Ethanol percentage flex fuel

[Fless]

I'll be filling up on Saturday -- provided the pump has E85 -- after a run up to the north side of the city, so I'll be checking percentages before and after.

 

[gooffeyguy]

Thanks for the information. 71.76% sounds pretty plausible as a real value for E85. After I burn down this tank of zero, I will fill with E85 and test it with the bottle. Maybe my virtual sensor will be more accurate on the other end of the scale.

I have noticed in the past when running E10 my % has read 7% and even read 3% for one tank.

I think if you're having a problem with it not calculating accurately with a known/tested fuel, then something that's involved in the calculation isn't working correctly.

Oxygen sensors, MAF sensor, knock sensor maybe?, or even in the ECM calibration. Have you checked to see if you have the latest calibration?

Sent from my SM-G930V using Tapatalk

 

[wsteele]

I have noticed in the past when running E10 my % has read 7% and even read 3% for one tank.

I think if you're having a problem with it not calculating accurately with a known/tested fuel, then something that's involved in the calculation isn't working correctly.

Oxygen sensors, MAF sensor, knock sensor maybe?, or even in the ECM calibration. Have you checked to see if you have the latest calibration?

Sent from my SM-G930V using Tapatalk

Since I started watching this stuff, mine has never accurately calculated the E% when running E10 fuels (or 0% for that matter). It has gotten as high as 38% (when I first started to investigate it as warm ups when running open loop got downright smelly and was beginning to worry me that my cats would be negatively affected).

As I posted earlier in the thread, when filling with 0% and resetting with the Tech 2, it stayed down at 3% (where the Tech 2 sets it). But the next time I fueled with E10 (actual measured E% of 6%), it hopped right back up into the high teens.

Clearly something is not working correctly. I had high hopes when reading the explanation Chris (@iamdub) posted about how the virtual sensor E calc works, that maybe my Canister Purge Valve was not operating properly as it is the only thing called out in that explanation that might affect the calc, other than O2 and trim input. Coincidentally, my Evap monitor also never completed, so again, high hopes. Unfortunately, I replaced the Canister Purge Valve with a new OE unit and also replaced the cap with an OE cap and while my Evap monitor completes now, E% calcs are still screwy.

I replaced all four O2 sensors with OE units recently as the ones in the truck were original and felt I was probably living on borrowed time with them anyway. I did it more because I wanted to choose when I did it, versus any indication any of them weren't functioning properly. Clearly, that was also not the problem.

I do have the latest calibration, something I ran down right away at the suggestion of Steve (@Fless).

As I have posted a few times in my lower moments on this issue, I suspect I may never know why my Virtual Sensor doesn't work and may never get it to function properly. Like so many things in life, it is really hard to fix something that is not clearly broken.

As I have posted a few times on this and predecessor threads, I feel like I may end up just resetting it with the Tech 2 anytime it starts to creep up into E% ranges that cause a very rich open loop condition and call it good. I likely will never be running E85 normally as it just isn't competitive price wise at the station I can buy it at here, so I know my percentage will always be 10% or less.

 

[swathdiver]

You can create a custom PID... just enter the information that I posted in those screen shots.

Your girls are smart... they can figure it out.

I got my last backwards. The kids have Apple phones and tell me that Torque is not available. So they have Dash Command and on that one they cannot pull up alcohol, so they tell me.

 

[BG1988]

GM, in all of their infinite wisdom, did away with the physical flex fuel sensor on the GMT900 platform, it is probably sitting in a box on a shelf, along with the cabin air filter, lights under the dash and on the door panels, at GM headquarters.

The GMT800s have an actual FF sensor but the GMT900s use an algorithm, based off of different parameters including the O2 sensors, to deduce the ethanol percentage.... or perhaps a crystal ball.... lol

if this is true should the hybrid be able to run E85 as well? it has the same injectors as the flex models

 

[kbuskill]

if this is true should the hybrid be able to run E85 as well? it has the same injectors as the flex models

I have no idea, as I am not familiar with the Hybrid Tahoes... does it have a yellow gas cap???

 

[kbuskill]

I got my last backwards. The kids have Apple phones and tell me that Torque is not available. So they have Dash Command and on that one they cannot pull up alcohol, so they tell me.

If that app allows custom PIDs then they should still be able to enter the information and get it to work.

I don't have any Apple phones because I hate them and prefer Android so I'm not exactly sure what is or isn't available for them.

 

[wsteele]

if this is true should the hybrid be able to run E85 as well? it has the same injectors as the flex models

The sure way to find out is too run the tank down real low and then fill it with E85. Clearly you will have the volumetric capacity with the injectors. Does Circle K even sell E85?

 

[BG1988]

The sure way to find out is too run the tank down real low and then fill it with E85. Clearly you will have the volumetric capacity with the injectors. Does Circle K even sell E85?

the only station with E85 is chevron down the street 3-4 miles away


it only has 30 pound injectors not sure if this is enough

 

[wsteele]

I guess it is a moot question, given only Chevron sells it down the street.