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Damper A device, better known as a shock absorber, used for controlling and smoothing the motion generated from the suspension reacting to road irregularities. DBC Dynamic Brake Control - brake pressure builds up faster and with greater strength when you apply the brake suddenly. It shortens stopping distance as much as possible even if the brake pedal has not been pressed with enough force. DBC works using hydraulics, meaning that pressure can be applied quickly and accurately, and its computer enables it to ascertain whenever the brake pedal is pressed faster than usual. To ensure the greatest possible degree of safety, the DBC computer is connected to other suspension control systems: Anti-lock Braking System (ABS), Automatic Stability Control + Traction (ASC+T), Automatic Differential Brake (ADB-X), Hill Descent Control (HDC) and Dynamic Stability Control (DSC). DCAS Distance Control Assist System - helps drivers control the distance between themselves and the vehicle in front. The system uses a radar sensor installed in the front bumper which is able to determine the following distance and relative vehicle speed of both cars. :: Click for detailed DCAS information DDE Digital Diesel Electronics - determines exactly when fuel injection is to start, as well as the volume of fuel supplied and charge pressure. This ensures unprecedented fine tuning under all running conditions. The result is even greater economy, improved smoothness and a reduction of harmful emissions. DDE are also responsible for speed regulation and start clearance after the change code has been checked along with the electronic immobilizer. Dead Axle A rear axle that does not turn or transmit torque but simply carries the vehicle weight. Found in FWD cars. Decklid A hinged panel providing access to the luggage compartment. Detonation The secondary ignition of the air/fuel mixture in the combustion space causing extreme pressures. Detonation is caused by low gasoline octane ratings, high combustion temperatures, improper combustion chamber shape, too-lean mixtures, etc. Detonation produces dangerously high loads on the engine, and if allowed to continue, will lead to engine failure. Detonation, unlike preignition, requires two simultaneous combustion fronts (fuel burning in two or more places in the combustion chamber at once); whereas preignition occurs when the fuel-air mix ignites (with single burning front) before the spark plug fires. Both preignition and detonation produce an audible "knock" or "ping," but detonation does not produce the rapid "wild pinging" noise that is typically associated with preignition. The extreme pressures of detonation can lead to preignition, but even worse the high temperatures of preignition can cause detonation. Diesel Catalytic Converter Petrol engines use a three-way catalytic converter, which reduces oxides of nitrogen (NOx) and oxidise hydrocarbons (HC) and carbon monoxide (CO). Newer diesel engines use an oxidation-type catalytic converter to oxidise hydrocarbons and carbon monoxide using the oxygen present in diesel exhaust. The post-oxidisation also serves to reduce the soluble organic fraction of particulates. The catalytic converter consists of a ceramic block with a honeycomb structure: the channels of this honeycomb possess a high-performance platinum washcoat. Diesel Fuel Diesel fuel, like gasoline is a complex blend of carbon and hydrogen compounds. It too requires additives for maximum performance. There are two grades of diesel fuel used in automobiles today: 1-D and 2-D. Number 2 diesel fuel has a lower volatility and is blended for higher loads and steady speeds, therefore works best in large truck applications. Because number 2 diesel fuel is less volatile, it tends to create hard starting in cold weather. On the other hand number 1 diesel is more volatile, and therefore more suitable for use in an automobile, where there is constant changes in load and speed. :: Click for detailed Diesel Fuel information Differential The differential is the thing that works both drive axles at the same time, but lets them rotate at different speeds so that the car can make turns. When a car makes a turn, the outer wheel has to turn faster than the inner wheel, due to the difference in the length of the paths they take. The differential is located between the two wheels, and is attached to each wheel by a half-shaft rotated through a bevel gear. Four-wheel drive cars have a separate differential for each pair of wheels. A grooved, or splined, axle side gear is positioned on the splined end of each axle. The side gears are driven by "spider" gears, which are little gears mounted on a shaft attached to the differential case. As it is supported by the differential case, the side gear can turn inside the case. :: Click for detailed Differential information Differential - Fluids For lubrication fluid, a very heavy oil, must be used in rear axle housings. Special hypoid oils are used in the Differential case. Even another type of fluid, or oil must be used in a Positraction (a.k.a. LSD - Limited Slip Differential ) type differential. :: Click for detailed Differential - Fluids information Digital Instrumentation An instrument panel where digital displays replace the traditional analog (needle) instruments and gauges. Often, digital instrumentation utilizes LCDs (liquid crystal display) to indicate the various functions. The advantage of digital readout is the instant recognition of the numeric display. DIS Driver Information System - in the instrument cluster is the car's display and information centre. It provides information on the current operating status, including for example auto check control messages and - depending on the car's equipment - radio, telephone and navigation data. DISA Differentiated Intake System - The intake pipes are joined by a connecting valve that is closed at low engine speeds, but which guarantees impressive torque values because of the lengthy route the air has to take. At high engine speeds, the valve opens so that the air intake route is shortened, thereby increasing engine performance. Disc Brake A type of brake consisting of a flat rotor (disc) that turns with the wheel