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Thread: Race fuel

  1. #1
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    Race fuel

    ok my question is how does race fuel work? I just put in a 13:1 je piston in.. what is the benefit of running race fuel? what makes it better then just running premiem pump gas? if someone could explain how it works and why it is needed for higher compression pistons? lol I know I sound like an idiot

  2. #2
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    First off as you raise your compression you need a higher octane fuel. The reason is pre-detonation. The higher the compression the quicker a lower octane fuel will ignite. If you dont run a fuel with a high enough octane than the gases in the combustion chamber will explode before they are suposed to causing major engine problems. With 13.1 compression ratio you will should run at least a 110 octane fuel.
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  3. #3
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    Originally posted by tfuchs
    First off as you raise your compression you need a higher octane fuel. The reason is pre-detonation. The higher the compression the quicker a lower octane fuel will ignite. If you dont run a fuel with a high enough octane than the gases in the combustion chamber will explode before they are suposed to causing major engine problems. With 13.1 compression ratio you will should run at least a 110 octane fuel.
    Ok.. so I just finished the project last night.. 13:1 piston and a hotcam 2.. I have not even started it yet. I was thinking of running a 50/50 mix of race fuel and pump gas. but that probably still wont put me up at 110 octane cause the race fuel its self is only 110. do you think I should run straight race fuel or will 50/50 be fine? thanks for the reply

  4. #4
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    Originally posted by FireFighterI
    Ok.. so I just finished the project last night.. 13:1 piston and a hotcam 2.. I have not even started it yet. I was thinking of running a 50/50 mix of race fuel and pump gas. but that probably still wont put me up at 110 octane cause the race fuel its self is only 110. do you think I should run straight race fuel or will 50/50 be fine? thanks for the reply
    With only 13:1, you might be just fine with a 50/50 mix of something like VP110 and 92 Pump gas. BUT.... What are you really saving in not running straight 110? If the 110 is $7/gal and 92 is $3.00/gal, it will cost you about $16 and the hassle of mixing fuels each time to fill your tank. In addition, you will probably get the ratios mixed up when you mix them a 2nd and 3rd or more times. If you run straight 110, you'll spend about $22.50 to fill up (3.2 gallons). So you spent $6.5 dollars more, but didn't run around to two different places and have a consistent fuel to boot.

    I just can't understand why anyone would spend $500+ to hop up their motor, and then they won't spend another $6 to fill their tank with the right fuel.


    The other option is to use some of the lesser expensive race fuels found at pumps like the 100 octane unleadeds from Union 76 and VP. They run about $6/gal.


    Whatever you decide, get the jetting dialed on a dyno and don't change fuels all the time (like a lot of ppl do). You need to jet for a specific fuel. Changes in different fuels can affect jetting as much as 2 - 3 jet sizes - so you're gambling if you switch.


    I have mine specifically jetted for two race fuels - VP C12 and Sunoco MO2X Oxy fuel. They both use the same jetting, verified on a dyno. The oxy makes another 0.5 hp - FWIW. Oh - and the tank gets drained after a riding weekend and the fuels get put back into sealed metal cans to preserve them.
    Chuck
    '06 Venom Performance Modified TRX511ER
    61.57 hp and 37.96 tq

  5. #5
    Join Date
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    Originally posted by sandmanblue
    Oh - and the tank gets drained after a riding weekend and the fuels get put back into sealed metal cans to preserve them.
    I keep my Klotz in a plastic 5 gallon can. The little air thing closed and i shove a balled up napkin in the top. Is it sealed up good enough?

  6. #6
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    If you dont want to spend the money on race fuel try using avtiation fuel its 100 octane and up instead of race fuel is just an average of 110 octane. The aviation gas has a lot higher standards and it only costs me around 4 dollars a gallon. Ran it iwith 13.1 compression all year with no problems

  7. #7
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    Originally posted by MX MaNiAc 06
    I keep my Klotz in a plastic 5 gallon can. The little air thing closed and i shove a balled up napkin in the top. Is it sealed up good enough?
    I can't tell if that's a joke or not.

    Assuming you're serious--no that's not good enough. At a very minimum it should be in an AIR TIGHT container. If the container doesn't pressurize itself if it gets hot than it's not air tight.
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  8. #8
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    Originally posted by tfuchs
    ....The reason is pre-detonation....
    Just an FYI: the term is detonation. Pre-detonation is a nonsense word. The a/f mixture does not detonate at all under normal circumstances--it deflagrates. Deflagration = burn and it is the good kind of combustion; detonation = explode and it is the bad kind of combustion.
    "It ain't what you don't know that gets you into trouble.
    It's what you know for sure that just ain't so. "

    --Mark Twain

  9. #9
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    Originally posted by 450R-156
    If you dont want to spend the money on race fuel try using avtiation fuel its 100 octane and up instead of race fuel is just an average of 110 octane. The aviation gas has a lot higher standards and it only costs me around 4 dollars a gallon. Ran it iwith 13.1 compression all year with no problems
    I know a lot of ppl say to use av-gas, but it is a fact that this fuel is not meant for anything but high altitude, low rpm engines in a relatively mild state of tune being used at low ambient temperatures. While the octane may be high enough, that alone is not justification to run a fuel meant for a very different engine than a 10,000 rpm small displacement engine used at sea level... I think it's worth just saying that you should do some research on this. Problems associated with av-gas are power output and throttle response. I wouldn't recommend it at all.....
    Chuck
    '06 Venom Performance Modified TRX511ER
    61.57 hp and 37.96 tq

  10. #10
    Join Date
    Mar 2007
    Posts
    33
    Originally posted by sandmanblue
    With only 13:1, you might be just fine with a 50/50 mix of something like VP110 and 92 Pump gas. BUT.... What are you really saving in not running straight 110? If the 110 is $7/gal and 92 is $3.00/gal, it will cost you about $16 and the hassle of mixing fuels each time to fill your tank. In addition, you will probably get the ratios mixed up when you mix them a 2nd and 3rd or more times. If you run straight 110, you'll spend about $22.50 to fill up (3.2 gallons). So you spent $6.5 dollars more, but didn't run around to two different places and have a consistent fuel to boot.

    I just can't understand why anyone would spend $500+ to hop up their motor, and then they won't spend another $6 to fill their tank with the right fuel.


    The other option is to use some of the lesser expensive race fuels found at pumps like the 100 octane unleadeds from Union 76 and VP. They run about $6/gal.


    Whatever you decide, get the jetting dialed on a dyno and don't change fuels all the time (like a lot of ppl do). You need to jet for a specific fuel. Changes in different fuels can affect jetting as much as 2 - 3 jet sizes - so you're gambling if you switch.


    I have mine specifically jetted for two race fuels - VP C12 and Sunoco MO2X Oxy fuel. They both use the same jetting, verified on a dyno. The oxy makes another 0.5 hp - FWIW. Oh - and the tank gets drained after a riding weekend and the fuels get put back into sealed metal cans to preserve them.

    So I can run straight 110 race fuel in at and it wont hurt it at all? my jetting was perfect before I put in the piston and came in... i am running a 185 main and 52 pilot... do you typically have to change the jetting after putting in a higher compression piston and changing the cam?

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