BETTER FUEL MPGs

Discussion in 'Engine, Fuel and Exhaust' started by porkchop, Jan 4, 2009.

  1. porkchop

    porkchop Active Member

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    This may sound crazy but here we go.

    I have allways used super unleaded 93 octain fuel since my bike was new and was averaging 43 44 MPG then i added a V&H fuelpak and as expected the MPG went down to 38/39, I now there is a trade off wen you add more fuel, but get this, I fueled up with reg unleaded 87 octain on advice from a buddy and my MPG went back up to 42 MPG!!! Whats going on here????:wall
     
  2. STEVE07

    STEVE07 Well-Known Member Staff Member Super Moderators

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    You quit twisting your right hand so far back:D
     
  3. porkchop

    porkchop Active Member

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    Well this was a problem at first but I started riding in my normal mode when i began checking MPGs. I have run several tanks of super with the fuelpak and the MPG stayed consistant the ran three tanks of reg it to was consistantly higher and the bike even runs better on it, It just doesnt make sense to me.
     
  4. Bud White

    Bud White Well-Known Member Retired Moderators

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    low Octane promotes pinging
     
  5. NEWHD74FAN

    NEWHD74FAN Experienced Member Retired Moderators

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    The key is that if you use lower octane gas AND take it easy, the EFI will compensate by retarding the timing closer to TDC and guess what, volumetric efficiency improves and emissions go down...EPA proved it in the 70's...but the performance also goes down because you are gearing up quicker and running in the fuel mileage sweetspot of 40 mph...kinda boring huh...!
     
  6. glider

    glider Veteran Member

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    Volumetric efficiency is a ratio of the volume of fuel and air that enters the cylinder during induction to the actual capacity of the cylinder under static conditions. Retarding the timing using lower octane fuel will not only diminish power but also MPG too.
    Likewise a cooler intake air charge will increase cylinder fill and give better volumetric efficiency in this way.

    There's little to be gained IMO doing this to any internal combustion engine. The ill effects would outweigh the benefits in my book.
     
  7. porkchop

    porkchop Active Member

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    I didnt see any performance drop or any pinging, it seemed to run great with plenty of power. I was worried about it pinging or (labor knocking) but i did roll the throttle a couple of times to see but all was good. This realy goes against every thing i ever thaught befor about gas and octain. Wonder if it has any thing to do with the fuepak letting it run so good on lower grade gas?
     
  8. porkchop

    porkchop Active Member

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    Im not real sure what you are saying about the ill effects, can this hurt anything?
     
  9. gsxrboy96

    gsxrboy96 Member

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    Ok, im not sure if i will answer your questioin or not, but i will give you a lil insight, The popular misconception of fuel is that bigger(octane number) is better, that coudlnt be further from the truth, the idea fuel is the lowest octane number without promotoing pinging or any type of spark knock, and why? the higher octane fuel has a higher detenation number, which slows burning and the combustion process, so theoretically, i guess it could produce less mpg by waisting fuel, YOu just have to be careful that you dont let the motor detonate, and being a air cooled motor, i wouldnt take that chance, they run hot as it is, just my two cents.


    p.s..... another thing to consider, I know for a fact that fuel makers are playing with ethanol numbers in fuel, and reguardless of octane rating, this is going to effect mpg.
     
  10. glider

    glider Veteran Member

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    Yes, it can damage the engine.

    In reply to gsxrboy96, you are absolutely spot on with what you posted, however not all people can detect a ping in an engine and thus would be better running 93 or what they call hi test in their area rather than taking a chance with a lower grade fuel.