle can still be steered (to avoid obstacles) while braking.

• Adaptive Cruise Control
  An advanced computer system for speed organizing, which keeps a certain distance between one car and the car ahead of it on the road.

• Adaptive Suspension
  This is where the suspension system can be made more or less firm by a computer as the car travels along changeable road conditions.

• Air Bags
  Properly known as a ‘Supplemental Inflatable Restraint System’ (which is quite a mouthful - so no wonder everyone refers to it as an air bag); these are safety devices which inflate in an instant in the unfortunate event of a collision, to provide a cushioning effect which lessens the shock of impact.

  Air bags operate automatically when controlling sensors give the alert, though the presence of these in a car should not give people a false sense of security, which might make them not bother to wear seatbelts. The use of seat and shoulder belts will maximize the effectiveness of air bags.

• Air Injection
  This is an environmentally friendly measure which sends boosts of air into the exhaust of the engine, for purposes of burning off any fuel which escaped initial combustion, to make emissions `cleaner.’

• Alloy Wheels
  This is a term which is an example of how strange a language can sometimes be. It is used in everyday speach to denote any wheels that are made from a combination of metals (an alloy) rather than traditional steel, as most wheels are. However, steel is actually a combination of carbon and iron - and therefore is itself an alloy!

• All Wheel Drive (AWD)
  This is where all the wheels are utilized as active drive wheels for greater control in challenging road conditions. It works by dividing up the engine torque between the front and rear wheels in varying amounts depending on the needs.

  AWD is designed as an on-road control system and is therefore not the same as Four Wheel Drive (4WD or 4x4). (See also Torque).

• Alternator
  This is a generator powered by the engine that provides the electricity to power the car’s electrical components as well as for charging the battery.

• Axles
  Each axle (front and rear) holds the wheels in place and allows them to revolve. The word is derived from `axl’ which is an old English word meaning `shoulder.’

• Catalytic Converter
  The proper name for what is often known as a catalyst or sometimes just a cat. This is a device fitted to the exhaust and used for making the exhaust gases less harmful to the environment. It accomplishes this task by a process of chemical reactions that change the properties of the emissions but not the converter itself - hence it is a catalyst.

• Chassis
  This is the basic structure (frame) of an automobile.

• Clutchless Manual
  A hybrid gearing mechanism where, although it is an automatic transmission, the driver can himself / herself change gears manually in sequence.

• Coefficient of Drag (CD)
  This is a number that is a measure of an automobile’s resistance to the air it passes through, with lower numbers meaning the car has greater aerodynamic properties. It is one factor that influences the smoothness of ride and better fuel economy.

• Coolant
  Coolant is a water and anti-freeze mixture that takes heat away from the engine (to stop it overheating) and transports it to the air in the radiator.

• Composite Headlamps
  These are improved headlamps for enhanced illumination as compared to the standard sealed beam units. They often, but not always, contain replaceable halogen bulbs with separate acrylic lenses.

• Curb Weight
  This means the weight of any vehicle with a full tank of gas but without any load or passengers.

• Differential
  The differential is the gear assembly that connects to the drive shaft, or both sides of an axle. It transmits drive power to the wheel axles, and allows opposite wheels to turn at different speeds when the automobile turns a corner. (See also Drive Shaft, Drivetrain, and Transaxle).

• Disc Brakes
  A mechanism for braking where, what are called brake pads, are attached to a hydraulic caliper, which stands astride a disc attached to the wheel. The caliper can close in a vise-like grip to slow the disc and therefore the wheel.

  Experts say that disc brakes work better in wet driving conditions than drum brakes. (See Drum Brakes).

• Displacement
  The displacement of an engine, usually given in either cubic inches or liters, is a measure of the volume of its cylinders. How much air they can draw in is a theoretical gauge to both size and power output.

• Distributor
  Part of the ignition, which sends pulses of electricity to the spark plugs.

• Drag Coefficient (dc)
  See Coefficient Of Drag (CD).

• Drive Shaft
  The shaft that sends power through to the differential from the transmission in a standard rear wheel drive system. (See Differential, RWD, and Transaxle).

• Drivetrain
  Sometimes known as the powertrain, this is the collective name for all the components that are directly involved in the power production that is needed to get and keep the automobile moving. This includes the engine (obviously) as well as the likes of the clutch, transmission (or gearbox) driveshafts, differential, and wheel axles.

• Drum Brakes
  A braking system where a metal drum is attached to the wheel, and the rotation of this, and so the wheel, is slowed and halted by curved devices called brake shoes being pressed hard against the brake lining which causes friction on the inside of the drum.

• Dynamo
  See Alternator.

• Electrochromatic Mirror
  This is a rearview mirror that contains light sensitive properties, so that it can darken to avoid glare from following vehicles’ headlamps at night.

• Electronic Fuel Injection (EFI)
  There are different types of fuel injection systems, but all have replaced the carburetor for introducing fuel into the engine with much more precise control and timing. This has many advantages in fuel economy terms, as well as providing better engine performance and reliability, with lower exhaust emissions.

• Electronic Stability System
  These computerized systems aid safer driving by combating the effects of both understeer and oversteer. (See Oversteer and Understeer).

• FWD (Front Wheel Drive)
  In this arrangement, the motive force from the engine is applied the front wheels only rather that the rear wheels, as is the norm. FWD cars have benefits which include; more space at the back for passengers or load; and better grip in wet weather (because the front wheels are pressed down by the heavier weight of the engine). But FWD cars can also be inclined to understeer when driven with temper or haste. (See Understeer).

