looking for Spindt AFR calculation 1

[gsz]

Can anyone provide the equation for calculating air fuel ratio based on exhaust gas emissions (CO, CO2, HC, and O2)?
Thanks much.

 

[strokersix]

You need to write the chemically balanced equation making an assumption for the fuel composition (usually octane for gasoline). This will be an approximation, of course.

Mike

 

[Marquis]

gsz
I tackled this some months ago, there's a little bit on it in Heywood, I'll see if I can dig something up tommorow- if I don't get back to you, it's because I'm either too busy, or can't find the equations *L*

 

[gsz]

Thanks. Found it in my archives. (SAE paper 650507). In VB in looks like this:

Function spindtAFR(O2percent, COpercent, CO2percent, HCppmC, HCratio)

O2 = O2percent
CO2 = CO2percent
CO = COpercent
HC = HCppmC

q = O2 / CO2
r = CO / CO2
Fb = (CO2 + CO) / (CO2 + CO + (0.0001 * HC))
Fc = 12.01 / (12.01 + 1.008 * HCratio)
spindtAFR = Fb * ((11.492 * Fc * ((1 + 0.5 * r + q) / _
(1 + r))) + ((120 * (1 - Fc)) / (3.5 + r)))

End Function