Tuning: More fuel necessary?

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    -Acra slip-on

    -K&N airfilter in a modified airbox


    Can the original ECU adapt to this changes or is a aftermarket solution necessary?

    Since its only a 400cc bike its not worth 500usd+shipping for example Coober ecu.

    Its winter here in Sweden so I cant test it and check sparkplugs etc

    If needed, has anyone done a proper test of Boosterplug?




    Only proper way to find out is stick it on a dyno and measure the afr.

    Personally I think people overestimate the ‘tuning’ capacity of the stock ecu.
    As far as I know the ecu on modern bikes only adjusts the fuelling using the lambda readings on small throttle openings at low revs.
    And why is a 400cc bike not worth a decent ecu? You obviously thought it was worth the decat, akrapovic and K&N filter? They add up to quite a few euros as well. Why invest in those and not finish it properly with some dynoruns and mapping it properly?

    • This reply was modified 6 months, 2 weeks ago by NampusNampus.



    Well, Acra came with the bike and decat I did myself.

    Is there an alternative to Boosterplug for the 401? Theres several for 701.

    I see that many here drill holes in the airbox-lid. That is the wrong way to do it.

    Will send unfiltered air to your engine since intake is above the filter.


    @Dennis  I read on the duke 390 forums about guys drilling their airbox covers and installing these little filters in the holes (Link below). This solves the concern of letting in unfiltered air. Also I have not yet installed the booster plug, but I have watched a few reviews and all seem to be good. I also can’t justify spending the money for the Coober ECU, when a slip-on, de-cat, added airflow, and booster can equal less than $500 total.




    Whilst I have the 701, have installed the boosterplug and the airbox mod with three holes and added foam underneath the holes.

    Been very happy with the results, the boosterplug definitely smoothed out the acceleration and I feel it has a bit more at that low to medium rev range.


    I tried the boosterplug and the rapidBike easy together which richened things up in open and closed loop but now i’ve gone back to just the RBE as I mainly wanted to reduce the sudden transition from lean to rich when you open the throttle, along with the loss of torque when settling at cruising revs.

    Cheap option is just unplug the 02 if you can deal with engine light, made things a lot smoother for me.

    Powertronic is cheap but the one I got wouldn’t read the throttle position. Planning to try the full race rapidbike for the later throttle-by-wire duke, mainly for the engine brake reduction feature.

    This is with a stock bike though.

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