NGK AFX Reading Question

[Gh0st]

In my truck I'm getting a "stoich" reading of 14.4 to 14.50(rarely ever goes higher) on my wideband. Is this correct for the NGK AFX with ~E10 or should it still be reading 14.6 for stoich?

[Gh0st]

The AFX is compatible with fuels other than gasoline. The AFX’s display is designed to
show AFR values based on a gasoline scale with 14.57:1 AFR as the stoichiometric ratio.
The display will simply show AFR on a gasoline scale even though the fuel used may
have different properties (stoichiometry for methanol is approximately 6.5:1). As long as
you understand this, interpreting the values should be easy.

This is where I'm confused. "on a gasoline scale"

Since I'm not running pure gasoline(because of the ethanol), I shouldn't see stoich of 14.57 right? The wideband should be telling me the true air fuel.

[MMGT1]

E10 is Stoich at 14.1 from what I found. A quote from Greg for you:

"To work effectively with Ethanol blends, you really need to switch to units of Lambda to avoid confusion. (lambda = AFR/stoichAFR)

Almost any hydrocarbon fuel makes peak torque somewhere near lambda=0.9. For pure gasoline this is an actaul AFR of (14.68)*(0.9)=13.2 AFR. With e10, it would be calculated based on lambda with a different stoich point: (14.13)*(0.9)=12.7 AFR. Both mixtures, although numerically different, look the same to the combustion process.

e10 isn't a huge difference, but e85 get much more significant: (9.85 stoich)*(0.9)=8.9 AFR, which still looks the same as 13.2 with gasoline as far as the combustion process is concerned.

Wideband sensors also don't know what %ethanol blend you're burning. The UEGO (wideband) sensor just measures oxygen percent and delivers a lambda number. The cheaper widebands just multiply this measured lambda by 14.6 to give unexperienced users a number they're used to seeing in magazines. Don't tune to AFRs (instead of lambda) using ethanol blends, it will only mislead you.

Greg Banish"

[superwagon]

The ngk display should be showing 14.57 if you are at lambda 1.00 for whatever fuel you are burning.

[Gh0st]

E10 is Stoich at 14.1 from what I found. A quote from Greg for you:

"To work effectively with Ethanol blends, you really need to switch to units of Lambda to avoid confusion. (lambda = AFR/stoichAFR)

Almost any hydrocarbon fuel makes peak torque somewhere near lambda=0.9. For pure gasoline this is an actaul AFR of (14.68)*(0.9)=13.2 AFR. With e10, it would be calculated based on lambda with a different stoich point: (14.13)*(0.9)=12.7 AFR. Both mixtures, although numerically different, look the same to the combustion process.

e10 isn't a huge difference, but e85 get much more significant: (9.85 stoich)*(0.9)=8.9 AFR, which still looks the same as 13.2 with gasoline as far as the combustion process is concerned.

Wideband sensors also don't know what %ethanol blend you're burning. The UEGO (wideband) sensor just measures oxygen percent and delivers a lambda number. The cheaper widebands just multiply this measured lambda by 14.6 to give unexperienced users a number they're used to seeing in magazines. Don't tune to AFRs (instead of lambda) using ethanol blends, it will only mislead you.

Greg Banish"

Yep, but the wideband doesn't show lambda.

The ngk display should be showing 14.57 if you are at lambda 1.00 for whatever fuel you are burning.

Shit...maybe a recal will fix it then. It's always reading richer than 14.57

[Gh0st]

This guy has the same issue. His wideband is not outputting ON THE DISPLAY a reading of 14.57 for stoich:

http://www.hptuners.com/forum/showpo...9&postcount=13

[Gh0st]

Hopefully someone with the NGK AFX will chime in here and help me out...

I can think of two problems here:

1. My narrowbands are NOT putting me at stoich, hence such a rich reading at the wideband.

2. The wideband is a piece of shit.

[DSteck]

The close loop PI control logic puts bias on the trims that leaves them on the rich side. I wouldn't sweat it. Make sure you have power and ground from your battery though.

[Gh0st]

guess i'll just roll with it then. thanks dude

[MikeOD]

The NGK seems to be one of the better "consumer" widebands I've used...I'd trust what it's saying...but like everyone else said, ignore the screen. Use the 5 volt output from the NGK, and tune to lambda numbers...that way you'll get the car dialed in regardless of fuel.

[LSxpwrdZ]

Also if you are getting a different afr on the wideband while in closed loop then modify your o2 switch points to help dial the closed loop stoich in. I do this alot so that customers wanting to stay in CL will actually get stoich.

[Gh0st]

Not getting lambda = 1 in my logging either. Either my wideband is wrong or the narrowbands are switching too rich.

[Gh0st]

Nevermind, it's all good.