WB tuning FlexFuel Vehicle with part ethanol

Okay I know I am nit-picking now, but I am trying to squeeze out any other error I may be inflicting in my tuning process. It is a flexfuel vehicle and has enough ethanol content in the 93 octane to consistently command a 14.47 AFR (from the Stoich table) with the O2's instead of 14.67. I have a PLX M-300 using the 0.5/10 EIO in the config. I also jumpered a wire to another EIO with voltage and they are both logging 14.67 and 2.35 volts respectively. Confirmed "disco" voltage with meter as well as possible too.

If I am interpreting right, the commanded is taking into account the alcohol content represented in AFR to achieve Lambda and Lambda is Lambda no matter what the fuel despite different AFR's. Damn even when I type it, it sounds nuts. lol.

I am using the AFR% error for MAF and VE tuning with this setup. Should I make an adjustment to the WB config and/or histograms to bring it in line with the ethanol content or is stoich stoich don't worry its okay?

After the tune testing. WB is still registering 14.67 (2.35 volts) and commanded still 14.47. Same question above, adjustments to be made or ?

thanx in advance,
tomy

Quote:

---

Originally Posted by seven ends

Okay I know I am nit-picking now, but I am trying to squeeze out any other error I may be inflicting in my tuning process. It is a flexfuel vehicle and has enough ethanol content in the 93 octane to consistently command a 14.47 AFR (from the Stoich table) with the O2's instead of 14.67. I have a PLX M-300 using the 0.5/10 EIO in the config. I also jumpered a wire to another EIO with voltage and they are both logging 14.67 and 2.35 volts respectively. Confirmed "disco" voltage with meter as well as possible too.

If I am interpreting right, the commanded is taking into account the alcohol content represented in AFR to achieve Lambda and Lambda is Lambda no matter what the fuel despite different AFR's. Damn even when I type it, it sounds nuts. lol.

I am using the AFR% error for MAF and VE tuning with this setup. Should I make an adjustment to the WB config and/or histograms to bring it in line with the ethanol content or is stoich stoich don't worry its okay?

After the tune testing. WB is still registering 14.67 (2.35 volts) and commanded still 14.47. Same question above, adjustments to be made or ?

thanx in advance,
tomy

---

You're at about +/-0.6% error between the two. Seems very close to ideal.

14.47 is 5% or less ethanol. Factory considers this below tolerance to adjust anyway.

Regardless of the percent error I am trying to understand how a flexfuel vehicle should be tuned with a WB based on a fuel outside of a 14.7. In the example we are talking about here +/- 0.6% error.....so I am copying and pasting percent error result with 0.6% error.....then when I test the tune with the same error in resulting histogram again.....am I now doubled at 1.2% error for test results even though in reality I am still half that?

For a "flexfuel" vehicle with the stoich table for afr from gasoline down to alcohol....if I wanted to setup my WB config or histograms to accomodate the AFR error to whatever the "known" fuel percent is....for logging AFR% error do I adjust my WB config scale, histogram input, or both to get real AFR to AFR % difference?

Edit: For example a custom PID for AFR error to adjust for 5% difference in fuel AFR with a revised function as:
100*(([SENS.120]/1.0138)-[SENS.121])/[SENS.121]

thanx
tomy

The custom PID for AFR error adjusting the 5% on the WB AFR don't work in my example above....it wreaks. I dumped the csv's out and reasoned that one out. The WB AFR is still moving towards the commanded AFR despite the fact Lambda is 14.67 on the WB and 14.47 in the commanded. I guess that is the meaning of lambda is lambda. I noticed on the commanded WOT values that the difference was around 0.10 whereas in the commanded stoich is was more like 0.50. I am assuming more transients in the stoich and longer in cruise vs. wot to create more dramatic differences. I think I am concluding that with my FlexFuel vehicle I can WB tune the AFR% Error on any mixture of gasoline and ethanol without altering any PID's, functions, histograms, etc. but probably not E85 or E100 because they would be outside the AFR capability of my WB since those values would be below 10 AFR.

TGIF
:chug:

I am worse than the stock market. Changed my mind once again after a few more threads herein and elsewhere. I finally derived at the function below for a Lambda % Error custom PID. I plan to do my next tuning VE and MAF with this type of error...should take out the 5% ethanol content error I am getting now and also close the 0.10 to 0.50 gaps I mentioned earlier. Below is the function formula in the custom PID. Divided the WB AFR by 14.67 to get Lambda and the Commanded Stoich AFR I am getting with this tank of gas by 14.47 (5% ethanol).

100*(([SENS.120]/14.67)-([SENS.121]/14.47))/([SENS.121]/14.47)

My truck was cold and still in closed loop but just to test to see if it worked and what the comparison looked like I took a quick scan attached. The two Error percentages are plotted against each other on the 3rd chart. I don't think most of us would be happy otherwise knowing we left approaching 2% error in our tuning...after all we are still multiplying by half % when we get under 1% to get it closer and closer to zero.

Looks promising to me so will give it a shot! :yay:

I used the revised function for Lambda described in previous post and retuned vehicle. Tune still settling in but looks like it went in the right direction. Differences shown in attached snapshots of LTFT and AFR between Unadjusted and E05. Notable difference by the time you double the error by not adjusting; error in tune itself plus error in testing. I would have blamed and thrown the WB away otherwise. This is a flex fuel vehicle that adjusts it commanded by the ethanol content it thinks is in the tank. So for me, this vehicle, I will adjust both the commanded and tested (14.47 vs. 14.67 in this case) to Lambda and take that error to tune VE and MAF tables.

I also want to recognize WS6, ECTune, Runn, EFICalib, Marcin, Scott, Russ, Bill, to name a few whose posts herein have been a huge aid in setting me straight on Ethanol tuning, Bias, to also name a few things.

Happy holidays to all you guys and thanx.
tomy

something to remember when you are tuning.....

the sensor measures Lambda....not AFR
it converts Lambda into voltage...which software converts into AFR
so it doesnt matter what fuel you use...
stoich = lambda 1.0
as an example e85 lambda 1.0 is like 9.765 AFR? or something like that....
but stoich is still lambda 1.0

you can make a custom PID for AFR error based on Equivelance ratio.... EQ raio of 1.0 is stocih
0.85 is the same as saying 12.5:1 on standard gas or 8.3:1 on E85

the tune on flex fuel vehicles(If I remember correctly) changes the AFR that lambda 1.0 represents....so your EQ ratio is still 1.0 for stocih :)

Quote:

---

Originally Posted by soundengineer

something to remember when you are tuning.....

the sensor measures Lambda....not AFR
it converts Lambda into voltage...which software converts into AFR
so it doesnt matter what fuel you use...
stoich = lambda 1.0
as an example e85 lambda 1.0 is like 9.765 AFR? or something like that....
but stoich is still lambda 1.0

you can make a custom PID for AFR error based on Equivelance ratio.... EQ raio of 1.0 is stocih
0.85 is the same as saying 12.5:1 on standard gas or 8.3:1 on E85

the tune on flex fuel vehicles(If I remember correctly) changes the AFR that lambda 1.0 represents....so your EQ ratio is still 1.0 for stocih :)

---

Could you help me plug custom pid for AFR for E85? Stoich being 9.799
I'm using plx wideband plug into ECU thru EGR.