Flex Fuel Sensor Compensation

[Javcolin]

Hi,

Setup B18 Turbo tuned on 93 Octane,
Hondata V3 white board

I finally complete my 93 octane Tune and Switch to Ethanol.

I'm using a Continental Flex Fuel sensor. while I was tuning with 93 octane I enabled the Ethanol sensor to check is it was reading or not and it showed 5% content which is about right,

When I depleted my fuel tank to add pure ethanol I must have left some fuel in as the sensor read 75% today I added another 2.5 gal of pure ethanol and the E-Contend went up to 99% which according to the manufacturer is about right,

My Wiring is 12v from a switched power, ground to analog board ground wire and then the signal to AN0 on the analoge board

When I first fire her up she started no problem but was way too rich, so I took the close loop Values on the Ethanol compensation and slowly lower them down to around 16% so my AFR were where I have them on my 93 octane tune.
I then went out for a test drive and was way too lean, so I went back to stock values 35% and still was lean while crusing, I went as high as 45% and still lean.

I did a WOT pull and was way too lean at 70% compensation

According to my math I should have been almost spot on at 38%

Have you guys seen much higher percentage values as mine or there is something wrong with my flex fuel numbers?

I assume the Sensor only reads the content and the compensation table is an adder to the main fuel tables correct?

Does this figueres make sense to you? or they are way too high? if so what should I look into?

[Spunkster]

Fuel

Stoichiometric AFR
____________________________

Pure Gasoline

14.7:1


10% Ethanol Gas

14.04:1


15% Ethanol Gas

13.79:1


E85

9.75:1


Pure Ethanol

9:1


Diesel

14.6:1*

[Javcolin]

I went for another test drive,

At WOT I manage to bring the AFR very close to my AFR on 93 octane, I entered 87% on the openloop Table, I don't know if this alue is ok as long as it gets me back to my AFR or if this number is too high.

Again I dialed in the idle but while driving it was too lean then i went to 38% on the closeloop table at idle is wat too rich and driving around was lean. so I don't know what to do there.

I empty my fuel tank and added gas, I checked my Idle and part throttle and was good. Idle at 0 to -3 with fan on was 0 to 2 percent part throttle was 0 to 3% so i don't know what might be wrong when actiating the Flex fuel function,

I wired the ground to a chassis ground this time.

Any thoughts?

Thanks

[Spunkster]

Without the calibration and datalogs showing the actual AF ratio, it's hard to say what might be happening.

[Javcolin]

Hi,

I dump the Ethanol and top up 93 octane and noticed that all of my 93 octane cal. was way off from original. later on I checked my FPR and found that the FP dropped below 40 psi with no apparent reason, son I raise the FP to 43.5 and was almost back to what it was. had to twick it a bit tho. once i have it all good again will try the Flex fuel feature.

By the way all the tune followed the ethanol trend being way too lean.

Thanks

[DaX]

I too felt like the stock values loaded in the ethanol fuel compensation (open loop) table were too lean for my setup. I adjusted mine as shown below. Honestly though, I haven't run 93 octane fuel in almost 2 years because I can always get E85. I have been on the dyno twice since the initial dyno tune, and made countless street tuning tweaks, so I can't honestly say how my car would run on my flex fuel setup if I put some regular pump 93 in there. It would probably require tweaking.

Clipboard01.png (69.3 KiB) Viewed 2461 times

[Javcolin]

I too felt like the stock values loaded in the ethanol fuel compensation (open loop) table were too lean for my setup. I adjusted mine as shown below. Honestly though, I haven't run 93 octane fuel in almost 2 years because I can always get E85. I have been on the dyno twice since the initial dyno tune, and made countless street tuning tweaks, so I can't honestly say how my car would run on my flex fuel setup if I put some regular pump 93 in there. It would probably require tweaking.

Clipboard01.png

Thanks for sharing,

The only reason I'm doing dual Tune and not a pure e85 one is. I can only get Pure ethanol in bulk but more so is that I leave my car siiting for long periods of time a few months here and there, and don't really want to leave the Ethanol in there that long, although I have teflon hoses ethanol friendly injectors pump etc. I might be paranoid from peope horror stories after a long period of time car being stored with ethanol in it.

But if i get the same result next time I try it, I will just do my own e85 ish and keep a single tune.

[DaX]

Mine is definitely set up for flex fuel and I like it that way in case I can't find E85. All I'm saying is I haven't tested how it runs on 93 pump in almost 2 years. Mine gets run at least every 2 weeks. If not for some reason, I will swap over to 93 and run it for about 2-3 minutes to flush the system. I have done that a few times, but I just haven't really driven it around on 93 in a while.

[UPSer]

Hi, I'm trying to figure out if there is a way to mathematically calculate the ethanol fuel compensation values using the Stoichiometric AFR information that Spunkster posted? Here's how I think it's done using E85 as an example:

E85
9.75:1

Pure Gasoline
14.7:1

(14.7 - 9.75) / 14.7 = 0.3367

.3367 × 100 = 33.67 %

I think about 34% more fuel is required if you run E85. If my calculation is totally wrong, please show me if you know how. I'm sorry if I turned this into a math class.