Automotive terms Modern (D)
Automotive Technical terms and abbreviations overview used in the industry, Guide and explanations.
The following are examples of Mid Modern technical terms recommended for general use worldwide. For in-depth specific terms also see terms for historic vintage and specific areas such as Paint.
DATA LINK CONNECTOR (DLC):
Current acronym/term applied to the federally mandated, diagnostic junction connector that is used to monitor ECM/PC/TCM inputs, processing strategies, and outputs including diagnostic trouble codes (DTCs).
DEAD CENTER:
The extreme top or bottom of the piston stroke.
DECELERATION BUMP:
When referring to a torque converter clutch in the applied position, a sudden release of the accelerator pedal causes a forceful reversal of power through the drivetrain (engine braking), just prior to the apply plate actually being released.
DELAYED (LATE OR EXTENDED):
Condition where shift is expected but does not occur for a period of time, for example, where clutch or band engagement does not occur as quickly as expected during part throttle or wide open throttle apply of accelerator or when manually downshifting to a lower range.
DETENT:
A spring-loaded plunger, pin, ball, or pawl used as a holding device on a ratchet wheel or shaft. In automatic transmissions, a detent mechanism is used for locking the manual valve in place.
DETENT DOWNSHIFT:
(See kickdown.)
DETERGENT:
An additive in engine oil to improve its operating characteristics.
DETONATION:
An unwanted explosion of the air/fuel mixture in the combustion chamber caused by excess heat and compression, advanced timing, or an overly lean mixture, Also referred to as "ping".
DEXRON:
A brand of automatic transmission fluid.
DIAGNOSTIC TROUBLE CODES (OTCs):
A digital display from the control module memory that identifies the input, processor, or output device circuit that is related to the powertrain emission/driveability malfunction detected. Diagnostic trouble codes can be read by the MIL to flash any codes or by using a handheld scanner.
DIAPHRAGM:
A thin, flexible wall separating two cavities, such as in a vacuum advance unit.
DIESELING:
The engine continues to run after the car is shut off caused by fuel continuing to be burned in the combustion chamber.
DIFFERENTIAL:
A geared assembly which allows the transmission of motion between drive axles, giving one axle the ability to rotate faster than
the other, as in cornering.
DIFFERENTIAL AREAS:
When opposing faces of a spool valve are acted upon by the same pressure but their areas differ in size, the face with the larger area produces the differential force and valve movement. (See spool valve.)
DIFFERENTIAL FORCE:
(See differential areas)
DIGITAL READOUT:
A display of numbers or a combination of numbers and letters.
DIGITAL VOLT OHMMETER:
An electronic diagnostic tool used to measure voltage, ohms and amps as well as several other functions, with the readings displayed on a digital screen in tenths, hundredths and thousandths.
DIODE:
An electrical device that will allow current to flow in one direction only.
DIRECT CURRENT (DC):
Electrical current that flows in one direction only.
DIRECT DRIVE:
The gear ratio is 1:1, with no change occurring in the torque and speed input/output relationship.
DISC BRAKE:
A hydraulic braking assembly consisting of a brake disc, or rotor, mounted on an axle shaft, and a caliper assembly containing, usually two brake pads which are activated by hydraulic pressure. The pads are forced against the sides of the disc, creating friction which slows the vehicle.
DISPERSANTS:
Suspend dirt and prevent sludge buildup in a liquid, such as engine oil.
DOUBLE BUMP (DOUBLE FEEL):
Two sudden and forceful applies of a clutch or band.
DISPLACEMENT:
The total volume of air that is displaced by all pistons as the engine turns through one complete revolution.
DISTRIBUTOR:
A mechanically driven device on an engine which is responsible for electrically firing the spark plug at a pre-determined point of the piston stroke.
DOHC:
Double overhead camshaft.
DOUBLE OVERHEAD CAMSHAFT:
The engine utilizes two camshafts mounted in one cylinder head. One camshaft operates the exhaust valves, while the other operates the intake valves.
DOWEL PIN:
A pin, inserted in mating holes in two different parts allowing those parts to maintain a fixed relationship.
DRIVELINE:
The drive connection between the transmission and the drive wheels.
DRIVE TRAIN:
The components that transmit the flow of power from the engine to the wheels. The components include the clutch, transmission, driveshafts (or axle shafts in front wheel drive), U-joints and differential.
DRUM BRAKE:
A braking system which consists of two brake shoes and one or two wheel cylinders, mounted on a fixed backing plate, and a brake drum, mounted on an axle, which revolves around the assembly.
DRY CHARGED BATTERY:
Battery to which electrolyte is added when the battery is placed in service.
DVOM:
Digital volt ohmmeter
DWELL:
The rate, measured in degrees of shaft rotation, at which an electrical circuit cycles on and off.
DYNAMIC:
An application in which there is rotating or reciprocating motion between the parts.
