Light Loading Operation

Discussion in 'Diesel Engines' started by We're Here, Jul 30, 2011.

  1. We're Here
    Joined: Aug 2007
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    We're Here Junior Member

    Do the electronic diesels mitigate the damage risk from consistent light load operation in comparison to the pre-electronic (mechanical) diesels? I'm certain that there is less fuel to carbon up things but I'm wondering if its really as simple as that. Opinions, please.
  2. Frosty

    Frosty Previous Member

    Its not a "carbon up" issue in my opinion it was always glazing of the cylinders resulting in a poor piston ring seal and a smokey engine.

    As long as the engine is given a high power output at some time I dont think it does harm.
  3. Submarine Tom

    Submarine Tom Previous Member

    Why do you ask. Are you grossly over-powered? If so, why? Choosing displacement mode over planing? If so, there may not be the economy there that you think there is.

    That is to say: liters-per-hour versus nautical miles-per-hour.

  4. Landlubber
    Joined: Jun 2007
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    Landlubber Senior Member

    ...according to my local Cummins reps, they do not glaze like they used to cos the xs fuel is not there to do so
  5. CDK
    Joined: Aug 2007
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    CDK retired engineer

    If light loads really could do harm to a diesel engine, industrial engines would have a shorter life than vehicle engines.
    But the opposite is true: a vehicle engine designed for 100 hp @ 4000 rpm is offered as a 50 hp @ 2500 rpm industrial engine with a 5 times longer life expectancy and longer service intervals. The only difference is the adjustment of the injection pump.

    In applications like generators and compressors an engine is running with little or no load at a fixed rpm most of the time and can do that almost indefinitely.

    I expect the glazing issue to be connected mainly with insufficient operation temperature and large engines running on bunker fuel.
  6. Frosty

    Frosty Previous Member

    Have a look down at the docks and see the fishing boats going no where but all lights on,--thats to load the generator 25% is sufficient.

    Truck drivers leave the engine running while they sleep for the heater as long as next day they haul 40 tons about no harm done.

    There is no excess fuel in the cylinder or it would fire and RPM increase. Sometime a turbo internal leak can cause an engine to run away simply burning the oil from the turbo.

    The man asked of carbon build up under light loads.
  7. We're Here
    Joined: Aug 2007
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    We're Here Junior Member

    The specific circumstances is a build that I'm considering. A 28' planning Maine lobsterboat design - weight not yet estimated but she'll be on the heavy side. Power being considered is a Cummins "B" series (QSB) with their highest output intermittent - 350 BHP.

    I'm sure that the "why" of it will be asked so my use calls for a long haul between port and fishing grounds (this boat will never lobster) and I'm looking for a mid-20s cruise speed. She might also try her hand at the Maine lobsterboat races. Thanks

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    FAST FRED Senior Member

    Under loading and its destruction is a problem. National Fisherman ran a 2 part series on it years ago.

    With your use getting to and from the fish grounds will easily be enough heavy load to make up for the tiny load just fishing.

    The problem would come if you decided to run at displacement speeds , say to FL.

    1200 miles at 6K, perhaps 30 hp required would require preventive measures to slow the underloading hassle.
    Burning 1.5 or 2 gph in an engine that would normally burn 10-15 gph , can cause the cylinder bores to burnish, blow by to dilute the oil , and if a turboed engine other turbo problems from lack of boost.

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