Presentation on theme: "Lambda Calculation from Exhaust Gas Measurements"— Presentation transcript:
1 Lambda Calculation from Exhaust Gas Measurements Determining how close the A/F ratio is to the stoichiometric point using exhaust gas analysis.Presented to East Bay ATA, Hayward, CAMay 5, 2004By: Robert J. Schrader President, Bridge Analyzers, Inc.
3 Why is Lambda Important? Lambda control is necessary for peak combustion efficiency in the Engine.Lambda control is necessary for peak CAT efficiency.Lambda Control Improves Reliability, Fuel Economy and Lowers Emissions.
4 Combustion Efficiency (CE) Engine out CE for Gasoline Fuel is no better than 95%.Tailpipe-out CE for CAT equipped vehicles improves to %.Factor of 10 improvementRequired for Current Emission StandardsCAT CE is very Lambda-Dependent
8 3-Way CAT vs Lambda NOx Reduction Bed CO/HC Oxidation Bed Requires Lambda to be not greater thanCO/HC Oxidation BedRequires Lambda to be not less thanModulation DepthCycles Rich and Lean Between the Limits Above.
9 Brettschneider Equation - a balance equation that calculates Lambda
10 Calculating A/F Ratio from Lambda Lambda = when the Oxygen available and Combustible Oxygen demands are in balance.This is the point of perfect stoichometric balance.At this point the A/F ratio is to 1.00 for Gasoline.Thus, A/F = x Lambda
11 Sensitivity to Combustion Efficiency (Pre CAT vs Post CAT) Brettschneider Lambda uses all the oxygen-bearing and combustible-bearing gases.Balance Equation - Calculation not affected by the degree of oxidation.Method is insensitive to combustion efficiency.Either Pre-CAT or Post-CAT gases may be used.
12 Lambda for Emissions Control = when Oxygen available and Combustible demands are in balance.ECM controls =1.000 at Cycles/Sec using ‘lambda sensor’ input.3-Way CAT operation requires to 1.020Lambda can be confirmed by exhaust gas measurement, either pre or post CAT.
13 Lambda for Fuel Control Diagnostics calculated from exhaust gas indicates air-fuel mixture independent of the engine controls. calculated from exhaust gas indicates air-fuel mixture independent of combustion efficiency.Cold (Open Loop) vs Hot (Closed Loop) vs CAT light-off operation can be evaluated. can be used to tune systems which do not have closed-loop control.
14 Qualifying EGA gas tightness prior to Lambda Calculation High Combustion Efficiency: Measure O2 post CAT - every 5% air leak adds 1.0% O2 to gases.Low Combustion Efficiency: Add CO and CO2 - should equal 15% for Gasoline.Compare both Methods. If O2 indicates air dilution - then confirm this with low CO and CO2 sum. They should agree.
15 iATN Lambda Calculator Created by iATN Tech Support staff, and available to iATN members on-line atPlug and Play either 4 or 5 gas values.Can select either US or European gasoline constants.Operates in Java - can be saved and run off-line by any Java-equipped net browser.
16 Bridge Excel Worksheet Available as attached Excel file by contacting:Plug and Play either 4 or 5 gas values.Can select either US or European gasoline constants.Operates on any PC with Excel - can be saved and run off-line using Microsoft Excel.
17 iPaq Palm Computer Worksheet Written by Miles Wada using the Brettschneider equation - a’la Bridge.Available for download at:Operates on the iPaq using CE Excel.Can operate on other CE-based units.
18 Palm Computer Worksheet in Excel. Written by Greg Meyer using the Brettschneider equation - a’la Bridge.Available from Greg via at:Operates on Palm OS computers in Excel.