| All
Wheel Drive (AWD) |
All
four wheels are driven by the engine. AWD systems are
superior to 4WD because they can be used under any road
conditions. AWD systems use a center differential to
allow the front and rear wheels to rotate at different
speeds. AWD provides better traction than front or
rear-wheel drive. |
| Alloy
wheels |
Wheels
usually made of aluminum alloy; installed to improve
appearance. Alloy wheels are less prone to corrosion and
can be significantly lighter than the equivalent steel
wheels. |
| Alternator |
A
device that converts rotational energy to AC current.
Alternators provide energy for the vehicle electrical
system. The alternator also recharges the battery. |
Anti-roll
bar
Sway bar
Stabilizer bar |
A
steel rod or tube that connects the right and left
suspension members together to resist roll or swaying of
the vehicle. An anti-roll bar improves the handling of a
vehicle by increasing stability during cornering or
evasive maneuvers. Most vehicles have front anti-roll
bars. Anti-roll bars at both the front and rear wheels
can reduce roll further. |
| Axle,
Live or Rigid |
A
"solid" or "straight" axle that
allows the movement of one wheel to affect the opposite
wheel. A live axle is inexpensive to manufacture and is
useful for heavy duty applications. |
| Ball
Joint |
Usually
refers to the outboard (wheel) end of a CV joint (halfshaft). The ball joint allows the wheel to
steer and move with the suspension and still receive
power from the engine. The term ball joint can also be
used to refer to how suspension components are attached. |
| Belts |
Belts
are used to drive many engine accessories. Most overhead
cam (OHC) engines use cogged (toothed) belts to drive
the camshaft(s). Belts drive the power steering pump,
water pump, air-conditioning compressors, etc. |
| Brakes,
Antilock (ABS) |
An
acronym for Antilock Braking System. ABS eliminates
wheel lockup during braking and loss of steering control
on slippery surfaces. Speed sensors monitor each wheel
and reduce brake pressure on any wheel rotating
significantly slower than the others. ABS systems are 2,
3, or 4-channel systems. 2-channel systems combine 2
wheels, such as the left front and right rear into one
channel. The right front and left rear wheel form the
other channel. Any wheel lockup causes brake pressure
reduction on both wheels of each channel. 3-channel ABS
systems combine the rear wheels into one channel. The
front wheels have individual channels. The most
sophisticated ABS systems use 4-channels, one for each
wheel, for maximum control and braking power. |
| Brakes,
Disc |
A
brake that uses a disc shaped rotor and calipers that
hold friction pads. The rotor is attached to the wheel
hub and spins with it. The calipers are stationary. When
the brake pedal is depressed, the calipers press on the
side of the side of the rotor. The friction pads slow
the rotor as needed. Most vehicles use disc brakes on
the front wheels. Disc brakes can shed heat and retain
their braking power better than drum brakes. |
| Brakes,
Drum |
A
brake that uses an enclosed rotating drum or
"can" and stationary pads (shoes). When the
brake pedal is depressed, the brake shoes contact the
sides of the "can" and slow the wheel. Drum
brakes are usually mounted on rear wheels. Drum brakes
are prone to "fade," or heat buildup, which
reduces their effectiveness. |
| Brakes,
Calipers |
Brake
pads are mounted to calipers, which "float"
next to the brake disc. The caliper ensures that the
brake pads exert even pressure on the disc. |
| Camshaft |
A
machined shaft with lobes that opens and closes engine
cylinder valves. The crankshaft drives the camshaft
through gears, belts, or chains. |
| Carburetor |
A
device that mixes fuel and air to provide a combustible
mixture. Air blowing over the fuel nozzles (jets)
results in an air-fuel mixture burned in the cylinders.
Carburetors were common on most vehicles before 1985.
Currently, most vehicles use some form of fuel injection
instead. |
| Clutch |
A
mechanism that uses plates coated with a high-friction
material to transfer power. Clutches are also used to
isolate rotating and non-rotating components. Clutches
can allow slip between components to reduce
"shock" loads between rotating and stationary
components. Manual transmission vehicles use a clutch to
transfer power from the gearbox to the wheels. Air
conditioning compressors use clutches as well. |
| Coil
Spring |
A
spring composed of hardened steel spiral wound used to
isolate a vehicle from the road. Coil springs are
preferred over leaf springs for their superior ride and
control. |
| Crankshaft |
The
shaft that converts the linear motion of the pistons
into rotation. The crankshaft is connected to the
transmission. |
| Constant
Velocity (CV) Joint or Halfshaft |
A
shaft that transmits engine power from the transmission
to the wheel. CV joints allow the wheel to steer and
follow suspension motion while receiving power. CV
joints are used in front-wheel drive, rear-wheel drive,
and all-wheel drive vehicles. |
| Differential |
A
mechanical gearbox or fluid coupling that allows wheels
to rotate at different speeds. |
| Distributor |
A
device that transfers voltage to the spark plug. A rotor
in the distributor spins and touches contacts that are
connected to spark plug wires. The wires then conduct
the voltage to the spark plug. |
| DOHC |
Acronym
for dual/double overhead cam (see Overhead Cam) |
| Driveshaft |
A
rotating shaft that transfers power from the
transmission to the rear wheels. |
| Engine,
Boxer or Flat |
A
designation for an engine where the cylinders are
arranged opposite (180 degrees apart) from each other.
