Jump to content
Ecoboost Owner Forums
Sign in to follow this  
Blaine109

A/F Ratio?

Recommended Posts

Does anyone know how to get the proper readings for the wideband O2 sensors to see what your A/F ratio is? I can currently read the volts for them but that is supposedly not how to properly read with the wideband sensors.

 

You have to build a calculator... I can't remember the exact signal name, but it the one right below the O2 Current (which is the one you are grabbing). It's the Lambda value. You then need to multiple the Lambda value by the stoich value of your fuel. Typically the most commonly used stoich value is 14.7. Since all we can get around here is gas with 10% ethanol (E10), i've used 14.1 in my calculator. The Dashdaq users guide has a couple of examples on how to set up a calculator...

Share this post


Link to post
Share on other sites
Hey Blaine...you should be At 14.7 at idle...ideally.

 

Ok, I've got it working now and am reading both banks. They both tend to be between 13.8 and 14.4 while idle. This was just a short little observation but will test some more but may explain some of my performance issues.

 

Tell me if I'm wrong but if the O2 sensors are reading incorrectly and are reading low (such as the 13.8 - 14.4) is the computer trying to compensate by adding more fuel to the air even though it may not need it? If so, will that give me a bogged down feeling that I sometimes have on light accelerations? I had a bad turbo and it leaked quite a bit of oil through the intake and I suspect (amongst other things) that the O2 sensors may be muffed up a bit from all the burnt oil.

 

If that's not the case, how much variance/tolerance is typical from the optimal 14.7?

 

I'm going to do a little more data logging though to confirm my readings.

 

Thanks for your help and I will also be posting up a quick tutorial later this evening on how to get this setup for those of you who want to read A/F Ratio's with your MyCal.

Share this post


Link to post
Share on other sites

Ok, so when I got home I left my car running idle in park for about 5 minutes while data logging. Here's my results for AFR:

 

Bank 1 AFR

Min = 13.634

Max = 14.810

Avg = 14.206

 

Bank 2 AFR

Min = 13.568

Max = 14.870

Avg = 14.163

 

Do these readings seem correct or should I be looking at possible O2 sensor issues or other related issues?

Share this post


Link to post
Share on other sites
Ok, I've got it working now and am reading both banks. They both tend to be between 13.8 and 14.4 while idle. This was just a short little observation but will test some more but may explain some of my performance issues.

 

Tell me if I'm wrong but if the O2 sensors are reading incorrectly and are reading low (such as the 13.8 - 14.4) is the computer trying to compensate by adding more fuel to the air even .

 

NO!! The lower numbers mean richer. Remember, when reading A/F numbers, lower means richer, higher means leaner, so if anything you're just a tad bit rich.

 

Not sure why they're reading a little rich. Bad sensors?? probably not, although possible. Without knowing what the actual PCM code is calling for under the conditions you're testing at, it's hard to know if this is normal or not.

Need to know what other folks are reading under similar conditions.

Share this post


Link to post
Share on other sites

Direct injection is a different animal when it comes to idle readings...I wouldn't be suprised if the car idled with A/F somewhat higher than the 14.7 a/f stoichiometric mixture...direct injection allows for much leaner air/fuel because it can more precisely deliver a proper mixture than traditional efi systems. So when the car is running with reduced or no load conditions an ultra lean burn can be acheived without detonation issues (in theory, mileage may vary based on fuel quality, additives, etc...)...which is also why these newer cars are able to run higher compression ratios while still running turbos...

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
Sign in to follow this  

×