A I B I C I D I E I F I G I H I I I K I L I O I P I R I S I T I U I V I Z

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. Commonly called ABS, such a system can control all four wheels or only two.

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.

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.

Often simply called a "catalyst": a stainless-steel canister fitted to a car's exhaust system that contains a thin layer of catalytic material spread over a large area of inert supports. The material used is some combination of platinum, rhodium, and palladium; it induces chemical reactions that convert an engine's exhaust emissions into less harmful products. So-called three-way catalysts are particularly efficient; their operation, however, demands very precise combustion control, which can be produced only by a feedback fuel-air-ratio control system.

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.

A special gearbox designed so that the torque fed into it is split and delivered to two outputs that can turn at different speeds. Differentials within axles are designed to split torque evenly; however, when used between the front and rear axles in four-wheel-drive systems (a center differential), they can be designed to apportion torque unevenly.

Properly called caliper disc brakes: a type of brake that consists of a disc that rotates at wheel speed, straddled by a caliper that can squeeze the surfaces of the disc near its periphery. Disc brakes provide a more linear response and operate more efficiently at high temperatures and wet conditions than drum brakes.

Double Overhead Camshaft: a DOHC engine has two camshafts in each cylinder head; one camshaft operates the intake valves, the other actuates the exhaust valves.

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.

A type of brake that has an iron casting shaped like a shallow drum that rotates with the wheel. Curved brake shoes are forced into contact with the inner periphery of this drum to provide braking.

A valvetrain with a total of four valves in the combustion chamber, typically two intakes and two exhausts. Compared to the more common two-valve-per-cylinder designs, a four-valve layout offers improved breathing and allows the spark plug to be located closer to center of the combustion chamber.

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.

A performance-oriented technique of down-shifting while braking that requires the driver to use all three pedals of a manual-transmission car simultaneously. To perform a heel-and-toe downshift, the driver brakes with the toe of his right foot and: while continuing to brake: uses the heel or the side of the same foot to blip the throttle and raise engine rpm as he downshifts. The left foot operates the clutch pedal in the normal fashion. The sequence is as follows: brake with the right toe; depress the clutch with the left foot; shift to neutral; while continuing to brake, blip the throttle with the side or the heel of the right foot to raise rpm; shift to a lower gear; let the clutch out; release the brakes. The technique is difficult to master, but after practice it can be performed in less than a second. This process is best for smooth power flow and long transmission life.

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.

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.

A vertical force directed upward, produced by the airflow around a moving object: such as a car body.

The path through a corner that best accommodates a late braking point, a high cornering speed, and the fastest-possible exit speed out of a corner.

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.

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.

The subjectively defined rpm range over which an engine delivers a substantial fraction of its peak power. The power band usually extends from slightly below the engine's torque peak to slightly above its power peak.

Pounds per square inch, the common unit of measurement for pressure. Normal atmospheric pressure at sea level is 14.7 psi.

A laterally aligned structural member that is attached to the body or the frame via vibration-absorbing rubber isolators. By bolting suspension or driveline components to such crossmembers, automotive engineers can reduce the transmission of noise and/or ride harshness to the body.

An aerodynamic device that changes the direction of airflow in order to reduce lift or aerodynamic drag and/or improve engine cooling.

An air compressor used to force more air into an engine than it can inhale on its own. The term is frequently applied only to mechanically driven compressors, but it actually encompasses all varieties of compressors-including turbochargers.

A spring consisting of a long solid or tubular rod with one end fixed to the chassis and the other twisted by a lever connected to the suspension.

An electronic control system that prevents wheelspin by detecting when a driven wheel is about to break traction, and then reducing engine power and/or applying the appropriate brakes to prevent it.

A gearbox with a number of selectable ratios, used to match the engine's rpm and torque to differing vehicle requirements.

A supercharger powered by an exhaust-driven turbine. Turbochargers always use centrifugal-flow compressors, which operate efficiently at the high rotational speeds produced by the exhaust turbine.

A handling condition in which the slip angle of the front tires is greater than the slip angle of the rears. An understeering car is sometimes said to push, because it resists turning and tends to go straight.

The collection of parts that make the valves operate. The valvetrain includes the camshaft(s) and all related drive components, the various parts that convert the camshaft's rotary motion into reciprocating motion at the valves, and the valves and their associated parts.

The VVT-I (Variable Valve Timing – Intelligent) technology achieves optimal timing by controlling the opening and closing of intake valve. The VVT-I computes RPM, throttle opening and other factors to constantly optimising timings. The other manufacturer only changes the timing at the extremely high or low RPMs. Toyota's VVT-i engine controls is incredible responsive, making changes in 1/1000th of a second. This results in engine that is powerful, efficient and clean.

A steering system whose geometry has a scrub radius of zero. This configuration minimizes the steering effects produced during acceleration (with front drive) or braking on varying traction surfaces.