Boxer engines are relatively flat compared to inline or
"V" engines. Common examples of boxer engines
are the Porsche 911 flat-6 and the Subaru flat-4. |
| Engine,
Diesel |
An
internal combustion engine that compresses fuel until it
ignites. A gasoline engine, in contrast, uses a spark
plug to start combustion. Diesel engines use kerosene as
fuel. Diesel engines usually provide better fuel economy
than a comparable displacement gasoline engine; at the
cost of lower power. |
| Engine,
Inline |
An
engine configuration where all cylinders are in one
plane. Most 4-cylinder and some 6-cylinder engines are
inline. An inline engine is cheaper to manufacture than
a "V" type of engine because the engine block
can be a simpler casting. |
| Engine,
V |
(e.g.
V-8):A "V" engine has two banks of cylinders
arranged like a "V". "V" engines
have an included angle of around 30-90 degrees that
separates the individual banks. "V" engines
are more compact than comparable inline engines. A V-8
is significantly shorter, and wider, than an inline-8. |
| Four
Wheel Drive (4WD) |
A
part time system that transfers engine power to all four
wheels. 4WD systems usually lack a center differential
that allows use in dry conditions. 4WD provides superior
traction compared with front or rear-wheel drive. |
| Four
Wheel Steering (4WS) |
A
mechanism that allows the rear wheels to steer. The
steering angle is usually limited to 2-3 degrees. 4WS
improves handling by allowing more stable cornering. |
| Front
Wheel Drive (FWD) |
The
front wheels receive engine power. FWD provides more
traction than rear-wheel drive (RWD) in poor road
conditions because more weight is over the drive wheels.
FWD also allows better use of interior space than RWD
because all drivetrain components are concentrated in
the front of the car. |
| Fuel
Injection |
A
device (injector) that sprays fuel into air to provide a
combustible mixture. Fuel injection provides better
metering of fuel and air than carburetors. This results
in more power, improved fuel economy, and lower
emissions. The simplest systems use single or dual
injectors in a central chamber to supply all cylinders.
More sophisticated systems use an injector at each
cylinder to precisely meter fuel. |
| Generator |
A
device that converts rotational energy to DC current.
Generators were used in older cars to provide electrical
energy for the vehicle. |
| Horsepower
(bhp) |
The
power produced by an engine. Net horsepower or bhp
(brake
horsepower) and Kw (kilowatts) are the standard units.
Higher horsepower increases vehicle top speed. Equal
displacement (size) engines that rev higher often produce
more power than lower revving engines, because more air
and fuel is burned in a given time. A typical 3.0L 24V
V-6 produces 190 bhp @ 6400 RPM. A lower revving 3.0L
12V V-6 produces 160 bhp @ 5000 RPM. The 24-valve V-6
makes 190 bhp because it can rev higher (and breathe
better) than the similar 12-valve V-6. |
| Independent
Suspension |
A
suspension where the motion of one wheel does not affect
the opposite wheel. Independent suspension allows a
vehicle to provide a more level and stable ride. |
| Leaf
Spring |
A
type of spring made up of several thin, curved, hardened
steel plates. The plates are attached at the ends to the
underbody. The curved shape of the plates allows them to
flex and absorb bumps. |
| Lights,
Driving |
Auxiliary
lights that extend the reach of standard headlights.
