Slow speed but new engines.

Discussion in 'Diesel Engines' started by Vikendios, May 14, 2006.

  1. Vikendios
    Joined: May 2006
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    Location: Greece

    Vikendios Junior Member

    I am trying to understand the pros and cons of the fuel delivery systems in the new crop of EPA compliant diesels in the 500 HP range.
    Cummins uses common rail, like all luxury diesel cars, but CAT says it doesn't like common rail (why ?) and uses, if I understand well, individually pressurised injectors with a built-in hydraulic piston using lube oil. Both of course are electronically controlled. I could not be sure of what Yanmar and Volvo (in its new D9's) are doing.
    My boat builder suggests a pair of CAT C9's Acert on my 49 feet 50 000 lbs modified planing hull.

    My questions are as follow :

    (1) Which will be more reliable and economical, the CAT's or the Cummins QSC8.3 ?

    (2) I plan to do a lot of hull speed crusing at 10 % power, and has been told that it doesn't foul or damage these new electronically controlled engines. Is that true ?

    Thanks to all for any input.
  2. StianM
    Joined: May 2006
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    StianM Senior Member

    Personaly I would like to belive that a cimpressor charged diesel is behter than a turbocharged one if you are going to runn on 10% power.

    I also belive that bether combustion ocour when you have higher bost preshure regardles to electronic control or not.

    I know that my fathers KAD volvos has traditional system, but the other models I'm not able to tell if they have comon rail or not
  3. Vikendios
    Joined: May 2006
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    Vikendios Junior Member

    Mechanical compressors

    None of the engines produced today by the four big makers in my power range have mechanical compressors. Interestingly enough even Volvo dropped them for the replacement to their KAD line, now discontinued. Anyway on the KAD 32 that I had on a speedboat, the mechanical compressor only clutches in at high power settings. It also got stuck quite often...

    So let's forget about air delivery and concentrate on fuel delivery... My questions remain !!!
  4. jmac
    Joined: Feb 2006
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    jmac Junior Member

    You can get a wealth of information on both of those engines at
    Both are good engines. I think the QSC8.3 490hp low idle is 600rpm. The HP at 800 rpm is 68hp. I have been told on boat diesel that these engines can run anywhere on the power curve by some people a lot more knowledgable than me. I am not sure if the Cat is meeting the new Tier2 regulations yet. Pretty sure cummings, yanmar and volvo are though. Check out boatdiesel and I am sure there is a thread relating to your question. Not sure if you have to join or not.
  5. StianM
    Joined: May 2006
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    StianM Senior Member

    They can make it as electronic as they want it, but higher savaging air preshure will allways make bether combustion.

    Cummins is making a hell of a noice and so is the cat. I would not have anny off them.
  6. gonzo
    Joined: Aug 2002
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    gonzo Senior Member

    Cummins are cheaper and lighter. They last about 65% of the life of a Cat. What tradeoff is better depends on your budget and expectations.
  7. Vikendios
    Joined: May 2006
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    Location: Greece

    Vikendios Junior Member

    Lurning Curve

    Thanks Gonzo.

    Through Boatdiesel and manufacturers'sites I have learned a lot about marine diesels in just two weeks. Volvo gets my award for clear intelligent web sites. Cummins for espousing the latest technology and being proud of it. Caterpillar gets the prize for the most confusing mumbo-jumbo and marketing hype. 'Acert' indeed ! Means nothing except 'We're not ready to buy commom rail from Bosch'.
    Yanmar is in such a state of overhaul, moving from roots in japanese tractor engineering to marinising BMW and Scania blocks (will the samurai's commit harakiri ?) that I'm not sure where they're going.

    In the end I'm ordering my boat with Cat C9A's. I'll just trust the builder and hope for the best.
  8. Col.JPstapp
    Joined: Jul 2006
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    Location: Seattle, WA

    Col.JPstapp Marine Engineer


    I am glad to see that you have taken it upon yourself to acquire the knowledge about the product you are about to purchase. Your summary of the information available on the web for marine engines is beyond exceptional! I even got a pop-up on the Volvo site asking to rate their webpage (outstanding). Acert indeed!!! LOL.

    I am a marine engineer employed by one of the BIG 4 (or 5 or now 3 depending on how you slice it). After all the trouble and research how did you not find what you desired? Was it lack of information, miss information, poor information, or did you not want to take the responsibility of that decision? I am extremely curious to this issue since I combat it every day and wish to fix it (if that is in the relm of possiblities in one's life time). If I have learned anything it is that a builder's interest does not necessarily run parallel with an end user's.

    I am sorry for bringing this whole issue up since it appears that you have already made your decision some time ago. I would be interested in finding out more information if you are still interested in the subject. Please let me know.


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    FAST FRED Senior Member

    I would like to inquire how to get a fuel map from most engine mfg.

    Like others I'm interested in quite long periods of displacement operation and only about 5 or 10% of the time is the fuel burn for fast operation needed.

    It would be very usefull to have the fuel map (sorta looks like one drawing of a cloud superimposed on another).
    The center "cloud" is the area where power can be extracted at lowest fuel burn , the next area higher burn ect.

    BMEP map? Is perhaps the engineers name.

    Are these TOP SECRET or ??? There sure not on any web sites I have yet found.

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