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Da Di Dr Du
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.
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 ( Drivetrain ) 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
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.
A
B
C
D
E
F
G
H
I
J
K
L
M
N
O
P
Q
R
S
T
U
V
W
X
Y
Z
EEC
An abbreviation for: 1. Evaporative emission control. 2.
Electronic engine control.
ECC
abbreviation for Electronic
Climate Control
EGR
system The EGR system (Exhaust Gas Recirculation system)
is designed to reduce emissions. To be precise, it lowers the amount
of nitrogen oxide (NO) in the exhaust emissions. Nitrogen oxide is
formed at very high combustion temperatures. What the EGR system
actually does is direct part of the exhaust gases back into the
intake manifold, which in turn helps reduce the combustion
temperature and consequently lower the amount of NO in the exhaust
gases. The EGR flow is controlled by the engine computer which opens
or closes the EGR valve depending on the operating conditions. One of
the most common problems related to EGR is the intake passage or the
EGR valve getting clogged with carbon deposits causing restrictions
to the EGR gas flow. This turns the "check
engine" light
on and sets the code PO401 - insufficient EGR flow (this is a
common problem for the Acura / Honda V6 engine, for example).
This problem happens mostly if a car makes only short trips so it
can't warm up fully, or when the oil is not changed regularly.
EGR
Valve The Exhaust Gas Recirculation (EGR) valve sends some of the
exhaust
gas back into the cylinders to reduce combustion temperature.
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This
is required because nitrous oxides (nasty pollutants) form when the
combustion temperature gets above 2,500 degrees F. This is as a
result of the formation of nitrous oxides when the nitrogen in the
air mixes with the oxygen. |
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When
it's sunny, the nitrous oxides from the exhaust get together with
the hydrocarbons in the air to form smog. This is when the EGR valve
comes in handy. By recirculating some of the exhaust gas back through
the intake manifold to the cylinders, we can lower the combustion
temperature. Lowering the combustion temperature lowers the amount of
nitrous oxide produced. Consequently, less of it comes out the tail
pipe. There are two types of EGR valves. One operates through the use
of a vacuum, and the other operated through the use of pressure. Both
types allow the exhaust gas in to lower the combustion temperature
when it gets too high.
ELC
abbreviation for Electronic
Level Control
Electric-Drive
Cooling Fan
1.
An engine-cooling fan driven by an electric motor.
2.
An electrically controlled fan that cycles ON and OFF with the air
conditioner control, if predetermined system and/or ambient
temperatures are exceeded.
Electric
Fuel Pump Used previously for heavier vehicles, they have
only recently become operational in cars. The replacement types
usually use a diaphragm arrangement like the mechanical pumps, except
that it is actuated by an electrical solenoid. It uses a small
turbine wheel driven by a constant speed electric motor. The entire
unit is located in the fuel tank and submerged in the fuel itself.
When the engine is running the pump pump operates continuously, thus
exerting a constant pressure which supplies the maximum fuel demands
of the engine. When less fuel is required, the pump does not deliver
at full potential, because the turbine is not a positive displacement
type like the mechanical pump. Consequently, the turbine will run
without pumping fuel and so, needs no means of varying fuel delivery
rate like its mechanical counterpart. Since the fuel can flow past
the spinning turbine blades, there is no need for pump inlet and
outlet valves nor is there any need to vary its speed. A relay for
the electric fuel pump is used to complete the circuit to the fuel
pump. This cuts off current to the fuel pump in the event of an accident.
Electronic
Climate Control (ECC) A system used to regulate the temperature
and humidity of a vehicle's cabin.
Electronic
Level Control (ELC) A device that automatically regulates the
ride height of a vehicle under various load conditions.
Electronic
Fuel Injection Injectors are opened by solenoids operated
by an electronic control unit, as opposed to mechanical injection
systms. Since the fuel has no resistance to overcome, other than
insignificant friction losses, the pump pressure can be set at very
low values, consistent with the limits of obtaining full atomization
with the type of injectors used. The control unit, depending on the
operating conditions of the engine, determines the amount of fuel to
be injected. The conditions depend on manifold pressure, accelerator
enrichment, cold-start requirements, idling conditions, outside
temperature and barometric pressure. The systems work with constant
pressure and with 'variable timed' or 'continuous flow' injection.
The advantages. To begin with, it has fewer moving parts, no need for
ultra-precise machining standards and quieter operation. Also, there
is less power loss, a low electrical requirement, no need for special
pump drives, no critical fuel filtration requirements, no surges or
pulsations in the fuel line. More than anything else, it costs lesser
than its mechanical counterpart.
Electrical
System In electric ignition internal-combustion engines,
those components required to convert the electricity produced by the
generator into a high-voltage spark for the plugs. Includes:
generator or alternator, points, condenser, coil, distributor and
spark plugs plus wiring.
Emissions
The exhaust that comes out of a vehicle's tailpipe or tailpipes.
Harmful emissions are reduced on most newer vehicles (except diesels)
through the use of a catalytic converter. Cats are designed to reduce
the amount of hydrocarbons (HC), carbon monoxide (CO) and oxides of
nitrogen (NOx) that exit a vehicle and are therefore vented into the
atmosphere. Other kinds of pollution-reduction devices have been used
on cars and trucks over the years, including a positive crankcase
vent valve, a charcoal canister and an air injection reactor pump.
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Engine
The
gasoline engine transforms the heat produced from burning gas into a
rotating force. Do you see how many rotating and moving parts it has?
All of them need lubrication to last longer. That's why it's very
important to change the engine oil as often as the owner's manual recommends.
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Engine Types
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F-Head
Side exhaust valve and overhead inlet valve.
- L-Head
Both valves on one side of the cylinder.
- T-Head
Exhaust valve on one side and inlet valve on the other side of the
cylinder. (Twin-camshafts).
- I-Head
Both valves located directly over the piston. Also called
valve--in-head or overhead valve engine.
- SOHC
Single overhead camshaft.
- DOHC
Double overhead camshafts.
- HEMI
and HEMI-HEAD
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Exhaust
The
system of exhausting the burned gases from an internal-combustion
engine consisting of piping or tubing, silencers, and, at times, resonators. |
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Exhaust
Emission Controls Systems
or adjustments designed to limit noxious gases in an engine's
exhaust. Such controls can be grouped into two broad categories:
those designed to reduce or eliminate the formation of harmful
pollutants in the engine itself (e.g., retarded spark setting)
and those designed to destroy or otherwise alter the pollutants after
they have been formed (e.g., air injection, thermal reactors, and
catalytic converters). Evaporative emission controls prevent
gasoline vapors from escaping into the atmosphere from the fuel tank
and carburetor and crankcase controls recycle fumes from the
crankcase through the engine.
Exhaust
Manifold A part with several passages through which
exhaust gases leave the engine combustion chambers and enter the
exhaust pipe.
Usually
constructed of cast iron, the exhaust manifold is a pipe that
conducts the exhaust gases from the combustion chambers to the
exhaust pipe. It has smooth curves in it for improving the flow of
exhaust. The exhaust manifold is bolted to the cylinder head, and has
entrances for the air that is injected into it. It is usually located
under the intake manifold.
Exhaust
System Tubing and other components that move the engine's waste
products (aka exhaust gases) from the engine to the tailpipe.
Most late-model vehicles feature an exhaust system with one or two
exhaust manifolds, at least one catalytic converter and one or two
mufflers. Race vehicles may use a "straight-through"
exhaust, which does not have a catalytic converter or a muffler. See dual
exhaust. |
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