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      05-24-2016, 09:51 PM   #1
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E85 Fuel Ratio

There seems to be a lot of people tuning with different mixtures of E85, but no discussions of AFR's. It seems to me that most people are running very lean on their tunes.

I would like to start a discussion on this topic to see what the community thinks. Seems to me that many people are causing harm unless I am not understanding this correctly.

Gasoline stoichiometric = 14.7
Gasoline max power rich = 12.5
Gasoline max power lean = 13.23

E85 stoichiometric = 9.765
E85 max power rich = 6.975
E85 max power lean = 8.4687
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      05-25-2016, 12:01 AM   #2
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Our o2 sensors read lambda (0.88, 0.89, 0.90 etc). When you see a e85 tune set to 12.3 AFR its just a 14.7 stoic based number conversion not the true AFR.

For example if your running straight E85 with a lambda of 0.88 your going to see an AFR of 14.7x 0.88=12.9 AFR but your actual AFR is 0.88 x 9.765= 8.5.

Think about it, if your AFR with E85 was a true 12.5 how would you explain using so much more fuel than pump gas with the same AFR?
      05-25-2016, 02:04 PM   #3
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^ What that guy said. Oxygen sensors don't read in AFR.
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      05-25-2016, 03:23 PM   #4
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Quote:
Originally Posted by Nonecure View Post
There seems to be a lot of people tuning with different mixtures of E85, but no discussions of AFR's. It seems to me that most people are running very lean on their tunes.

I would like to start a discussion on this topic to see what the community thinks. Seems to me that many people are causing harm unless I am not understanding this correctly.

Gasoline stoichiometric = 14.7
Gasoline max power rich = 12.5
Gasoline max power lean = 13.23

E85 stoichiometric = 9.765
E85 max power rich = 6.975
E85 max power lean = 8.4687
Air fuels don't change with the type of fuel you run. Yes e85 burns about 30% faster than your standard 91/93 octane e10 fuel. But I'm typically at 14.7 it ideal and low throttle crusing and in the low 13's during wide open throttle.
With my turbo 600whp s2000 I typically run high 10's and low 11's air fuel during wide open throttle weighed it's e85 or 91octane.
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      05-25-2016, 03:51 PM   #5
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Quote:
Originally Posted by Riceball777 View Post
Air fuels don't change with the type of fuel you run. Yes e85 burns about 30% faster than your standard 91/93 octane e10 fuel. But I'm typically at 14.7 it ideal and low throttle crusing and in the low 13's during wide open throttle.
With my turbo 600whp s2000 I typically run high 10's and low 11's air fuel during wide open throttle weighed it's e85 or 91octane.
They very much DO change with the type of fuel you run. You don't think they are changing because and oxygen sensor doesn't read in AFR, it reads in lambda.

Stoich for all fuels is 1.00 lambda. That means if you have a wideband and gauge that's calibrated for gasoline. It's going to read 14.7:1 AFR REGARDLESS of the fuel you have in there or the mixture.

The actual stoich of E10 (pump gas) is more like 14.13. When you are in the "10's" on E85 you are actually in the "6's", using a properly calibrated wideband setup for ethanol.
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      05-25-2016, 06:46 PM   #6
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Stanlalee and Milan dropping knowledge on people. Thanks for the refreshing technical posts guys. Spot on.
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      05-25-2016, 10:28 PM   #7
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      06-13-2016, 07:33 PM   #8
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Yes please do go ahead and run your cars on E65 - E85 at a lambda 1 or at gasoline stoichiometric of 14.7 and let us know how it drives.

Over 50% ethanol on our platform the stoichiometric or lambda is not the same as you would run for gasoline or fuel blends with less than 50% ethanol

If you do the DME will start to throw a CEL, and lambda codes if you do. The DME will even lean you out ridiculously also, resulting in flatline 0 trims. When you experience this then you know something is wrong.
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Last edited by BuraQ; 06-13-2016 at 07:54 PM.
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      06-13-2016, 09:34 PM   #9
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Quote:
Originally Posted by BuraQ View Post
Yes please do go ahead and run your cars on E65 - E85 at a lambda 1 or at gasoline stoichiometric of 14.7 and let us know how it drives.

Over 50% ethanol on our platform the stoichiometric or lambda is not the same as you would run for gasoline or fuel blends with less than 50% ethanol

If you do the DME will start to throw a CEL, and lambda codes if you do. The DME will even lean you out ridiculously also, resulting in flatline 0 trims. When you experience this then you know something is wrong.


Lambda is an equivalence ratio. Lambda = (AFR / AFR stoich).

