Flex fuel tune commanding 11:1 afr

[carlsonauto]

Like the title says i am running a flex fuel tune and i just got it working but now that its saying it sees 60% ethanol (which is low but whatever) its commanding an afr of 11:1 or so do i need to change the method im using to display the units so that it plays nicely?? Im using afr because the eqr settings are greek to me... do I need to learn it or can I stick to what im familiar with without pulling my hair out??

:edit: I know that the way it displays the units to me has nothing to do with how the pcm sees them but from what I can tell in my tune everything looks like it should play nice.. am I missing something because of the way I have it displaying to me or is there something I am missing all together??

[carlsonauto]

I also have my lc1 set up to read afr as well and I know there are a ton of variables that can be easily overlooked because of the different methods of reading and displaying fuel mixture via wideband... here is a copy of my tune if anyone wants to take a peek at it.. new os bluetruc.tun

[GMPX]

That sounds about right actually, I checked a log from my car when it had just 26% ethanol and commanded AFR never got higher than 13.2, even at idle. Unfortunately one of the negatives with E85 is the increased fuel consumption because it has to run a lot richer all the time.

[carlsonauto]

actually i totally agree that that sounds correct for an actual afr but I think maybe I should have maybe been more clear (was eating lunch and posting with my phone) I have been tuning it as if it had gas in it rather than E85 and realistically as long as everything is correct it (the engine) really doesnt know the difference if one is still using the WB02 with the 14.7 stoch desired oxygen content is the same in the exhaust regardless of fuel being used. I guess where my confusion comes in is what do i need to change to make all the numbers play nice with eachother (pcm vs WB02)???? If i run an AUTOVE right now its going to try to about double the fuel due to my WB02 wanting stoch at 14.7 and the pcm wanting it at 11:1 or roughly thereabout.. I am very unfamiliar with anything other than a 14.7 stoch since that is what i have used for years tuning cars.... I would very much like to keep using that as the stoch at least on the display for my lc1 until I figure out what means what (if possible) but at the same time I need to make everything play nice so I can redo my tune via AUTOVE since my "flex fuel" sensor works now and everything is all out of whack.... Thanks, Jake

[carlsonauto]

Unfortunately one of the negatives with E85 is the increased fuel consumption because it has to run a lot richer all the time.

In my experience mileage is not much different on an engine that is tuned properly for E85. Also the higher the ethanol content the better and its easier it is to tune for it properly because it becomes less prone to detonation. E85 is also a ton more forgiving when the tune isnt quite right....

[GMPX]

In my experience mileage is not much different on an engine that is tuned properly for E85.

So what is the trick? From factory it's usually a big difference.

[joecar]

To make all the numbers match do the following:
- test the alcohol content of your fuel to determine the stoich AFR ($30 kit);
- set that stoich AFR value in B3601 and flash the tune into the PCM;
- log GM.EQIVRATIO (commanded fuel/air) and EXT.WO2EQR1 (measured fuel/air), these will match if your airmass models are correct.

[joecar]

Take WO2AFR1 and divide by 14.7 (giving you Lambda or 1/EQR) and multiply by the stoich AFR of your fuel.


Or take WO2LAM1 and multiply by the stoich AFR of your fuel.

[carlsonauto]

So what is the trick? From factory it's usually a big difference.

u can get away with a leaner tune safely and it likes timing.... just dont go nutts on it cuz it will go the other way... Also I usually lean toward the higher side of compression ratios than I probably should too and in my opinion E85 likes as much as you can give it.. makes normal fuel a bit** tho and some guys will argue that one all the way to the bank.. I dunno I just play till its happy.... I constantly tune my stuff even if its really good, for me thats the fun part. If it couldnt be tinkered with for me there wouldnt be a point. If i could just push a button and it was perfect it would be way too boring and i would find a new thing to play with cuz thats just plain boring.. I have yet to blow an engine up on E85 that I could blame on anything but my utter stupidity (was other issues but i knew about them and beat on it anyway).

[carlsonauto]

and like i said before the less gas you have the more you can tune it for the E85 and see the benifits.. If you are running 26% Ethnol then you are literally seeing the worst of both worlds.. detonation properties of regular gas so u cant turn up timing and the lower btu of the ethanol hampering the economy because you cant tune properly....