Common Rail Diesels Revisited

[packeteer]

I've read that article. I don't really agree with it
My injectors are much quieter with the 2 stroke. that said, I usually run a quality fuel treatment instead as my vehicle will sit for weeks at a time

[chris95040]

Originally Posted by Compass790

Interesting post thanks. Only question I would have is how could water or grit be less damaging in a common rail fuel injection system that runs at maybe 30,000psi & has smaller openings in injector than a mechanical system that runs at 2500 psi approx ?
Maybe ask your tech about that

Not sure he implied exactly that, but it's a good point. Anyways, I took his major point to be the field serviceability in the event of a problem.

Even if the common rail injectors are 5x more likely to fail, I dunno, I might *still* prefer them. I've been tinkering with engines my whole life, but the injection pump on my diesel is an absolute mystery to me. I think I'd really like a setup that lets me just carry spares.

[leftbrainstuff]

Originally Posted by DeepFrz

One of the things causing damage to mechanical fuel injected engines is dirty fuel. I see so many people espousing that 30 micron filters are enough when most of the damage done to high-pressure pumps is caused by particles less than 7 micron. I have heard statements like "don't use 2 um filters as they get dirty too fast". The real solution is to clean your fuel system and keep it clean and use a properly installed fuel polishing system. That's just MHO.

+1

If your 2 micron final filters get clogged quickly then fix the cause. A dirty tank or dirty fuel.

We run three stage filtration on our Liberty 458. 30 micron primary Racors, a 10 micron secondary Racor P Series and 2 micron tertiary filters.

Common rail and old style mechanical injection both have pros and cons. Neither cope well with dirty fuel or water ingestion.

Our Perkins 4-236 suits us fine. We carry a spare injector and a spare cav mechanical pump. Ideally I'd like 4 spare injectors.

I can do without the turbo. Extra complexity taking up valuable engine room space.

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[packeteer]

3 stage filtration is a good idea. in my car I run 2 stage. factory 10 micron and stanadyne 2 micron.

[UNCIVILIZED]

I would think that if you're using it much, the turbo charger is going to put more heat into the engine room, not less. Non?
As in cars at least, turbocharged engines have typically had more issues created by higher heat loadings. Though obviously most such engines aren't diesels.

[Compass790]

Originally Posted by chris95040

Not sure he implied exactly that, but it's a good point. Anyways, I took his major point to be the field serviceability in the event of a problem.

Even if the common rail injectors are 5x more likely to fail, I dunno, I might *still* prefer them. I've been tinkering with engines my whole life, but the injection pump on my diesel is an absolute mystery to me. I think I'd really like a setup that lets me just carry spares.

Yes I thought later that it was just the wording. I have rebuilt my mechanical injection pump but its only for a single cylinder. Have to say it wasnt rocket science. Process was all there in the workshop manual for a Yanmar YSM8. I do have a fair bit of mechanical fitting experience but the guy who pop-tested my injector encouraged me to have a go.Wouldn't recommend trying it if you have no mechanical experience but if you have stripped & rebuilt a motor successfully I'd say it should be achievable.

[packeteer]

Originally Posted by UNCIVILIZED

I would think that if you're using it much, the turbo charger is going to put more heat into the engine room, not less. Non?
As in cars at least, turbocharged engines have typically had more issues created by higher heat loadings. Though obviously most such engines aren't diesels.

cars usually have intercoolers too.

fwiw, I run an EGT gauge on my exhaust (post turbo). with the factory intercooler, 800 degrees C is not unusual.

[Dockhead]

Originally Posted by UNCIVILIZED

I would think that if you're using it much, the turbo charger is going to put more heat into the engine room, not less. Non?
As in cars at least, turbocharged engines have typically had more issues created by higher heat loadings. Though obviously most such engines aren't diesels.

Yes, I suppose it does, but the Yanmar turbos (and probably all marine turbos) are water cooled, so not that hot on the outside. A turbo requires a bit more length of dry exhaust, so that probably puts more heat in the engine room.

This is not a problem if you have decent ventilation. My engine room stays reliably within 10C of ambient temperature. I monitor the temperature.

Turbos and diesels go together like cookies and cream. I have really learned to love them after 2000 hours and 7 years of experience with this one. Note that you can't even buy a diesel car without a turbocharger any more.

It's a dead simple device with only one moving part. For you, Uncivilized, the overwhelming argument for a turbo engine in a sailboat will be that it allows you to use an engine which might be half the weight, of a non-turbo engine with the same power. This has a big effect on sailing performance. My turbo Yanmar is light enough compared to the non-turbo option on my boat, that it actually more than makes up for the weight of the heavy duty generator.

