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Air-fuel ratio, lambda and engine performance – x-engineer.org
ECU Lambda mapping FAR is known as plus or minus FAR(ideal)...
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We have seen what is and how to calculate the stoichiometric (ideal) air-fuel ratio. In reality, internal combustion engines do not work exactly with ideal AFR, but with values close to it. Therefore we’ll have an ideal and a actual air-fuel AFR. The ratio between the actual air-fuel ratio (AFRactual) and the ideal/stoichiometric air-fuel ratio (AFRideal) is called equivalence air-fuel ratio or lambda (λ).λ=AFRactualAFRideal(3)For example, the ideal air-fuel ratio for a gasoline (petrol) engine is 14.7:1. If the actual/real AFR is 13.5, the equivalence factor lambda will be:λ=13.514.7=0.92Depending on the value of lambda, the engine is told to work with lean, stoichiometric or rich air-fuel mixture.Depending on the type of fuel (gasoline or diesel) and the type of injection (direct or indirect), an internal combustion engine can function with lean, stoichiometric or rich air-fuel mixtures.
Equivalence factor Air-fuel mixture type Description λ < 1.00 Rich There is not enough air to burn completely the amount of fuel; after combustion there is unburnt fuel in the exhaust gases λ = 1.00 Stoichiometric (ideal) The mass of air is exact for a complete combustion of the fuel; after combustion there is no excess oxygen in the exhaust and no unburnt fuel λ > 1.00 Lean There is more oxygen than required to burn completely the amount of fuel; after combustion there is excess oxygen in the exhaust gases
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