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Thread: HP and fuel requirements

  1. #1
    gnarley
    Anybody have an approximate fuel flow per minute for a given size engine, say a 454 or 502 making 500 HP, 750 HP and 1000 HP with the RPM?
    I am working with a tech from Aquamist in England to put something together for boats and they have no experience with boats it seems as you can read below.
    I am new to boat engines. I need help from you and so far you have provided me with the information I need. I can now work of a system that might be suiyable for your aplication. I have a few questions:
    1) Duration of the run, like a poker run
    2) Approximately the fuel flow per minute, lbs/min will do.
    3) ambient temperature.
    4) any intercooler for force induced type?
    5) Horse power in your particular application.
    I do not have any real world data for the boat, I have have onr for a real race plane? ;-)
    Here it is http://www.aquamist.co.uk/rescr/rescr.html look in the gallery section and click the "Lancair-IV-USA link"
    My response may not be suitable for the context of the discussion, I can only speak in general terms. You can post our company's name is you like but without my name if possible.
    Regards
    (name deleted as requested)
    ERL Ltd
    Iroko House
    Bolney Avenue
    Peacehaven
    E.Sussex
    BN10 8HF
    England

  2. #2
    GEOO
    Engine's run about .5 lbs per hour per hp. 500hp=250lbs per hour, 750hp=375lbs per hour, 1000hp=500lbs per hour. divide by 60min to get per min. figures, 500hp=40lbs per min.
    The fuel flow changes with the hp being made, not by the ci (size) of the motor.
    A natural 500hp engine makes 500hp at the crank, each piston is making 62 hp. If the engine was a blown to make 500hp, the blower might take 75 hp to turn. so the crank puts out 500hp but the pistons are putting out 71 hp per piston. so you need to burn enough fuel to make 575hp so to make the same power a blown engine uses a higher .56-.6 lbs per hp. The larger blowers use more power and require up to .6 lbs per hp.
    Most boat mechanics also like to run the blown engines rich to help cool the combustion chambers. ie. 11.2- 12.0 A/F ratio.
    When you run water injection you do not want to run a rich engine . 12-12.5 is better. A rich engine with water added is too much liquid in the combustion mix.
    (Just a few notes I believe are true):wink:

  3. #3
    Infomaniac
    Take a look at most dyno sheets. They will express fuel consumption as how many pounds of fuel per brake horsepower per hour. Brake specific fuel consumption. Some will have actual air/fuel ratio.
    Gas weighs about 6 lbs per gallon and that value is used to calculate weight and balance of airplanes.
    The engine dyno sheet posted last night by HavasuHangin was a well tuned in blower engine by the BSFC for over 1,000 HP
    If you take the 1,000 HP and figure .56 lbs per HP per hour. that ends up being about 93.3 gallons per hour.
    Would be nice to sustain 1,000 HP for an hour.
    Oh yea, when I buy a fuel pump for gasoline, I always use 10 GPH per 100 HP as a general rule.

  4. #4
    gnarley
    Originally posted by GEOO
    Engine's run about .5 lbs per hour per hp. 500hp=250lbs per hour, 750hp=375lbs per hour, 1000hp=500lbs per hour. divide by 60min to get per min. figures, 500hp=40lbs per min.
    Thanks for the info, I think you added a zero where there shouldn't be one though, 40 pounds of fuel a minute seems high for 500 HP? I think you meant 4lbs?
    Originally posted by Infomaniac
    If you take the 1,000 HP and figure .56 lbs per HP per hour. that ends up being about 93.3 gallons per hour.
    I think you calculated wrong? 1000 x .56 = 560 / 60 = 9.3
    560lbs per hour and 9.3lbs a minute.
    Just wanted to have correct numbers

  5. #5
    Infomaniac
    560 is the pounds of fuel per hour. Fuel weighs 6 lbs per gallon so divide by 6 to get gallons per hour.
    That was the scenario 1,000 HP engine running at a BSFC of .56
    About 1.55 gal per minute or 9.3 lbs per minute

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