The O2 measures the lambda (chemical equilibrium sensor), the XDF has a calculation for AFR. That calculation is X * .00024414 * 14.7 where X is O2 output

Let's break that down:
Original eq: Lambda = AFR / AFR(stoich)
Re-arrange: Lambda*AFR(stoich) = AFR
Account for hardware: (O2 output * scalar) = Lambda, scalar =.00024414
Account for gasoline: AFR(stoich) = 14.7
Substitute: (O2 output * .00024414) * 14.7 = AFR (value in table), look familiar?

Lambda of 1 is lambda of 1 for every single fuel that burns, including propane and any gas released from your ass if you combust it. When you type in 14.7 you're actually typing in lambda 1. If you run anything that burns, the computer will attempt to get to lambda of 1. If that afr isn't actually 14.7:1 (say it's like 9.7:1), then you will use some trims to get there, but the car still thinks your at 14.7:1 even though you're really at 9.7:1 because it only knows lambda, and is calculating based on gas. But if trims go up too much (because you fail at using the fuel scalar correctly), you will get mixture codes.

Say the gas you're blowing out your ass is at chemical equilibrium at an afr of 4:1 because you're so full of shit. If the N54 O2 sees the combustion products from your ass and is tuned to 14.7:1 (lambda 1 actually, because conversions in the xdf), it will add more of your shit until it sees lambda 1 on the O2 sensors. But really you're emptying your shit tank really fast because the actual afr is 4:1. If your fuel scalar isn't set to account for this, you'll trim out, run lean (for your fuel type, even if that's technically 6:1), and *hopefully* blow up. Cheers.

Last edited by V8bait; 06-13-2016 at 09:40 PM.
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      06-13-2016, 10:15 PM   #10
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Ohhh jeezus.... nooo please nooo.. So if your not tuning for lambda and your tune for a E60-85 afr of 13.6 which is really a lambda of 1.4... that makes total sense. I guess the super duper closed loop system adjusts for it....
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      06-13-2016, 11:00 PM   #11
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Quote:
Originally Posted by 3000GT MR View Post
Ohhh jeezus.... nooo please nooo.. So if your not tuning for lambda and your tune for a E60-85 afr of 13.6 which is really a lambda of 1.4... that makes total sense. I guess the super duper closed loop system adjusts for it....
13.6/14.68=.926

So .926 lambda
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      06-13-2016, 11:11 PM   #12
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I don't understand any of this^^^^ but a buddy of mine went stright E85 with fuel it stage 3 and PI. His bank one is reading 14.7 no matter what we do to the fuel. Is this a messed up O2 sensor or something else?
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      06-13-2016, 11:23 PM   #13
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Quote:
Originally Posted by Milan View Post
13.6/14.68=.926

So .926 lambda
Wrong. 13.6 e85 afr is 13.6/9.7 (if we were being accurate in our tables), around 1.4 and reeeel lean.

13.6 gasoline afr is 13.6/14.7. (What the computer sees in tables since it's calibrated for gas), slightly rich.

But you type in 13.6 to a table and you get your .926 lambda value, which is your ACTUAL fuel target. With gas, that .926 is 13.6:1, with E85 it's .926*9.7 so like 9:1, that's why you burn around 40% more fuel with e85.

/done

Last edited by V8bait; 06-13-2016 at 11:33 PM.
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      06-14-2016, 10:26 AM   #14
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Quote:
Originally Posted by V8bait View Post


You still don't understand lambda? Holy shit fuck.
Quote:
Originally Posted by 3000GT MR View Post
Ohhh jeezus.... nooo please nooo..
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      06-14-2016, 01:15 PM   #15
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This is why its so much easier to talk about lambda rather than AFR. I wish the car tuning community would transition accordingly.
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      06-14-2016, 01:21 PM   #16
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The documentation I found was stating the following:

Gasoline stoichiometric = 14.7
Gasoline max power rich = 12.5
Gasoline max power lean = 13.23

E85 stoichiometric = 9.765
E85 max power rich = 6.975
E85 max power lean = 8.4687

The table provided by 3000GT shows lambda of 0.9 is 13.2 gas or 8.7 E85. That is too lean to run E85. I don't know the answer, but it just seems to me that adjustments need to be made for running E85 to run a little richer.

It seems to me that if you are targeting lambda 0.87 on gas, you would want to target 0.75 on E85 under full power.
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      06-14-2016, 04:10 PM   #17
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Quote:
Originally Posted by Nonecure View Post
It seems to me that if you are targeting lambda 0.87 on gas, you would want to target 0.75 on E85 under full power.
Yes and no. Firstly good luck fueling it. Secondly this isn't PFI this is DI. Thirdly you're generally not using E85, you're using <E85, so like E50-E80. But otherwise, yes.