and a stationary component called the caliper. DISI Direct Injection Spark Ignition - fuel is injected in one of two ways, depending on operating conditions. With lean burn operation (at low to mid loads), the engine is run unthrottled (similar to diesel) with fuel injected after the air has entered, causing a higher fuel concentration near the spark plug for easy ignition. This is known as the stratified charge mode. The overall air/fuel ratio is lean for better fuel consumption. At mid to high engine loads, fuel is injected during the air intake stroke to promote good mixing. This process is known as the homogenous mode of operation. Fuel injected and evaporating directly in the combustion chamber cools the air slightly for higher volumetric efficiency and power. It also allows a slightly higher compression ratio for improved fuel efficiency. Since all fuel being injected goes directly into the cylinder, it can be metered more precisely, promoting improved transient control for reduced engine-out emissions. Displacement is the volume of air/fuel mixture "displaced" by the pistons during a single engine cycle. In terms of a single cylinder, displacement is the volume of the space traveled by the piston. The two factors that make up engine displacement are bore and stroke. Distributor A device in the ignition system of an internal combustion engine that routes high voltage from the ignition coil to the spark plugs in the correct firing order. It consists of a rotating arm or rotor inside the distributor cap, on top of the distributor shaft, but insulated from it and the body of the vehicle ("earth"). The metal part of the rotor contacts the central high voltage cable from the coil via a spring loaded carbon brush. The metal part of the rotor arm passes close to (but does not touch) the output contacts which connect via high tension cables to the spark plug of each cylinder. As the rotor spins within the distributor, electrical current is able to jump the small gaps created between the rotor arm and the contacts due to the high voltage created by the ignition coil. :: Click for detailed Distributor information Distributor Cap As the rotor rotates inside the cap, it receives the high voltage from the ignition coil, then passes it to the nearest connection, which is a metal projection in the cap, which is connected to a Spark Plug. :: Click for detailed Distributor Cap information DME Digital Motor Electronics - a microprocessor-based system that controls the ignition, the fuel injection, the oxygen sensor and numerous ancillary functions. DME provides raw data to an on-board computer that uses an alphanumeric display to provide you with information such as the average fuel consumption, the distance you can still cover with fuel in the tank, an average speed, outside temperature and more. (aka Engine Control Unit (ECU)) :: Click for detailed DME information DOHC Double OverHead Cam - An engine configuration with two overhead camshafts per row of cylinders. One camshaft operates the intake valves and the other operates the exhaust valves. This is the usual arrangement in engines with multi-valve cylinder heads. Compared to single overhead cam designs, the direct drive used in all DOHC engines requires fewer moving parts. :: Click for detailed DOHC information Double-VANOS VAriable NOckenwellen Steuerung (German) - A combined hydraulic and mechanical camshaft control device managed by the car's DME engine management system. The VANOS system is based on a discrete adjustment mechanism that can modify the position of the intake camshaft versus the crankshaft. Double-VANOS adds continuous adjustability to the intake and outlet camshafts. :: Click for detailed Double-VANOS information Downforce and Weight - Theory Friction supplies the resistance to sliding that we use everyday. Without friction we couldn’t walk or crawl and nails wouldn’t hold. Consider a block of some material, a cube about an inch on a side. The block is lying on a surface, say a table. The block has some weight because of gravity. We’ll call that weight Fv, the vertical force, because it acts straight down. If you push on the block with a force (F) parallel to the table, you can make it slide on the surface. If you push hard, it will slide right off the table. If you push against it very lightly, it won’t move. :: Click for detailed Downforce and Weight - Theory information DRC Dynamic Ride Control - Audi's suspension concept used in the RS 6 (at the time of writing).This consists of a special shock absorber system that counteracts pitch and body roll movements without using any electronic devices. When DRC is installed, the diagonally opposed shock absorbers on the car are linked together hydraulically. A central valve varies the shock absorber operating characteristic, for instance when the steering wheel is turned and the car is cornered, so that movement around the longitudinal axis (roll) is significantly reduced. :: Click for detailed DRC information Drifting Refers to the difference in slip angle between the front and rear tires of a car. When the rear wheels are slipping at a greater angle than the front wheels, the car is drifting, or oversteering. The rear end of the car appears to chase the front end around a turn, the driver utilizes both front tires and the rear tires to control the actual direction of the car. More throttle induces more rear wheel slip angle and the rear of the car wants to overtake the front. The goal is for the driver to achieve steering lock and use the throttle to fine tune the car's angle and direction. :: Click for detailed Drifting information Drive-by-wire Technology in automotive industry replaces the traditional mechanical and hydraulic control systems with electronic control systems using electromechanical actuators and human-machine interfaces such as pedal and steering feel emulators. Drivetrain The drive train serves two functions: it transmits power from the engine to the drive wheels, and it varies the amount of torque. "Power" is the rate or speed at which work is performed. "Torque" is turning or twisting force. Multiple ratio gearboxes are necessary because the engine delivers its maximum power at certain speeds, or RPM (Rotations Per Minute). In