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Thread: Altering B3671 Stoich table for better economy with ethanol blended fuel?

  1. #1
    Junior Member
    Join Date
    Sep 2005

    Default Altering B3671 Stoich table for better economy with ethanol blended fuel?

    In the US, our gas is getting worse. We are seeing 10% ethanol at most pumps and 15% is coming soon. As I log commanded AFR, I see it drop from 14.68:1 to more like 14.3 or 14.1 with the ethanol blended fuel. It seems that this is a result of the B3671 table (E38). Fuel economy drops with the ethanol blended fuel, partially because the engine is commanding a richer stoich. Trying a little experiment, I added .8 to the stoich table across the board. Now with pure gasoline, the commanded AFR is 15.48 and with the blended ethanol fuel, my commanded AFR is 15.1-15.3:1. I added .5 to the EQ ratio on my PE multiplier and the commanded AFR at WOT is still 12.44 like it was before.

    I have not verified if the AFR is actually leaner with the wideband, but on a GM vehicle with a flex fuel capability, why wouldn't this approach work to achieve a leaner cruising AFR and improve economy?

    2013 Corvette Grand Sport A6 heads/cam/boost coming
    2009 Pontiac G8 GT
    Vararam, EFI Live tuned, Cruising in 4 cylinder mode, hauling on 8.
    2000 Pewter Ram Air Trans Am M6 heads/cam 508 rwhp/445 rwtq SAE Mods list, Idle Sound Clip, WOT video, 183.092mph video
    2008 GMC Yukon Denali XL 6.2L K&N FIPK, variable valve timing tuned to the max w/EFI Live.

  2. #2
    Senior Member
    Join Date
    Apr 2007


    I know this post is a few months old and with no responses but I was wondering if there were any adjustments that could be made to benefit fuel mileage.

    2003 GMC Sierra Denali. 6.0L, 4L65E, E-fans

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