[scottsee]

I remember when I was trying to wrap my brain around that last year.. no fun.. This is what I use..

Stoich Values:
Gasoline = 14.7
Methanol = 6.40

Weight:
Water = 8.33lbs/gal
Methanol = 6.59lbs/gal

Specific Gravity:
Gasoline = .737
Methanol = .791

Specific Gravity Differences:
Gasoline = 1.07 more dense than methanol
methanol = .93 less dense than gasoline

Equation to get Percent Methanol to Water Injection by Mass:
(Methanol Weight per Gallon)(Volume of Methanol in Mixture) = Methanol Total Mass
(Water Weight per Gallon)(Volume of Water in Mixture) = Water Total Mass

(Methanol Total Mass)(100)
(Meth Total Mass) + (Water Total Mass) = Methanol Percent by Mass

Equation to get Actual Percent of Methanol Injected:
(Methanol Percent by Mass)(Total Percent of Water Injection Mixture) = Methanol Percent Injected

Equation to get Mixture Stoich Value:
(Meth % by Mass)(Meth S.G. Difference)(Meth Stoich) + (gas %)(gas S.G. Difference)(gas Stoich) = Mixture Stoich Value

Equation to get REAL AFR:
(Mixture Stoich Value/WBO2 reading) x 14.7 = REAL AFR


Example:
75% meth injection to 25% water by volume at 20% of fuel delivery and a WBO2 reading of 11.2:1AFR.

Percent Methanol in Water Injection Mixture by Mass:
(6.59lbs/gal)(.75) = 4.9425

(4.9425)(100)
4.9425 + 2.0825 = 70% Methanol by Mass of 20% Water/Methanol Injected

Equation to get Actual Percent of Methanol Injected:
(70%)(20%) = 14% Methanol injected to Fuel

Mixture Stoich Value: (.14)(.93)(6.4) + (.86)(1.07)(14.7) = 14.36

Real AFR: (11.2/14.36) x 14.7 = 11.47 REAL AFR