POWER SPORTS and ELECTRONIC FUEL INJECTION GLOSSARY
Specific systems for specific markets have in the meantime been developed on the basis of the L-Jetronic. These systems include the LE-Jetronic without lambda closed-loop control for Europe and the LU-Jetronic system with lambda closed-loop control for countries with strict exhaust gas emission legislation. The most recent stage of development is the L3-Jetronic which differs from its predecessors.
Eleventh letter of the Greek alphabet, used in some countries to express the ratio between the air quantity actually used and that is theoretically necessary to make the air-fuel mixture to feed to the engine.
LAMBDA CLOSED-LOOP CONTROL
The lambda sensors supply a signal which represents the instantaneous mixture composition. In the control unit, the signal of the lambda sensors is compared with an ideal value, thus controlling a two-position controller. Dependent upon the result of comparison, either an excessively lean air-fuel mixture is enriched or an excessively rich mixture is leaned. Fuel metering is influenced via the opening time of the injection valves.
LAMBDA CLOSED-LOOP CONTROL TESTER
On L-Jetronic systems with lambda closed-loop control, this tester serves to check the integrator voltage, the lambda sensor signal, and the open-loop/ closed-loop control function. Special adapter lines are available for connection to the lambda-sensor cable of the various vehicle models. Measured values are shown on an analog display.
LAMBDA OXYGEN SENSOR
The oxygen sensor is a dual-threshold unit capable of indicating both rich and lean mixtures. The radical transitions, which characterize this sensor's response curve, facilitate mixture adjustment to achieve an optimum air-fuel ratio.
LAMBDA PROGRAM MAP
The Lambda Program Map is used for precise adaptation of the air-fuel ratio at all static operating points once the engine is warm. This map is stored electronically in the digital circuit section of the ECU. The reference data is determined empirically through tests on an engine dynamometer.
Because the lambda sensor's response pattern varies depending upon the direction of the monitored mixture transition, a symmetrical control arrangement would produce the slightly lean exhaust mixture. Because catalytic converter efficiency is optimal in the lambda=0.99...1.0 range, the control system must be able to counteract this tendency. An asymmetrical controller oscillation pattern can shift the mixture into the optimal conversion range.
Environmental considerations dictate that leaded fuels be used exclusively in those engines with exhaust valves that require the combustion products of lead-alkyl compounds for lubrication. This basically applies only to a small number of older vehicles and sales of leaded gasoline are decreasing steadily.
This definition applies to engines whose cylinders can be fed much leaner air-fuel mixtures than those used in traditional engines.
Pollutant reduction based on the catalytic converter is an external process without any direct influence on the engine's internal combustion process. Yet another strategy relies on modifying internal processes by focusing on such factors as combustion-chamber design, valve timing, exhaust-gas recirculation, compression ratio, ignition timing and air-fuel ratios.
Lambda has been selected to identify the excess-air factor used to quantify the spread between the actual current mass Air/Fuel ratio and the theoretical optimum (14.7:1). A lean mixture yields an Air/Fuel ratio which is higher than the theoretical optimum, i.e. 15.5:1 is a lean mixture.
The LH-Jetronic is closely related to the L-Jetronic. The difference lies in the hot-wire air-mass meter which measures the air mass inducted by the engine. The result of measurement is thus independent of the air density which is itself dependent upon temperature and pressure.
The L-Jetronic is an electronically controlled fuel-injection system which injects fuel intermittently any form of drive. It combines the advantages of direct air-flow sensing and the special capabilities afforded by electronics.