VVC AUTO 85.5 - Smog Technician - Level 1 - Lambda

LAMBDA CALCULATION FROM EXHAUST GAS MEASUREMENTS

Determining how close the A/F ratio is to the stoichometric point

using exhaust gas analysis.

Presented to East Bay ATA, Hayward, CAMay 5, 2004

By: Robert J. Schrader President, Bridge Analyzers, Inc.

What is Lambda?

point. ricstoichometperfect the- balancein areO2for Demand eCombustibl and O2 when 1.000 toequal is Lamdba

oxidation. completeattain toO2for Demand eCombustibl the vsProcess Combustion the toavailable O2 of ratio theis Lambda

)( OxygenfordemandesCombustibl

availableOxygenLambda

• 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

0.00

0.50

1.00

1.50

2.00

2.50

3.00

3.50

4.00

0.90 0.91 0.92 0.93 0.94 0.95 0.96 0.97 0.98 0.99 1.00 1.01 1.02 1.03 1.04 1.05 1.06 1.07 1.08 1.09 1.10

Lambda

% C

once

ntra

tion

CO - Carbon Monoxide

H2 - Hydrogen

O2 - Oxygen

11.00

11.50

12.00

12.50

13.00

13.50

14.00

14.50

15.00

15.50

16.00

0.90 0.91 0.92 0.93 0.94 0.95 0.96 0.97 0.98 0.99 1.00 1.01 1.02 1.03 1.04 1.05 1.06 1.07 1.08 1.09 1.10

Lambda

% C

once

ntra

tion

CO2 - Carbon Dioxide

CAT Oxidation and Reduction Efficiency vs Lambda

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

0.950 0.960 0.970 0.980 0.990 1.000 1.010 1.020 1.030 1.040 1.050

Oxidation Efficiency

Reduction Efficiency

CAT Out Gases

0.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35

0.40

0.45

0.50

0.950 0.960 0.970 0.980 0.990 1.000 1.010 1.020 1.030 1.040 1.0500

100

200

300

400

500

600

700

800

900

1000

H2 - Hydrogen

NOx - Oxides of Nitrogen

CO - Carbon Monoxide

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

point. ricstoichometperfect the- balancein are demand eCombustibl and O2 when 1.000 toequal is Lambda

oxidation. completeattain toO2for demand ecombustibl the toO2) (as availableOxygen of ratio theas calculated is Lambda

)(OxygenfordemandeCombustibl

availableOxygenLambda

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 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.

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 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.

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.

Bridge Excel Worksheet

Available as email attached Excel file by contacting: [email protected]

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.

iPaq Palm Computer Worksheet

Written by Miles Wada using the Brettschneider equation - a’la Bridge.

Available for download at: http://www.aeswave.com/

Palm Computer Worksheet in Excel.

Written by Greg Meyer using the Brettschneider equation - a’la Bridge.

Available from Greg via email at: [email protected]

Operates on Microsoft PC in Excel.

A/F Ratio From Lambda

A/F = 14.71 x Lambda

Case Study September 1993 Mazda Protege 1.8L, Manual Trans, No

EGR Failed Smog Check for

Timing (FA99), GP HC & NOx

Initial Failing Inspection (GP)

ASM 5015Result HC CO CO2 NO O2 RPMGP 247 0.49 13.8 2000 1.2 1624

Standards

HC CO CO2 NO O2Fail 92 0.55 716GP 281 2.05 1,961AVG 21 0.06 150

NOx Case ScenarioLambda Calculator

Case Study November 1993 Mazda Protege 1.8L, Manual Trans, No

EGR Failed its Pre-repair

Baseline Inspection at a CAP station for for Timing (FB48), HC & NOx

Pre-repair Baseline (GS)

ASM 5015Result HC CO CO2 NO O2 RPMFail 186 0.43 16 1095 1 1683

Standards



Case Study December 1993 Mazda Protege 1.8L, Manual Trans, No

EGR Passed & Certified

Post Repair CertificationASM 5015

Result HC CO CO2 NO O2 RPMPass 74 0.21 15.5 308 0.08 1590

Standards



Automotive

VVC AUTO 85.5 - Smog Technician - Level 1 - Lambda