Ethanol percentage flex fuel

[wsteele]

So the virtual ethanol sensor settled at 17% again, on gas I know for a fact was 5% Ethanol. At a minimum, I know it is not getting the calculation right. What is causing it is still a little up in the air.

My guess now is maybe something that the sensor logic uses is not performing properly, next step is to try and determine if the evap system has a problem. Additionally, I am starting to get the feeling that maybe these things are not all that accurate in the first place and when anything is even a little off, the errors can get quite large.

Along with looking at the evap system, I am going to do a few more tests, going back to 0% ethanol at my next fill up, resetting the percentage and then on the subsequent fill up, again use 0% and make sure it stays at the 3% baseline the Tech 2 reset it to.

I am going to try really hard to not let this thing bug me, if I can’t fix it. It isn’t all that much work to verify the Ethanol content and if low enough, reset it with the Tech 2.

 

[swathdiver]

So the virtual ethanol sensor settled at 17% again, on gas I know for a fact was 5% Ethanol. At a minimum, I know it is not getting the calculation right. What is causing it is still a little up in the air.

My guess now is maybe something that the sensor logic uses is not performing properly, next step is to try and determine if the evap system has a problem. Additionally, I am starting to get the feeling that maybe these things are not all that accurate in the first place and when anything is even a little off, the errors can get quite large.

Along with looking at the evap system, I am going to do a few more tests, going back to 0% ethanol at my next fill up, resetting the percentage and then on the subsequent fill up, again use 0% and make sure it stays at the 3% baseline the Tech 2 reset it to.

I am going to try really hard to not let this thing bug me, if I can’t fix it. It isn’t all that much work to verify the Ethanol content and if low enough, reset it with the Tech 2.

SOP at the dealer is to drain and clean out the fuel tank before refilling with E10. How long did you let it decide to settle at 17%?

 

[wsteele]

SOP at the dealer is to drain and clean out the fuel tank before refilling with E10. How long did you let it decide to settle at 17%?

It actually decides. It just quits moving around and flat lines on the number it likes, after its routine is done. I drove maybe 25 miles total, but it quit moving around after maybe half that. That was my error after resetting it with the Tech 2 after the 0% fill, it stayed at 3% and never moved because I never refilled it. I think the true test is to do that, then refill with 0% again and see if it stays at the reset 3% level.

 

[mattbta]

Am on my third tank of E85 from Kwik Trip and my truck says it is at 63%

I'm at 66% on my 04 after 1.5 tanks from there.

 

[swathdiver]

It actually decides. It just quits moving around and flat lines on the number it likes, after its routine is done. I drove maybe 25 miles total, but it quit moving around after maybe half that. That was my error after resetting it with the Tech 2 after the 0% fill, it stayed at 3% and never moved because I never refilled it. I think the true test is to do that, then refill with 0% again and see if it stays at the reset 3% level.

What I'm getting at is that it sometimes re-computes even days later. When you do the reset, you do not have to use E0, E10 is ok.

 

[kbuskill]

What I'm getting at is that it sometimes re-computes even days later. When you do the reset, you do not have to use E0, E10 is ok.

It's funny that you mention this recalculating days later. I was beginning to think I was crazy.

My wife filled up with 89 octane (E10) the other day and after driving it for a while, plenty long enough for it to calculate the E%, I checked it and it said 3%. A couple days later I checked the same tank of fuel again and it said 17%.

I thought that once it detected a refueling event that it recalculated the E% after, approximately, 7 miles and that was it until you refueled with at least 3 gallons of fuel or more.

I have watched this with the Tech 2 and after fueling it will show that the Ethanol content relearn is enabled but only for a few miles.

 

[wsteele]

What I'm getting at is that it sometimes re-computes even days later. When you do the reset, you do not have to use E0, E10 is ok.

So far, about 60 miles and three starts and it is the same exact number. I leave the dongle in and watch it every trip (as I did with the 0% tankful). When I reset it, when I had fuel with 0%, it stayed at 3% for the whole tank. What I didn't (don't) know is if I refilled it with 0% again, if it would stay at 3% after it recalculated or jump higher.

If I use the Costco E10, which right now is measuring 5% (with the bottle and water method), it will jump up, right now it is saying 17%, but have seen it as high as 38% (using the same Costco E10.

