Thoughts on common rail diesel engines

Talulah

Talulah

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I currently have a Yanmar 4JH4E engine. This is a normally aspirated engine.
A few years ago Yanmar replaced that engine with the 4JH5AE. Very similar with a few minor tweaks.
i.e. electric fuel pump. Serpentine belts instead of v belts.
Yanmar now do a 4JH57. This has the same power and footprint but has common rail diesel injection.
I'm assuming common rail diesel injection is to bring down emissions but I may be wrong. I also assume it's a lot more complicated.
So is ecu controlled common rail diesel injection on a 53hp a step in the right direction? Is this progress or is it best kept simple?
 
Fundamentally it because common rail engines are cheaper to produce than older one pump and injector per cylinder types. Any other actual or perceived advantage is a bonus (they are quieter for example).
 
I think that the use of the boat is probably the largest consideration in terms of ecu v mechanical (I don't think that the common rail bit is as important).

I'm much more comfortable with a twin engine high speed MB operating mostly within day sail range of base using ECU than say a yacht (or single engine MB) auxiliary doing a long passage but dependent on that single engine for say a long tricky entrance at the other end.

Horses for courses as always.
 
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Putting electronics into important bits of saltwater boats is fundamentally a retrograde step. If my two plotters and various sailing instruments die I can still navigate: if an engine ECU dies a single-engine motor boat can be crippled. Even with a sailing yacht I suspect more people really rely on their engine than do on their electronic toys. I've had old boats with dodgy and grossly underpowered engines, but current small marine diesels are awesomely reliable, and we do get to trust them perhaps more than we should.

Have had two common rail diesel cars for last 15 years, both have suffered from random 'drop down into limp-home mode' faults, current normally 140mph car can be down to 5mph up inclines and 40mph downhill in this mode. Always clears after random 5-30 mins, and neither main agents or independent garages have ever diagnosed reason for fault, even once when handed to them with fault in progress. It can though go 20-30 thousand miles without it happening.
 
It's a terrible idea.Electronic injectors,very high pressure pumps and ecus on a small inboard? Madness. It reminds me of the time Nigel Calder wrote an article advocating that all boats should have CanBus electrics.Now that was plain stupid.
 
I wonder if it's because they can no longer get the necessary part to do it "the old way"? Sooner or later, we're going to find that more and more of the small diesels from which boat engines are derived will be brought up to modern emissions standards and it becomes more and more difficult for the manufacturers to do anything different, given the relatively small number of units they're going to sell.
 
I believe its a combination of emissions requirements and the older technology being obsolete.
Fortunately my new Marine Power Chinese engine still uses totally non electronic injection so no worries on that score so the option to avoid common rail is still there if you can drag yourself away from the big names.
As for refinement, the MP 446 is as refined as any cr engine, and in fact quieter than some of the rattly, modern car diesels.

The other issue I have with electronics on boat engines is the ecu invoking limp mode at the drop of a hat. This is at best a major inconvenience and at worst, potentially dangerous - you can imagine the possible consequences of a sudden loss of 75% or more of available engine power without warning. Repairs are not a diy proposition and even carrying a spare ecu is pointless (apart from the great expense) as they are not 'plug & play'.

Avoid at all costs imho.
 
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30boat said:
It's a terrible idea.Electronic injectors,very high pressure pumps and ecus on a small inboard? Madness. It reminds me of the time Nigel Calder wrote an article advocating that all boats should have CanBus electrics.Now that was plain stupid.
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Yes, but most boats do have canbus now- which is what NMEA2000 is. Why is that stupid?

A friend of mine who is a diesel engine expert says that common rail is much more robust, more tolerant of poor fuel, easier to repair than mechanically injected diesels. I'm not an expert and have no opinion, but there's one data point for you.
 
I'd argue about the "more robust" comment. Modern engines in general do tend to be more reliable, but common rail engines are subject to more and different failure modes than those with mechanical pumps and injectors. I've not had a mechanical injector system fail in service but I have been sidelined by a fault in a common rail diesel that involved a tow, an overnight stay and £150.00 Garage bill. I stress the term "fault" as it was traced to a wiring glitche. Not something the recovery driver could diagnose and fix by the road.
 
Having owned 3 common-rail diesel cars over about 130K, I've never experienced any problem.
Replacing old-fashioned injector/metering pump with CR head will allow higher rpm, greater economy and one less tricky mechanical part to malfunction.
For those who like to pour cold seawater over their engines, there is definitely a downside of ECU protection.
A definite advantage - IMHO - but one which will only prove itself in service.
 
jwilson said:
Putting electronics into important bits of saltwater boats is fundamentally a retrograde step. If my two plotters and various sailing instruments die I can still navigate: if an engine ECU dies a single-engine motor boat can be crippled. Even with a sailing yacht I suspect more people really rely on their engine than do on their electronic toys. I've had old boats with dodgy and grossly underpowered engines, but current small marine diesels are awesomely reliable, and we do get to trust them perhaps more than we should.

Have had two common rail diesel cars for last 15 years, both have suffered from random 'drop down into limp-home mode' faults, current normally 140mph car can be down to 5mph up inclines and 40mph downhill in this mode. Always clears after random 5-30 mins, and neither main agents or independent garages have ever diagnosed reason for fault, even once when handed to them with fault in progress. It can though go 20-30 thousand miles without it happening.
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I had the same issue on a VW Golf TDi 90. Frightening on a motorway or dual carriageway when it happens. I think they diagnosed it as a faulty air mass meter, but we sold it shortly after repair so am still not sure.

