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Thread: Flex fuel

  1. #1

    Flex fuel

    Anyone working on a flex fuel system for the coyotes?

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    As far as I know, the copperhead pcm was never intended to us an ethanol content sensor, so wiring one in would not be feasible.

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    The new vehicles don't use a sensor in the tank, they use the wideband readings and can adjust for e85 fuel content. The new f150 flex fuel does it that way anyway..

    If I remember correctly there is at least one person that has been getting good results from his flex fuel tune working with Eric Brooks.

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    HPT Employee Eric@HPTuners's Avatar
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    Quote Originally Posted by toyoguru View Post
    The new vehicles don't use a sensor in the tank, they use the wideband readings and can adjust for e85 fuel content. The new f150 flex fuel does it that way anyway..

    If I remember correctly there is at least one person that has been getting good results from his flex fuel tune working with Eric Brooks.
    This is correct. The logic is there and the parameters that go along with it are all populated with data in all of the Mustang calibrations I have looked at. I added the switch to enable it, but have not added all of the other parameters that go along with it. The few guys that have tried it so far had great results though.
    Eric Brooks
    HP Tuners, LLC

  5. #5
    So besides enabling the switch what else needs to be done besides injectors.

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    Advanced Tuner Witt's Avatar
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    Quote Originally Posted by RickClarke23 View Post
    So besides enabling the switch what else needs to be done besides injectors.
    There is a spark-alcohol adder and a stoich-ethanol parameter as well as a few other minor things. As of right now you can only tune 2 or so 2011 OS's that Eric unlocked the switch for but you have to use other software to work the alcohol tables and create an underlay tune until he finishes adding everything else.

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    HPT Employee Eric@HPTuners's Avatar
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    Quote Originally Posted by Witt View Post
    There is a spark-alcohol adder and a stoich-ethanol parameter as well as a few other minor things. As of right now you can only tune 2 or so 2011 OS's that Eric unlocked the switch for but you have to use other software to work the alcohol tables and create an underlay tune until he finishes adding everything else.
    Its in more than 2 now. I'll get the other parameters in soon.

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    Eric, could this be adapted to work with a car that swaps between e10 and ms109 with a stoich of 13.xx? Since the stoich is changing and we're not actually measuring ethanol.

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    HPT Employee Eric@HPTuners's Avatar
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    Quote Originally Posted by PST View Post
    Eric, could this be adapted to work with a car that swaps between e10 and ms109 with a stoich of 13.xx? Since the stoich is changing and we're not actually measuring ethanol.
    I don't see why not. There may be a clip for how far up the stoich will go. I will check into this and get back to you.
    Eric Brooks
    HP Tuners, LLC

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    Advanced Tuner Witt's Avatar
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    Quote Originally Posted by Eric@HPTuners View Post
    Its in more than 2 now. I'll get the other parameters in soon.
    My personal vehicle uses FSFD2, would make my day to have that switch available, I can take care of the other tables with something else until you have them defined. Ethanol content has been all over the place in the northeast as winter blends are being phased out.

  11. #11
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    eric were you able to get that file i emailed you to enable it. 14 GTCS

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    My strategy now shows the flex fuel switch but not sure if the other parameters that go along with it are there. If I start mixing in E85 with my 93 what should the stoich be configured at in tune? 14.08 or 9.76?
    2013 Mustang 5.0 A6
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    2016 Ford F250 6.7L
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    Advanced Tuner Witt's Avatar
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    Quote Originally Posted by imsuperman View Post
    My strategy now shows the flex fuel switch but not sure if the other parameters that go along with it are there. If I start mixing in E85 with my 93 what should the stoich be configured at in tune? 14.08 or 9.76?
    There are some things that aren't populated in the stock tune that need to be taken care of first. For now you have to use SCT to edit those tables and HPT to turn on the switch. I have an underlay tune I'm using with the tables populated but I'm still waiting for Eric to add the switch to my strategy.

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    Quote Originally Posted by Witt View Post
    There are some things that aren't populated in the stock tune that need to be taken care of first. For now you have to use SCT to edit those tables and HPT to turn on the switch. I have an underlay tune I'm using with the tables populated but I'm still waiting for Eric to add the switch to my strategy.
    I'll admit to not being familiar with the tuning limitations of the Ford PCMs, but in other vehicles where I have added flex fuel capabilities, I have used a stock flex fuel tune from a similar engine as a base, then added back the model-specific characteristics from the original file.
    Where I am going with this -- What is the reason you don't use a flex fuel F-150 file for the Mustang, then transfer the Mustang-specific tables to the F-150 base? I'm sure I am not the first person to think of this, so I'll bet there is a very obvious reason. Please enlighten me.

  15. #15
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    Could someone explain the deductive fueling logic (virtual flex fuel logic if you want to call it that)? How can the 02's sense the change? People have said before to me that it just senses the car go lean when ethanol is added to the tank. The reason I don't understand this is, if the PCM commands Stoich, it has no idea what fuel it's using, it could easily command 14.7 with pure ethanol. Sure it wouldn't burn that well, but how does it know?

