Cummins vs Yanmar

Discussion in 'Diesel Engines' started by vjb, Jun 4, 2006.

  1. jmac
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    jmac Junior Member

    Fast Fred

    The Cummings QSB5.9 common rail engine is one of the most modern and QUIET engines on the market. You must be thinking of the old 5.9l engines. These engines are no smoke at idle also. Comparing the Yanmar to this technology is not equal.
     
  2. Frosty

    Frosty Previous Member

    I personally dont weant any common rail engine in a boat that I am on.

    If it stops there is really no point in even opening the engine room. If its not a filter forget it.

    I dont think they will ever be popular in sea going private boats.

    Ok Ok some yards may be fitting them but I dont want one.
     
  3. FAST FRED
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    FAST FRED Senior Member

    The Cummings QSB5.9 common rail engine is one of the most modern and QUIET engines on the market.

    Perhaps , but as most cruisers I can NOT take apart an electronic control and rebuild it with parts at hand at sea.

    The mechanical engines may use 15% more fuel and be 3X as loud , but for CRUISING , Electric control is just not realistic.

    A truck can pull over and await a tow and then spring $3000 for a black box, on a Cruiser a lightning strike might cause the Rescue tow to claim salvage , and OWN the boat.

    Should one be someplace where there IS a tow service , perhaps 1% of the world?

    FF
     
  4. seo
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    seo Junior Member

    In my opinion the Steyr integral head-block is a very logical step forward It gives you a simpler, more rigid, engine with fewer parts. How common is a valve failure in a modern engine, anyway? The big bad thing is dropping the cap off a stellite-faced valve, but when that happens the block is coming out, so no big difference. However you drive the cam, it's subject to failure. Gear, chain, or belt. The difference that I can discern is that with a belt, if you observe the renewal interval you won't have troubles. But who knows when a gear is going to shed a tooth?
    I remember when Cat came out with their first V8 bored-in-block engine, the family that became the 3208, and everybody said that it was a "throw-away" piece of junk because it wasn't a wet sleeve engine. But they worked out pretty well.
    Steyr makes good stuff, whether it's engines or firearms.

    The secret to a quiet engine is a good installation. Mufflers are important, but so is the enclosure. I've been around 6-71 Detroits that were very quiet when the enclosure was shut. Not a cheap undertaking, but it can be done.
     
  5. FAST FRED
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    FAST FRED Senior Member

    Gear, chain, or belt. The difference that I can discern is that with a belt, if you observe the renewal interval you won't have troubles. But who knows when a gear is going to shed a tooth?

    Most cruisers will go out after 100 hours of local ,( in range of the tow boat) cruising.

    I have NEVER heard of an industrial engine marinized that lost the timing gear or chain.

    A single belt between DISASTER (loosing the entire monoblock ) is not for most offshore boats .

    I contacted Steyer about if the loss of a timing belt could cause loss of the valve train .

    They claimed it was a rare event , but COULD bend the valves thru piston contact.

    I would LOVE to be able to Spec a Steyer for the box keel project as light weight is important , but so is getting back to port.

    FF
     
  6. seo
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    seo Junior Member

