InfrareV

Let's say for the sake of argument you're hitting .8 lambda with gasoline. How would you go about calculating what your lambda would be with a fuel change to say E85 given you're injecting the same amount of fuel? Do you suppose cross multiplication is applicable?

Maybe:

(1/(1+14.7))/0.8 = (1/(1+9.76))/X

This gives you 1.167, which is maybe in the ballpark? You'll obviously go lean if you don't add any fuel.

The math sort of works, but I'm not sure I buy it.

Edit: Also I'm under the impression E85 is denser then gasoline? Surely that needs to be taken into account?

Maybe:

(1/(1+14.7))/0.8 = 1.04(1/(1+9.76))/X

This gives you 1.214, which definitely isn't right the added density should make it richer when compared to the original equation?

I'll get there eventually, maybe...

Edit 2: I think this looks better. 0.8 Lambda is 11.76:1 on gasoline, that equates to 7.84% gasoline by weight. E85 is 1.04 times the density of gasoline and if the same volume were injected you would be at 8.15% E86 by weight. This is an AFR of 11.27:1 and a lambda of 1.155?

0.8 * 14.7 = 11.76

(1/(1 + 11.76)) = .0784

.0784 * 1.04 = .0815

(1/.0815) - 1 = 11.27

11.27 / 9.76 = 1.155

Iam Broke

E85 requires ~30% more fuel than E10. Don't think you can get there by the math you have. Better buy a wideband, larger injectors and a fuel pump.

joecar

There is a very simple way to add fuel... what tuning software are you using...?

joecar

The EQR or Lambda stays almost the same... the Stoich AFR changes (there is a parameter for this in your calibration)...

e.g. so if your PE commands EQR 1.165 then AFR = 9.76/1.165 = 8.38

you then measure using wideband as suggested and make adjustment;

you then have to watch the injector duty cycles to make sure the injectors still have room.

joecar

And watch out, you're getting lambda and EQR mixed up.