BEHOLD- MY FUEL TABLE FULL OF LAMBDAZ!! IT'S M'F***ING MAGIK UP IN THIS XDF!!
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      06-14-2016, 04:53 PM   #18
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Quote:
Originally Posted by V8bait View Post
Yes and no. Firstly good luck fueling it. Secondly this isn't PFI this is DI. Thirdly you're generally not using E85, you're using <E85, so like E50-E80. But otherwise, yes.

BEHOLD- MY FUEL TABLE FULL OF LAMBDAZ!! IT'S M'F***ING MAGIK UP IN THIS XDF!!
Firstly thanks for the replay. Good luck fueling it? I haven't had any issues so far, am I missing something? I measured it recently and it is actually at E85, but you are correct that it will vary. I haven't seen summer blend go below E75.

It looks like you are going slightly lean at low rpm, is that to spool faster? Targeting 0.83 i'm sure is ok. My point was that we need to run a little more rich than gas, and that is what you are doing.

So why were you blasting BuraQ for saying that you can't target lambda 1 on E85?
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Last edited by Nonecure; 06-14-2016 at 04:59 PM.
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      06-14-2016, 05:11 PM   #19
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Quote:
Originally Posted by Nonecure View Post
Firstly thanks for the replay. Good luck fueling it? I haven't had any issues so far, am I missing something? I measured it recently and it is actually at E85, but you are correct that it will vary. I haven't seen summer blend go below E75.

It looks like you are going slightly lean at low rpm, is that to spool faster? Targeting 0.83 i'm sure is ok. My point was that we need to run a little more rich than gas, and that is what you are doing.

So why were you blasting BuraQ for saying that you can't target lambda 1 on E85?
Yeah if you can fuel it that's step 1, lots of people can't fuel that rich with e85. My point with DI is you don't need to go as rich to begin with. And if you're verifying ethanol, cool. However lots of times it's not full strength e85 so going that rich isn't always useful. I'm lean in the cruise areas, has nothing to do with spool, i use spool mode for that.

BuraQ is on blast because he has no idea what he's doing after all this time still lol. Just read his post, I can't believe people let him touch their car. Understanding this stuff is like the pre-req for tuning 101. You absolutely can target lambda 1. Which in the tables is around 14.7

Last edited by V8bait; 06-14-2016 at 05:33 PM.
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      07-02-2016, 03:38 PM   #20
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Quote:
Originally Posted by Nonecure View Post
The documentation I found was stating the following:

Gasoline stoichiometric = 14.7
Gasoline max power rich = 12.5
Gasoline max power lean = 13.23

E85 stoichiometric = 9.765
E85 max power rich = 6.975
E85 max power lean = 8.4687

The table provided by 3000GT shows lambda of 0.9 is 13.2 gas or 8.7 E85. That is too lean to run E85. I don't know the answer, but it just seems to me that adjustments need to be made for running E85 to run a little richer.

It seems to me that if you are targeting lambda 0.87 on gas, you would want to target 0.75 on E85 under full power.
Your numbers are pretty close to what I think E85 should be. Ethanol should be run as lean as possible to extract the most power. Keeping EGT and IAT in check... I don't think your lambda numbers reflect the best mixture for E85. I think 0.80 is plenty rich.

Unless your getting pre-ignition or high EGT I fail to see the benefit of rich Ethanol mixtures.

Last edited by 2009BMW335Xi; 07-02-2016 at 03:49 PM.
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      07-02-2016, 03:41 PM   #21
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Here are my estimates. If these numbers are wrong. I'd like to know.

Ratio Lambda Condition
12.8:1 0.87 Lean Best Torque (LBT)
12.2:1 0.83 Mean Best Torque (MBT)
11.8:1 0.80 Rich Best Torque (RBT)
For Gasoline
7.8:1 0.87
7.5:1 0.83
7.2:1 0.80
For Ethanol
richer than this, your applying a bandaid for another issue.
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      07-02-2016, 06:44 PM   #22
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Quote:
Originally Posted by V8bait View Post
Wrong. 13.6 e85 afr is 13.6/9.7 (if we were being accurate in our tables), around 1.4 and reeeel lean.

13.6 gasoline afr is 13.6/14.7. (What the computer sees in tables since it's calibrated for gas), slightly rich.

But you type in 13.6 to a table and you get your .926 lambda value, which is your ACTUAL fuel target. With gas, that .926 is 13.6:1, with E85 it's .926*9.7 so like 9:1, that's why you burn around 40% more fuel with e85.

/done
The tables are defined using a gasoline scale....

You basically said the same thing as me
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