• Galvanized Steel
  This is steel that has been given a coating of zinc to prevent rusting.

• Gear Ratio
  This how many turns is required from a smaller pinion gear to power a driven gear through one full revolution. (See Pinion).

• Global Positioning System / Satellites (GPS)
  Originally developed for the military, this is a set of satellites that constantly broadcast signals down to earth which when received, are used to work out the exact geographical location of the receiver. This has recently appeared as an option for automobiles, and can also be referred to by the abbreviation satnav (satellite navigation) in many countries.

• Head Rest / Restraint
  A small padded and adjustable cushion which when present on a car seat can protect against whiplash injuries to the neck.

• Horsepower (hp)
  The standard unit for measuring engine power: 1 hp is the power required to lift 550 pounds of weight one foot high in a second.

• Independent Suspension
  This is where each wheel on an axle can move up and down at a different rate to the other, rather than always moving together.

• Metallic Paint
  A paint which contains tiny dots of metal in its makeup to give it extra quality.

• Normally Aspirated
  An engine that is not fitted with either a turbo or supercharger. (See Supercharger and Turbocharger).

• Overdrive
  This is the highest gear in a transmission that is used for reasons of fuel economy when at cruising speed (and not to make the car go faster, as is quite widely believed).

• Oversteer
  The opposite of understeer, this is when the vehicle turns much more than was desired by the driver. It is a condition more commonly found when cornering forcefully in RWD than FWD vehicles because sudden power to the rear wheels can cause them to slide sideways. (See also Electronic Stability System, FWD, RWD, and Understeer).

• Pearl Paint
  This car paint has minuscule flecks of mica in it to reflect light in a lustrous way that is particularly attractive to the eye. Mica is a group of mineral silicates, which form in hexagonally shaped plates of crystal.

• Pinion
  This is the name of a small-toothed driving gear which fits into a larger driven gear wheel called a rack or ring; as in rack and pinion steering, for the most well known example. (See Gear Ratio).

• Powertrain
  See Drivetrain.

• Push
  See Understeer.

• RWD (Rear Wheel Drive)
  This is where all the drive power needed for the car goes through the transmission to the rear axle, and so only rear wheels are powered, with the front wheels just being used for steering alone.

• SatNav
  See Global Positioning System / Satellites (GPS).

• Spoilers
  These are devices which improve tire traction (grip) by increasing what is known as downforce on a car. They improve braking, stability and cornering at speed by breaking up the clean aerodynamic lines of the bodywork, and using the force created as a vehicle passes through the air to press the car down onto the road.

• Standard
  This refers to equipment that is included in the base list price of an automobile.

• Supercharger
  This is a mechanism that pressurizes air to increase engine power, but unlike a turbocharger it is driven by a belt or gearing and thus though stronger, is more complex.

• Suspension
  This is the system of springs and shock absorbers etc. which suspend the automobile above the wheels, and prevent the occupants from bouncing around in their seats (unless they want to, but that’s another story entirely).

• Tachometer
  This sits on the instrument panel and shows the speed that the crankshaft is rotating at in RPM (revolutions per minute) to give a measure of how hard the engine is working.

• Torque
  This is a rotating or twisting force. Torque is what it’s all about; the engine power developed from the cylinders, rods and pistons is sent through to the crankshaft for converting into a rotating motion (torque) which then is used through the transmission (or gearbox) to get the wheels moving.

• Traction Control
  Having this system fitted helps to reduce wheel spin during acceleration, so allowing for improved driver control.

• Transaxle
  This mechanism combines the duties of a differential and a transmission, and is commonly used in front wheel drive (FWD) automobiles. Having a transaxle means that there is no need for the drive shafts which are used to connect the differential to the transmission in rear wheel drive (RWD) cars.

• Transmission
  This is the gearing, and is used for controlling the behavior of the engine. Turbocharger (Turbo)
  This piece of equipment is driven by flowing exhaust gases, and works to increase the power produced by the engine by allowing it to burn up more fuel than it ordinarily could. The turbocharger achieves this feat by pressurizing the air taken in by the engine - more air means more combustion, of more fuel.

• Understeer
  The opposite of oversteer, this is when a vehicle turns much less than the driver desired it to. This is a state of affairs that is more commonly encountered when cornering aggressively in FWD than RWD vehicles because sudden power to the front wheels can cause them to lose traction and push onwards without turning well. (See also Electronic Stability System, FWD, Oversteer, and RWD).

• Unibody Construction
  This is where the automobile’s bodywork does not have need of a separate frame for the providing of support to the car’s various mechanisms, because the frame and body have been merged into one.

• Weight Distribution
  A very important consideration for pickup trucks and the like, but also cars as well, this is how the total weight will be carried by each axle and tire. Components parts such as axles, springs, bearings, and tires will have much less of a service life if they have to bear more than an equal share of the load. The safety of the vehicle can also be compromised with a poor weight distribution.

• Wheelbase
  This is the distance between the front and rear wheels, measured from the center of each.
  
  
• VIN
  Acronym for Vehicle Identification Number. This is a unique number that identifies your vehicle. Although its primary purpose is to identify your vehicle, it often contains important information concerning the equipment and options that were installed on your vehicle at the factory. This information allows the Repair Center to order the correct parts for your vehicle. Any professional estimate or Repair Order will have this number on it.

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