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outbound 03-10-2016 11:10 AM

Turbo diesels
 
In the past small naturally aspirated diesels were the auxiliaries in cruising sailboats. Even on passage with a modicum of knowledge you could keep one going. Perhaps not all cyclinders but enough to propel the boat. You could have extra belts, filters and an injector feeling fairly confident.
Now virtually all recent boats have small turbo diesels. You would have difficulty even spec'ing a new boat with a naturally aspirated engine.

So the question to you wrenches is:

If the turbo goes, won't even spin, will the engine function at all? If so at what perecentage of its original shaft HP?. Are you better off physically removing it from the system? Given how expensive they are is it worth it to carry a spare(we carry a spare alternator)? If the engine can run without a turbo what does that do to the engine?


Thanks.

killarney_sailor 03-10-2016 11:14 AM

Re: Turbo diesels
 
I had an interesting experience with my son who is a BMW tech and who works with their very complex diesels. He looked at my old Westerbeke, which I can fix a lot of things and just laughed. He said that diesel turbo units are about the most complex items he encounters. You need a lot of training and access to special tools. I imagine a Yanmar one would be simpler, but still far from simple. Perhaps best to talk to Yanmar and see if they have a DIY manual for changing a turbo. If not, it would be a non-starter (if you pardon the pun).

outbound 03-10-2016 11:28 AM

Re: Turbo diesels
 
K does that mean it won't run at all if the turbo shat the bed?

BTW I have a turbo'd ecodiesel in my jeep summit. It's wonderful but I asked the local wrench what to do if it won't start when we are out fly fishing on the beach. His reply was "pray you can get a 4x4 tow truck before the tide comes in and alway park well above the high tide line".

BarryL 03-10-2016 02:49 PM

Re: Turbo diesels
 
Hey,

If the turbocharger locks up so that the shaft won't turn, no, the engine won't run. The turbocharger is driven by exhaust gas, if the exhaust can't get past the turbine vanes then the exhaust can't get out. If the exhaust can't get out, the engine can't run (no gas out = no air in).

There are situations where the turbocharger won't work (generate pressure) but the engine will still run - burned turbine or compressor, etc, the engine will still run but will make much less power.

Personally I have no experience with turbocharged marine diesels so I can't offer any advice on spare parts.

Barry

Quote:

Originally Posted by outbound (Post 3383745)
If the turbo goes, won't even spin, will the engine function at all? If so at what perecentage of its original shaft HP?. Are you better off physically removing it from the system? Given how expensive they are is it worth it to carry a spare(we carry a spare alternator)? If the engine can run without a turbo what does that do to the engine?

Thanks.


Erindipity 03-10-2016 05:07 PM

Re: Turbo diesels
 
In my opinion, modern, auto-based, high-rpm Turbodiesels don't belong in smaller Sailboats. Who needs that much added power? Anyway, they aren't common. Bog-Standard non-Turbo Marine Diesels are still the most common kind, by far.
As to whether a Diesel will run with a frozen Turbo- it depends.
A friend of mine bought a Mercedes 300TD with a frozen Turbo. It still ran, but slowly, and smokily. He replaced the Turbo, and the Car ran again as well as it ever would. After a couple of years, I bought it from him, and put another 100K miles on it. Oil, a couple of lamps, wiper blades, and tires were all that I replaced. And then a tree fell on it...
My current 300TD has over 350K original miles on the clock...
The 30 year old Volvo Diesel on my boat is also original, but it isn't Turbocharged. It runs like a top- tickle the manual fuel pump lever a few times, and it starts right up.

(Those old MB Diesels were _heavy_; the 300TD 125HP Turbo series engines weighs something like 1,100 pounds. I've lifted a couple, with much mechanical assistance.)

"If the engine can run without a turbo what does that do to the engine?"
Again, it Depends.
Mechanical Fuel Injection pumps were calibrated for Turbo use, and would dump too much fuel into the cylinders at higher engine RPMs if the Turbo froze, leading to Smoke in the exhaust, and engine Coking. This could also cause Glow Plugs to burn out.
Older Diesel fuels were only fair lubricants, (Sulfur...), but raw Diesel getting past the rings could lead to cylinder scoring on starting when cold.
If you are talking about modern EFI Diesels, with modern low-Sulfur Diesel fuel, you have to be a bit more specific. I have no idea what each manufacturer has in the way of Exhaust Sensors and Sensing. It's all very Proprietary these days.

