For conversasion sakes only; diesel economy for displacement boat

Discussion in 'Diesel Engines' started by parkland, Sep 27, 2013.

  1. parkland
    Joined: Jul 2012
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    parkland Senior Member

    Just wondering what opinions I could get on this.

    Pretend you have a 40 ft trawler full displacement boat. Let's say 16,000lbs.
    Pretend it is 100% finished except for the engine, trans, shaft, and prop.
    Engine bay has room for almost any imaginable engine.
    Now pretend there is a 10,000,000$ prize, for whoever can make 1000 miles, with the least amount of fuel, all crossing the finish line at the same time.
    The engine could be a boat engine, tractor engine, truck engine, etc.
    It can be modified, but only with low cost stuff, no expensive elaborate stuff.

    To the best of my knowledge, a boat about this size would usually have about 60-100 HP. Let's pretend it takes exaclty 70 HP to move the boat at the desired speed.
    So the question is; what engine choice would you make, and how would you modify it to be extremely effecient?


    Little 3 cyl with turbocharger?
    Cummins 5.9 running at 1000RPM ?
    Air cooled?
    Dt466 without turbo and way increased timing?

    Lets hear all the ideas!
     
  2. parkland
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    parkland Senior Member

    I'm thinking 6 liter I6 engine,
    Compression bumped to about 20:1
    No turbo
    Set uo to run at 1200 RPM
    Possibly ceramic coatings on piston tops, valves, and heads.
     
  3. TeddyDiver
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    TeddyDiver Gollywobbler

    There's no question about some adequatly sized turbo charged modern common rail engine taking the prize. What your question lacks is the time, ie speed, for the trip to have more precise answer.
    BR Teddy
     
  4. parkland
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    parkland Senior Member


    Would a common rail really have any benefit at a steady RPM and power output? The high pressure pump takes more power to run...

    We could specify a time, but we could just leave that alone and go with the steady constant 70 HP, and whatever the time is, it is.
     
  5. rubenova
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    rubenova Junior Member

    I recall boat tests that showed vessels with huge diesel that had surprisingly high range figures at idle. A larger engine would take longer to warm up, but over 1000 miles may minimize the impact. I'll throw into the hat a huge idling diesel, over propped to make a little heat. May need to limit the cooling in some way...
     
  6. jonr
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    jonr Senior Member

    You are looking for the diesel engine that produces the best BSFC at 70 HP. My guess would be one of the car engines - because of the small size and that lots of engineering dollars have been spent on them.

    A 1.9L or 2.0L VW diesel can do 197 g/kW-Hr at 70HP.

    I assure you that the best economy won't come from a large, idling engine.
     
  7. whitepointer23

    whitepointer23 Previous Member

    a 510 hp daf, paccar engine uses 2 lt an hour at idle in neutral according to the onboard computer. this is in a truck. averages 65 lph loaded.
     
  8. whitepointer23

    whitepointer23 Previous Member

    i wonder how an old gardner would go, they were the first diesel to reach 50% efficiency.
     
  9. Mr Efficiency
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    Mr Efficiency Senior Member

    "they all cross the finish line at the same time"
    I'm thinking what exactly that time is, is the key question, and the answer will vary with that.
     
  10. rubenova
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    rubenova Junior Member

    I'm curious JONR, please elaborate on assuring a large idleing diesel wouldn't be part of the winning combination. It seemed to be a consistent trend in boat tests with boats in this size range topping out in the 30-40 knot range.

    Kind regards,

    Rubenova
     
  11. jonr
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    jonr Senior Member

    Look at any BSFC graph - none of them are most efficient at idle.
     
  12. rubenova
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    rubenova Junior Member

    BSFC is a great indicator of fuel used under load. Admittedly not much data has been recorded (BSFC wise, that I've seen) at idle. The data I've seen showed estimated range at different rpm and speed, and at idle it generally is considerably more than at other speeds. There are certainly boats larger and smaller that this is not true, but with research and further tuning a combination could probably meet the imagined criteria and win the 10 million.
     
  13. Mr Efficiency
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    Mr Efficiency Senior Member

    Question is a can of worms, imo. The answer is "it depends".
     
  14. rubenova
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    rubenova Junior Member

    whitepinter23 do you have the engine brand and model, I would like to try and find a brochure and/or dyno chart.
    Thanks!
     

  15. Mr Efficiency
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    Mr Efficiency Senior Member

    Gardner diesel was from UK, out of business now I think, certainly had a solid reputation as a marine diesel engine for many years. A slow revving unit compared to today's engines.
     
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