Driving lights have a narrower beam than headlights. |
| Lights,
Foglights |
Auxiliary
lights that provide a wider beam pattern than standard
headlights. Foglights are usually mounted lower than
headlights to illuminate below fog and reduce reflected
glare. |
| Lights,
Halogen |
Lights
that provide brighter, longer lasting illumination than
standard incandescent lights. Halogen bulbs are filled
with a gas such as iodine. This gas reduces the gradual
evaporation of the tungsten filament and increases its
life. |
| Lights,
Projector Beam |
A
special type of headlight that uses a spherical
reflector to tightly control the light beam. Projector
beams are relatively expensive compared to standard
headlights. |
| Limited
Slip Differential (LSD) |
A
differential that reduces speed differences between
wheels. An LSD improves traction by preventing a
slipping wheel from receiving all the engine power. |
| Lockup
Converter |
A
automatic transmission with a mechanical clutch that
bypasses the fluid coupling of the torque converter. A
lockup converter is more efficient because there is no
wasted energy in the transmission fluid of the torque
converter. Most automatic transmissions have a lockup
converter for the highest ratio (usually 4th or 5th
gear). |
| MacPherson
strut |
A
combined damper (shock absorber) and spring unit.
MacPherson struts are used in most front-wheel drive
vehicles for compact packaging. MacPherson struts also
allow relatively long springs that can increase
suspension travel and increase bump absorption
capability. |
| Multi-link
suspension |
A
general term for independent suspensions that are
controlled with several link arms. These links restrict
undesired motion of the suspension. Multi-link
suspensions provide better handling and ride control
than simpler types. They are also more expensive to
manufacture. |
| Octane |
A
numeric rating of gasoline’s resistance to detonation
(premature ignition). The higher the octane
number, the less chance of detonation. High octane
(above 91) is usually worthwhile only if the
manufacturer specifically recommends it. Octane is
actually a hydrocarbon(C8H18). |
| Oil |
(e.g.
10W-30):Engine oil comes in various ratings: SAE 5W-30,
10W-30, 10W-40, etc. For example, a 10W-30 rated oil
will flow like a light SAE 10-weight oil at low
temperatures. The "W" signifies that it is a
"winter" rated oil. The "30"
designation means that at engine operating temperatures,
the oil will behave like a heavier SAE 30-weight oil.
Low viscosity at colder temperature allows the oil to
circulate more quickly and protect vital engine parts.
Higher oil viscosity at elevated temperatures prevents
direct metal-to-metal contact. |
| Oil,
Synthetic |
Oil
that is not derived from raw petroleum. Synthetic oil
has superior engine protection properties compared to
conventional mineral oil. Synthetic oil costs 3-5 times
more than mineral oil. |
| Overdrive |
A
transmission ratio below 1:1. For instance, a manual
transmission fifth gear ratio could be 0.70:1. Overdrive
ratios improve fuel economy by reducing engine RPM at
highway speeds. |
| Overhead
Cam (OHC) |
OHC
means overhead cam. The cam is above the cylinder head.
SOHC engines have a single cam over the cylinder head.
DOHC engines have two cams above the cylinder head. All
OHC, SOHC, and DOHC engines are also OHV. |
| Overhead
Valve (OHV) |
An
acronym for overhead valve. This simply means that the
intake and exhaust valves are above the cylinder head.
OHC means overhead cam. The cam is above the cylinder
head. SOHC engines have a single cam over the cylinder
head. DOHC engines have two cams above the cylinder
head. All OHC, SOHC, and DOHC engines are also OHV. |
| Oversteer |
A
situation that occurs when the rear wheels contribute to
steering the vehicle more in a given direction. This
often occurs under hard braking while turning. The rear
of the vehicle loses adhesion and starts to rotate in
the direction of steering. Oversteer can be used to
better place the vehicle coming out of a corner.
Usually, oversteer is undesirable because it is
difficult to control and can result in a disastrous
spin. Most cars are designed not to oversteer under
normal conditions. |
| Pushrod |
A
metal rod that transmits the motion of the camshaft to
the valve actuators. Pushrods are used by non-overhead
cam engines to open and close valves. |
| PS |
Pferdestarke
is a measurement of metric horsepower. |
| Rear
Wheel Drive (RWD) |
The
rear wheels receive all the engine power. RWD is
preferred over front-wheel drive (FWD) for its superior
handling and acceleration capabilities. RWD provides
less traction than FWD in poor road conditions because
less weight is available over the drive wheels. |
| RPM |
Revolutions
per minute. RPM indicates how many times the engine
crankshaft rotates per minute. |
| SOHC |
Acronym
for single overhead cam (see Overhead Cam) |
| Spark
Plug |
The
spark plug converts high voltage energy into an arc that
passes between its electrodes. The arc causes the
gasoline-air mixture in the cylinder to ignite and
expand, providing power by pushing down the piston. |
| Starter |
A
motor powered by the battery that rotates the crankshaft
before the engine is started. |
| Steering,
Power |
Assist
provided by the engine to reduce steering effort. Power
steering is essential to make large, heavy vehicles
manageable. Small vehicles often do not require power
steering. |
| Steering,
Rack and Pinion |
A
common steering type. The steering wheel is connected to
a pinion gear that meshes with a rack, or linear gear.
