Tuner Pro Stoich AFR parameter question

I have a few questions on Tuner Pro and stoich and AFR. I am running a 7.4L, ECM 7747 and Bin ATPY.

Ok I appologize if this is confusing. I am trying to get a better understanding of how this works. My truck is running good. I have done many datalogs and adjusted the BLM's using one of EagleMarks tutorials.

Anyway Looking thru other parameters on Tuner Pro, I see Stoich AFR and with posts I have read on here that stoich of E10 fuel is 14.2 not 14.7. So i changed that to 14.2 and I havent seen any change on my WB. Now in the notes on that parameter is does say about changing settings for hex address 0x2AA and a 02 error parameter. I cant seem to find these. The Notes give an example: that if you are using a fuel with a stoich of 16.1, the change needs to be 161.

I wanna put in the Highway Lean patch, and I see that it has the AFR of 16 to 15 range depending on engine load. What I dont understand that if the ecu doesnt adjust for afr but for stoich how does it adjust to acheive a afr of 16? Does the ECU work like a speadsheet and assume it is tuned to stoich and take say 5% of fuel out of the main fuel map to get it from a afr of 14.2 to 16?
I guess this question kinda falls in line with the Stoich AFR setting as well.

Thank you for your time

Ian

Want to be more confused, read this thread on AFRs and Stoich. Ive read it numerous times and still scratching my head.

http://www.gearhead-efi.com/Fuel-Inj...g-using-Lambda

It's not that bad, let me see if I can come up with a few points to make it clearer.

First when in Closed Loop your Narrow Band O2 sensor adjusts fuel to Stoich! Not 14.7 to 1 AFR. It just so happened that gasoline Stoich AFR is 14.7 to 1.

Now that ethanol has been added to fuel it has changed the Stoich AFR, if 10% E in fuel then the Stoich is 14.13 to 1 AFR. Your stock narrow band O2 sensor still adjusts to Stoich. Nothing has changed, the ECM/PCM can handle the fueling adjustments through INT/Short Term Fuel Trim and BLM/Long Term Fuel Trim.

If you change your Stoich AFR in your bin your will not see any change on your Wide Band O2 sensor! :yikes: Yeah like that makes sense right? Read above, the NB O2 sensor adjusts to Stoich.

So what happens if you make a change to Stoich AFR in your bin? Well your fuel trims will change! The Stoich AFR parameter is the starting point for fueling calculation that the ECM/PCM runs, then other things like injector size and cubic inch then using your VE tables.

So why if you changed your Stoich AFR to 14.13 and the fuel your using is 10% Ethanol which is 14.13, so why does my Wide Band read 14.70 ? :mad1:

Because your WB is not an AFR gauge, it's a Lambda gauge and when reading Stoich it is 1.0. The gauge you have is set up to show AFR and in programming Lambda 1.0 = 14.7 to 1 AFR. So if you can reprogram your WB gauge it's way easier to start using Lambda and also on a 1 volt scale. The 5 volt is way to accurate for these old systems and jumps all over driving you nuts!

What happens in Lean Cruise to allow AFR other then Stoich? It runs Open Loop, no O2 sensor feedback! :popcorn:

Thank you Eagle!! Makes much more sense now... And I did read that Link before Brian and yes I had to reread it a few times... LOL. My WB is programmable, and I can switch it to show lambda, I may just give that a shot. Reading Lambda may take some getting used too

I think I finally get it now too. Thanks Mark