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Old 20-02-2010, 06:18   #16
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I am not so sure we will see them in widespread use anytime soon in marine applications.

The purpose of all this development of diesel fuel systems has been to make diesel engines in cars perform more like gasoline engines. Especially, to increase the RPM range and power to weight ratio.

The new diesel cars, with very high pressure small diameter turbos, and common rail injection systems, are amazing. In some cases (BMW) they are better than gasoline engines, much more torque with the same power.

But the design values for marine use are completely different. We care nothing about RPM range and very little about power to weight ratios. A diesel only needs precise fuel metering when it starts to push the envelope in terms of power out of a given quantity of air. We are almost never in that situation; at cruising speed and RPM we are only putting a little fuel into the compressed air mass, and a simple mechanical injector will do just as good a job as a common rail.

My own propulsion engine, a Yanmar, is turbocharged and intercooled, and I question the sense of having a turbocharged engine in a sailboat. What is the purpose of all of this complexity (and so many things to break)? It allowed the makers to produce a wider range of engines on a single block, for one. It allowed them to get a more powerful (and expensive) engine out of a smaller and cheaper block.

But from my point of view, the only advantage is that it is somewhat more efficient, somewhat lighter, and somewhat quieter, than a natural aspirated engine would be. Is it worth the greater risk of breakdowns? The greater risk of something breaking which I can't fix? Or can't get fixed?

I like the idea of common rail engines in our boats even less.
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Old 20-02-2010, 06:36   #17
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Quite popular wish the 350hp+ sport fishing and long range crowd.
I know of a number of 850hp Cats and some John Deeres.
I understand that correct propping has no room for error.
If the engine does not "un-load" as boat speed increases, the ECU will not feed fuel, which will not allow speed increase,--etc--etc.
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Old 20-02-2010, 07:08   #18
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Common Rail s a product or BSO (Euro) and EPA (USA) emmisons regulations. lt is just not possble to meet these standards without this technology. Diesels (l before E) under certain HP/KW are exempt or excluded for now. (l believe this is under 80 hp?)

Nearly all, lf not all over the road and larger lndustral diesels are common rail now. There are few engines in the boating market that are not marinized from land based units so fix your old ones or get used to the benefits of new technology.
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Old 20-02-2010, 07:12   #19
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there are some serious Luddites in this thread.

Common Rail is here, now starting around 100hp. It's been here for 5 years or so. It's truly amazing the amount of power to displacement you get and the minimal repairs necessary.
Yes common rail can be run at lower speeds do to increased finite control of the fuel.
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Old 20-02-2010, 07:34   #20
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JG1417, 35,000 PSl s a bit high but not by much. Bosch and others can get to pressures above 25,000 PSl but only while running and only mometary. That said Del's warning is no less important and one needs to be very careful. At rest, (Engine off, when you would need to bleed the system) the common rail residual pressures are much lower but can still do harm. On some systems Accumulators mantain min. pressure for restarting. lt is not all bad and with a little help you can learn what you need to know. We still have a few years with our old mechanical engines but the window is closing. "These are not your grandfathers diesels anymore"
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Old 20-02-2010, 08:27   #21
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I think that this argument may be academic rather soon. Once the world's economies start humming again, we will see the price of crude, diesel and gas rise (as it did in 2007-08). That put a chill on boat usage, sales, etc. The problem is, the rest of the world wants what the U.S. and Western Europe have had for a century. That can only add to the demand for oil and greater prices for it. The problem will kind of solve itself eventually when the "the last black, thick, stinking gob of oil oozes from the earth" (to butcher a quote of Tristan Jones'). The best alternative is to continue to develop electric auxiliaries (which have come some ways in the past 15 years). Though certainly I am no mechanic, from what I have seen and read of them, the electric systems are somewhat simpler. I think Schock puts one in a version of their Harbor 20 or 25. No doubt, the "times they are a changin'" to quote Bob D.
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Old 20-02-2010, 09:24   #22
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Old 20-02-2010, 09:41   #23
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My thinking exactly...
Stay with old stuff and you will not be required to go this route even if the industry does.
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Old 20-02-2010, 10:10   #24
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One advantage the new electronically controlled diesels have is they are much quieter running than the older ones.I think the reason for that is the fuel charge is spread out over the combustion cycle which reduces the knocking.Instead of one squirt of fuel the engine gets many smaller ones timed for a smoother power stoke.

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