Fuel Mixture Gas Grade

Discussion in '2-Stroke Engines' started by narutokun0420, May 4, 2012.

  1. narutokun0420

    narutokun0420 New Member

    Which gas grade do you use in your MB?
     

  2. DeathProof

    DeathProof Member

    i only use premium 91% full grade the less the ethanol the better
     
  3. Fabian

    Fabian Well-Known Member

    "No" ethanol is better!
     
  4. DeathProof

    DeathProof Member

    ethanol bad!
     
  5. DeathProof

    DeathProof Member

  6. LR Jerry

    LR Jerry Well-Known Member

    I only use 93 premium 100% gas in all my small engines. To my good fortune there's a station where I live that sells it.
     
  7. DeathProof

    DeathProof Member

    exactly! jerry knows the higher the grade of gas the better so screw ethanol!
     
  8. Skyliner70cc

    Skyliner70cc Active Member

    Standard grade 85 octane for standard compression engine

    Grade 87 octane for slant head higher compression engine.

    Grade 89 octane for high compression after market heads.

    I'm at high altitude so add 2 points to each octane grade of fuel for your lower altitude area.

    I've never had an issue with ethanol in fuel. I occasionally see phase separation but that is with my choice of lubricant which I add to the tank. A quick shake of the fuel tank fixes that easily.
     
  9. tooljunkie

    tooljunkie Member

    there is some kind of additive to neutralize the effects of ethanol if i recall.
    here's the $1.22 question-how do you know you are getting what you pay for?
    i have a story.
    as part of my job,i am a mixing technician for the helitorch backburn team.
    prepping the burn mixture using gas and a gelling agent,regular pump gas
    requires 5-10 % water in order to dilute the ethanol.
    then fuel gels.
    our fuel supplier provides us with premium(low or non ethanol)to fuel our small engines.
    during training,we attempted to mix a barrel of gelled fuel for the helitorch.
    it wouldnt gel til i added 2 gallons of water,telling me it wasnt premium.
    the instructor confirmed this,only regular pump gas needs water added ,not premium.
    now we need to have our fuel tested.
     
  10. motorpsycho

    motorpsycho Active Member

    i run the cheapest gas I can get...always 87 octane.
    in my opinion, in a h.t. engine, anything over 87 octane is a waste of money, unless it has a milled head or a an aftermarket high compression head.
    This is just my opinion because i can't see paying the extra money for premium fuel, when you gain nothing from it in a low compression engine.
    The extra cost of the fuel just goes out the exhaust.
     
  11. DeathProof

    DeathProof Member

    it costs me $5.85 -$6.00 for a gallon of gas for 2 weeks. ill use premium wats 6 bucks nowadays
     
  12. narutokun0420

    narutokun0420 New Member

    well i live in West Virginia nothing but hills everywhere i'm currently using 87 at 16:1 it seems to do ok 24-26mph up hill 36mph on flats was curious if 93 would do better
     
  13. Cavi Mike

    Cavi Mike Member

    If your engine isn't high-compression, anything over 87 doesn't do anything. In fact, you may have LESS power. Yes, that's right people, LESS.

    Octane does not have anything to do with power.

    Let me repeat this:

    Octane has nothing to do with power.

    The octane rating is a fuels resistance to detonation. Detonation is when a fuel auto-ignites. Auto-ignition is when a fuel will combust under compression and high-heat alone, without spark. A high-compression engine on low-octane gas will auto-ignite the air/fuel mix well before top-dead-center and puts an enormous amount of stress on the rotating assembly. This is why you need to run high-octane gas in high-compression engines.

    Low compression engines don't have this problem and therefore don't need high-octane gas. In fact, almost every engine runs with a small amount of detonation but if you run higher-octane than your engine was designed for, you'll completely eliminate this small amount of detonation. This means the only source of ignition will now be your spark plug and with only one flame front, you'll have a less complete burn of your fuel resulting in less power and more carbon build-up in your combustion chamber.

