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# air to fuel ratio

### EFI Tuning Fundamentals

Discussion and questions related to the course EFI Tuning Fundamentals

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Guy's in the video AFR . I can't understand lambda in those short words . And in the calcuation where did the 12.5:1 came from . Is that a readind based on a dyno pull ?

I'll try to explain better:

Lambda is a measurement that is always relative to the stoichiometric AFR of a particular fuel. For example on pump gas with a stoich value of 14.7:1, if we are running with a measured AFR of 14.7:1 then the lambda value would be 1.00 (14.7/14.7 = 1.00).

The way to convert from AFR units to lambda is: Lambda = Measured AFR / Stoichiomteric AFR

If for example the engine was running on pump gas with a measured AFR of 12.5:1, then lambda would be 12.5/14.7 = 0.85

If you want to convert the other way, simply multiply the lambda value by the stoichiometric AFR for the particular fuel. For example if we have a measured lambda value of 0.95 and the stoichiometric AFR is 14.7:1, the AFR would be: 0.95 * 14.7 = 13.97:1

I trust this makes things easier to understand.

Hi,

I am using NTK wideband AFR sensor with HKS AFK I, Is there any configuration to convert the value reading of AFR to Lambda in the ECU "AEM, G4 or Haltech" ? or I need to buy special gauge to read in Lambda.