| Idler
gear |
A
universal term for a gear that is positioned between two other gears
so that when the idler gear is switched between the gears, causes
the direction of one gear to be reversed. Common example is a "reverse"
gear used in transmissions. |
|
|
| Idle
speed |
The
low speed a motor runs at when in neutral and throttle fully closed.
|
|
|
| I-4 |
A
term sometimes applied to inline four cylinder engines. Not a "V"
motor. I-6 can be used to describe an inline 6 cyl. |
|
|
| IFS |
An
abbreviation for Independent Front Suspension. |
|
|
| Ignition |
See
Ignition system. |
|
|
| Ignition
coil |
See
Coil. |
|
|
| Ignition
cutout |
Same
as Rev limiter. See Rev limiter. |
|
|
| Ignition
points |
A
mechanical switching device used to send electricity to spark plugs
that was used in mechanical ignition systems until the mid 1970's.
At the end of a set of breaker points are a set of electrical contacts
which open/close in conjunction with a turning cam in the distributor.
When the points are closed, the energy field of the primary windings
collapses and is transferred to the secondary coils of the ignition
coil (which steps up it's voltage proportional to the difference
in windings between the two coils). The high voltage is sent to
the distributor cap and ultimately a spark plug. It's voltage is
enough to jump the gap at the end of a spark plug and ignite an
air/fuel charge.
The
gap between the electrical contacts on the points is critical. If
the gap is too wide, the timing will be retarded. If the gap is
too narrow, the timing will be advanced. A dwell meter and a set
of feeler gauges should be used to set the proper gap. The contact
surfaces of the points wear out from the effects of continued electrical
arching and require periodic adjusting and replacing.
Ignition
points were replaced by an electronic ignition module which switches
the coil electronically rather than mechanically.
|
|
|
| Ignition
switch |
A
key-operated switch usually mounted on the steering column or dash
for use of starting and shutting off the engine and accessories. The
ignition switch is wired between the battery and the ignition system
and the battery and the starter motor. |
|
|
| Ignition
system |
A
system that produces a "spark" at the spark plugs at the
proper time which ignites the air/fuel mixture in the combustion chamber.
Components of an ignition system include the distributor (or distribution
block), coil, battery, wires and spark plugs. |
|
|
| Ignition
timing |
The
production of spark plug's "spark" at the precise time for
optimal power output. The spark must ignite the air/fuel mix when
the piston is at a specific point at the top of it's travel on the
compression stroke. The position is measured by the number of degrees
(measured in crankshaft rotations) TDC during it's compression stroke.
|
|
|
| Illuminated
entry |
Interior
lamps which come on when the door is opened. Allows easier access
to occupants. Many luxury models have a feature in which interior
lamps and miniature lamps near the door lock illuminate when the door
handle is pushed or pulled. The lamp near the door lock makes it easier
to unlock the car door at night. Also see Keyless entry. |
|
|
| AMP |
See
Indicated Mean Effective Pressure. |
|
|
| Impeller |
The
main rotating device used in pumps to circulate fluid and produce
pressure. Looks like a wheel or disc with vanes that protrude from
the center. Commonly found inside automatic transmission torque converters
and water pumps. |
|
|
| Inboard
brakes |
Brake
discs or drums which are located near the center of the vehicle rather
than near the wheels. Such brake systems are widely used on Formula
and Indy-type race cars and production high-performance vehicles.