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    Quote Originally Posted by AKDMB View Post
    Could someone explain the deductive fueling logic (virtual flex fuel logic if you want to call it that)? How can the 02's sense the change? People have said before to me that it just senses the car go lean when ethanol is added to the tank. The reason I don't understand this is, if the PCM commands Stoich, it has no idea what fuel it's using, it could easily command 14.7 with pure ethanol. Sure it wouldn't burn that well, but how does it know?
    You're looking at it backwards. Stoichiometric AFR is different depending on the fuel used. Fortunately, O2 sensors don't read AFR. Rather, their output is dependent on how far from stoichiometric the mixture is (regardless of how much ethanol is in the fuel).
    14.7 is stoich with gasoline, and stoich is around 9.75 with E85. Both mixtures would look the same to an O2 sensor.
    I'm not sure exactly how a Ford PCM calculates it, but in other flex fuel vehicles I have seen that work off of O2 feedback (no ethanol sensor), the PCM is able to determine the ethanol content by how much fuel trim it needs to reach stoichiometric. If it runs less fuel to achieve stoich, it will conclude it is running lower ethanol fuel. The more it has to increase the fuel trim, the higher the calculated ethanol level would be. The ethanol percentage that it calculates will then influence the other adjustments it makes from its "ethanol" tables. It appears that the Ford PCM uses a similar process.

  17. #17
    Advanced Tuner AKDMB's Avatar
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    Quote Originally Posted by SaabV View Post
    You're looking at it backwards. Stoichiometric AFR is different depending on the fuel used. Fortunately, O2 sensors don't read AFR. Rather, their output is dependent on how far from stoichiometric the mixture is (regardless of how much ethanol is in the fuel).
    14.7 is stoich with gasoline, and stoich is around 9.75 with E85. Both mixtures would look the same to an O2 sensor.
    I'm not sure exactly how a Ford PCM calculates it, but in other flex fuel vehicles I have seen that work off of O2 feedback (no ethanol sensor), the PCM is able to determine the ethanol content by how much fuel trim it needs to reach stoichiometric. If it runs less fuel to achieve stoich, it will conclude it is running lower ethanol fuel. The more it has to increase the fuel trim, the higher the calculated ethanol level would be. The ethanol percentage that it calculates will then influence the other adjustments it makes from its "ethanol" tables. It appears that the Ford PCM uses a similar process.
    I guess my main question boils down to this, if you had e85 in the tank and you fill up with pure gasoline why would the car struggle to achieve a 9.875 Air Fuel ratio with pure gas? The 02's would read 1.0 lambda and it would still think everything is ok right? I understand fuel trims, where the car can't achieve desired lambda so it applies fueling correction, but in the above example why would the car have any trouble reaching desired fueling?

    Also, how is the car supposed to know that the fuel trims indicate a different ethanol content instead of just like a vacuum leak or a mechanical issue that would normally throw off fueling?

    I might be looking at this way wrong, but I still don't understand lol. It might be better to just focus on the application instead of the concept.
    Last edited by AKDMB; 09-10-2015 at 08:45 PM.

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    You're still looking at it backwards. It is not targeting a specific AFR because it doesn't know what is in the tank. It is targeting stoichiometric, or Lambda = 1. So in your example of refilling with gasoline, when the engine restarts, it will be too rich (lambda less than 1). It will then adapt the trim to get back to stoich. It wouldn't "struggle" to get to 9.875, it would adapt toward 14.7 because that is stoich for gasoline.

    Your second question about how it recognizes different fueling vs a vacuum leak is one of the weaknesses of this system. There are safeguards built in, such as only applying the ethanol adaptation when there has been a significant change in fuel level (otherwise it only adapts ST and LT fuel trims as usual). But yes, a vacuum leak when you fill with gasoline could be adapted as a higher ethanol content and cause the PCM to run ethanol fueling (and timing!) when there is only gas in the tank.

    I think the concept will make more sense if you stop thinking in terms of AFR. The PCM doesn't care what the AFR is while adapting to the new tank of fuel. It only cares about achieving a stoich mixture. Whatever AFR that turns out to be doesn't really matter.

  19. #19
    Advanced Tuner AKDMB's Avatar
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    So, the widebands can sense stoich or lambda 1.0 regardless of fuel. They know a perfect burn regardless of what the PCM says it is.

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    Yes! A wideband or a narrowband will output a particular voltage based on its relationship to stoichiometric. That's the entire basis of how an O2 works! That's also the reason that O2 sensors are also known as lambda sensors. Remember, an O2 measures oxygen content. It doesn't know (or care) what kind fuel was burned.

    Your second sentence is what I'm referring to when I say you are looking at it backwards. The PCM is not "saying" anything. It is certainly not "saying" what a perfect burn is. Rather, it is trying to figure it out! It is not commanding a certain AFR and figuring out the fuel trim as a result. That wouldn't work, and is why this isn't making sense to you. Rather, it is adjusting the fuel trim to come up with lambda = 1 (whatever that AFR works out to be is the result, not the starting point).