Adverse effects by using the wrong fuel?

Discussion in 'Engines' started by KrazyKraut, Aug 1, 2008.

  1. KrazyKraut

    KrazyKraut Banned

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    I know German planes were marked with B4 or C3 triangles so crews wouldn't use the false octane fuel on the specific planes. But then I also read of US trials of Japanese fighters using US fuel (which greatly enhanced performance).

    So what are the effects of using fuel of higher or lower octane for engines not designed for that number?
     
  2. kool kitty89

    kool kitty89 Well-Known Member

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    As long as the engines are strong enough to handel the increased power obtained at higher boost settings (which high octane fuels allow) they should work fine once tuned to run on those fuels. (of course, boost settings would need to be increased to have a significant impact on performance)

    The Merlin III is a good example of this, while not designed to run on 100 octane fuel, it was found to be capable of this, allowing emergency boost to be increased to +12 psi (from +6.25 psi). Increasing power from 1,030 hp (6.25) to 1,160 hp (+9 psi) to ~1,300 hp (at +12 psi)
     
  3. mad_max

    mad_max Member

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    If the engine (for example the BMW 801 which required C3) was run at a normal power level for C3 and B4 was in the tanks by chance; there would be detonation involved.

    SuperchargersOnline.com :: Detonation, Knock, and Pre-Ignition 101

    A number of things could happen. In very little time, the top of the pistons would burn through most likely.

    Now if it was detuned to be able to run on B4 which would reduced power , then there would be no problems. Expect the power would be reduced significantly though.

    Running a higher rated fuel than an engine can use or set up to use would be no problem. It wouldn't make more power just from the fuel though. The engine could produce more power, but would have to be set-up to properly to make it. Higher boost pressures, advance in the timing, proper fuel mixture and a change to cooler plugs probably. Of course the said engine must be strong enough to handle the higher power.

    As for the Japanese aircraft and producing more power on US 100/150...well it's possible if this fuel was of higher octane than the Japanese variety. If someone could find the fuel tests of the Japanese fuel(s), then we may take a stab at the answer.
     
  4. Soren

    Soren Banned

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    Another factor consider here is wether the engine is configured for natural or synthetic fuel, cause there's a difference. German engines didn't run very well on Allied fuel and lost power, as evident in the Allied testing of German a/c.

    Note: German C3 fuel equates to Allied 150 grade fuel, despite the 96 octane number.
     
  5. kool kitty89

    kool kitty89 Well-Known Member

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    What about the C2 fuel?
     
  6. mad_max

    mad_max Member

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    Soren,

    At times yes C3 was almost the same rating as 100/150, at other times was equal to 100/130. And those engines run just fine on non-synthetic fuels. It's a myth that they won't.

    I've talked to an engine rebuilder that has overhauled quite a few DB's and he sets them up to factory specs. He runs them at 100% power on 100LL wit no problems at all. Of course with 100LL they won't run them at WEP settings just as the Merlin's he rebuilds.

    My questions:

    His answer when I asked the question on fuels and how they run them without having a synthetic fuel with the qualities of German fuels of WW2. Mike Nixon of Vintage V-12's sent me this answer to my question.

    From someone who knows from practical experience with no bullshit involved.
     
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