At the beginning of 2010, MAN Diesel & Turbo launched the first so-called “Tier II fuel optimization” for a limited number of MAN B&W low speed diesel engines.
The company has now looked at its complete engine program and investigated if the same SFOC reduction could be achieved. Against this background, it has been established that SFOC can be lowered by 1-2 g/kWh for a number of engines, while still complying with Tier-II NOx limits.
In the first release of the MAN B&W Tier II Engine Program, the SFOC on mechanically controlled engines had increased by up to 6 g/kWh (MC & MC-C), whereas the electronically controlled engines, designated ME, saw a fuel penalty of only up to 4 g/kWh, thanks to the much better possibilities on the ME types for adjustment and control of the fuel injection and the opening/closing of the exhaust valve.
These new, Tier-II SFOC reductions are obtained through a combination of several factors depending on engine type, such as:
• increased scavenge-air pressure
• reduced compression ratio (two-stroke Miller timing)
• increased maximum combustion pressure
• adjustments of compression volume and design changes
In order to distinguish between the different IMO Tier-II versions of fuel optimization, another number is introduced after the Mark designation, whereas the IMO Tier-I engines have no additional number, that is:
• S80ME-C8/9 = original Mk 8/9 engine that complies with Tier I
• S80ME-C8.1/9.1 = original Mk 8/9 engine that complies with Tier II
• S80ME-C8.2/9.2 = the new fuel-optimised version that complies with Tier II