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Discussion and questions related to the course Understanding AFR
Your tips about the lambda targets are being very useful to me.
However, I still have two doubts in my head: the target lambda values you recommend in class, can be considered for pump gas and E85? Or should I take into account the fact that the stoichiometric AFR of E85 being less than gasoline, use target lambda values slightly richer than those recommended here? For example: at 1 bar, instead of using 0.80 when pump gas, use 0.77 or 0.78 when E85.
My second doubt is: here in brazil, being common the use of E100, and if we consider this rule that I quoted above, being the stoichiometric value of E100 of 9:1, should I consider lambda values richer than the ones you recommend?
Lambda is always the same whatever fuel you are using.
Its AFR that varies dependant on fuel type. AFR = Lambda * Fuels Stoichmetric Ratio.
Rob, you did not understand what I meant. I know the relationship between AFR and lamnda. I mean like this: 0.80 at medium boost is the most recommended for both pump gas and E100? The cooling power of both and/or other characteristics as energy eficiency of both does not make it necessary for each type of fuel force us to have a richer value of lambda specific for each fuel? An example cited by Andre is in the case of methanol, which must be rich enough to arrive at a lambda of 0.68. See that the recommended lambda E100/gas pump are quite different than for methanol when on positive pressures.
I actually find that ethanol blends respond well at pretty similar lambda targets to pump gas. The reality is that often on E85 you can tune slightly leaner because we don't need to rely on excessively rich mixtures in order to keep the engine safe.
Andre, thanks for your response, was very enlightening.