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 are
O2for 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
on
cen
trati
on
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
on
cen
trati
on
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 1.050
0
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
HC CO CO2 NO O2Fail 92 0.55 716GP 281 2.05 1,961AVG 21 0.06 150
NOx Case ScenarioLambda Calculator
Case Study
December 1993 Mazda Protege 1.8L, Manual Trans, No
EGR Passed & Certified
Post Repair Certification
ASM 5015Result HC CO CO2 NO O2 RPMPass 74 0.21 15.5 308 0.08 1590
Standards
HC CO CO2 NO O2Fail 92 0.55 716GP 281 2.05 1,961AVG 21 0.06 150
NOx Case ScenarioLambda Calculator