Sale ends todayGet 30% off any course (excluding packages)

Ends in --- --- ---

Wideband AFR in relation to alternative fuels

Understanding AFR

Forum Posts



Tech Articles

Discussion and questions related to the course Understanding AFR

= Resolved threads


Could someone please explain this to me? I tried watching the video over a couple of times in the understanding AFR and just couldn't understand it. I typically run pump gas 93 octane as well as E85 and I know my AEM UEGO meter always reads 14.7:1. How can I properly convert this number while running E85 so that while I'm reviewing data logs and adjusting the fuel table I'm using the right correction factor to reach my AFR targets?

G'day Brian.

This is the main reason we like to tune our air to fuel ratio in units of Lambda, as Lambda 1.0 is stoich, no matter what fuel you're using.

14.7:1 is stoich on gasoline

9.8:1 is stoich for E85.

If you've got a complete target air to fuel ratio table sorted in units of AFR for gasoline, multiply every cell by 0.67, and you'll have the equivalent table, still in units of AFR obviously, but adjusted to be based around the stoich ratio of e85, 9.8:1

Thanks Zac I appreciate it, I do understand how much easier it is to use the lambda scale vs. the AFR especially while making corrections. I just don't think my AFR meter will allow me to display in units of lambda I will have to check the user manual on it.

Had a quick look, and yeah, seems like its a build-time option to get it to display in Lambda:

Is the X-Series UEGO controller/sensor compatible with alternative fuels such as E85, methanol, ethanol, CNG, etc?

Yes. The lambda display mode and faceplate is recommended when using fuels other than gasoline. The AFR display

mode uses the gasoline stoichiometric ratio of 14.65 which might be confusing for alternative fuels. Remember that AFR

= (lambda * stoichiometric ratio).

No it’s not the x series it’s the 30-4110, looked up the manual and it looks like there is a rotary switch on the back to change it to a lambda display. Thanks for the help

Attached Files


If you keep your meter in AFR using different type of fuel the reading should be the same you shoot for as with 93 Octane, we know Ethanol has different stochiometric value, etc. but in reality your WB sensor doesn't know if it is ethanol, VP, pump gas etc. as its main purpose is to measure How much air is there,

You can do a couple of things, one program the WG (if it its programmable) to E85 Stoich. and target the same AFR as you would do for 93 octane, Second. you can leave everything as it is, and shoot for your normal AFR, third, you change to lambda, either your meter or some dataloging has the ability to change from AFR to Lambda values to be displayed.

I normally leave my WD to AFR and my datalogs in lambda then as i send my ECU WB signal i can overlay the 2 and i have not seen drastic changes ie. AFR been overly rich/lean compared to Lambda

Hope that Helps

We usually reply within 12hrs (often sooner)

Need Help?

Need help choosing a course?

Experiencing website difficulties?

Or need to contact us for any other reason?