MAN diesels are being acknowledged by more and more boat-owners and builders as an engine of choice; superior in quality to the perhaps better-known US makes. This is not to say these brands don't deliver a fine blend of performance and fuel efficiency, just that MAN does the job with a little more finesse.
One example of this finesse is the recently released D28 Series diesel, a development of the proven direct-injection D 2866.
A straight six, it displaces 12.8lt and has a bore of 128mm and stroke of 166mm 11mm greater than the D 2866. It develops 515kW (light-duty rating) at 2200 revs and sans gearbox weighs a reasonable 1215kg dry.
Compared to the D 2866, it develops 15% more power from 7% greater displacement and weighs only 5% more. But apart from its next-generation electronic engine management system, perhaps the most impressive feature of this engine is its flat torque curve. A maximum of 2510Nm are provided from 1300-1800 revs and even at 800 revs the engine still develops 1300Nm!
Part of this broad, flat torque curve is due to the unusual exhaust gas to turbocharger system. In the MAN's design an internally-insulated exhaust system directs the uncooled exhaust gas direct to the turbocharger, which allows for more boost at lower revs. This means better out-of-the-hole performance and an ability to stay on the plane in adverse sea conditions instead of falling back into an inefficient semi-planing mode.
The maximum torque is 26% greater than the D 2866, which developed 2000Nm in the 1400-2000 rev range. And compared to the 12.0lt straight six Cat 3196, the D28 develops 23% more torque at 1000 revs, although for peak torque it does lose out to the Cat, which develops 17% more at 1400 revs. But the D28 develops 5% more power at 100 fewer revs and weighs only 3% more.
Due to the combination of a four-valve head and fuel injector located centrally in the combustion chamber, the D28 has a maximum full-load fuel consumption of 136lt/hr only 11% greater than the D 2866. Over the maximum torque range the full-load consumption varies from 80-110lt/hr and based on an average propeller power curve the consumption drops to 30-70lt/hr, excellent for a diesel this powerful.
MAN has long been able to compress a lot of output into compact dimensions and sans gearbox the D28 measures 1605mm long, 40mm more than the D 2866, while the width is 869mm (39mm more) and height 1070mm (72mm more).
MAN's engine monitoring and diagnostic system (MMDS) has all the benefits of electronic diesel control, such as control wires instead of cables to the upper and lower helmstations and constant monitoring of the engine's performance and conditions which may affect this.
Each of the helmstations has analog display of engine revs and total operating hours, engine oil and coolant temperature, engine and gearbox oil pressure and exhaust gas/charge air temperature, which is a direct indication of engine load. The MMDS will alter the injection timing according to engine load and the air/fuel ratio according to barometric pressure, so the engine will always function in peak operating condition unless a malfunction occurs.
This information is constantly recorded in the management's memory system and can be downloaded by using a laptop.
But MAN's system goes one further than other systems by automatically reducing engine output by 25% should an abnormality arise and an alarm be not taken into consideration. Other alarms, such as high bilge water, can be incorporated into the MMDS.
MAN fits a single-speed ZF gearbox as standard. While I would have preferred to see a two-speed box fitted to take full advantage of the engine's massive bottom-end torque, according to Seapower Australia a suitable unit for this engine is about two years overdue. Nonetheless I still believe that buyer resistance is a big problem in the realm of two-speed units.
Recently I interviewed a leading Aussie boatbuilder about why so few people opt for the two-speed units and I was told that buyers can't grasp the concept. For example, one buyer was a truckie who had been changing gears all his working life and all he wanted to do was put his gamefisher in gear and head for the open sea!
Perhaps ZF Australia should commence an education program to convince buyers of why they should opt for the two-speeders, which are only 15-20% more expensive than single-speed units. With all the develop ments in electronic engine management systems for diesels, it seems absurd that cruiser owners don't take full advantage of such brilliant technology.
That whinge aside, MAN has done a fine job in packaging its D28. And yes, like its V-block counterparts, you can still order the kitsch (sorry Seapower!) gold-plated rocker covers. At around $A100,000 complete with single-speed ZF, Seapower claims the D28 is priced below comparative engines and good value for what it offers.
Please note: In my last MAN review, I mentioned that the V-10 developed 1035hp instead of 1050hp. Well it does, and it doesn't. Following the US standard, I rate each horsepower as being 746W, which means that the 722kW V-10 develops 1035hp. But according to MAN, which uses the European (and Japanese PS system), each horsepower equals 736W, which for the V-10 translates to 1050hp.
Subsequently the D28 Series diesel develops 690hp by US standards and 700hp by European standards.
For more information on the D28, contact Natasha Wallwork at Seapower Australia, tel (08) 9335 9777.