Someone else commented:
"If the turbocharger locks up so that the shaft won't turn, no, the engine won't run."
Simply. Not. True. Turbochargers are not displacement pumps, like piston pumps or Roots Blowers. At low or no RPM, enough exhaust gas gets past the vanes to allow the engine to start and run. Turbocharging depend on high Turbo RPM to work at all. A frozen or weary Turbo just adds back-pressure to the exhaust system, and messes with Injection settings.
(BTW- the Failure Mode is the Turbo bearings. Lack of oil or very dirty oil is Death to them. The bearings either get frictiony, they freeze up after being run hard and shut down too quickly, or they fail spectacularly, causing vanes to hit what's around them that they shouldn't hit. I've rebuilt more than a few, but with this distinction- they were made by Varian, and they weren't used in boats, that I know of.)

"Now virtually all recent boats have small turbo diesels... You would have difficulty even spec'ing a new boat with a naturally aspirated engine."
Volvo, Yanmar and most other manufacturers still offer naturally aspirated Diesels, from one to four cylinders, I just checked, and Catalina, Hunter and Beneteau offer them; I just checked again. Where did you come up with that claim? (You may have something if you are talking about custom >$500K Mega yachts, but since you didn't make that claim, I am assuming that you aren't.)

ČErindipty

capta 03-10-2016 05:41 PM

Re: Turbo diesels
 
If a turbo packs up you will have a decrease in air into the cylinders, a richer mixture because there won't be forced (turbo) driven air getting in. But the engine will still take air in naturally. A blown turbo will not hinder the exhaust as it is a turbine. The engine will still run, at reduced power of course, and smoke like a hippie. The smoke was the first indication you'd blown a turbo on the big sportfish boats. A dead giveaway. It happened fairly regularly. We carried spares, and with as much a a million bucks on the line in a tournament, our budget was somewhat greater than most sailors.
If you wanted to remove your turbo permanently, you would require different injectors at the very least. Possibly new pistons, rods and rings as well, and then you'd have to mess with timing. PITA.

CarbonSink62 03-10-2016 05:46 PM

Re: Turbo diesels
 
Quote:

Originally Posted by Erindipity (Post 3384633)
...I've rebuilt more than a few, but with this distinction- they were made by Varian, and they weren't used in boats, that I know of.)
ČErindipty

If they were made by Varian, I would doubt they were on an engine.

Their 'turbos' are vacuum pumps.

AFAIK

Ken

Erindipity 03-10-2016 06:07 PM

Re: Turbo diesels
 
Quote:

Originally Posted by CarbonSink62 (Post 3384729)
If they were made by Varian, I would doubt they were on an engine.

Their 'turbos' are vacuum pumps.

AFAIK

Ken

Ayup. The principles are the same; get the speed of the Vanes up to a high enough speed so as to direct Molecular Flow. With these Varian Turbopumps, I routinely logged Driver Current and Bearing Temperatures; if there was a sudden sharp rise unrelated to Pressure, the pump was removed for new bearings. They had hundreds of Varian Turbos to keep an eye on.
I've also rebuilt quite a number of Varian and PE Ion Pumps. Instead of simply replacing the Titanium and/or Tantalum Elements, as Varian and PE did at great expense, I literally beat the crap out of them, using a particularly peculiar form of Sandblasting.

But this has little to do with the ongoing discussion, so I shall end it here.

ČErindipity

outbound 03-10-2016 07:48 PM

Re: Turbo diesels
 
So the thing will run which is good to know. Question remains with enough hp to adequately move the boat. From the above helpful and appreciated posts. Abstract
May not fail catatrophically
May or may not destroy the rest of the engine. My concern is on passage as coastally you can just right a hurtful check. Specific question is blown turbo and need for several days of powering - what does that do to the engine?
Hp will decrease but how much? Yes Martha you do get waves even in the absence of wind sometimes and it's nice to stay ahead of the front and have an engine to get through that cut when you get to where you're going.

Btw emailed yanmar same questions as original post. Still waiting for an answer. Will share it if they respond.

Glad to hear naturally aspirated diesels are available. Haven't seen one in a new boat in quite some time. Maybe people wouldn't accept the extra weight to get to the same hp or the naturally aspirated version won't fit. Think it common to spec the lowest hp to adequately serve intended use due to weight and expense. I have 75hp on a 30k lbs. boat and think that adequate. Think less would not be.

albrazzi 03-10-2016 08:04 PM

Re: Turbo diesels
 
I think if I had one I would replace the turbo around the factory recommended interval and save the old one as a spare. All the debate on whether it will run without can be summed up by "Not well if at all" But then I wouldn't own one at least if there was a choice.

The reason they are so prevalent is HP/weight ratios and simply to sell them. Cars are made to showcase the new tech to create a market for new tech. Ever driven a new Cadillac with the 4 cyl turbo, try it you'll like it.


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