The brake discs are typically mounted to inner edge of axles or half-shafts
near the differential (rear). Reduced unsprung weight is the primary
benefit. |
|
|
| Inclinometer |
A
gauge installed in some four-wheel-drive vehicles which indicates
the it's sideways and fore-and-aft angle. Useful when making extreme
maneuvers to prevent a rolling over. Also a popular aftermarket add-on
accessory. |
|
|
| Independent
suspension |
A
suspension design used on front or rear wheels where each pair of
wheels is sprung independently of the other. When one wheel encounters
a bump, the other wheel is not affected. All modern automobiles use
independent front suspension. Independent rear suspension is widely
used on modern vehicles, especially passenger cars, because it reduces
unsprung weight and provides a smoother ride and usually better handling. |
|
|
| Indicated
horsepower |
The
theoretical power output of an engine (HP/torque) by looking at it's
cylinders calculated from the indicated mean effective pressure. Power
output doesn't take friction and power usage into consideration so
this measurement is always higher than brake horsepower. |
|
|
| Indicated
mean effective pressure (IMEP) |
The
average of pressures developed inside a cylinder during one complete
combustion cycle (intake, compression, power, exhaust). IMEP is used
to calculate indicated horsepower and torque. |
|
|
| Indicated
torque |
See
Indicated horsepower (above). |
|
|
| Induction
coil |
See
Coil. |
|
|
| Induction
stroke |
Same
as intake stroke. See Intake stroke. |
|
|
| Induction
system |
The
system that produces and delivers an air/fuel mixture to an engine's
cylinders. The carburetor (Fuel injection system on EFI vehicles),
intake manifold, intake valves and intake ports are parts of the induction
system. |
|
|
| Inertia |
The
tendency of a body or object to remain in motion, when in motion,
or, if still, the tendency to remain still unless affected by some
outside force. Outside effort is required to start, stop or change
direction of a body already in motion. |
|
|
| Inertia
reel |
The
part of the seat belt that locks the shoulder strap (or lower strap)
when a high rate of deceleration, or angular acceleration occurs. |
|
|
| Inertia
switch |
A
switch activated by a certain amount of inertial change that turns
on or off another device. Inertia switches are used to turn off fuel
pumps in fuel injected vehicles to prevent a fire in case of a collision.
Inertia switches are also positioned on front bumpers or other locations
of a vehicle's front end to trigger air bags in the event of an accident. |
|
|
| Indefinitely
variable transmission |
See
Continuously variable transmission. |
|
|
| Inflation
pressure |
The
pressure of air inside a tire. A tire's proper inflation pressure
is labeled on the tire. Always check the vehicle owners manual for
special pressure ratings. Common passenger car tires are typically
rated at 35 psi. High performance tires and some truck tires can require
as much as 60 psi or more. |
|
|
| Injected |
A
term used to describe a fuel injected motor. |
|
|
| Injector
|
A
device used in fuel injection systems to spray a metered amount of
fuel into the airstream to produce a specific air/fuel ratio. The
air/fuel charge is then burned in the engine's cylinders. Injectors
are typically electromechanically switched by an onboard computer
to adjust fuel amounts in order to compensate for different engine
speeds. |
|
|
| In-line
engine |
An
engine that has all of it's cylinders aligned in one row. A motor
called a "straight six" would have all six cylinder in one
row rather than a "V" shape. Also called an "I"
engine (e.g.. I-6 for six cylinder). |
|
|
| Input
shaft |
A
shaft that receives power and drives other gears or devices. For example,
a transmission has an input shaft which drives other gears. |
|
|
| Insert |
A
type of sleeve bearing that contains no rollers or balls. Used in
engines for connecting rods.
Can
also be a replacement bearing or bushing which adapts to a worn
part to allow an original part to fit snug with a worn part.
Also,
valve guide replacements or hardened valve seat replacements (often
installed on older motors that were designed for leaded gasoline).
|
|
|
| Inside
diameter (ID) |
A
measurement of the maximum span of the inner walls of an object or
bore. |
|
|
| Inside
hood/trunk release lever |
A
lever or pull handle remotely located inside the passenger compartment
that releases the hood or trunk latch. The handle is |
|
|
| Instrument
cluster |
A
collection of gauges or instruments mounted in the dashboard in front
of the driver, e.g.. oil pressure, coolant temperature, voltage, speed.
