air / fuel ratio

Discussion in 'Softail Models' started by traveller, May 16, 2013.

  1. traveller

    traveller Member

    Does anyone have an opinion as to what the air/fuel ratio should be for the best all around mileage and power. I have mine but I really would like to hear yours, thanks.
  2. biscuit

    biscuit Junior Member

    Depends if you're the EPA or 'just' a rider.AND how you ride.

    I recall reading some time back that the later model Harleys (96 " and up)came from the factory with a mandated A.F.R or around 15:1 or maybe even somewhat higher.I know it was a pretty lean and hot running mixture.(Dont shoot me if it's not absolute-i'm using my memory here)

    I had always been told the best 'Stoichiometric Air-Fuel Ratio'(AFR) for performance was regarded as around 13.3 :1.But i believe it's considered lower now.

    I run an Auto-tuned Thundermax on my bike. With my current map,the A.F.R from 0 to 29 degrees of throttle is 13.542:1. Once you twist that throttle harder from 29 up to 88 degrees (all the way),the A.F.R drops to 12.5:1. A fair bit richer for that extra performance.

    This means when you ride normally,you get good economy;and when you're going for it your fuel delivery is so much more.

    In my case,i ride(solo)the same bit of twisty road once or sometimes twice a month.I never go over 3000 rpm and always return around 44 to 46 mpg. I just cruise along at the Limit of 80 kph,but i think that economy is pretty good.
    This is 3rd and 4th gear stuff,a smidgeon of 5th,with some 1st and 2nd gear hairpins.I have done a few rides with 60-70 miles of highway running,followed by twisty roads.This gave the best i've ever achieved- almost 60mpg.

    I have tried experimenting with different A.F.R's on my Zippers maps-I raised it up to 13.831 :1 in the idle to 3328 rpm, in the 0 -29 degrees of throttle position where i mostly ride;and later up to 14.063:1 in an attempt to see what sort of economy i could get.The bike 'felt' fluffier(for want of a better word),sounded different and according to my Zippers high-tech speedo/tacho combo,the head temps were a little bit hotter.Who knows if that's my imagination or not.

    What i DO know is that an A.F.R of 13.542 seems to work ok for me and the way i ride; and can give pretty good fuel economy coupled with reasonable performance. Cant speak for the higher throttle positions or A.F.R.s because i rarely venture there.
  3. Bodeen

    Bodeen Well-Known Member Staff Member Moderator Contributor

    My carb. doesn't know the difference.........:D
  4. STEVE07

    STEVE07 Well-Known Member Staff Member Super Moderators

    I have mine set as follows:

    Idle 13.5-1
    Cruising 14.5-1
    Rolling on the throttle for hills or increasing speed 12.5-1
  5. wannaride

    wannaride Active Member

    But your bike does. AFR is on every combustion engine (is a steam engine considered a combustion engine, if so not them).