As the pinion rotates, the rack moves side to side, this
moves the steering linkage, causing the wheels to pivot
left or right. |
| Supercharger |
A
device that compresses air before the engine receives
it. The denser air allows the engine to produce more
power. For automotive applications, a supercharger
usually refers to an engine driven air pump. |
| Tappet |
A
pivoting actuator than opens and closes cylinder valves. |
| Tires,
All Season |
Tires
that provide acceptable traction for winter snow and
slush driving conditions, without excessively
compromising dry and wet traction. |
| Tires,
Aspect Ratio |
(e.g.
"60-series tires"): Tire aspect ratio is refers
to the ratio between the tread (section) width and the
sidewall. For example, a 205/50-15 tire would have a
sidewall height of 0.50 x 205 or 102.5 mm. Lower aspect
ratios(e.g. 40-series) provide superior handling at the
cost of increased ride harshness. |
| Tires,
M+S rating |
Tires
especially designed to perform well in mud and snow. M+S
tires are usually superior to all-season tires under
these conditions. The tradeoff is often higher noise and
reduced tread life. |
| Tires,
Ratings |
(e.g.
300AB):The tire treadwear rating gives an approximate
idea of the expected usable life of the tire. A tire
rated 300 will probably last 50% longer than a tire
rated 200 under identical conditions. Note that since
each manufacturer rates tires by its own standards, 300
rated tires from two manufacturers may not provide
identical tread life. The traction rating (the first
letter) is the manufacturer’s rating of wet traction.
"A" is best, "C" is worst. The
letter gives some indication of the tire’s resistance
to hydroplaning (losing contact with the road at speed).
The temperature rating (the second letter) is the
manufacturer’s rating of the tire’s resistance to
heat build-up. "A" is best, "C" is
worst. Heat is the enemy of tires. The cooler the tire
temperature, the longer it will last. |
| Torque |
A
measure of the twisting force. Torque is measured in
lb.-ft. (pound-foot) or N-m
(Newton-meters).
The RPM at which the engine produces maximum torque is
important. For instance, if Engine A produces 200
lb.-ft. @ 3000 RPM, and Engine B supplies 200 lb.-ft. @
5000 RPM, then Engine A will accelerate better at low
speeds. Engine B will accelerate better at high speeds.
|
| Torque
Converter |
A
fluid coupling used in automatic transmissions to
transmit power from the engine to the wheels. The torque
converter allows the transmission to be engaged while
the vehicle is stopped. The transmission fluid absorbs
power and prevents engine stalling. |
| Torsion
Bar |
A
type of spring that twists as it is compressed or
stretched. Torsion bar springs are simple and rugged |
| Traction
Control |
A
general term for limiting wheel slip under acceleration.
Traction control systems usually apply brakes and reduce
throttle when wheel slip is detected. |
| Turbocharger |
A
type of supercharger that uses a turbine to drive a
compressor. The turbine, driven by hot gases in the
exhaust manifold spins the compressor. The compressor
increases the intake air density, and combined with
additional fuel, produces more power. |
| Twist
Beam Axle |
A
semi-independent axle often used on rear suspensions of
front-wheel drive vehicles. A horizontal beam connects
the two rear wheels together. The beam can twist to
reduce the effect of one wheel’s motion on the other
wheel. A twist-beam axle is less expensive than a fully
independent suspension. It is also more compact. |
| Understeer |
Understeer
occurs when the front wheels provide less steering than
desired in a given direction. Usually the front wheels
have lost adhesion and cannot steer effectively. This
results in the vehicle "pushing" ahead and
responding sluggishly to the steering wheel. Reducing
speed can allow the front wheels to regain traction.
Most vehicles are designed to exhibit understeer in
normal conditions, because it is easier to control than
oversteer. |
| Valves |
(e.g.
24 valves) Signifies the total intake and exhaust valves
in an engine. For example, a 24-valve V-6 would have 4
valves per cylinder: 24/6=4. A 16-valve V-8 would have 2
valves per cylinder: 16/8=2. More valves allow the
engine to breathe better at high RPM and produce more
power. |
| Water
Pump |
A
pump that circulates coolant within the engine block and
cylinder head. The water pump is driven by the engine
crankshaft. |
| Wheel
Size |
(e.g.
"15 X 7"): Wheel size is defined by the
diameter and width of the wheel. A "15 X 7"
wheel has a 15-inch diameter and a 7-inch width. |
