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  1. #1
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    Fuel/compression

    What kinda fuel or real octane booster , or mix of fuels do I need to run 170lbs compression? This will b a 1st for me and don't wanna burn her up

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  3. #2
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    https://youtu.be/JWOevmVGwY8

    I finally figured out video to put on here. These are not the tight heads
    Last edited by Merc 2.5; 12-07-2021 at 03:50 PM.

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  5. #3
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    Have an airport near by?

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    170 psi cranking on a 2.5 25 timing should be good at 95.5 to 96 octane. Been running that mixture for years with no problem. Mix avgas with pump premium or 110 race fuel with pump premium, works for me.

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    VP110 is rated up to 12:1 compression. Not sure what 170 works out to but if thats not enough go higher

    https://vpracingfuels.com/product-category/marine/
    Hydrostream dreamin

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    Quote Originally Posted by Capt.Insane-o View Post
    Have an airport near by?
    Yep

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  10. #7
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    Quote Originally Posted by Stoker boy View Post
    170 psi cranking on a 2.5 25 timing should be good at 95.5 to 96 octane. Been running that mixture for years with no problem. Mix avgas with pump premium or 110 race fuel with pump premium, works for me.
    What's the ratio tho

  11. #8
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    Two stroke “compression ratio” doesn’t jive with what the fuel companies talk about for four stroke engines.

    like said above…..go to the airport and get some 100LL and you’ll be plenty safe for 25-26 degrees of timing. For the most part, Any engine is going to make its most power on the lowest octane fuel you can run before detonation so if you want to get picky you might pick up a few mixing down to 96 octane or so. In my experience the gains aren’t worth the risks so I’d rather be over and safe…just my opinion…


    '95 STV "The Blue Goose"


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    Quote Originally Posted by Merc 2.5 View Post
    What's the ratio tho
    If you want to know how to compare your 2.5 two-stroke in automotive four stroke engine terms like 10:1 compression ratio. Go online and look at compression ratio explained, however in my opinion doing that on your two stroke would be a waste of time.

    As far as mixing goes. 2.5 gallons of 91 pump premium = 227.5 + 2.5 gallons of 100 aviation fuel = 250 Total they equal 477.5. Divide that total by number five because it’s 5 gallons = 95.5 octane.

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  14. #10
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    The Air port I work at sells 100LL .I get to smell it burning in Airplanes all day long.. Smells great !! Right now it's 6.00 a gallon. I use it all the time in my boats/ ATVs /Sport Bike love it !!

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    I ran 100ll av for years at 175-180 psi.

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  18. #12
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    It has a much better shelf life to. I run it everything that isn't used on a weekly basis and I put hundreds of gallons thru my X motors over the years.

    Joe

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    Quote Originally Posted by Keaten View Post
    The Air port I work at sells 100LL .I get to smell it burning in Airplanes all day long.. Smells great !! Right now it's 6.00 a gallon. I use it all the time in my boats/ ATVs /Sport Bike love it !!
    I bought some 100LL last week $5.53 a gallon. 110 race fuel $12.50 a gallon.

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    Quote Originally Posted by Stoker boy View Post
    I bought some 100LL last week $5.53 a gallon. 110 race fuel $12.50 a gallon.
    I think a lot of politicians own airplanes .. not many hang out at the track ..

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    Click image for larger version. 

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