It wasn't common rail though, but electronic failure nevertheless.

Seems to me that engines have become so reliable these days; doubt it will be possible to buy normally aspirated and injected engines down the line.
 
Talulah said:
I currently have a Yanmar 4JH4E engine. This is a normally aspirated engine.
A few years ago Yanmar replaced that engine with the 4JH5AE. Very similar with a few minor tweaks.
i.e. electric fuel pump. Serpentine belts instead of v belts.
Yanmar now do a 4JH57. This has the same power and footprint but has common rail diesel injection.
I'm assuming common rail diesel injection is to bring down emissions but I may be wrong. I also assume it's a lot more complicated.
So is ecu controlled common rail diesel injection on a 53hp a step in the right direction? Is this progress or is it best kept simple?
Click to expand...

Insofar as sailors are wandering to places where back up is either unavailable or poor, I would have thought that a simple engine would be better even if a bit more expensive and using a bit more fuel. Something of lowish output converted from a truck rather than a high output lightweight.

Bit like my motorbike. I would be nervous of taking my BMW 1200GS to anywhere remote - ECU, canbus, fuel injection and needing a computer to read failure codes. I would be less nervous of taking my old Norton - carburettors, points and coils, traditional 12v wiring. Yes I know the Norton would be less reliable but when it breaks I can repair it. With the Beemer I have no hope.

That said lots of people sail off into the blue yonder having had all maintenance work done by a yard and with little or no personal skills. Chatting to a guy just finishing a circumnavigation, I asked him what were the most difficult bits of it expecting him to talk of escaping hurricanes etc. The answer was repairing a gearbox in Pogo Pogo.
 
As almost all diesel engines have gone the common rail route there is no avoiding it in the future. The smaller yacht engines will no doubt keep the conventional injection pump and injectors for the moment. When common rail engines started to appear in cars about 15 years ago they got the name of 'common fail', but they have improved over the years. The problem is going to be when your common rail boat engine gets to around 15 to 20 years old. A conventional injector might cost around £50 and injector to overhaul and replace the nozzle(this varies), a common rail injector in an industrial engine about £200. And when you have four injectors to do....... Yes they are far quieter, use less fuel, and have less emissions but the advantages start to disappear when they go wrong. A convention diesel system will soldier on a bit and give warnings of impending problems, a common rail engine will simply stop or not even attempt to start. But this is the future and we will have to live with it, just keep your fuel nice and clean, and the engine compartment completely dry. The fuel quality is vital in a common rail engine, they will not tolerate any kind of bad fuel, dirt or water, if you feed this into the system you will be faced with a huge bill.
 
Dockhead said:
Yes, but most boats do have canbus now- which is what NMEA2000 is. Why is that stupid?

A friend of mine who is a diesel engine expert says that common rail is much more robust, more tolerant of poor fuel, easier to repair than mechanically injected diesels. I'm not an expert and have no opinion, but there's one data point for you.
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Easier to repair IF you have the readout equipment and IF you can fix the indicated fault. Neither are likely to be possible in a small boat miles from anywhere. Conventional diesels are easier to repair under the constraints of a small boat that may be miles from anywhere.
 
The future in sailing is lighter and faster hulls, sailing yachts that skim along in light airs at a reasonable speed. The need for a big diesel on the majority of leisure yachts will recede and probably be replaced by an electric motor as electric energy storage and generation technology improves. I really think we are in the end game of old style diesels, they have turned out to be false economy as well according to recent reports on the BBC. No one will push the technology when newer technologies are advancing at such a pace. There is no reason at all why electronics cant be made robust enough for a marine environment.
 
having a "lighter, faster" hull, I would commend, in the Med, old-fashioned, heavyweight, long-keeled designs, which can carry their way through a typical chop. Perhaps the answer would be that no-one be permitted to purchase a common-rail head diesel without producing proof of understanding the technology?
A point which might well piss-off the nay-sayers (who usually rely upon prejudice to replace common-sense understanding).
 
I guess a very similar conundrum was posed some years ago when petrol outboards went from carbs to efi. I don't see many outboard owners complaining about reliability problems. There is no reason why correctly marinised electrical components should suffer from limited lifespan. I would not go back to a noisy and smoky traditional diesel after my current common rail model. Failures of electrical components are obviously a greater likelihood, but then correct and intelligent interpretation of the diagnostic PC can normally sort that out. Compared to your car I believe most CR marine engines have fewer sensors and therefore potential failure points anyway.
 
Keith-i said:
I guess a very similar conundrum was posed some years ago when petrol outboards went from carbs to efi. I don't see many outboard owners complaining about reliability problems. There is no reason why correctly marinised electrical components should suffer from limited lifespan. I would not go back to a noisy and smoky traditional diesel after my current common rail model. Failures of electrical components are obviously a greater likelihood, but then correct and intelligent interpretation of the diagnostic PC can normally sort that out. Compared to your car I believe most CR marine engines have fewer sensors and therefore potential failure points anyway.
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Serious question; How far (and for how long) do you stray from port? (Sorry, that sounds derogatory I know but it is not meant to - I'm trying to find out how people make up their minds on this question).
 
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Keith-i said:
I guess a very similar conundrum was posed some years ago when petrol outboards went from carbs to efi.
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I have never owned an outboard with EFI. The only ones I have any knowledge of are fitter to sports boats which never go far from land and are used mainly for day boating, waterskiing and racing. As mine have only ever been used to drive tenders, I don't suppose I'd worry unduly it it had efi, I always have oars, but I"m not sure I'd want efi on a cruiser's outboard.
 
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