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

  1. #71
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    Quote Originally Posted by samgm2 View Post
    Boy, no kidding. I am 50. The 555 was old when I was a kid! I wouldn't use a 555 for anything anymore.
    555 was new when I was a kid LOFL. So its only a couple years before it got "old" then. Yes why use a 555 when you can use an AVR. I use them as engine simulators and as a "virtual" flex fuel sensor LOL.

  2. #72
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    Quote Originally Posted by samgm2 View Post
    I have yet to find anyone that has confirmed that the flex parameters actually enable flex fuel operation. So far I have confirmed that people can shut it off, but I know of no one that has turned it on when it was off by default. This was certainly true of HP Tuners. Their flex fuel stuff didn't work for turning the function on. EFILive appears to have discovered more of the parameters, however. I am very interested in the answer and might just go ahead and burn up another license to find out.
    Didnt I tell you that Sam? Didnt make any of the details up! It was all hours of work - WITH - production VFS flex fuel tunes. Have never come across a tune that wouldnt work with the hard sensor selected. But some do not run the sensor fail test and go to the default ethanol content.

  3. #73
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    The AVRs are a decent chip to mess with. I'm pretty sure there are other PPC chips available perhaps a ARM series, though my experience setting up the Dev tool chain with Cortex A8s has been less then great.

    I don't see why the virtual sensing of E85 content can't be used. You could 'just' as easily add a few CHT and EGT sensors to combine with the O2 sensor to pretty accurately estimate E85 content.

    The 3900 V6 I'm messing with has Flex Fuel capability stock. I'm fairly sure the fuel system is different to handle the E85. Only certain elastomers and polymers are compatible with E85. I'm not sure however if straight gas parts are the same part number or not.

    E85 has a huge advantage as its published octane rating is well over 105. If memory serves around 110. It should also burn a bit cooler (hence the reason CHT and EGTs with O2 would give you a decent idea what concentration you are running... especially if you throw air mass numbers into it as well... the stochiometry then becomes a somewhat simple thermodynamic calculation which I'm pretty sure the CPU can handle on the fly or at least an external AVR could).

    When I priced a new E85 fuel pump from my project car they were around $350-$450 US.

    I'm guessing GM is using the same parts for all cars but I could be wrong.

  4. #74
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    Quote Originally Posted by NateD4 View Post

    I don't see why the virtual sensing of E85 content can't be used. You could 'just' as easily add a few CHT and EGT sensors to combine with the O2 sensor to pretty accurately estimate E85 content.

    The 3900 V6 I'm messing with has Flex Fuel capability stock. I'm fairly sure the fuel system is different to handle the E85. Only certain elastomers and polymers are compatible with E85. I'm not sure however if straight gas parts are the same part number or not.

    It should also burn a bit cooler...

    When I priced a new E85 fuel pump from my project car they were around $350-$450 US.

    I'm guessing GM is using the same parts for all cars but I could be wrong.
    GM "virtual fuel sensor" flex fuel control uses O2 sensors to estimate and adjust for ethanol content. For some reason they have recently started going back to hard sensors. This may be due to the price. Originally (several years ago) they were around $400 as a part. Now they can be found for ~$80. Always driving cost out. Given every platform needs to be calibrated for VFS to work properly, a low cost (GM cost probably $5-$10), a hard sensor is a simpler value proposition.

    Have been running E85 for around 3 years now...all on stock fuel system. Steel lines - bare metal exposed, rubber hose, normal Walbro pump. There is no corrosion - even on bare steel. The rubber hose is fine. Injectors are fine. Though I would guess on a car or truck that needs to deliver to a 100,000 mile warranty, is why GM is now using nylon when it is not using coated steel.

    The injectors and valve seats are made from a slightly different material to meet durability objectives on flex fuel.

    FYI - Intake valve temp is about 30C lower on E85. Approx 130C vs 160C on gas. So nice and cool.

    Cheers.

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    Quote Originally Posted by gmh308 View Post
    Didnt I tell you that Sam? Didnt make any of the details up! It was all hours of work - WITH - production VFS flex fuel tunes. Have never come across a tune that wouldnt work with the hard sensor selected. But some do not run the sensor fail test and go to the default ethanol content.
    I have a setup that I wish to be a truly flex fuel compatible automobile but I do not have a E38. I have a gen III 1mb pcm. I wish to run flex fuel and use something to simulate the flex fuel sensor signal or the sensor itself. If this is possible for the E38 Is it possible for the Gen III PCM?

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    Quote Originally Posted by lt1stang View Post
    I have a setup that I wish to be a truly flex fuel compatible automobile but I do not have a E38. I have a gen III 1mb pcm. I wish to run flex fuel and use something to simulate the flex fuel sensor signal or the sensor itself. If this is possible for the E38 Is it possible for the Gen III PCM?
    2006 Silverado 5.3L PCM does Flex Fuel.

  7. #77
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    Quote Originally Posted by gmh308 View Post
    2006 Silverado 5.3L PCM does Flex Fuel.
    I failed to mention that it is turbocharged and I want to use a COS to run a 2 or 3 bar map.

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    Fuel composition sensor - GM part # 12570260 - for use with 2002 to 2005 Gen III Flex Fuel engines.


    Regards,
    Taz

  9. #79
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    Holy Rip-off Batman, $313 for a FF sensor!, must be made by Mercedes.
    It would be interesting to know what the sensor is that GM Holden are using on the 2010+ Commodore's. Holden's (we are talking E38 here) don't use the virtual sensor algo's, they have a real sensor, I've heard it's part of the fuel pump?
    Need official EFILive help, please go here.
    For tuning support please post your questions on this forum (or other auto forums).
    Sorry if I don't respond to your PM, don't take it personal.


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    Quote Originally Posted by GMPX View Post
    ... Holy Rip-off Batman, $313 for a FF sensor! ...
    Yes sir ... GM list price is just over $600.


    Cheers,
    Taz

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