Lambda Calculation from Exhaust Gas Measurements

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

2. What is Lambda? • Lambda is Oxygen Balance

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 99.0-99.5%. • Factor of 10 improvement • Required for Current Emission Standards • CAT CE is very Lambda-Dependent

5. Engine-Out Gas Values

6. CAT Oxidation and Reduction Efficiency vs Lambda

7. CAT Out Gases

8. 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.

9. Brettschneider Equation- a balance equation that calculates Lambda

10. 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

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 •  = 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.

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 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.

16. 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.

17. iPaq 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 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 email at: gsmeyer@attbi.com • Operates on Palm OS computers in Excel.

19. A/F Ratio From Lambda A/F = 14.71 x Lambda