Self-Adjustment Of Mixture Formation, Basic Function - GF07.10-P-1055A
Engine 139, 176, 177, 254, 256, 260, 264, 274, 279, 282
Engine 177, 256
Example illustration of the shifting of the lambda characteristics map
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 λ 1) the injection duration must be adjusted The injection duration is determined from the characteristics map depending on he 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