 

[swathdiver]

So far, about 60 miles and three starts and it is the same exact number. I leave the dongle in and watch it every trip (as I did with the 0% tankful). When I reset it, when I had fuel with 0%, it stayed at 3% for the whole tank. What I didn't (don't) know is if I refilled it with 0% again, if it would stay at 3% after it recalculated or jump higher.

If I use the Costco E10, which right now is measuring 5% (with the bottle and water method), it will jump up, right now it is saying 17%, but have seen it as high as 38% (using the same Costco E10.

Ok. Yeah, it goes all over the place right after refueling. Have you seen your LTFTs as you pull away from the pumps? Freaked me out for a moment until I remembered what was going on! LOL

It's a pretty neat system but all that time figuring out the alcohol content seems to me a waste of fuel. I know it's trying to maximize efficiency but if there was a real alcohol sensor it would be spot on after a mile or so. An alcohol sensor is at the end of my "To Do List" along with an air density meter.

 

[wsteele]

Ok. Yeah, it goes all over the place right after refueling. Have you seen your LTFTs as you pull away from the pumps? Freaked me out for a moment until I remembered what was going on! LOL

It's a pretty neat system but all that time figuring out the alcohol content seems to me a waste of fuel. I know it's trying to maximize efficiency but if there was a real alcohol sensor it would be spot on after a mile or so. An alcohol sensor is at the end of my "To Do List" along with an air density meter.

I haven't had the LTFT up on the graph at the same time. It is very easy to do and will give it a try.

I have to be a little careful adding things to the live data chart, when I am driving, things get pretty busy (and pretty distracted). When I am driving along with my readers, trying to read the chart, not good.

My problem with my "virtual sensor" is when it makes a really big calculation error (like when it thinks it is 38%, when the actual E content is say 5%), when warming up, things get really rich. Once it drops into closed loop, things seem to clean up pretty quickly, the garage takes a while to air out.

 

[kbuskill]

Just wanted to update.

Installed new upstream O2 sensors on the Burb and reset the Ethanol percentage with the Tech2. Drove down an topped off with 89 octane advertised as (10% E).

Immediately got on the interstate and set the CC at 75 and drove 40+ miles.

During this time the E % bounced all over, from 3% up to 18.5% and finally settled at 3.1% and staying there for the remainder of the trip.

Next day I checked the E % and it was back up to 13.7%.

At this point I think the truck recalculates the E % after every cold start or something... I don't know what the heck is going on with it.

 

[wsteele]

Just wanted to update.

Installed new upstream O2 sensors on the Burb and reset the Ethanol percentage with the Tech2. Drove down an topped off with 89 octane advertised as (10% E).

Immediately got on the interstate and set the CC at 75 and drove 40+ miles.

During this time the E % bounced all over, from 3% up to 18.5% and finally settled at 3.1% and staying there for the remainder of the trip.

Next day I checked the E % and it was back up to 13.7%.

At this point I think the truck recalculates the E % after every cold start or something... I don't know what the heck is going on with it.

I have seen the exact same thing with the percentage being a different number the next day than the last one displayed when I shut it down after getting home with a refill.

On mine though, it never recalculates again until I refill. It definitely doesn't recalculate every cold start.

 

[swathdiver]

I have seen the exact same thing with the percentage being a different number the next day than the last one displayed when I shut it down after getting home with a refill.

On mine though, it never recalculates again until I refill. It definitely doesn't recalculate every cold start.

Same here, it's got to be normal after watching it do this for four years. It was 62% a few days ago and 73% yesterday and hasn't been refueled in almost a month.

 

[wsteele]

Same here, it's got to be normal after watching it do this for four years. It was 62% a few days ago and 73% yesterday and hasn't been refueled in almost a month.

Mine never changes after it finally decides, the next cold start after a refill and drive round the day before. It might say 9% when I shut it down at the end of the day I filled it, then the next morning show 17% after startup. But after that, it stays solid at that number until I fill it again.

I think maybe the "virtual sensor" just doesn't do a very good job at getting the percentage really close.

I am still going to keep experimenting and also see if I can figure out why my evap monitor never completes and if that has anything to do with the "virtual sensors" inability to calculate my ethanol percentage more accurately. I did change the canister purge valve a few years ago and I think maybe it wasn't a genuine OE part, so maybe it is off just enough to keep the monitor from completing, screw with the ethanol calc, but not bad enough to throw a code. Just guessing here.

