IDLE STABILIZATION In order to overcome the increased friction in cold condition and to guarantee smooth idling, the engine receives more air-fuel mixture during the warm-up phase due to the action of the auxiliary air device.
IGNITION ADVANCE ANGLE CONTROL A program map containing the basic ignition timing for various engine loads and speeds is stored in the 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 instantaneous cylinder charge, engine speed, and mixture composition.
IGNITION DISTRIBUTOR The ignition distributor is the component of the ignition system which performs the most functions. It rotates at half the crankshaft speed. A 4-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 TIMINGSeveral 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 ignition system.
INERTIAIt is the resistance opposed by bodies to intensity variations (module) and/or to changes in their speed direction.
INLINE 4An engine having four cylinders in a row.
INJECTED-QUANTITY COMPARSION TESTER A comparative measurement can be made to determine whether there are differences in the delivered quantities from the individual injectors. To do so, the injectors are pulled out of the intake manifold and connected to the comparison 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 multi-vibrator. The division control multi-vibrator (DSM) receives the information on speed.
INJECTION VALVES The injection valves open at a given 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 exceeded.
INJECTORDevice used to feed fuel into the suction port, or alternatively, directly into the combustion chamber, as one or more jets suitably optimized and correctly directed.
INTAKE CHARGEThe mixture of fuel and air that flows into the engine.
INTAKE-TIMING CALCULATING Cylinder-charge density can be used as the basis for calculating the fuel mass required to obtain a stoichiometric air-fuel ratio. The injector constant, which varies according to injector design, can then be incorporated into the calculations to produce the injection duration.
INTERMITTENT INJECTIONThe 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 a system 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.
IRONHEADThe 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.