Engine AFR & Lambda Converter
Calculate true Air/Fuel Ratios and Lambda equivalents for custom fuel blends (E85, Methanol, Pump gas).
Mass of air per 1 unit of fuel
Universal ratio (1.0 = Stoich)
Emissions/Cruise Optimal (14.7 AFR eq)
Wideband Display Myths
An oxygen sensor physically reads Lambda. Most generic gauges multiply that Lambda value by 14.7 internally to display an "AFR" because people are used to gasoline numbers.
If you put E85 in your tank without reflashing the car, and the gauge reads "14.7", it means Lambda is 1.0. It does NOT mean the engine is currently burning 14.7 lbs of air to 1 lb of E85 (stoich E85 is 9.77 AFR).
Chemistry
Stoichiometric: The exact point where all oxygen is burned and all fuel is consumed. (Lambda 1.0)
Lambda: (Actual AFR) ÷ (Stoichiometric AFR).
A Lambda of 0.85 on Gas = 12.5 AFR.
A Lambda of 0.85 on E85 = 8.3 AFR.
In both cases, you tune the EMS table to target λ = 0.85.
Disclaimer & Legal Notice
All tools and calculators provided by Lapsite are for informational and educational purposes only. While we strive for mathematical precision, these results are approximations and should not be used as the sole basis for critical engineering, financial, or safety decisions. Lapsite Ltd and its creators provide no warranty, express or implied, regarding the accuracy or fitness of these calculations for any specific use.Always double-check calculations independently, especially for safety-critical components such as brakes, suspension, or structural changes. By using these tools, you agree that Lapsite Ltd is not liable for any mechanical failure, financial loss, or injury resulting from the use of this data.
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