That lighter engine with half the displacement (the non-turbo option was the 4 liter Perkins 83hp) is much happier running at low power output settings, as the cylinders need half the fuel to reach a reasonable operating temperature. And at all power settings from 1500 RPM to 3800 RPM it is sweet and smooth and quiet, a very different sound and feel from the rumbling and bellowing and shaking and thrashing of a big non-turbo 4-cylinder diesel. I've often been asked whether my Yanmar is a 6 cylinder, it's so smooth. That's because the turbo absorbs the exhaust impulses, and evens out the pressure. Of course, the lead-lined engine room also helps in this

So on turbos I'm definitely sold; I'll never have another boat without one.


Concerning common rail injection, I just don't have enough information yet, which is why I started this thread. Thanks to all for all the good information posted so far.

[capngeo]

Not in my boat, but I just bought a Cummins 6.7 in a Ram 5500 truck.... Turbo, Common Rail, EGR, and exhaust after treatment. I was nervous buying a new truck with all the "stuff" hanging off the engine. I did a lot of research. I looked hard at Ford; GM didn't have an offer in a class 5 truck, International was on slippery ground financially after their failed Maxxforce engine project. Ford has had a lot of problems with fuel contamination, and was in a V-8 configuration.

Cummins got the nod, and I ordered the rest of the truck built to my spec. All in all, after 3 months and 10k of HARD miles the truck has performed flawlessly. Too bad Cummins doesn't marinize the 6.7! Cummins is big in the commercial marine diesel market (if you can use a 1000hp+ engine)

[HKTim]

I've got a one year old L48 with Yanmar 4JH57 common rail engines. Initially we had some problems with the engines due to a bad fuel line system installation at the factory that took a long time to resolve (small air leak in the fuel circuit) and then a gummed up heat exchanger due to delivery crew (or factory) putting in the wrong type of coolant. Neither was a problem related to the engine and once we finally diagnosed and fixed each issue, the engines have worked well with no issues what so ever.

There is more instrumentation that comes as standard with the new Yanmars so its easier to monitor how everything is doing. If you are like me and your engine maintenance is limited to oil and coolant changes, checking /replacing the impeller and alternator belt etc, then the experience with these common rail engines is pretty much identical to what I did with my previous boat which had the Yanmar 4JH5E engines. If there were problems with the injectors, I'd be lost with either model of engine.

The engines run at lower RPMs. Max RPM is about 2500 whereas on the 4JH5E it was a little over 3000. Engine are supposedly quieter and more fuel efficient but its hard for me to guage either statement. But after a year I can say that they seem to do exactly what is expected - reliable motoring when needed.

[Dockhead]

Originally Posted by HKTim

I've got a one year old L48 with Yanmar 4JH57 common rail engines. Initially we had some problems with the engines due to a bad fuel line system installation at the factory that took a long time to resolve (small air leak in the fuel circuit) and then a gummed up heat exchanger due to delivery crew (or factory) putting in the wrong type of coolant. Neither was a problem related to the engine and once we finally diagnosed and fixed each issue, the engines have worked well with no issues what so ever.

There is more instrumentation that comes as standard with the new Yanmars so its easier to monitor how everything is doing. If you are like me and your engine maintenance is limited to oil and coolant changes, checking /replacing the impeller and alternator belt etc, then the experience with these common rail engines is pretty much identical to what I did with my previous boat which had the Yanmar 4JH5E engines. If there were problems with the injectors, I'd be lost with either model of engine.

The engines run at lower RPMs. Max RPM is about 2500 whereas on the 4JH5E it was a little over 3000. Engine are supposedly quieter and more fuel efficient but its hard for me to guage either statement. But after a year I can say that they seem to do exactly what is expected - reliable motoring when needed.

Thanks -- that's a data point.

[HKTim]

I should add that my engines were given a credible breaking in test which was a 70 day delivery from capetown to Hong Kong. Each engine had a little over 300 hours on the clock when the boat was handed over to me. In the past year I've put about 100 more hours on each engine.


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[01kiwijohn]

I'm without. I have about 40 years of experience with diesels in all kind of applications, dirt and other contaminated cause almost all failures. On my boat I have 2 oversized 2 micron filters and can switch ' on the fly.' even so, at each annual inspection I see a small amount of sediment in the secondary filter bowl.
Common rail should be a good improvement overall.

[buzzstar]

Any thoughts bout spares and the ability to use them?

[a64pilot]

Originally Posted by buzzstar

Any thoughts bout spares and the ability to use them?

First thing your going to need is diagnostic software as I assume these won't have OBDII connectors, but they will have something, so will Yanmar sell you the software and connector?