Operating Instructions - Snap-on Equipment

InterpretationLambda and AFR CalculationThe FGA Gas Analyzer uses the Brettschneider formula to calculate Lambda (λ)and Air Fuel Ratio (AFR) values during the emission tests.Lambda (λ) and Catalytic Converter EfficiencyLambda is another characterization of the stoichiometric perfect combustion point.The λ formula includes a factor for the specific fuel used. Different fuels havedifferent stoichiometric air-fuel ratios, but optimal combustion is always achievedwhen Lambda = 1.00. Smaller λ numbers indicate a rich air-fuel ratio; larger λnumbers indicate a lean air-fuel ratio.The figure below shows the relationship between certain pollutant exhaust gasesand catalytic converter efficiency. Optimal combustion (λ = 1) is characterized by ahighly-efficient conversion of the pollutants HC, CO, and NO x into CO 2 , H 2 O, and N 2 .Figure 5-3: Relationship Between Certain Pollutant Exhaust Gases and Catalytic Converter EfficiencyO 2 and NO x MeasurementO 2 and NO x gas concentration are measured using electrochemical (fuel cell)sensors. A fuel cell sensor provides an electrical response that is proportional tothe concentration of the sample gas.5-8