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

  1. #1
    Junior Member
    Join Date
    Sep 2005
    Posts
    26

    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
    Posts
    114

    Default

    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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