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"resetting" ecu for higher octane

Discussion in 'Technical Chat' started by rex99, Mar 1, 2010.

  1. Mar 1, 2010 at 5:55 PM
    #1
    rex99

    rex99 [OP] Well-Known Member

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    ive read on here before about being able to unhook the battery to "reset" the ecu to accept a higher octane fuel, yet i couldnt find that thread in the search.

    my question for anyone that has done this is simple-- when do you unhook the battery?? before or after you fill up the truck??

    TIA
     
  2. Mar 1, 2010 at 7:22 PM
    #2
    kevhogaz

    kevhogaz Low Speed, High Drag

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    What? Why would you need to reset the ECU to run a higher octane fuel?

    Disconnecting the battery for 30 seconds will clear your ECU's memory, but I've never heard of it adapting itself to different octane fuels.
     
  3. Mar 1, 2010 at 7:29 PM
    #3
    rex99

    rex99 [OP] Well-Known Member

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    i remember reading it in a thread a while back-- i tried to search for it but i couldnt find it (i shoulda subscribed....)

    anyway, from what someone posted, if you unhook the battery the truck will like you said "adapt" to the higher octane and give you better mpg/ more hp
     
  4. Mar 1, 2010 at 7:31 PM
    #4
    jandrews

    jandrews Carolina Alliance Southwest Region Ambassador

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    ECU adjusts timing based on knock sensors...higher octane resists knock better, and allow the engine to open up additional timing after an adjustment period.

    This is why the 1GR-FE has different power ratings for 87 octane and 91 octane.

    No reset necessary...after a few tanks of 91+ the ECU will adjust on its own.
     
  5. Mar 1, 2010 at 8:13 PM
    #5
    XrunnIT

    XrunnIT Well-Known Member

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    Yep.

    Personally though, i'd rather not wait the few tanks. A reset will force the ECU to relearn right away.
     
  6. Mar 1, 2010 at 8:30 PM
    #6
    ShadowFalken

    ShadowFalken Well-Known Member

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    Spot on.

    Unplugging the ECU would not only reset the adaptive fuel tables, but also the shift cells for an auto, the idle strategy and learned behavior and so on. The other thing to remember is that that type of reset will take the computer to the base tables. New vehicles adapt VERY quickly compared to just a few years ago. Even long term trim is not so long term any more. I have seen vehicles adapt to induced changes in seconds on long term tables. They are really quick trying to maximize emission control.
     
  7. Mar 5, 2010 at 8:00 PM
    #7
    Second Childhood

    Second Childhood New Member

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    I installed a TRD supercharger on my 1999 that requires 93 octane. The mixture control adjusted itself in about 500 miles. Slick computer. My only problem is in CA you can only get 91 octane. Still no problem it adjusts. Once in a whjile I treart it to Octane Boost. Went from 195 HP to 275. A beast now.
     
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