Lambda Calculation from Exhaust Gas Measurements Determining how

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, CA May 5, 2004 By: Robert J. Schrader President, Bridge Analyzers, Inc.

What is Lambda? • Lambda is Oxygen Balance

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.

Combustion Efficiency (CE) • Engine out CE for Gasoline Fuel is no better than 95%. • Tailpipe-out CE for CAT equipped vehicles improves to 99. 0 -99. 5%. – Factor of 10 improvement – Required for Current Emission Standards – CAT CE is very Lambda-Dependent

Engine-Out Gas Values

CAT Oxidation and Reduction Efficiency vs Lambda

CAT Out Gases

3 -Way CAT vs Lambda • NOx Reduction Bed – Requires Lambda to be not greater than 1. 020. • CO/HC Oxidation Bed – Requires Lambda to be not less than 0. 980. • Modulation Depth – Cycles Rich and Lean Between the Limits Above.

Brettschneider Equation - a balance equation that calculates Lambda

Calculating A/F Ratio from Lambda • Lambda = 1. 000 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 14. 71 to 1. 00 for Gasoline. • Thus, A/F = 14. 71 x Lambda

Sensitivity to Combustion Efficiency (Pre CAT vs Post CAT) • Brettschneider Lambda uses all the oxygenbearing 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.

Lambda for Emissions Control • = 1. 000 when Oxygen available and Combustible demands are in balance. • ECM controls =1. 000 at 0. 5 -1. 0 Cycles/Sec using ‘lambda sensor’ input. • 3 -Way CAT operation requires 0. 980 to 1. 020 • Lambda can be confirmed by exhaust gas measurement, either pre or post CAT.

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.

Qualifying EGA gas tightness prior to Lambda Calculation • High Combustion Efficiency: Measure O 2 post CAT - every 5% air leak adds 1. 0% O 2 to gases. • Low Combustion Efficiency: Add CO and CO 2 - should equal 15% for Gasoline. • Compare both Methods. If O 2 indicates air dilution - then confirm this with low CO and CO 2 sum. They should agree.

i. ATN Lambda Calculator • Created by i. ATN Tech Support staff, and available to i. ATN members on-line at http: //members. iatn. net/tech/lambda. html • Plug 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.

Bridge Excel Worksheet • Available as email attached Excel file by contacting: support@bridgeanalyzers. com • 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.

i. Paq Palm Computer Worksheet • Written by Miles Wada using the Brettschneider equation - a’la Bridge. • Available for download at: http: //www. aeswave. com/ • Operates on the i. Paq using CE Excel. • Can operate on other CE-based units.

Palm Computer Worksheet in Excel. • Written by Greg Meyer using the Brettschneider equation - a’la Bridge. • Available from Greg via email at: gsmeyer@attbi. com • Operates on Palm OS computers in Excel.

A/F Ratio From Lambda A/F = 14. 71 x Lambda