Also called Gauge cluster or Instrument panel. |
|
|
| Instrument
panel |
An
assembly often referred to as the "dashboard" that mounts
to the firewall in front of the passengers below the windshield. The
instrument panel contains the instrument cluster, gauges, and often
the radio and cooling vents. Also commonly called a Dash. |
|
|
| Intake
manifold |
A
primary engine component made of cast iron or aluminum usually mounted
near the top of the motor and consists of passages or "runners"
that lead to each cylinder. The the air/fuel mix travels through the
runners to the cylinders. |
|
|
| Intake
ports |
Passages
in the cylinder head where the air/fuel mixture flows from the intake
ports (runners) to the intake valve. |
|
|
| Intake
stroke |
The
first stroke in a four-stroke combustion cycle where the intake valve
is open and the piston moves downward from it's uppermost position
(TDC) to the lowest point in it's travel (BDC) creating a partial
vacuum that draws in an air/fuel mixture. Also sometimes referred
to as the Induction stroke. |
|
|
| Intake
valve |
A
valve that opens to allow an air/fuel mixture into the engine's cylinder.
Once the air/fuel mix has entered the cylinder, the intake valve closes
and forms part of the combustion chamber. Precise timing of the valves'
opening/closing is controlled by the camshaft, which is driven by
the crankshaft. |
|
|
| Integral
valve seat |
A
valve seat which is a machined into the cylinder head and does not
have an additional hardened valve seat pressed in. Integral valve
seats are often used in cast iron heads because it reduces machining
costs. The metal can be locally heat treated for greater hardness.
Aluminum heads always require hardened inserts. Due to the phase-out
of leaded gasoline, classic car cylinder heads that used integral
valve seats are often machined and retrofitted with hardened valve
seats so they can operate using unleaded fuel without damaging the
valve seats. |
|
|
| Intercooler |
An
induction technique used to increase an engine's output. A small heat
exchanger (a small radiator) is placed in the air induction stream
which lowers the temperature of incoming air from turbochargers. The
lower air temperatures results in a denser air/fuel mixture which
is more explosive when it burns therefore leading to increased power.
Using an intercooler also allows engineers to design motors with other
performance characteristics such as using higher compression ratios
and more advanced spark timing. |
|
|
| Interior
lamp dimming |
A
system where interior lamps automatically dim before shutting off.
A courtesy feature offered on many vehicles that allows the occupants
eyes to adjust to the dark, rather than turning off interior lights
'cold'. |
|
|
| Interior
noise |
The
level of sound in a vehicle's passenger compartment, measured in decibels
(on the A scale "dbA"). Factors that can lead to higher
sound levels inside an automobile are: vibration, hum, road noise,
exterior wind noise, loud tires engine and exhaust noise. Careful
designing and engineering and the use of undercoating and sound deadener
can isolate and reduce most noises and prevent them from entering
the passenger compartment. |
|
|
| Intermediate
gear |
Transmission
gears between the highest and lowest gears. In a four-speed transmission
it would be gears two and three. |
|
|
| Internal
combustion engine (ICE) |
An
engine that burns fuel within itself and produces power from it's
combustion. All automotive engines (and other common engines) are
internal combustion engines. An air/fuel mixture is burned in cylinders,
which is converted into mechanical energy by pistons and the crankshaft.
Even rotary engines such as produced by Mazda and Ferrari are internal
combustion engines.
In
a related note, the difference between and engine and a motor is
that an engine produces it's own power, while a motor produces power
from an external power source (usually electricity). Although engine
and motor are often used interchangeably.
|
|
|
| Interrupter |
Another
term for cutout. See Cutout. |
|
|
| Involute
gear teeth |
Gear
teeth that are cut in a slightly rounded fashion so when the teeth
mesh, the meshing action is of a "rolling" nature rather
than "sliding" nature. This reduces friction and prolongs
gear life. Almost all gears used in automobiles have involute teeth.
|
|
|
| (IRS) |
Short
for Independent rear suspension. See Independent rear suspension. |