    Three examples that I can think of right offhand:
    Detroit Diesel 12=71, in a trawler, stripped a timing gear at less than a thousand hours time. Engine disabled, in the end had to be removed from the vessel for rebuild and to fully survey to develop an opinion of Proximate cause.
    Cat 398 (or maybe a 399) V-12, anyway, in a small tug. I was not hands-on with this failure, but I think what happened was a bearing in an idler gear ran hot, wobbled, and broke the teeth on the idler.
    Volvo B-18 (gasoline) in inshore lobsterboat. Stripped the teeth off the cam drive gear. This engine has a steel gear on the nose of the cranks, and a fiber gear on the cam. The fiber gear stripped. Engine stopped. Repair was just a question of removing the timing cover and renewing the gear.
    The only engine that I'd guess is entirely immune to valve train problems is the Fairbanks OP, only because it doesn't have any valves or valve train. But on the other hand, Fairbanks engines don't have a reputation of much higher reliability than its Cleveland, Cat, EMD and Alco competitors. I can't back that up with any statistics.
    I suppose that for at-sea serviceability nothing exceeds the EMD design with its welded crankbase and modular "A-frame" cylinders assemblies. It isn't unheard of for a twin-screw boat to change out an A-frame at sea while the other engine soldiers on. Since the EMD is a two-stroke the valve train is more limited than in a four-stroke, but has all the same elements.
    Maybe the main issue isn't the configuration of the cam drive as much as it is whether an open valve impinges on the travel of the pistons. I remember with grim clarity screwing up the bolt-up of a Mercedes engine, getting the cam 180 degrees backwards. Half a crank, and a piston jacked a valve up into the cam, breaking the cam mounting pillars which were part of the head casting. New cylinder head time. Very sad day. Expensive way to learn the lesson to ALWAYS roll the engine over by hand before cranking it after a rebuild.
    It seems that higher-lift cams are an essential design feature of higher efficiency, higher speed engines. This translates directly to lighter weight, both in the machinery and the fuel load.
    If someone were to ask for the most reliable, most repairable engine possible, I might suggest a plain old NA Detroit 71 series. They're cheap, parts are available all over the world, everywhere, cheap. The unit-injector system is a lot simpler to repair than a Bosch-style, certainly than an electronic common-rail. Once the mysteries of the Woodward governor are mastered, it's not that hard to set up.
    But talk about heavy, hot, oily, and smoky! Puking, slobbering, and drooping, with an exhaust snarl that proclaims itself for miles around.
     
  7. FAST FRED
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    FAST FRED Senior Member

    I saw a 4-71 aluminum block on E bay and was REALLY tempted , but I'm not sure '71 parts are that easily found anymore.

    Sure there loads in Boats #Harbors and lots of rebuilding stuff seems aviliable, but a near by boat needed an early style Gov and had to buy an entire engine to get one!
    OK, it was only a grand , and he got a load of spare stuff, to use in the future , but the writing is on the wall for the 1936 DD 71 series.

    I'll probably not have hassles with the 6-71 in our lobster boat or the 8V 71 in our Greyhound bus conversion , but the clock IS ticking.

    Any suggestions for a engine choice 200hp rated with expectations of 160hp for 10% , 100hp for 75% and 15% spent at high idle in wake zones.

    Only 300 hours a year in pleasure service.
    I LOVE the Intl DT 466 as there cheap and bulletproof ,but at 1400lbs, plus tranny.

    The 4 cyl Cummins comes closest , although the 5.9 from light trucks would also work , but are so DAMN LOUD!!!

    FF
     
  8. brian eiland
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    brian eiland Senior Member

    I've heard good reports about Steyr as well, and they certainly weight in at a good figure for use on multihulls.

    I included Steyr as an option on my latest motorsailer...look towards the bottom of the web page:
    http://www.runningtideyachts.com/dynarig/

    Conventional Propeller Drive: For those clients concerned about the new diesel-electric technologies, there are several conventional propeller configurations:

    1)Tradition shaft drive from 'canoe stern' hull form (not shown)
    2)Outdrive style drive leg with chain-belt driving single or dual props
    3)Conventional propeller propulsion could be augmented with Steyr engine/generator combo-units to dispense with auxiliary generators.

    http://www.yachtforums.com/forums/15453-post14.html chain drive
    http://www.yachtforums.com/forums/32761-post63.html Steyr unit
     
  9. seo
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    seo Junior Member

    Fastfred,

    I think the 6-71 you're talking about is either a Greymarine or a very early "low-block" Detroit. The later "high block" engines came out, maybe in the '60's, and were built in the thousands upon thousands for marine, industrial, generator, pump, oil-field, truck, and tractor service. Every engine rebuilder that I know of and most auto-parts stores stocks parts for them.

    I remember going into a bar in Petersburg Alaska once, a block up from the salmon cannery we unloaded at. Behind the bar there was a jar of pickled hard-boiled eggs, a jar of pickled pigs' feet, a jar of Slim Jims, and a neat array of detroit injectors, Jabsco impellers, and a sign that read "we have 4 & 6 cylinder head gaskets. Ask your waitress."

    Of course you're right, someday Detroits will disappear, just like Model A's disappeared. But I'm pretty confident that for around-the-world parts availability, ease of repair, and solid balls of torque, a 6-71 will be the world champ for years to come.

