Welcome to the SR20 Community Forum - The Dash.
Register
SR20 forum logo

Thread: Fuel Ratio for E85?

+ Reply To Thread
Posts: 1-10 of 29
2014-08-09 22:07:20
#1
Fuel Ratio for E85?
What do you tune the fuel ratio for e85 for? I always thought it was the same as regular gas, you just have to add more fuel to get it to burn, but I've read some other things that say the fuel ratio should be closer to 9:1 or 8:1 instead of 11:1 which is confusing me. I've read some other stuff that says the wideband will 'autoconvert' or 'not care' about what fuel you're running and 11.5:1 on your wideband with pump or e85 will be what you want to see you'll just have to add more gas to achieve your desired AFR.

I currently shoot for 11.5:1 fuel ratio, if on e85 would I still want to read 11.5:1 on my wideband or something much lower? Just want to make sure I'm understanding this correctly. I think seeing 11.5:1 on my wideband is correct for pump gas, but when I put e85 in it, it may say 11.5:1 but the actual stoich ratio of e85 is in that 8.x range or whatever 'richer than stoich' would be for e85. So in other words, even though I see 11.5:1, the ACTUAL ratio of e85 is something much lower (where it should be for e85). I'd have to change my lambda settings to match e85 stoich ratios, but that isn't required (nor do I know if my wideband can do that).

So I think I should keep tuning for 11.5:1 to be shown on the wideband. Can someone confirm?
Last edited by gomba on 2014-08-09 at 22-19-55.
2014-08-10 06:57:41
#2
You are absolutely right. Keep tuning to 11.5, the wideband doesn't care what fuel you are using.

Source: I am running E85, tuning the same way as pump gas
2014-08-10 13:56:17
#3
Stoich for e35 and gas is 1.0 lambda. There is no need to change anything on your wideband since to dget AFR, you have to multiply by 14.7. So 1 lambda times 14.7 equals 14.7. However, you need to tune .3 richer for e85. And this is all dependent on if your fuel system is setup to handle e85 since it need 30 percent more flow.
2014-08-10 15:03:05
#4
From the first E-85 thread in The Manifesto:

Originally Posted by BenFenner
Just so no one is confused by VeryQuikSSS's posts, technically the car doesn't run any richer on E85. Or it shouldn't if properly tuned. Actually, because of the higher anti-knock index, you can run leaner than you normally would with gasoline if you felt like it.

"Lean" and "rich" typically refer to having more or less fuel than stoichiometric. This means that with gasoline, if you have an AFR of 14.7:1 your mixture is technically stoichiometric. With E85, as mentioned, the stoichiometric mixture is 9.765:1 which means that you need much more fuel per air molecule to reach a "perfect" combustion.

While the car will need more fuel with E85, technically it's not running "rich" as VeryQuikSSS has described. It just has more fuel.

Now, about the air/fuel ratio, and tuning. Tuning with a wideband sensor and E85 is effectively the same for both gasoline and E85 because the oxygen sensor reads unburnt oxygen, and doesn't care at all what fuel you use. If your Wideband displays lambda, good for you. You can use 1.0 lambda as stoichiometric as you always have and call it a day. You can also feel warm and fuzzy inside knowing your display is technically accurate too.

Those with displays that show air/fuel ratios instead of lambda like "14.7:1", "12.0:1" and "15.5:1" can tune the same exact way they always have as well. While technically the air/fuel ratio while running E85 might be 9.765:1, the display will show "14.7:1". This is technically incorrect, but completely useful and easily interpreted if you just assume you're using gasoline, and use the values you've always tuned to. This means that you can tune to "12.0:1" ratio on the gauge and it will result in the proper amount of fuel being delivered for boost whether you're running gasoline, E85, propane, hydrogen, etc.


The first sentence about running lean is of particular relevance.



Originally Posted by gomba
So I think I should keep tuning for 11.5:1 to be shown on the wideband. Can someone confirm?
I can confirm this is the correct way to do it. You're on the right page. However now that you're using a fuel with much better knock tolerance than gasoline you can go a bit leaner and still be safe. Maybe consider 12.0:1 as displayed on the gauge.
Last edited by BenFenner on 2014-08-10 at 15-09-38.
2014-08-10 16:28:48
#5
Thanks Ben. I did some extra searching/reading on the net after I made my post and was pretty sure I was understanding it correctly and it's good to hear that I had it correct.

btw, I already made an e85 tune for my car. Seems to be running pretty good so far.

Originally Posted by ebinkerd
However, you need to tune .3 richer for e85.


What do you mean by .3 richer? Do you mean 30% or -.3 from the ratio, meaning a little richer?
Last edited by gomba on 2014-08-10 at 17-15-20.
2014-08-10 17:47:00
#6
I would keep the AFR's at what you had them on 93 octane for a few months and during that time test the integrity of the e85 you are getting. A lot of people run into problems with the octane rating being inconsistent throughout different batches, even from the same gas station. This could cause issues if you decide to lean out or throw some more timing in.

If the e85 tests out consistent, lean it out to 12.0 for faster flame travel. That's where the power is.
2014-08-10 18:32:59
#7
Originally Posted by gomba


Originally Posted by ebinkerd
However, you need to tune .3 richer for e85.


What do you mean by .3 richer? Do you mean 30% or -.3 from the ratio, meaning a little richer?


He means 30%.

I just tested my duty% on E85.

370cc 3bar, 84% at 7100rpm. SR20VE.

Guess I need bigger injectors to handle turbo+E85
2014-08-10 19:02:22
#8
Originally Posted by Dala
Originally Posted by gomba


Originally Posted by ebinkerd
However, you need to tune .3 richer for e85.


What do you mean by .3 richer? Do you mean 30% or -.3 from the ratio, meaning a little richer?


He means 30%.

I just tested my duty% on E85.

370cc 3bar, 84% at 7100rpm. SR20VE.

Guess I need bigger injectors to handle turbo+E85


I'm at 75% on 72lb injectors running 12 lbs on a 2871r

Originally Posted by D-Unit121
I would keep the AFR's at what you had them on 93 octane for a few months and during that time test the integrity of the e85 you are getting. A lot of people run into problems with the octane rating being inconsistent throughout different batches, even from the same gas station. This could cause issues if you decide to lean out or throw some more timing in.

If the e85 tests out consistent, lean it out to 12.0 for faster flame travel. That's where the power is.


Supposedly the amount of ethanol changes throughout the seasons.

-G
Last edited by gomba on 2014-08-10 at 19-04-33.
2014-08-10 21:08:09
#9
I tune e85 turbo cars to 12.2 Afr. There's a winter and a summer blend for e. We test multiple stations when the season changes
2014-08-11 01:55:16
#10
Originally Posted by weaselman50
I tune e85 turbo cars to 12.2 Afr. There's a winter and a summer blend for e. We test multiple stations when the season changes


what do you find in your testing? Do most stations have high % of ethanol?


Also, have any of you running e85 had any issues? Such as with the tune itself or hoses/seals wearing away from the fuel? Any other advice?

Thanks!
+ Reply To Thread
  • [Type to search users.]
  • Quick Reply
    Thread Information
    There are currently ? users browsing this thread. (? members & ? guests)
    StubUserName

    Back to top