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Thread: 2016 Silverado flex fuel tuning

  1. #1
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    2016 Silverado flex fuel tuning

    My truck has no fuel sensor and the tune is set up for a virtual flex fuel sensor. That sounds pretty cool, just keep the lambda whatever it is with the original stoichiometric value and target values, right? I guess that's what happens but I also that it would back calculate the actual alcohol percent and report it in the alcohol percent pid. Wrong. It magically stays at 9.8% which is the value for E10 a/f 14.1. The target a/f ratios are all relative to the original 14.1 stoichiometric value. I guess I could do a math function and calculate the actual a/f and look up the alcohol% in a table but probably not. I'm going to install a fuel sensor and hope it's just a matter of toggling the tune to actual sensor from virtual and all the a/f table magically take care of themselves. Is it that easy? Was hoping it was well explained in the Tuning School book but I don't see anything.

  2. #2
    Senior Tuner Higgs Boson's Avatar
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    is your truck a factory flex fuel vehicle?

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    It doesn't have a sensor. I understand that 2016's are capable of running flex fuel with a sensor as the wiring harness is there and the materials are compatible. There is a flex fuel tune in the repository so I plan to do a table compare and swap the right tables after installing the sensor. Sound right?

  4. #4
    Senior Tuner Higgs Boson's Avatar
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    Quote Originally Posted by littlefield View Post
    It doesn't have a sensor. I understand that 2016's are capable of running flex fuel with a sensor as the wiring harness is there and the materials are compatible. There is a flex fuel tune in the repository so I plan to do a table compare and swap the right tables after installing the sensor. Sound right?
    what I am asking is if your truck is a factory flex fuel vehicle. asked another way, does your truck have a yellow gas cap? can it run E85 without alteration to the calibration or hardware?

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    It has a black gas cap. The owners manual says regular gas only. My tune has virtual sensor selected. I’m running an E20 mix now and haven’t noticed anything bad happening performance wise.

  6. #6
    Senior Tuner Higgs Boson's Avatar
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    Quote Originally Posted by littlefield View Post
    It has a black gas cap. The owners manual says regular gas only. My tune has virtual sensor selected. I’m running an E20 mix now and haven’t noticed anything bad happening performance wise.
    there is no way to enable the virtual sensor on a black cap vehicle so you are not accomplishing anything by running E20 except throwing off your fuel trims and getting worse mileage. they all say virtual, it doesn't mean anything on a black cap vehicle.

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    I must not be making myself clear. Typical. I’ve ordered the sensor and associated piping and have a flex fuel tune for the truck. Should be able to convert it, correct?

  8. #8
    Senior Tuner Higgs Boson's Avatar
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    Quote Originally Posted by littlefield View Post
    I must not be making myself clear. Typical. I’ve ordered the sensor and associated piping and have a flex fuel tune for the truck. Should be able to convert it, correct?
    yes, you were clear about that part and yes you can install a sensor and it will work.

    i was addressing everything else you were talking about. not sure what all this virtual and E20 talk was for if your question was simply "can I install a flex fuel sensor."

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    Well, under my engine/ fuel/flex fuel tab I have flex fuel enabled and virtual fuel sensor selected. According to the description, if this is selected virtual fuel calculations are used. Whatever the heck that is. Sounds to me like the computer maintains target lambda as alcohol concentration changes. When a fuel sensor is used the stoichiometric values for the different alcohol contents are put into the Stoichiometric AFR table. With the virtual sensor all the values are 14.08, must use fuel trim for the different concentrations. Don’t understand exactly what it’s doing. I ran some E20 and saw no change in the alcohol content pid output although I should be able to see something on the actual calculated a/f ratio. I think the Virtual sensor thing is just a wide range fuel trim using nothing but O2 sensor data, no real target a/f targets for anything but E10. At this point it’s academic.
    Last edited by littlefield; 12-03-2018 at 08:20 PM.

  10. #10
    Virtual flex fuel is crap. GM had this brilliant idea that once you put in 5 gal or more fuel in, it will try to "calculate" the ethanol percentage by how far off the fuel trims go on the next drive cycle. However, they never really stated what the drive cycle is and how long it takes to complete. If the cycle does not complete on the drive following the fuel refill, it reverts back to the previous "learned" value. This design created many people filling up with e85 and then getting a check engine light on the second drive cycle, because now it's running lean and the computer thinks it has e0 not the e85 actually present. And to top it off, GM never thought about letting us set the correct ethanol percentage in the computer with GM equipment. This means draining the fuel tank and running e0 /e10 or drive it with a near empty tank and then refill with e85 and attempt the drive cycle learn. And then there's the problem when it's actually learned the correct ethanol percentage and either the battery dies or they had another issue and the ECM had the codes cleared....well, it reverts back to e0. So, in summary, it's a crap system.

