MAN engines / common rail diesels

[Nick_H]

Does anyone have any experiences or opinions, good or bad, with these engines, particularly around 800hp manufactured in last 3-4 years?

Also what are the benefits of common rail diesels? I know the auto industry is moving over to them almost entirely. Are VP D12's common rail?

 

[spannerman]

Can't help with the MAN diesels, but the trend now is common rail, VP have it on their new D series engines and Yanmar are just getting into the game with a BMW engine that is actually a Steyer.
Although the D12 is not a common rail as in the smaller VP engines, it uses a dedicated lobe on the camshaft to operate a pump on each individual injector to provide the injection pressure, but the timing of the injection sequence is controlled electronically.
The advantages are that it is easier to profile the injection timing curve and modify according to inputs from sensors monitoring, rpm, engine temp, air and fuel temp, boost pressure, cam angle, and a few other parameters depending on manufacturer.
By controlling the injector electronically you can have sequenced injection instead of just one shot as on the older mechanical types.
The result is easier and cleaner starts hot and cold, automatic fast idle for warming up, and the engine can protect itself from abuse by shutting down to low RPMs if there is a fault, i.e. overheat, low oil pressure.

 

[oldharry]

Dont know the MANs personally, but Common rail diesels have electrically controlled injectors running off a single high pressure supply - hence the term 'common rail'. Injection is by electrically controlled valves, controlled by the EMS, which allows very precise timing and quantity of the charge for each cylinder, according to the engine load and speed This gives better fuel economy, and a much cleaner burn with significantly reduced emissions. It also means that amateur repair is virtually impossible without access to specialist computerised diagnostic and set up equipment!

 

[Nautical]

RNLI use em in the Trent and so far have proved very reliable although they are running at commercial rating. MAN probably one of the best reputations in the higher end of the industry next to MTU and Cat.

Common rail as per previous posts , if thinking newish 3-4 year old boat would not consider motors that are not common rail as the emissions and fuel economy are generally better plus if we eventually get taxed on emissions then oldy stuff will be hit hardest.

 

[Sammo]

Yes as Harry says self maintenance is not associated with common rail, I recently was told I needed a new injector in a sprinter. No recons so I had to buy a new one at £199.00. Previous I could have took the injector up the road and had it cleaned and reset for a tenner.
Another consideration of course is that single rail needs electric to run


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