 

[kbuskill]

Mine never changes after it finally decides, the next cold start after a refill and drive round the day before. It might say 9% when I shut it down at the end of the day I filled it, then the next morning show 17% after startup. But after that, it stays solid at that number until I fill it again.

I think maybe the "virtual sensor" just doesn't do a very good job at getting the percentage really close.

I am still going to keep experimenting and also see if I can figure out why my evap monitor never completes and if that has anything to do with the "virtual sensors" inability to calculate my ethanol percentage more accurately. I did change the canister purge valve a few years ago and I think maybe it wasn't a genuine OE part, so maybe it is off just enough to keep the monitor from completing, screw with the ethanol calc, but not bad enough to throw a code. Just guessing here.

Mine wasn't completing the EVAP monitor test either.

I kept having a intermittent P0455 gross leak. I replaced the purge solenoid because it wasn't sealing all the way when commanded to by the Tech2 as it had charcoal pellets, from when I changed the canister, stuck in it.

The gross leak then became a small leak, I just replaced the fuel cap the other day and so far no codes and my EVAP monitor shows complete.

 

[wsteele]

Mine wasn't completing the EVAP monitor test either.

I kept having a intermittent P0455 gross leak. I replaced the purge solenoid because it wasn't sealing all the way when commanded to by the Tech2 as it had charcoal pellets, from when I changed the canister, stuck in it.

The gross leak then became a small leak, I just replaced the fuel cap the other day and so far no codes and my EVAP monitor shows complete.

If your evap monitor is completing and you still are getting haywire ethanol calculations, I might be barking up the wrong tree hoping fixing my evap monitor issue might fix my "virtual sensor" calculation problems.

In the end, I may just end up resetting it periodically with my Tech 2, anytime calculations get so far off base things start getting smelly when cold idling. It hasn't gotten back up into the high 30's (when running <10% gas) since I reset it the first time.

 

[kbuskill]

If your evap monitor is completing and you still are getting haywire ethanol calculations, I might be barking up the wrong tree hoping fixing my evap monitor issue might fix my "virtual sensor" calculation problems.

In the end, I may just end up resetting it periodically with my Tech 2, anytime calculations get so far off base things start getting smelly when cold idling. It hasn't gotten back up into the high 30's (when running <10% gas) since I reset it the first time.

I'm just confused as to why it recalculates it the following day.

I was under the assumption that once it detected a refueling event, of at least 3 gallons, that it went into ethanol relearn mode and that it took X amount of miles to complete the process and once it was done that was it.

Apparently my Burb didn't get the memo... lol

Like you though, once it recalculated the next day it kept that percentage for the remainder of the tank. Who knows.... I think GM shouldn't have cheaped out by getting rid of the physical FF sensor, or the cabin air filter for that matter.

 

[wsteele]

I'm just confused as to why it recalculates it the following day.

I was under the assumption that once it detected a refueling event of at least 3 gallons that it went into ethanol relearn mode and that it took X amount of miles to complete the process and once it was done that was it.

Apparently my Burb didn't get the memo... lol

Like you though, once it recalculated the next day it kept that percentage for the remainder of the tank. Who knows.... I think GM shouldn't have cheaped out by getting rid of the physical FF sensor, or the cabin air filter for that matter.

Yes, at least at this point, I would say the "virtual sensor" is kind of a lame substitute for a real sensor.

 

[wsteele]

I filled the Yukon up with ethanol free gasoline this morning on a near empty tank. After the running around I did (maybe 20 miles total), the virtual sensor settled on the value that I have 21.38% Ethanol in the tank (reality is less than 1%).

I will see what it says when I restart it later today, but definitely, something is not working in my virtual Ethanol sensor.

 

[kbuskill]

I filled the Yukon up with ethanol free gasoline this morning on a near empty tank. After the running around I did (maybe 20 miles total), the virtual sensor settled on the value that I have 21.38% Ethanol in the tank (reality is less than 1%).

I will see what it says when I restart it later today, but definitely, something is not working in my virtual Ethanol sensor.

What was the E % before filling up?

 

[wsteele]

What was the E % before filling up?

I think it thought I had 17% (the actual percentage in that tank was about 6%, tested with my bottle). I might be able to get some history data from my scanner and get exactly what it thought, but I think 17% is very close).

Edit: I know the definition of crazy is doing the same thing and expecting a different result, I was just hoping maybe with a fresh tank of zero, the sensor would start to get a clue on its own.