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Thread: E38 Flex Fuel: On the fly timing and fueling - anyone interested?

  1. #21
    Forum tyhee Site Admin GMPX's Avatar
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    Guys, forget the 555 timer, too old, will drift with temp. What this really needs is a nice little 8 pin AVR or PIC micro to generate the signal, it would cost about $2.50 for all the parts (if that).

    Early on when I was playing around with 'fooling' the ECM in to using the ethanol tables for an LPG application I had suggested to the shop that we were testing with that we make a board that simulates the ethanol signal.
    For this LPG application it was decided that on the fly variable ethanol % was not needed, I mean, you are on LPG or you are not! And adding in to the custom OS the option to force the ethanol percentage was much easier.

    As a project this could go two ways, a simple dial in the car with some markers on a label to show the percentage of ethanol (cheap), or, something with a 7 segment display showing the percentage selected (expensive).

    Lets all be thankful that GM left that legacy code to use a real ethanol sensor even though they have never released a car using the E38 and a flex fuel sensor.

    Cheers,
    Ross
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  2. #22
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    Quote Originally Posted by GMPX View Post
    Guys, forget the 555 timer, too old, will drift with temp. What this really needs is a nice little 8 pin AVR or PIC micro to generate the signal, it would cost about $2.50 for all the parts (if that).

    Early on when I was playing around with 'fooling' the ECM in to using the ethanol tables for an LPG application I had suggested to the shop that we were testing with that we make a board that simulates the ethanol signal.
    For this LPG application it was decided that on the fly variable ethanol % was not needed, I mean, you are on LPG or you are not! And adding in to the custom OS the option to force the ethanol percentage was much easier.

    As a project this could go two ways, a simple dial in the car with some markers on a label to show the percentage of ethanol (cheap), or, something with a 7 segment display showing the percentage selected (expensive).

    Lets all be thankful that GM left that legacy code to use a real ethanol sensor even though they have never released a car using the E38 and a flex fuel sensor.

    Cheers,
    Ross
    Yes great that GM left that code in there and even greater that you uncovered access to it!

    Yes I found the 555 based setup also jumped around a lot with noise but I thought that was my lack of expertise with the circuitry. Seems the in vehicle supply line noise was too high as it was only stable with a battery supply. Ran a digital oscillator with a display but that has to have frequency and waveshape setup every power off.

    So settled on an AVR with a pot. . A little over $2.50, but not appreciably and very flexible.
    Last edited by gmh308; March 14th, 2010 at 12:10 PM.

  3. #23
    Forum tyhee Site Admin GMPX's Avatar
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    It's funny these days how 'most' small projects are easier to do with an AVR than traditional methods.
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  4. #24
    EFILive Reseller ringram's Avatar
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    Cant efilive be used to intercept the final value of ethanol content via DVT?
    Then we would have full control from software and a new roadrunner style approach for E38's!?
    Or perhaps a USB controlled device and kit to adapt to pin 40 can be used if it must be a physical input!?
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  5. #25
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    Default Flex Fuel Fail

    Just an FYI - some calibrations if set up to fail on no hard sensor and go to default ethanol value as set in the calibration via EFILive wont actually fail.

    The ethanol content can still be varied through applying the right frequency but they dont fail if the frequency input is not there.

    i.e. if the default value on hard sensor failure is 50% normally the diagnostic will fail the sensor and go to the default value in the diag run time after start up.

    Flex Fuel Option

    {B0178} Flex Fuel Option Yes
    {B0184} Flex Fuel Sensor Type Actual Sensor
    {B0185} Flex Fuel Default Percentage 50 %
    {B0186} Flex Fuel Sensor Diagnostic Enabled
    {B0187} Flex Fuel Diagnostic Run Time 3.0 Seconds

    This is not OS specific just calibration specific. i.e. OS 12619078 from a VE/G8 cal wont fail whereas same OS from a Chev truck will fail. No VE/G8 OS's seem to fail, or the earlier VZ OS's.

    More flex fuel options still hiding under the covers .

  6. #26
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    Does this mean I could add a sensor to a G8 from a new VE? Just have to run the wire and fill in the calibration tables?

  7. #27
    Forum tyhee Site Admin GMPX's Avatar
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    New VE, how new? They are E85 capable these days anyway.
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  8. #28
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    Yeah, that's what I mean. A VE that has the flex fuel sensor, just meant a "newer" ve, or one with flex fuel capabilities. Anyone have a part# or approximate cost on something like this?

  9. #29
    Forum tyhee Site Admin GMPX's Avatar
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    I think they use different injectors too, so you would need a new set of them (I can't confirm that though). I would expect the whole pump / sender / sensor assembly would run close to $300 - $400 (wild guess).
    Aside from that, E85 prices are as expected a joke here in Australia (only a max of 20 cents per/L cheaper), I can't see it being worth your while if you have no other reason other than wanting to run E85 out of curiosity.
    Last edited by GMPX; March 29th, 2011 at 02:42 PM.
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  10. #30
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    I already run E85 on my G8. Prices here in Illinois aren't bad at all, 70 cents less than premium, and right now I'm able to get 10 dollars off a fillup in Illinois until the end of June thanks to the Illinois Corn growers association, along with a 340 dollar rebate at the end of the year as long as I use at least 75 gallons. I can run 27-29 degrees of timing at WOT on e85 with no issues, and only about 23-24 on 93. The injectors won't need changed, I'm already running them and injector duty cycle at wot is ~80%. I'd just like the capability of adding the sensor, which I confirmed isn't part of the pump/sender unit, it is indeed a separate unit, just can't find a part number on it. For 400-500 bucks in parts, to have the flexibility of running any blend of gasoline and ethanol would be worth it to me, but if it gets crazy it's not worth it to me, I'll just update my tune to reflect my E85 blend.

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