IDLE STABILIZATION
In order to overcome the increased friction in cold condition and to gurantee smooth idling, the engine recieves more air-fuel mixture during the warm-up phase due to the action of the auxillary air device.

IGNITION
The functionof the ignition system is to initiate combustion in the the compressed air/fuel mixture by igniting it at precisely the right instant. In the spark-ignition engine, this function is assumed by an electric spark in the form of a short duration discharge arc between the spark plug's electrodes.

IGNITION ADVANCE ANGLE CONTROL
A program map containing the basic ignition tining fo various engine loads and speeds is stored inthe memory of the M-Motronic ECU. This ignition advance angle is optimized for minimal fuel consumption and exhaust emissions.

IGNITION-ANGLE CALCULATION
The "reference ignition angle" is calculated based on the engine's current steady-state operating status. Its essential determinants are instaneous cylinder charge, engine speed, and mixture composition.

IGNITION COIL
an essential part of a engine’s ignition system. It consists of two wire coils wound around an iron core. The primary coil, which is connected to the car battery, has only a few turns. The secondary coil, connected via the distributor to the spark plugs, has many turns. The coil takes in a low voltage (usually 12 volts) from the battery and transforms it to a high voltage (about 15,000–20,000 volts) to ignite the engine.

IGNITION DISTRIBUTOR
The ignition distributor is the component of the ignition systme which performs most functions. It rotates at half the crankshaft speed. A4-cylinder distributor has, for instance, 4 outputs which each generate an ignition pulse each time the rotor turns.

IGNITION DRIVER STAGE
Ignition driver stages featuring multistage power transistors control the flow of primary current through the coil, replacing the breaker points found on earlier ignition systems.

IGNITION ENERGY
Approximately 0.2 mj of energy is required per individual ignition for igniting an air/fuel mixture by electric spark, providing the mixture has a stoichiometric composition. Rich and lean mixtures require over 3 mj. This amount of energy is but a fraction of the total energy contatined in the ignition spark, the ignition energy

IGNITION SYSTEM
Electrical system devised to produce timed sparks from engine spark plugs. Consisting of a battery, induction coil, capacitor, distributor, spark plugs and relevant switches and wiring.

IGNITION TIMING
Several mechanical parts (ignition spark plug, timing valves, fuel injectors) will work perfectly timed with the piston movement.

IGNITION VOLTAGE
The excess-air factor lambda and the cylinder pressure which is determined by charge and compression have, together with the spark-plug electrode gap, a crucial influence upon the required ignition voltage and, thus, upon the required secondary available voltage of the igntion system.

INDUCTIVE IGNITION SYSTEMS
The spark-ignition engins's inductive (coil) ignition system generates the high-tension voltage to provide the energy then employed to create an arc at the spark plug. While inductine ignition systems rely on coils to store ignition energy, an availbe alternative is storage in a condenser.

INERTIA
It is the resistance opposed by bodies to intensity variations (module) and/or to changes in their speed direction.

INLINE 4
An engine having four cylinders in a row.

INJECTED-QUANTITY COMPARSION TESTER
A comparitive measurement can be made to determine whether there are differences in the delivered quantities from the individual injectors. To do so, the injctors are pulled out of the intake manifold and connected to the comparsion tester. The triggering unit generates the electrical pulses needed to operate the injectors. The injected-fuel quantity from up to eight injectors can be compared in this manner.

INJECTION PULSES
The generation of the basic injection duration is carried out in a special circuit group in the ECU, the division control multivibrator. The divsion control multivibator (DSM) recieves the information on speed n from the frequency divider and evaluates it together with the air-quantity signal Us. For the purpose of intermittent fuel injection, the DSM converts the voltage Us into square-wave control pulses. The duration Tp of theis pulse determines the basic injection quantity, i.e. the quantity of fuel to be injected per intake stroke without considering any corections.

INJECTION VALVES
The injection valves open at agiven pressure and atomize the fuel through oscillation of the valve needle. The injection valves inject the fuel metered to them into the intake passage and onto the intake valves. They are secured in special holders to insulate them against the heat radiated from the engine. THe injection valves have no metering function themselves, and open their own accord when the opening pressure of e.g. 3.5 bar is exceede.

INJECTOR
Device used to feed fuel into the suction port, or alternatively, directly into the combustion chamber, as one or more jets suitably atomised and correctly directed.

INSTRUMENT CLUSTER
The instrument cluster is a plastic unit, which houses the vehicle’s monitoring devices. Such devices include the temperature gauge (or light), fuel gauge, speedometer, charging system gauge (or light), ABS Light, Brake Warning Light, or any other light or gauge that monitors a system necessary for the operation of a motor vehicle. The instrument cluster is mounted in the dashboard and can be removed as a separate unit from the vehicle. It is illuminated by small light bulbs that are fed by a printed circuit. These bulbs screw into the back of the cluster. When these bulbs burn out, you must remove the cluster from the vehicle in order to replace them.

Intake Charge
The mixture of fuel and air that flows into the engine.

INTAKE MANIFOLD
The network of passages that direct air or air-fuel mixture from the throttle body to the intake ports in the cylinder head. The flow typically proceeds from the throttle body into a chamber called the plenum, which in turn feeds individual tubes, called runners, leading to each intake port. Engine breathing is enhanced if the intake manifold is configured to optimize the pressure pulses in the intake system.

INTAKE MANIFOLD GEOMETRICS
Valve timing is not the only factor that shapes the gas-exchange process: Intake and exhaust-tract configuration are also vital. Periodic pressure waves are generated within the intake manifold during the cylinder's intake pstroke. These pressure waves proagate through the intake runners and are reflected at their ends. The idea is to adapt the length and diameter of the runers to the valve timing in such a way that a pressure peak reaches the intake valve just before it closes. This supplementary pressurization effect increases the mass of fresh gas entering the cylinder.

INTAKE OSCILLATION BOOST
Each cylinder has an individual, fixed length intake runner, usually connected to a plenum chamber. The energy balance is defined by a process in which the induction force from the piston is converted into kinetic energy int he gas column upstream form the intake valve. This kinetic energy then serves to compress the fresh charge.

INTAKE-TIMING CALCULATING
Cylinder-charge density can be used as the basis for claculating the fuel mass required to obtain a stoichiometric air-fule ratio. The injector constant, which varies according to injector design, can then be incorporated into the calculations to produce the injection duration.

INTERMITTENT INJECTION
The L-Jetronic, an electronic fuel-injection system with analog technology, intermittently injects the fuel as a function of the quantity of air drawn into the engine, the engine speed, and a number of other actuating variables. The L3 Jetronic is asystem which uses digital technology. This means that it can take over additional control functions which would otherwise have been impossible with analog technology, the overall result being that the injected fuel quantity is better adapted to the engine's various operating requirements.

IRONHEAD
The first generation of Sportster models (produced from 1957 until 1985). Unlike other models with nicknames that describe the look of the cylinder heads on particular engine ("Knucklehead", "Shovelhead", "Flathead", etc.), the Ironhead name comes from the fact that the cylinder heads on these models were cast iron whereas the heads on other models at that time were made of aluminum.