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Fuel Supply Hose

in General Tech Discussion 13 years ago
I am building an Aerospool Dynamic using the 912ULS. Fuel system assembly instructions are limited. I have a question about the fuel hose size supplying the fuel pump. The factory supply hose is 5/16" ID with an AN-6 female swivel for the firewall. I don't understand why this hose is 5/16" when the system is 1/4" prior to the firewall. The airplane uses 1/4" fuel hose from each tank to an Andair fuel selector which uses 1/8"NPT inlet fittings and then continues to a Facet fuel pump, also with 1/8" NPT fittings. Each tank is selectable. So, Why does the pump inlet hose jump to 5/16"? Fuel flow is only as good as the most restrictive flow. Will there be an issue if the fuel tubing is left at 1/4" to the firewall and then stays 1/4" to the pump? I would really appreciate the reasoning behind the jump up in fuel hose size.
Thanks.
Brad

  • Re: Fuel Supply Hose

    by » 13 years ago

    Brad,

    Don't know what Rotax recommends but I ran into the same thing. All my fuel lines from tanks to filters to electric pumps to valves and check valves is all 1/4". The only 5/16" I have are the original two or three feet of firesleeved hose that came with the engine. I used a reducer to mate the two different sizes. I have never had any problems at all with fuel pressure or fuel flow even at full throttle.

    Bill.
      
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  • Re: Fuel Supply Hose

    by » 13 years ago

    Bill,
    Thanks very much for that! Makes me feel much better. I have a an email into Rotax about this, so I will post their reply when I get it. Makes no sense to me at all. I am planning to do the same thing you did, so I am very glad to know that it works for you.
    Thanks again,
    Brad
      
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  • Re: Fuel Supply Hose

    by » 13 years ago

    Hi Brad

    I think it stems from the fact that the fuel pump was not made for the rotax 912. It is a standard auto fuel pump used on older cars that have carbs. The old Saab use's a fuel pump which is very similar.

    Mark
      
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  • Re: Fuel Supply Hose

    by » 13 years ago

    Thanks Mark,
    That makes sense.
    Brad
      
    Report
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