    A later-series 3304 Cat with turbo would probably fit your power requirements. Lobstermen around here pretty much use the B model Cummins, John Deere/Lugger, or the Volvo 60 series. It's possible that a turbo/intercooled 4-cyl. B model would be enough power, but you'd be running it right at the peak of its power curve, I think.

    I personally do not like Cummins engines, but it is an ancient prejudice that springs from a traumatic experience with a VT1710 engine. The C models have a good reputation, and after a rough start with lots of fuel-injection problems the B model seems to be okay. What can you say about a company that would fit their engines with CAV injection. I think CAV is part of the far-flung and infamous Lucus (Prince of Darkness) Electric, LTD. Source of the old joke, "Why do the English drink warm beer?"

    My prejudiced impression is that the "400 hp" Yanmar is a pretty short-lived engine at that power setting. I mainly see them in yachts, where their quiet running is a big plus. And, I don't know about now, but in years past it was pretty easy to get a dealer's medallion for Yanmar, which means that low-volume builders may pitch them pretty hard because their mark-up is better. The opposite extreme of that used to be Caterpillar, which seemed to not like to sell engines to almost anyone. These are ancient opinions of mine, in New England, and may not bear any semblance to current reality.

    The answer to the joke is "They have Lucus Refrigerators."
    seo
     
  10. seo
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    seo Junior Member

    This is a possibly interesting bit of trivia about Steyr engines. A few years ago I surveyed a 35' Canadian-built yacht with a diesel engine that said "BMW" on the label. I said that getting parts might be a problem, because BMW had gotten out of the marine diesel business (remember the BMW I/O drives?). The seller (I was working for the buyer) told me that this was a BMW engine from a BMW truck, and Germany was teeming with them. I've been to Germany, and had never seen a BMW truck, but didn't argue. I also knew that back when BMW tried to get into the sailboat auxiliary business their little one and two cylinder engines were made by Hatz, and Austrian company. Nice engines.
    To end a long story, it turned out that the BMW six-cylinder was made by Steyr. Parts were marginally availble by ordering from Europe. The prices were astounding; like $700 for a piston, not including the rings or wrist pin.
     
  11. FAST FRED
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    FAST FRED Senior Member

    That aluminum 4-71 is sounding better & better!

    Our Greymarine came out of the Can , when in '95 the gov decided to sell off the "war reserve".

    As the Navy was more than chopped in half , 600 ships to 230 by BJ Bubba , I guess they ran out of ca$h.

    The 3-1 Twin Disc was made by Oliver Farm Tractor and shows no wear.

    Great long lasting stuff , but the 6 at 2800 lbs is far too heavy for the next boat.

    FF
     
  12. FAST FRED
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    FAST FRED Senior Member

    Cummins 4B-250, rated for 200 hp continuous at 2800 rpm.

    IS faster turning than I would like , but the power matches up with the requirements fairly well

    The top speed is a minor deal as most cruising would be ay about 100hp /5gph for economy.

    Any Idea how these hold up?

    FF
     
  13. seo
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    seo Junior Member

    Fast Fred,
    It sounds like the engine you have is a Greymarine, not a Detroit. They are on the one hand nearly twins, but on the other hand they are not organ donors for each other.
    As a former Navy civilian employee involved in testing newbuilds, the reserve of stocks of antique weapons and machinery seemed absurd. Why keep a fleet of 400 hp tugs built in the 1940's? I'm sure than when the Army's horses and mules were sold that many saw it as a dark day, but I don't think it worked out that way.
    I've never seen an aluminum-block 4-71. My guess is that it was for use in a minesweeper. I have seen a non-magnetic 12-278a Cleveland, and a stainless steel Baldt anchor, and other interesting artifacts of the minesweeper fleet. The comments I heard on the Cleveland is that it was somewhat different from a plain iron one, and a real pain in the neck.
    My main question is how much weight you'd save. My guess is a hundred pounds or so.
    I've never seen a turbo-charged and intercooled 4-71, but the pistons and rods from a 6-71 might work. As I remember it the big name marine tweak-shop on 71's was called Johnson & Towers. I once had some experience with a boat that had a pair of high-output J&T 12-71's. Thank goodness that the USN was paying the repair bills. They had a short life-span at 100% power settings. Velocity impingement of the cylinder sleeves, mainly.

