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Thread: Fuel ?

  1. #1
    Canadian Beaver Inspector jkindt's Avatar
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    Fuel ?

    Will these Fuji motors run on AvGas 110LL or is race gas such as VP Fuels the only way to go for running high compression without detonation?


  2. #2
    Click avatar for tech links/info, donation request K447's Avatar
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    Aviation gasoline octane is rated differently than road gasoline, so the Avgas does not have nearly the octane you might think it does. In fact, it is close to premium pump gas in terms of equivalent octane. It also has much more lead than road gasoline, despite the Low Lead name.

    Search for avgas on GH, you will find several good threads.

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    PolarisNut's Avatar
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    Don't use AVGAS, use high octane gasoline, if you need it. AVGAS is not designed for low elevation, high rpm motors. I use a mix of Turbo Blue 110 and 93 pump gas, and it works well (paid $5.50/gal this year)...but there's no need unless your compression is very high, or you have triple pipes, and high compression.

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    Canadian Beaver Inspector jkindt's Avatar
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    I will just try to keep my compression low enough to run 92 octane and call it good. I was just concerned because of the heads already being '92 octane' heads, then adding a bunch more displacement through bigger bore pistons. But I will have to have the head machined anyways, so I will just request a '92 octane' machine job.

    Or should I just rejet the carbs and run it on Nitromethane?

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    u887266's Avatar
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    I can say one good thing about avgas is the fact that it is test everyday for octane level. So when you buy avgas you are always getting 110 octane, as to pump gas where the longer it sits in the tank the lower the octane level goes.

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    Canadian Beaver Inspector jkindt's Avatar
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    I sure do get mixed opinions on this topic. If I live at an elevation of 3000' does that mean that I am effectively running the motor at 3000' in the air as opposed to sea level? I am in effect, flying my ski!!! What is the actual difference in race gas and AvGas as far as the motor is concerned? Race gas is expensive because it is shipped in barrels as opposed to held in tanks and shipped in large fuel trucks like the pump gas or AvGas is. It is almost as bad as the price of nitromethane!

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    She likes the bike. But the ski gets her wet!!!! xlint89's Avatar
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    As K447 menttioned, search for avgas on here. It'll explain alot about the digfferences betwen the 2.

    You can always add some octane booster to your 93 octane pump gas. That will help a little bit if you're running near the edge of your ocatne limits.

  8. #8
    Click avatar for tech links/info, donation request K447's Avatar
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    Quote Originally Posted by xlint89 View Post
    As K447 mentioned, search for avgas on here. It'll explain a lot about the differences between the 2.

    You can always add some octane booster to your 93 octane pump gas. That will help a little bit if you're running near the edge of your octane limits.
    Octane booster is often rated in 'points'. A 'point' of octane is one tenth, or 0.1 difference.

    So a can that boosts your tankful by 6 octane 'points', raises 93 octane gasoline to 93.6 octane.

    Read the reviews on octane boosters carefully. Base your purchase decision not on what the can label says, but on what the real world test results are.

    And I don't mean testimonials like 'It worked great for me!'
    I mean actual A-B instrumented tests, done by reputable testing organizations.

    There is a huge amount of good information around on this stuff. It might take some time to hunt it down, but the info is available.

    Also keep in mind that as the octane rating increases, the burn speed of the fuel typically decreases. It is easy to reach a point where further increasing the engine's need for octane results in an overall decrease in actual power output. The extra octane is being used to prevent engine damage, not produce more power.

  9. #9
    Canadian Beaver Inspector jkindt's Avatar
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    Too complicated! I will just build it to work with 93 octane pump gas and call it finished! Its not a race ski anyways!

  10. #10
    u887266's Avatar
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    Something else that can be done, is you can all diesel to gas and that will bring your octane level up. I dont know what the ratio is, but I have freinds that are occupaional racers and that is how they get high octane fuel for there cars without paying a arm and a leg for race gas. If you thing about it, all diesel is, is high octane fuel.

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