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  1. #1

    Join Date
    Jul 2011

    Default Pipe change on EFI - How do I know if I need a tune?

    I have what I think are Screamin Eagle pipes right now, with no baffles. I'm thinking about removing the mufflers (which are actually acting as megaphones/"loudeners" because the baffles are gone).

    Should I treat it like a carb bike and just check for smoothness/ridability, and check my plugs? Should I reinstall my speedo to check for check engine lights?


  2. #2

    Join Date
    May 2015


    Most stock EFI Ecus have a very narrow band to self correct in Can your existing ECU (assuming you have a stock ECU) compensate?: Maybe. If it cant, thats why there are aftermarket ECUs to bolt in. I have a 2008 Street Bob with open drag pipes with an 02 bung. But the stock ECU couldn't compensate: So I went with an aftermarket ECU, no probs

  3. #3

    Join Date
    Sep 2009


    Taking off the mufflers and baffles of a twincam sounds like a great idea to make your bike run like shit. Efi twin and come stock lean from the factory running a large portion of their afr maps at stoich (14.6 to 1) afr called closed loop which is designed to compensate for minor changes. Ie slip on mufflers. When you change things on this efi system it can compensate but not for taking the whole damn mufflers off. The bikes stock need to be tuned. Case in point. Don't do what you are saying. And buy a good tuner. A GOOD tuner like Tts or powervision or Pcv

  4. #4


    Why don't you re-install the baffle? Sound is great if running 1/4 mile at WOT, but for everyday are robbing yourself.

    I agree with a liar box (HD tuning is expensive, and unnecessary), as you are able to much of the tuning via laptop.

    Treat you tuning like a carburated bike was your initial question. The answer is yes-ish.

    A motor is a motor when is comes down to the brass tacks, and when it comes to combustion, the only difference between the two is the delivery system. The gentleman above have given you much of the information, as to the how and why your run-ability sucks ass, and I'll try to explain some routes you could take (some may not agree with me, and I welcome comments...I don't learn other wise)

    A Harley Davidson isn't the most efficient design to begin with (I will get pummeled for that comment), and if you add EPA standards to the equation they are tuned, factory, very lean to accommodate the tree hugger's.
    The ECU, and mechanical component's, are chosen to meet these standard's. Three thing's that get done with a new H-D: intake, cam/s with more duration, exhaust, and a generic tune.

    That generic tune doesn't always jive with all H-D's. There is a lot of fine tuning that can be done, but without a way to interface with the ECU (except at the dealership), you dead in the water.

    Enter the "Liar Box"/ Aftermarket Tuner. This little baby is totally programmable (depending on how much bread your willing to fork over). Basically they tell the ECU little lie's about the state of certain sensors (air temp, throttle opening, amount of air being sucked in, oxygen sensor information...).
    The trade off is that you have tuned your bike to run at it's best. Not Big Brother's requirement's, or the constraints of the "Factory's Special Tune" that came out of a Dollar Store fire sale.

    Keyword here (and misfitJason mentioned it) is "get a GOOD tuner". You get what you pay for, and if you plan on doing any modification in the future, you will be happy you spent the extra bread.
    Another added benefit to spending the dough on a good tuner is that you can (some time's) transfer them from bike to bike...sell one buy get it. If not then it becomes a selling point when/if you do sell it.

    Long winded...I know. Do your research until you come up with a good solution, as seem to be doing, and execute it. If it doesn't work, use explosives!!!

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