order to use the same engine RPM's at different road speeds, it is necessary to change the "Gear Ratio" between the engine and the drive wheels. Just like a bicycle, the car has to switch gears in order to move at a wide range of speeds. There are actually two sets of gears in the drive train; the Transmission and the Differential. The transmission allows the gear ratio to be adjusted, and the differential lets the drive wheels turn at different speeds. Manual transmissions usually have four or five speeds, and often have "overdrive", which means that the output shaft can turn faster than the input shaft for fuel economy on the highway. Some use an electric Clutch and a switch that controls whether the overdrive is engaged or not. An interesting development on a few cars is the "clutchless" manual transmission, which uses a stick shift and an automatic electric clutch. Speed and position sensors, mini computers, and throttle controls keep the engine from over-revving when the driver shifts gears. As with many automotive "inventions", this is an old idea which may now reach feasibility due to the computer revolution. Automatic transmissions commonly use three forward gears to blend speed and torque. In the case of a three-speed transmission, first gear delivers maximum torque and minimum speed for starting. Second gear offers medium torque and speed for acceleration and hill climbing. Third gear allows maximum speed with minimum torque for highway travel. A reverse gear permits backward movement. :: Click for detailed Drivetrain information Drive Shaft The drive shaft, or propeller shaft, connects the transmission output shaft to the Differential pinion shaft. Since all roads are not perfectly smooth, and the transmission is fixed, the drive shaft has to be flexible to absorb the shock of bumps in the road. Universal Joint "U-joints" ,allow the drive shaft to flex (and stop it from breaking) when the drive angle changes. Drive shafts are usually hollow in order to weigh less, but of a large diameter so that they are strong. High quality steel, and sometimes aluminum are used in the manufacture of the drive shaft. The shaft must be quite straight and balanced to avoid vibrating. Since it usually turns at engine speeds, a lot of damage can be caused if the shaft is unbalanced, or bent. Damage can also be caused if the U-joints are worn out. :: Click for detailed Drive Shaft information Driving Techniques - Brake Torquing A procedure generally used in performance tests to improve the off-the-line acceleration of a car equipped with an automatic transmission. It is executed by firmly depressing the brake with the left foot, applying the throttle with the car in gear to increase engine rpm, then releasing the brakes. :: Click for detailed Driving Techniques - Brake Torquing information Driving Techniques - Heel and Toe 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. :: Click for detailed Driving Techniques - Heel and Toe information DRL Daytime Running Lights - A system which activates the low beam headlights at a reduced intensity during daylight to keep the car highly visible to other vehicles. On some models, a dash-mounted sensor automatically switches between DRLs and the normal intensity low beams according to the lighting conditions (nighttime, tunnel, etc.). DSC Dynamic Stability Control - is a further development of the Anti-lock Brake System (ABS) and Automatic Stability Control and Traction (ASC+T) slip control systems. :: Click for detailed DSC information DSG Direct-Shift Gearbox designed by BorgWarner. The DSG driving experience combines the driving excitement of a manual with the comfort of an automatic. Inside the cockpit, drivers experience superbly ergonomic and intuitive design, and engage Tiptronic® mode simply by using paddle shifters located on the steering wheel (optional). Whereas in conventional single clutch manuals, power flow is interrupted whenever the driver steps on the clutch pedal, with DSG the clutch for the first gear opens exactly as the other clutch engages the next gear, producing shifts in less than .2 seconds. When compared to a manual, DSG can deliver faster shifts, better acceleration figures and more economical fuel consumption. DSG is available as an option in the TT and A3. DTC Dynamic Traction Control - allows you to drive at the limits without fear of exceeding them. It increases wheel slip on the drive wheels in order to ensure optimum traction on any surface. A further advantage of DTC is that it enables the skilled driver to drift round bends in a controlled process, enjoying even greater and more thrilling driving dynamics. Dynamic Drive Uses active stabilisers on the front and rear axles to counteract the vehicle's tendency to roll in a corner. Working together with acceleration and position sensors, a management system and other components, such as a compensation tank for sound control, the system ensures supreme agility at all speeds, balanced reactions to load changes and remarkably precise steering. The stabilisers continually adapt to suit the driving situation and the changes to the vehicle's self-steering behaviour. For example, when driving on the straight, Dynamic Drive reduces the pressure of the stabilisers, treating them individually, so allowing for a highly comfortable ride - a particular benefit for rear-seat passengers. :: Click for detailed Dynamic Drive information Dynamometer A device used to measure the power output of rotating machinery. In it’s simplest terms, a dynamometer is a power-absorbing brake, incorporating an accurate method of measuring how much torque (and horsepower) is being absorbed. Braking is accomplished through friction (usually a hydraulic absorber) or by an electric dynamo (converts energy to electricity). Modern computer-controlled dynamometers for high-performance automotive use have sophisticated speed controls that allow the operator to select the rpm point or range of speeds through which the torque is to be measured. Then the operator opens the throttle and the dynamometer applies the precise amount of load to maintain the chosen rpm points; horsepower is read out directly on a gauge and/or computer screen.

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