    High octane does not run hotter.
    High octane does not contain more power.
    High octane does not run cleaner.
    In fact, running higher-octane than the engine was designed for will actually do the opposite of all of those things.
     
  14. motorpsycho

    motorpsycho Active Member

    $6.00 is the difference between getting one galllon or two gallons.
    $6.00 is lunch at wendys, $6.00 is a couple of gallons of milk for my kids, etc.
    I can do a lot with $6.00 rather than blowing it on one gallon of gas for a toy.
    besides that, premium fuel in one of these engines won't do a darn thing to help it perform better or make more power.
    you want more power? mill the head, give it some higher compression, port the cylinder, put on an expansion chamber, tune the carb...and THEN at that point, you may have to go to running high octane to make it run better because of the higher compression.
    But seriously, you would need A LOT of compression on one of these engines to have to worry about running high octane fuel.
    putting anything higher than 87 octane in a stock h.t. engine is useless, and you may even lose some performance by running higher octane fuel.
    high octane does not make more power in a low compression engine.
    It takes more energy to ignite high octane fuel than it does low octane fuel.
    so, essentially, by putting high octane fuel in a low compression engine, is making the engine work harder to ignite the fuel.
     
  15. tooljunkie

    tooljunkie Member

    one or two points,as an intermittent user,so called premium gas contains less ethanol,so fuel will absorb less water.it stores longer.
    i prefer to use it,mileage and power are irrelevant.
    a friend has a 35mpg car that gets almost 40mpg on premium.it has nearly 400,000 km's on it and it runs like a top.never had any serious mechanical issues.i put some of the low maintenance on the fuel used.
     
  16. motorpsycho

    motorpsycho Active Member

    If you think so...:whistling:
     
  17. Fabian

    Fabian Well-Known Member

    Completely agree with Cavi_Mike

    The octane number 'on it's own' has nothing to do with horsepower and excessive octane can reduce power given all other previous variables remain fixed.

    Having said that, a heavy oil/fuel ratio will reduce octane with 2-stroke lubricating oil displacing the amount of fuel that can be passed through a given jet size, in effect, leaning out the mixture.
    In such cases, an increase in octane is required to elevate the the oil/fuel mix back to where it needs to be to prevent detonation, should the engine suffer from detonation at reduced octane, together with increased jet size; compensating for altered air/fuel ratio.
     
  18. HeadSmess

    HeadSmess Well-Known Member

    an efi car with what is now a fairly high compression ratio compared to twenty years earlier, can monitor its fuel useage, and adjust as necessary. hi octane fuel is less likely to detonate, even on a lean mixture.

    so, by reducing the chances of knocking, an efi equipped car can reduce fuel consumption when using a higher grade of fuel,simply because it can use less without knocking. therefore fuel economy will go up.

    a stock HT prefers the lowest octane stuff you can stuff into it. its made in china, designed in russia, with the intention of running on , quite possibly, vodka...AKA ethanol, when the going gets tough...

    as a side note, a cr250, with a static compression ratio of around 8.5:1, can get to OVER 16:1 when "on the pipe".

    you definitely need the highest octane you can get on a performance tuned twostroke.
     
  19. tooljunkie

    tooljunkie Member

    ahhh, the good old days,YZ125 on the pipe (front wheel in the air) was a lot of fun.
    too old and afraid to hurt myself now.
    my buddy dont like my bike (not fast enough)and cant seem to get past that.
    its not how fast.
    i find the higher grade fuel burns cleaner.i have done cylinder heads on many vehicles,the worst buildup in combustion chambers was vehicles that used farm fuel,its like the dye also causes carbon buildup.
    customers that run higher grade fuels have cleaner internals.
    i have worked on (give or take )10,000 vehicles be it oil changes or rebuilds or tuneups.
    i do believe there are benifits to running higher grade fuel.
    i only run premium on long trips,but again how good is any gas nowadays.
    three service stations yield three different results in fuel mileage on regular gas.
     
  20. LR Jerry

    LR Jerry Well-Known Member

    When I run the 93 octane 100% gas it runs much smoother on top end speeds.
     
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