  11. #11
    Senior Tuner Higgs Boson's Avatar
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    Quote Originally Posted by littlefield View Post
    Well, under my engine/ fuel/flex fuel tab I have flex fuel enabled and virtual fuel sensor selected. According to the description, if this is selected virtual fuel calculations are used. Whatever the heck that is. Sounds to me like the computer maintains target lambda as alcohol concentration changes. When a fuel sensor is used the stoichiometric values for the different alcohol contents are put into the Stoichiometric AFR table. With the virtual sensor all the values are 14.08, must use fuel trim for the different concentrations. Don’t understand exactly what it’s doing. I ran some E20 and saw no change in the alcohol content pid output although I should be able to see something on the actual calculated a/f ratio. I think the Virtual sensor thing is just a wide range fuel trim using nothing but O2 sensor data, no real target a/f targets for anything but E10. At this point it’s academic.
    refer to post 6.

    again, virtual sensor is for yellow cap vehicles.

    black cap vehicles must install the hardware and properly calibrate all the flex tables.

  12. #12
    Senior Tuner Higgs Boson's Avatar
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    Quote Originally Posted by Kyle_Customizer View Post
    Virtual flex fuel is crap. GM had this brilliant idea that once you put in 5 gal or more fuel in, it will try to "calculate" the ethanol percentage by how far off the fuel trims go on the next drive cycle. However, they never really stated what the drive cycle is and how long it takes to complete. If the cycle does not complete on the drive following the fuel refill, it reverts back to the previous "learned" value. This design created many people filling up with e85 and then getting a check engine light on the second drive cycle, because now it's running lean and the computer thinks it has e0 not the e85 actually present. And to top it off, GM never thought about letting us set the correct ethanol percentage in the computer with GM equipment. This means draining the fuel tank and running e0 /e10 or drive it with a near empty tank and then refill with e85 and attempt the drive cycle learn. And then there's the problem when it's actually learned the correct ethanol percentage and either the battery dies or they had another issue and the ECM had the codes cleared....well, it reverts back to e0. So, in summary, it's a crap system.
    GM definitely has the least logical, worst calibrations of any of the makes I have had a chance to work on. especially bad are the transmissions.

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    Quote Originally Posted by Higgs Boson View Post
    there is no way to enable the virtual sensor on a black cap vehicle so you are not accomplishing anything by running E20 except throwing off your fuel trims and getting worse mileage. they all say virtual, it doesn't mean anything on a black cap vehicle.
    So there are 3 options: fuel sensor, virtual and no virtual? Not sure what virtual does for you other than the complicated scheme described above. Still works with fuel trims like normal. Does it give you an indication of alcohol %?

  14. #14
    Senior Tuner Higgs Boson's Avatar
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    Quote Originally Posted by littlefield View Post
    So there are 3 options: fuel sensor, virtual and no virtual? Not sure what virtual does for you other than the complicated scheme described above. Still works with fuel trims like normal. Does it give you an indication of alcohol %?
    there are three options:

    1. black cap means E10 only (E0 - E20 won't hurt your car but it won't do anything either), Virtual setting means nothing no matter what you do, running over E10 only throws off your fuel trims and makes you run lean at WOT. you can manually adjust your stoich value if you know precisely what ethanol % you are running and you also have to manually readjust your spark to MBT for that mix, not ideal.

    2. black cap add a flex sensor, properly set up calibration and you can run E0 - E85, fueling and spark adjust automatically, physical sensor updates the ECM quickly and everything works great

    3. yellow cap, flex fuel vehicle from the factory, almost all are set to Virtual and calculation does work but slowly and unreliably. there were some very early day yellow caps with physical sensors and a more recent splash of sensors also (which is of course why sensors exist in the first place)

    my point is, stop messing around and install a sensor and set it up for flex fuel and enjoy.

  15. #15
    Senior Tuner LSxpwrdZ's Avatar
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    Flex Fuel is usually enabled as virtual on the newer trucks for all of them. You must look at the min/max ethanol percentages to see if it has the ethanol locked on 10% or will let it adjust for itself.

    Non-flex trucks were set to 10% min and 10% max so it locked E content to 10% thus giving the correct stoich point.
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    My alcohol reads 9.8% no matter what. Got a fuel sensor to put in and a 2016 Silverado flex fuel tune to put in. The truck has a very nice tune part throttle and WOT, can I expect to keep my power enrichment numbers the same?

  17. #17
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    I have a 2016 Silverado 5.3 installed the sensor. I have the hypertech max energy 2.0 tune for high octane (93) it enables enrichment to start at 4000 rpm and it actually leans out the EQ Ratio (Gas) in the 4096-5632 RPM range. It does not touch the Alcohol enrichment table though, but I wonder if it needs to be leaned as well.

  18. #18
    Tuner Camaro6's Avatar
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    If you installed a sensor, then select sensor instead of virtual.
    turn on the DTC parameters for flex fuel
    flex fuel enable
    you might have a second flex fuel enable under the Fuel Sys tab

    Within Flex Fuel tab - to make it react faster I do the following
    Change delay volume to 0.026
    Change transition volume to 0.026

    What is your ethanol percent reading now?
    You'll want to tune the alcohol parameters to the vehicle for best performance and mpg balance
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  20. #20
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    Yes I already have mine set to sensor with 70.6% Ethanol. What I was referring to was the Hypertech tune Which Leaned out the Power Enrichment for GAS only not the Alcohol table.