Shifting of the lambda characteristics map |
a | Controlled range of Lambda control factor |
b | Shifting of the lambda characteristics map |
c | Position of lambda characteristics map prior to self-adjustment |
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Overview
This document contains information on:
General
Function requirements
Function
General
The composition of the fuel/air mixture for combustion engines is defined by the combustion air ratio λ (lambda). The combustion air ratio λ (lambda) describes the mass ratio of air and fuel. Spark-ignition engines are usually operated with λ = 1, i.e. a ratio of 14.7 kg of air to 1 kg of fuel. For diesel engines, the ratio is 14.5 kg of air to 1 kg of fuel, i.e. λ = 1.3. The mass ratio changes depending on the load case. At λ < 1, the air mass part is reduced while the fuel mass remains the same, making the mixture richer. In the case of a lean mixture, the air mass part is increased while the fuel mass remains the same, and λ > 1. The self-adjustment controls and regulates the mass ratio. The combustion engine control unit evaluates the signals of the lambda sensor for this purpose. If the fuel/air mixture is adjusted frequently, the lambda characteristics map is moved accordingly.
Function requirements
Lambda control active
Engine idling or partial-load range
Function
If the mixture composition fluctuates too frequently from the middle controlled range (lambda 1), the injection duration must be adjusted. The injection duration is determined from the characteristics map depending on the operating states (engine speed and throttle valve angle/pressure in the charge-air distributor). The combustion engine control unit then moves the lambda characteristics map until the lambda control factor is approx. 0. The lambda characteristics map is stored in the combustion engine control unit.