tfi on & off

Discussion in 'TFI Questions Answered By Dobeck' started by ultrat, Jul 20, 2010.

  1. ultrat

    ultrat Senior Member Contributor

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    I'm wondering if a problem arises w/ the tfi to bi-pas it / shut it off, witch way is best turn down all pots to number 1 setting or disconnect ground wire ? ..
     
  2. glider

    glider Veteran Member

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    Either way will do the job of turning it off except don't turn the #4 pot to zero. Go to the upper end of the clock positions.
     
  3. DobeckTechSupport

    DobeckTechSupport Active Member Product Contributor

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    ultrat,

    Like glider mentioned, either way will work. We would recommend just unhooking the ground wire.
     
  4. ultrat

    ultrat Senior Member Contributor

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    TX for all your replies,,,,
     
  5. Breeze3at

    Breeze3at Well-Known Member

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    I don't want to start a big technical discussion here, because I wouldn't understand it,,, but is there an easy way to describe just unhooking the ground wires effect? On '07 and later models,we disconnect our O2 sensors and the TFI plugs into the 02 circuit (thereby doing some kind of electrical magic to confuse/overide the ECM's 02 signal input). If you disconnect the TFI's ground wire, but leave it in the system, isn't there some "need" for input to the ecm's 02 circuit?
    Will a trouble code show, or is the 02 input really not a necessity? I really like my TFI, I just want to understand this tiny bit about it.
    Type slow, I don't understand a lot about this. :newsmile030:
     
  6. Redfish-Joe

    Redfish-Joe Senior Member

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    In the kit they should have provided two resistors to plug into the O2 sensor wires. This will keep it from throwing a code.
     
  7. ultrat

    ultrat Senior Member Contributor

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    meaning the ecm never goes into closed loop, no codes. but where does that leave the ecm on cruise kinda like exides..?
     
  8. DobeckTechSupport

    DobeckTechSupport Active Member Product Contributor

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    Let's first examine how our TFI is functioning and will allow us to disconnect the ground wire and still have everything function. All we do and in fact all every EFI controller does is affect the injector pulse width signal in order to modify the fuel amount. With the TFI hardware this injector signal is just always being passed through the unit whether the processor is powered up or not. Unhooking the ground wire does not let the processor power up because that circuit is not complete. The power source is still there because we gain this from the injector plug in for all plug n play units, but without proper grounding the processor stays off and the injector signal stays stock or unaffected. When grounding is applied and the processor powers up then we affect the out injector pulse width based on our logic. As the injector signal is being passed through our TFI we will lengthen the signal or rather call it hold on the injector milliseconds more to add some fuel.

    In short, the injector signal is always going through the TFI whether the unit is powered up or not. When powered up the TFI will affect the signal. When not powered up the signal is just passed through.

    The second question here is how to deal with the O2 sensors. The O2 technology is used to trim fuel amounts to target a specific AFR only when the bike is running is CLOSED LOOP mode. Without bypassing this mode we would be unable to make any fuel adjustments to the stock curve. Why? Say we wanted to add some fuel. The O2 sensors would recognize the AFR getting richer and would reduce the ECU injector signal to pull the fuel back out. You get caught in a struggle back and forth of adding and subtracting fuel which creates a very rough ride for the end user. The key concept to remember here is the TFI is ONLY A PIGGY-BACK CONTROLLER. If the stock ECU injector signal is being affected by the sensors then we can only deal with the injector signal coming into our unit.

    In short we have to bypass this CLOSED LOOP mode and make the ECU believe it's running in OPEN LOOP mode in order to add the fuel the bike modifications need to perform the best.

    Remember some vehicles modified with the TFI must not be used on public roads and in some cases may be restricted to close course competition. The TFI is not intended for use on emission controlled vehicles.
     
  9. harley@16

    harley@16 Junior Member

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    Does anyone know what the difference between the AFR in open and closed loop is? I had heard that when in open loop the AFR goes to a richer setting.
     
  10. Breeze3at

    Breeze3at Well-Known Member

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    Doebecktechsupport; THANK you for that well written reply. You adressed just what was puzzling me, and in a way that I understand. Thanks for your continued tech support on this forum.