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  1. #1
    MR MAC's Avatar
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    Will a higher octane fuel help lean engine?

    Just a question..

    If a engine is running slightly lean will a higher octane fuel like super unleaded help correct it?

    I don't wanna sound thick but I'm not too up on how fuel octane effects engines...

    Any help would be appreciated

    Ian


  2. #2
    Kristian Keppel Waterholics's Avatar
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    Don't you think it will be better just to buy a FPR and up the furl pressure instead of buying more expensive gas.

  3. #3
    SurfRider's Avatar
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    Absolutely NOT. Lean is lean. Higher octane only helps with detonation. And you only need a higher octane fuel if you are detonating!

  4. #4
    How do you know if you are detonating? Just for conversation/informational purposes.

  5. #5
    MR MAC's Avatar
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    Like I say it's just a question... My r2 and c3 runs rich in the uk


    So is it best just to run high octane fuel all the time then?


    Detonation = pre ignition of fuel in the cylinder??? Am I correct in saying that?


    I be totally honest, I know what I'm doing with modding but fueling is not ever been quite explained to me


    Ian

  6. #6
    Kristian Keppel Waterholics's Avatar
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    Quote Originally Posted by MR MAC View Post
    Like I say it's just a question... My r2 and c3 runs rich in the uk


    So is it best just to run high octane fuel all the time then?


    Detonation = pre ignition of fuel in the cylinder??? Am I correct in saying that?


    I be totally honest, I know what I'm doing with modding but fueling is not ever been quite explained to me


    Ian
    Exactly higher fuel octane does not get you a leaner AFR, less fuel pressure does. So like I said in my first post don't run the higher octane just run a FPR and tune AFR. You might save money that way.

  7. #7
    Basically my question is this. I have a c3 and a r2 reprogram...do I need to run premium gasoline? Is there any way to read the knock sensor to know whether you have a detonation issue or not?

  8. #8
    SurfRider's Avatar
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    Quote Originally Posted by MR MAC View Post
    Like I say it's just a question... My r2 and c3 runs rich in the uk

    So is it best just to run high octane fuel all the time then?

    Detonation = pre ignition of fuel in the cylinder??? Am I correct in saying that?

    I be totally honest, I know what I'm doing with modding but fueling is not ever been quite explained to me

    Ian
    You certainly run a higher octane. Since you are not "lean", that is perfectly fine. Think of it this way. What "octane" does is make the fuel *harder* to burn. When there is a lot of pressure in the cylinder and things are hot, a low octane fuel may pre-ignite (ping or detonation) the fuel before the spark plug is supposed to. Please note that higher octane does not mean more power, it actually can mean less. Since the higher octane fuel is "harder to burn", it produces less power. So what you really want is the lowest octane fuel that you can run *without* detonation. For example if your ski can run at 91 octane and you put 120 octane fuel on it and ran it on a dyno, you would see more power with the 91 octane fuel. Hope that makes sense. Now, of course, if you build a higher compression motor and that needs higher octane, you can make more power, but you start to fight a slippery slope on that front.

    To Allstar71, it may be a bit hard to explain detonation unless you've ever driven a really old car, before they had "knock sensors", and you have a big load on it (e.g. driving fast up a really steep hill). The best I can explain is that it almost sounds like you have popcorn in your motor. You would hear some loud high pitch pinging noises, if your exhaust is so loud that is is masking the sound it might be hard to hear. Most modern engines have knock sensors now, so what you would feel is a reduction in power as they usually pull timing out of the motor to prevent damage.

    ---------- Post added at 04:30 PM ---------- Previous post was at 04:28 PM ----------

    Quote Originally Posted by allstar71 View Post
    Basically my question is this. I have a c3 and a r2 reprogram...do I need to run premium gasoline? Is there any way to read the knock sensor to know whether you have a detonation issue or not?
    That is a good question! Perhaps someone with the YDis software could answer that question. My guess is that it probably can, which would be really cool to know. I believe that R&D recommends no less than 91 octane with the R2 & C3 wheel. That would be "safe" for all conditions.

  9. #9
    MR MAC's Avatar
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    Top answer surf rider and that is just what I am after....


    Thanks for the education



    Ian

  10. #10
    TennR600's Avatar
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    Detonation is not pre ignition

    Detonation occurs after the sparkplug fires. A second flame front collides with the one from the plug. When these forces hit there is a HUGE presure spike. Short in duration. Strong enough to knock pieces of the piston away or even crack the piston. Its classic sound is a higher pitch knock. The sound resinates thru the engine block. It is caused by the mechanical load on the engine. Piston to wrist pin, pin to rod, rod to crank, etc.

    Pre ignition occurs before the plug fires. As the piston rises in the cylinder something ignites the fuel air early. This creates a very high pressure condition in the combustion chamber. Problem is the duration is very long. This condtions usuly does not make any noise. The engine just blows up!!!! Pre ignition causes can be, over heated spark plug, carbon in the combustion chamber, a nick in the head, or edge of a metal head gasket sticking into the chamber, etc.

    Had to type this twice as I timed out the first time. Sorry for any spelling errors.

    Roy

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