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Thread: Switched to E85, changed stoich value and VE way off?

  1. #1
    Tuner in Training
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    Switched to E85, changed stoich value and VE way off?

    I drive a turbo'd 2006 Silverado WT 4.8L non flex fuel. I filled up with e85 last night, with only a few gallons of gasoline left in the tank, I drove for a few minutes to maybe get some of the gas outta the rails. Then uploaded a tune, I changed the values in all cells of the stoich table to 9.8 for e85. It started rough but I drove for a little while (10 miles maybe) and it stayed rich, and I had to take out 20% from the VE to get to lambda while driving. I ended up driving for over 40 minutes. The gas tune was pretty spot on. This morning the cold start was super lean, and just a little lean crusing, man am I confused, I thought all fueling would be adjusted to the change in stoich?

  2. #2
    HPT Employee Eric@HPTuners's Avatar
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    Quote Originally Posted by MustangPunk View Post
    I drive a turbo'd 2006 Silverado WT 4.8L non flex fuel. I filled up with e85 last night, with only a few gallons of gasoline left in the tank, I drove for a few minutes to maybe get some of the gas outta the rails. Then uploaded a tune, I changed the values in all cells of the stoich table to 9.8 for e85. It started rough but I drove for a little while (10 miles maybe) and it stayed rich, and I had to take out 20% from the VE to get to lambda while driving. I ended up driving for over 40 minutes. The gas tune was pretty spot on. This morning the cold start was super lean, and just a little lean crusing, man am I confused, I thought all fueling would be adjusted to the change in stoich?
    I have not converted a GM vehicle over to Flex Fuel, but have done a lot of Fords, and the same things happens with them. Re-adjusting the VE table is probably the easy way out. I believe the injector values are probably the reason for this.
    Eric Brooks
    HP Tuners, LLC

  3. #3
    Senior Tuner Iam Broke's Avatar
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    Check your fuel pressure, E85 requires ~30% more fuel so if your pressure is tanking, the IDC climbs and you are going to need to retune.
    '12 Camaro T3 2SS/RS LS3 M6, SLP TVS 2300, Flex Fuel

  4. #4
    Advanced Tuner sarg's Avatar
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    Did you check the actual percent of ethanol?

  5. #5
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    OP, you can get a "flex fuel sensor" (oem ones work fine) and a gauge/module to display the ethanol content of your gas. Make sure you get one with outputs, so you can log ethanol percentage in HPTuners. I think you could also just use the sensor if you just wanted to pipe the voltage directly to HP Tuners.

    http://www.zeitronix.com/Products/ECA/ECA.shtml


    Last edited by CarsonTech; 08-28-2013 at 08:42 AM.