What Octane Do You Use?

Discussion in 'Motorized Bicycle General Discussion' started by SubieGuy, Jun 5, 2013.

  1. SubieGuy

    SubieGuy New Member

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    I'm just wondering what octane gas you guys use!

    I've been using 91, but have 94 available. Would 94 be of any benefit?
     
  2. 5-7HEAVEN

    5-7HEAVEN Well-Known Member

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    Hard to say, not knowing anything about your bike and engine.

    FWIW, engine specs for my Tanaka 47R call for 92 octane. I WAS running 87 before finding this info. Now I run 92 w/100:1 Opti-2 oil.

    All is good.xct2
     
  3. SubieGuy

    SubieGuy New Member

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    Sorry I forgot to mention that! I've got a 66cc flying horse w/ shift kit on a mountain bike. Using ~ 40:1 semi synthetic lucas oil mix.

    I've always just assumed you use higher octane in two stroke mixes, because oil lowers the octane.
     
  4. scotto-

    scotto- Custom 4-Stroke Bike Builder

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    In my 212cc with 12.5:1 compression I'm running VP 110 octane and it's just purrrrfect. In my 99cc with 8.5:1 compression I'm running 100 octane pump gas and it doesn't seem to be hurting it any.

    As a rule, you only need high octane if you have a high compression engine.

    Adding a little nitro-methane to your fuel on the other hand.........:D

    Or NOS ;) Or a turbo! Supercharger anyone?
     
  5. 2strokebke

    2strokebke New Member

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    93 all the way.
     
  6. LR Jerry

    LR Jerry Active Member

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    This topic has been discussed several times before. I use to think higher octane better power. Higher octane is ment for higher compression. To better explain you want two things to occur in your cylinder; the detonation point and spark point to match. This gives you a complete burn. The higher the octane the higher the detonation point. Most of these small engines are low compression so that their easy to crank. From all the research I've done compression below 9.1:1 will run best on 87 octane.
     
  7. dodge dude94

    dodge dude94 New Member

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    Dayum. That's hella better than my truck! No wonder you're so fast. ;)


    I use 91 as that's all we buy. The chainsaw and powerhead for the trimmer and cultivator both require 91 octane, so we just buy all 91 for all the small engines. In other news, what IS the average compression ratio on these 66cc engines?
     
  8. KenX

    KenX New Member

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    93 with no ethanol.
     
  9. soup325

    soup325 New Member

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    I have started using 98 RON from caltex.

    I purchased it, more for the longer shelf life rather than the higher rating.

    I think the engine runs a bit better, plus its only another 20cents more a litre.
    I may be able to get 1.4L/100km mileage. Currently, it is 1.8L/100km.

    Running a 48cc, 2stroke. running 40:1 mix, about 25ml per litre of gas.

    I would rather run 100-130 avgas if I could (the green stuff). Not the week 100LL.
     
  10. curtisfox

    curtisfox Well-Known Member

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    For what its worth, my son went to small engine class at the colage for two years. and was told to run none ethanol fuel in all small engines that means high octain 92 is what we have here. And we put a few drops of SeaFoam witch is a stblizer and and additive all in one,desolves water,and cleans,and don't need anyother additive................Curt
     
  11. xseler

    xseler Well-Known Member

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    87 no-ethanol. Why force feed it champagne when it's perfectly happy with beer?
     
  12. LR Jerry

    LR Jerry Active Member

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    Most of these engines are 8:1 or less compression. The ethanol debut has gone on for quite some time here as well. To my good fortune there's a station here in my town that sells 100% gas. So I run 87 octane 100% gas.
     
  13. KenX

    KenX New Member

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    All that's available here to my knowledge is the 93 no ethanol.
     
  14. Trey

    Trey $50 Cruiser

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    For many years off and on, I've done lawn-care work. My experience has been that any petroleum based, non marine, 2 cycle oil, and any pump gas will run any piece of lawn equipment. Obviously the mix ratio may be different per the manufacturer. I have never destroyed or damaged any equipment in any way by choice of oil brand name, or gas octane rating.

    Your engine is similar to all of those engines. I would treat it the same as all of those engines. Some members feel strongly that synthetic oil and a certain octane is better than other options for whatever reasons, and they may be right.

    My 4-Stroke gets low-grade pump gas, and 1oz per Gallon of Sea Foam.
     
  15. LR Jerry

    LR Jerry Active Member

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    Seafoam is also good for washing your oil case out as well. Read my thread "EZ Oil Change".
     
  16. mew905

    mew905 New Member

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    Last time I checked my compression, my tester said 90 PSI @ 1811 ft elevation. That was tested with a B&D 18v drill. I did notice however depending on your ports, your pressures vary with speed (higher RPM = higher compression). IF I'm doing my math right that means 13.45 psi atmospheric pressure so 90 PSI from 13.45 PSI = 6.7:1 compression @ around 1500 RPM. Expansion chambers, port timing and altitude will all affect this. Jaguar says he gets ~125 PSI and he's at a higher altitude than I so it could easily be more.

    Back to the original question: I run 91 octane Shell Nitrogen enhanced, I have a choice between 87, 89 and 91, so I use the highest I can get, and despite what other people say around here, yes it does help my performance, it feels smoother, doesn't bog as much and I get a higher top speed out of it. Torque isn't enough to feel a difference so I don't know about that. But yes, if you've never tried a higher octane, try it, your ride may be more enjoyable. Sometimes things can be vastly different than what calculations predict ;)
     
  17. curtisfox

    curtisfox Well-Known Member

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    Seafoam is the reasion, i have seen 87 enthoanal at small engine repair sitting in a ice cream bucket for a couple of hours after purches,that had water in the bottom. Seafoam breaks it down and passes it through.
    I mow quite often at the lake 5 hours each time and have tried both and after. have a lot of truble with 87,i will run nothing but 92 now,much better now.
     
  18. Dan

    Dan Staff
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    I have tried higher octanes but didn't see any difference in a China girl. I don't have a running one now.

    It would be really cool if we got a minimum of 3 china girl riders, preferably more. Each one rides one half gallon 87, 89 and 91 octane threw and keeps careful track of MPG and general engine happy. I bet weather would be a factor too. Temperature and barometric pressure.

    Be really cool to know and group projects are always fun.


    This just in from the motorbicycling.com scientific advisery board. ** octane outperforms all other octanes and master links are still best. nananananaa
     
  19. Wickedest1

    Wickedest1 Member

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    Mobil1 93 octane...87 makes her run crappy...93 and she's happy...
     
  20. KenX

    KenX New Member

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    Right or wrong I've just understood that 2 cycle engines should not have ethanol used in them. It would certainly be more convenient if it didn't matter. I guess I can research this a bit.
     

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