Truck diesels

Discussion in 'DIY Marinizing' started by parkland, Nov 7, 2012.

  1. Navygate

    Navygate Previous Member

    Jonr: Varying the boost gives the luxury of enjoying the reliable, economical long life of a near naturally aspirated diesel of minimal size appropriate for average daily light loading while having in stand-by up to twice the torque for heavier loading situations.

    Aktmboyd: Boost is hugely adjustable from the cockpit through a variety of means. The most common, and perhaps easiest, is via the waste gate as you mentioned. What I described in my previous post relies on a comprehensive system design which incorporates all the variables.
     
  2. aktmboyd
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    aktmboyd Senior Member

    But wouldn't that change the efficiency of the motor widely. I can't see the need for wanting to controll something that is so effectively self regulating. In a Diesel engine you cannot go to a lean condition like on a gas engine, all it will do is go to a flame out situation where there is not enough fuel/air ratio to ignite and create the needed pressure inside the combustion chamber. So why reduce the air consumption when you can effectively reduce the fuel consumption.
     
  3. Navygate

    Navygate Previous Member

    I see your point but what I'm proposing wouldn't effect the self regulating beauty of the turbo. I don't believe it would change the efficiency of the motor significantly. It would certainly reduce the power output but that was my whole point. In my experience, a 200Hp turbo diesel doesn't last half the life of a naturally aspirated 200Hp diesel. Most boats only use half the power they're fitted with and rightly so. It's prudent to have that reserve power, just as it is to have reserve buoyancy.
    Does my reasoning make any more sense now?
     
  4. woodboatwayne
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    woodboatwayne Junior Member

    diesel engines typically run better and last longer operating close to 80%
    of peak power or at whatever the 100% duty cycle is. This is necessary to keep the combustion chamber hot enough to burn most of the fuel. If you don't know what speed this is look at the specs and find the commercial
    HP @ RPM and run the engine around that RPM
     
  5. jonr
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    jonr Senior Member

    I'm not convinced that a turbo diesel and the same engine without a turbo charger operated at the same HP will have any less wear or efficiency.
     
  6. aktmboyd
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    aktmboyd Senior Member

    The naturally aspirated engine of the same size will need a lot more fuel tomake the same hp's. Which is extreme heat, egt's will be crazy high, lots of stressor the engine, oil will be supper heated. Engine life expectancy a lot less than I would want.
     
  7. aktmboyd
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    aktmboyd Senior Member

    I can't see the want for a non turbo'd diesel. Or a restricted air diesel. Maybe if the motor had cylinder deactivation, it might be different. Than I can see lessening the air to the motor to keep it running. But do they even have that for diesels, especially marine engines. Run a turbo leave it be and you and the motor will be happier.
     
  8. woodboatwayne
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    woodboatwayne Junior Member

    At least cummins , perkins, Detroit and Isuzu have made the same engine
    family in both turbo and natural versions. It must work or they wouldn't
    do it. The problem with marine applications is when you start adding electronics to control them
     
  9. FAST FRED
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    FAST FRED Senior Member

    >I can't see the want for a non turbo'd diesel.<

    The reason is simple , most diesels are oversize compared to the hourly power output required for most cruisers.

    Few run near rated HP for hours on end towing or pushing.

    Turbos are great at adding peak power , but die when 30-50 hp is required from a 250 hp rated engine.

    To have a turbo survive it must be under positive boost , which for some folks is far more HP than they want at the moment.

    Less to buy , less to fix , no intercoolers , just makes an easier boat to live with.

    With no boost a turbo is just an expensive spinning silencer..

    Now if your boat is 14,000HP at 98 RPM , turbos are great.
     
  10. parkland
    Joined: Jul 2012
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    parkland Senior Member

    A non turbo diesel would probably have higher compression, so it should burn cleaner at light load.

    I also agree, turbo's can be nice, but if not required, simply a failure point.
     
  11. Rurudyne
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    Rurudyne Senior Member

    I was under the impression that superchargers were the better choice for large diesels when a broader powerband, or rather one that set in earlier, was desired?

    There are "marine" superchargers at any rate.
     
  12. FAST FRED
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    FAST FRED Senior Member

    Anything can be done but usually CO$T is a big factor.

    I assume the 1st poster was interested in simply having an efficient ,reliable ,low cost truck engine power his boat.

    Most pleasure boats do not operate enough hours a year to justify any experiments with installing superchargers or anything else.

    To me the best installations use keel cooling and a dry stack , so a replacement engine is a simple R&R after finding the next engine .

    Lobster folks sometimes make a deal with scrap yards , and get notified of a new wreck with the same engine there running comes in.

    A sitting spare is the cheapest parts source , or Big Bang insurance.
     
  13. parkland
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    parkland Senior Member


    I agree, it seems like any time someone has issues, it's because of moisture or wet exhaust problems.
    Keel cooling and dry exhaust solves so many problems.
    Something to bear in mind though, this is only diesel engines from trucks or tractors, not gas engines. Marine gas engines have a lot more differences than diesels.

    I wonder if you could keep a fan clutch on the engine, but install a centrifugal fan, so the engine room fan turns on when a certain temperature is reached? that would be a good setup.
     
  14. Westfield 11
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    Westfield 11 Senior Member

    Do they still make a non-turbo truck diesel? My Ford pickup is 14 years old and it has a turbo engine and I think the Cummins in Rams are turbo too. Removing such an integral component on a computer controlled fuel injected engine is a bit more complicated than just unbolting the part and replacing it with a straight exhaust pipe. I suppose you could limit yourself to older engines over 15 years old, but they are beginning to get a bit thin on the ground as the fleet ages and is worn out and scrapped. Would you ever buy a junkyard motor that you couldn't hear run? Maybe for parts, but to power an offshore boat? I think not......
     

  15. Westfield 11
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    Westfield 11 Senior Member

    What would the fan be doing? There is no radiator on a keel cooled engine..... Usually the problem is running too cool in the winter when the water is cooler as opposed to running too hot in summer. A correctly sized keel cooler is optimized for summer and relies upon the thermostat to limit flow in winter to keep the engine in the correct temp range.
     
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