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Da
Di
Dr
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Dashboard
The section immediately behind the windshield that houses the
instruments, accessory controls, and glove box.
Dash
Controls The dash board, behind the steering wheel
displays the control panel of the car. Duplicate fragments of the
control panel are found in the interior of your vehicle, such as
automatic door locks, extra light switches, etc. Many functions of
the car are carried out through the dash board, like turning on the
headlights, windshield wipers, horn, turn signals, air conditioning,
cassette player, etc. It also contains all of your gauges; gas,
temperature, tachometer, etc., which enables the monitoring of the
operating conditions of your engine and charging system, fuel level,
oil pressure and coolant temperature. It ensures that all the
controls are within the drivers reach.
Diagnostic
Code Code numbers obtained by accessing the diagnostic
mode of an engine management computer. This code can be used to
determine the area in the system where a malfunction may be located.
Diagonal
Brake System kit A dual-brake system with separate hydraulic
circuits connecting diagonal wheels together; right front to left
rear and left front to right rear.
Diesel
Engine An internal-combustion engine in which the fuel is
injected into the cylinder near the end of the compression stroke and
is ignited by the heat of the compressed air in the cylinder. No
spark plug or carburetor is needed.
Diesel
Fuel Injector The diesel fuel injector is a pressure valve, but
it has specific components that allow it to disperse the diesel fuel
in set patterns, depending on the design of the valve. Diesel fuel
injectors receive the pressurized impulse from the diesel fuel pump,
and allow the fuel to enter the combustion chamber when it is needed.
If the diesel fuel injectors get clogged, engine performance suffers.
Diesel
Fuel Pump Diesel fuel pumps inject a specific amount of fuel
during a specific time, and control the injectors by the pressure
waves of the fuel that they pump. The diesel fuel pump has mechanisms
in it, which allows more or less fuel to be pumped. If less fuel is
pumped into the cylinders, this slows the engine, and vice versa. It
thus also regulates the speed. A series of gears link them to the
crankshaft or the camshaft, allowing the fuel pump to be driven
directly by the crankshaft of the engine. Some may be belt or chain driven.
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
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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. |
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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. The differential case can be
turned, revolving around the axle gears. The differential pinion (a
pinion is a small gear that either drives a larger gear or is driven
by one) shaft turns the ring gear, which is fastened to the
differential case. The propeller shaft (drive shaft) connects
the transmission output shaft to the differential pinion shaft. The
turning differential case is mounted on two large bearing holders.
These bearings are called carrier bearings. The propeller shaft
rotates the ring gear pinion, and the pinion turns the ring gear. The
ring gear then turns the differential case and pinion shaft, but the
axle side gears will not turn. By passing the differential pinion
shaft through two differential pinion gears that mesh with the side
gears, the case will turn and the axle side gears will turn with it.
During turns, the side gears turn at rates dictated by the radius of
the turns, and the spider gears then turn to allow the outer wheel to
turn faster than the inner one.
Differential
Gears The gears that convey engine power to the driving
axles and are arranged so as to permit the rear wheels to turn at
different speeds as required when the vehicle is negotiating a turn.
Differential Housing See
Differential
photo above
and axle
housing.
Direct
Injection A
fuel injection system which is generally used in diesel engines and
forces fuel directly into the combustion chamber. It requires very
high injection system pressure to overcome the pressure within the
combustion chamber.
Disc
Brake A type of brake in which two friction pads grip a
steel disc that is attached to the wheel, with one pad on each side.
Distributor
A
unit in the ignition system designed to make and break the ignition
primary circuit and to distribute the resultant high voltage to the
proper cylinder at the correct time. The high voltage comes from the coil
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to
the center terminal of the distributor cap and passes down the
rotor. As the rotor turns, contact is made with each successive
terminal on the circumference of the distributor cap. From there, the
voltage goes into the spark plug wires and to the spark plug.
Generally when your vehicle has its timing adjusted, it is the
distributor that is adjusted. Also called "ignition distributor." |
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Distributor
Shaft The
metal shaft inside the distributor that has a cam wheel which
revolves with the shaft and forces the points to open. A spring
causes the points to close. The distributor rotor is mounted on the
top of this shaft.
Drivebelt(s)
The belt(s) used to drive accessories such as the
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alternator,
water pump, power steering pump, air conditioning compressor, etc.
off the crankshaft pulley. |
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Drive
Train That combination of gears, clutches, shafts, etc.,
that transmits the engine power to the wheels.
Driveshaft
Any shaft used to transmit motion. Commonly used when referring to
the axleshafts on a front wheel drive vehicle.
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,
or "U-joints" allow the drive shaft to flex (and stop it
from breaking) when the drive angle changes.
There
are two types of drive shafts, the Hotchkiss drive and the Torque
Tube Drive.
Drive
Wheel/Axle The drive wheel is the end of the axle shaft; it has
lugs protruding from it. The lugs are separate pieces that are
mounted in the drive wheel. The drive wheel bolts onto the brake drum
and the wheel rim of the car itself. It is usually a disc about six
or seven inches in diameter. Occasionally the drive wheel and the
axle shaft are all one piece
Driving
Wheel The
wheel(s) which is driven by the engine
through the drivetrain.
Also called the "driven wheel"
Drum
Brake A type of brake using a drum-shaped metal cylinder
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attached
to the inner surface of the wheel. When the brake pedal is pressed,
curved brake
shoes with
friction linings press against the inside of the drum to slow or stop
the vehicle.
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Dual
Exhaust An exhaust
system that
features two pipes running to the rear of the vehicle. A
"true" dual exhaust system will route exhaust from one side
of a V6 or V8 engine to the rear of the vehicle through one pipe and
route exhaust from the other side of the engine through another pipe.
On any relatively new vehicle, a true dual exhaust system will
feature at least two catalytic converters, as well as two mufflers
and two tailpipes. Some other dual-exhaust setups feature one muffler
with two entries and two exits.
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