    I think you'd have the same luck with a Cummins 4-cylinder B model as with the six. They are not works of art, but do okay. I'm surprised that they sell a marine model with a 200hp continuous rating. Is that commercial or yacht power curve? My cynical rule of thumb is that if you want to know how much power and engine REALLY puts out, look at the operating speed & output rating of the electrical generator version of the engine.
    There's a lot of money to be made by hyping the kw outpput ratings of propulsion engines, particularly for yachts. On the other hand there's nothing sexy about a generator that craps out after 800 hours.
     
  14. FAST FRED
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    FAST FRED Senior Member

    In order to really figure the worth of any particular engine a BMEP or fuel map is best.

    But the mfg only want to release max hp curves and "ideal" propeller curves.

    Almost useless.

    Is there a way you have found to get a fuel map from the mfg?

    I haven't!

    FF
     

  15. seo
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    seo Junior Member

    Fred,
    I have to admit that I approach this from the point of view of 1) a grubby knuckle engineer, and 2) someone who advises on modifications to existing and stock vessels.
    In that role, I pretty much observe what has worked in sister or similar vessels in the past. Particularly if I can get good data on 1) fuel consumption in gph vs speed vs shaft rpms then I can get a pretty good idea of how much power the engine is actually putting out, and a crude but maybe workable resistance curve of the hull.
    The problem that I've encountered is that there's always a tendency on the part of the client to bump the engine up one size, just so he knows he's got enough power. He can always throttle down a too-big engine, which is a lot cheaper than hot-rodding or re-powering an underpowered boat. I guess that's not really a problem.
    One hare-brained scheme that I've thought up is to make a gizmo that would fit between the halves of the propellor shaft flange, essentially a very short hydraulic cylinder with a rotating-seal coupling on the outside. The propellor shaft pushes forward on the rear flange, squeezing my custom spacer/coupling. The amount of hydraulic pressure that the squeezing produces in the spacer/coupling should convert directly to the amount of thrust the propellor is producing, which is the final object of propulsion machinery, right?. In combination with a good boat-speed log, fuel-flow metering set-up and engine tachometer, this might give you all kinds of interesting information.
    On the other hand, N. G. Herreshof's son L. Francis describes in one of his books his father's method of testing rigs on his America's cup boats. That was to first test the rigging wire in a testing machine so there was an accurate stretch vs strain graph, and then down near the deck put pairs clamps on the various shrouds and stays. The pairs of clamps were a set distance apart, measured by micrometer. When underway, the micrometer would measure the distance between the clamps, and the stretch of the wire rope indicated the strain that the shroud was under. This was a hundred years ago. NGH was an MIT-educated marine engineer.
    This example leads me to the idea that if you put a propellor shaft into a testing machine, and tested its compression-vs-thrust characteristics, you could do more or less the same thing that NGH did with the wire rope.
    By machining a pair of grooves around the shaft you could have a way of measuring compression, or delongation, or whatever you'd call it. At various speeds, with different propellors, you could measure the distance between the grooves on the turning shaft, you could get a figure for shaft compression, which would convert directly to propellor thrust.
    How's that for pie-in-the-sky?
    Practically speaking, the Cat industrial engine manuals have pretty complete sets of curves, including fuel burn vs power output vs engine speeds. If you had an engine with gear, and felt like taking it to a shop with a dynomometer, and rigging it up with juice, fuel, and cooling, then you should be able to produce your own curves. But that wouldn't be cheap.
    Some of this cock-eyed thinking I developed while sailing on ocean trips on an old diesel-electric drive tug. We ran 24 hours a day, and the captain was willing to humor me by allowing fluctuations of engine speed for a 4 hour period. The engine room day-tank was well graduated, so fuel burn was easy to figure. Engine output was measured in kw of electricity, which is simple. Boat speed was measured a) by the Loran and b) by dropping a half-full soda can overboard opposite the galley door, and timing it until it went past a certain point on the towing deck. It was great fun, and produces notebooks full of figures (this before the laptop era).
     
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