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Old 04-06-2013, 09:48 AM   #41
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Originally Posted by Marin View Post
Received this regarding my comments on turbochargers from my engine industry friend. Seems my perceptions are a bit off the mark. Thought it might be of interest to the rest of you.

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Marin---

Turbocharging isn't necessarily a bad thing. It is a frequently misunderstood thing though, that is for sure.

Here are some numbers that might be of interest to the forum member you mentioned with the NA John Deere engine in his Seahorse Marine boat.

His normally aspirated engine has a compression ratio of 17.6:1

The turbo version has a compression ratio of 17.2:1

His normally aspirated engine can produce a full load EGT of 1139F.

The turbocharged version will produce a full load EGT of 770F.

The turbo version "breathes" better. The exhaust valves run cooler because valve overlap bathes them in cool air for a period on each exhaust stroke.

The turbo version is capable of producing more horsepower, but that doesn't mean you need to use it.

Turbos on gasoline engines live in Hell and are routinely operated by drivers who treat them like they are a carburetor or a radiator. Ignorance is bliss until the costs of abuse are presented.

Turbochargers lead a relatively comfortable life on a diesel and can easily last the life of the engine, if for no other reason than the way the engine in a recreational "trawler" is operated, long periods at moderate power with an extended period of "cool-down" before the engine (and its lube oil supply) is shut down. Replacing the turbo on a JD 4045 only costs around $700 or so in any event. That should not scare anyone away from higher efficiency and greater available power.

The fear of turbos and the common belief of high expenses and dangers from mistreatment simply don't apply to the units fitted to small diesels on recreational vessels, trawlers in particular.

Here is a PDF with the power specs for the John Deere engine in question.

http://www.deere.com/en_US/docs/engi...045DFM7080.pdf

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Marin, I still believe your original thoughts are more on the mark.

Simply put if you look at th explanation above, you still have to read between the lines and assumptions are made about maintenance, that may not be true for everyone all the time.

How does one get more power out of a given displacement if it is not stressing the engine more????? Oh, we sprinkle on the fairy dust of marketing.

Temperatures, lubrication become even more critical.

Companies push turbochargers for many reasons and customers saving money is certainly not one of them.

JMHO

Richard
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Old 04-06-2013, 10:46 AM   #42
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How does one get more power out of a given displacement if it is not stressing the engine more????? Oh, we sprinkle on the fairy dust of marketing.Richard
You cannot buy a new diesel for off or on the road or pleasure craft that is not turbocharged. Turbos have been around for 50 plus years and are as much a part of old as well as new diesels. The major engine mfrs offer longer warranties today on their Tier iV diesels than they did 30 years ago on non turbo engines. Increased diesel longevity is all about design, materials and maintenance.

On boats, the biggest problem with old and new turbo engines is with those that have seawater aftercoolers. No way around this maintenance area, just like any other part that comes in contact with sea water.

IMHO, the best thing for repowering a trawler yacht is with a re-man non Turbo Cummins 5.9. Full warranty applies, much simpler than a new JD 4045 or 6068, parts readily available, the most popular 4 stroke diesel ever due to the pickup market and they last "forever." Footprints are much the same as Lehman and Perkins 6s.
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Old 04-06-2013, 02:47 PM   #43
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Yes Tom and a twin engined GB would suddenly have 420 hp. Sounds like an excellent plan for Marin. That would be a bit more than "Spray". He likes speed too.

May be good for many single engined trawlers here. I'd kill the Lehman first though. And killing Lehman's is hard to do.
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Old 04-06-2013, 08:12 PM   #44
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Well, just to add some contrast to the discussion, I'm a big fan of turbo charged, electronically controlled diesels. The turbo ensures there is always ample air for complete combustion, and as mentioned earlier, allows the engine internals to run cooler.

Electronically controlled, common rail diesels idle smoother, run smoother, start right up even when cold, basely smell at all, basely smoke, get better mileage, make less noise, and essentially eliminate light-loading issues. And they accurately report RPM, load %, GPH consumption, etc. The technology has been around for a very long time and is extremely reliable. Yes, they can break, but so can a mechanically controlled engine. Personally, I think the benefits far outweigh risks.
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Old 04-06-2013, 10:09 PM   #45
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Well, just to add some contrast to the discussion, I'm a big fan of turbo charged, electronically controlled diesels. The turbo ensures there is always ample air for complete combustion, and as mentioned earlier, allows the engine internals to run cooler.

Electronically controlled, common rail diesels idle smoother, run smoother, start right up even when cold, basely smell at all, basely smoke, get better mileage, make less noise, and essentially eliminate light-loading issues. And they accurately report RPM, load %, GPH consumption, etc. The technology has been around for a very long time and is extremely reliable. Yes, they can break, but so can a mechanically controlled engine. Personally, I think the benefits far outweigh risks.
Well put! The JD 4045 is actually smoother and quieter than the Lehman 120 that it replaced. I wasn't expecting that -- I was expecting a rougher engine with turbo whine. I enjoy the benefits you list every time I use the boat.
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Old 04-06-2013, 10:25 PM   #46
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Originally Posted by twistedtree View Post
Well, just to add some contrast to the discussion, I'm a big fan of turbo charged, electronically controlled diesels. The turbo ensures there is always ample air for complete combustion, and as mentioned earlier, allows the engine internals to run cooler.

Electronically controlled, common rail diesels idle smoother, run smoother, start right up even when cold, basely smell at all, basely smoke, get better mileage, make less noise, and essentially eliminate light-loading issues. And they accurately report RPM, load %, GPH consumption, etc. The technology has been around for a very long time and is extremely reliable. Yes, they can break, but so can a mechanically controlled engine. Personally, I think the benefits far outweigh risks.
The above quote, while I agree with the second paragraph, the first is simply not relevant to the second.

Diesels by design always have ample air (unless you ware a car company that took a gasoline designed engine and made it into a diesel for marketing reasons, but then who could be so stupid to do that???
I digress, having spent a number of years in cold, dark places, like Alaska and even further north, all of the diesel generators we had (cat diesels) ran constantly for 3 months at a time, then down for 1 hour oil change and then another 3 months, anybody would like to guess if turbocharged?

Our heavy equipment, cats, graders, basically did the exact same thing, but some of those were turbocharged because of different needs to occasionally have much more power. And they had far more problems, not every day or even every week, but at least every month.

By point here, everything else being equal, is that a turbo, while increasing power, will always add complexity, more maintenance and more $$$ period.

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Old 04-07-2013, 07:04 AM   #47
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HP is a great , almost useless yardstick for most trawler owners.

A far better but impossible to obtain is fuel burn per HP ,,,,AT THE RPM / HP THE BOAT WILL CRUISE AT.

Some diesels will make 16- 22 HP per gal of fuel at the WOT loading.

So what?

Yank them back to 1500-1800 with a std prop light load and you're only getting 8-10 HP for that gallon of diesel.
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