In the marine market, the use of turbocharging is the general approach taken by manufacturers to satisfy engine charge air needs with supercharging being relatively uncommon. With the Caterpillar C12.9 high performance marine engine, however, its designers have adopted a more radical approach. As Caterpillar marine application and installation team leader Hashim Marzuq explained, “the 1,000 hp (735 kW) engine has a supercharger that enhances the low-end available torque at lower engine rpm. It is electronically controlled, starting from 600-900 rpm.”
The use of a supercharger allows fast acceleration throughout the entire engine speed range but the air system also integrates this in series with its turbochargers. Other features of the engine include a common rail fuel system and dual aftercoolers, split into low-pressure and high-pressure sides with both being fresh water-cooled.
As a result of this integrated charge air system, the C12.9 marine propulsion engine is suitable for high-performance marine applications including yachts, fishing vessels and military craft, where rapid responses to power demands are required. The electronically-controlled C12.9 is currently offered in two power ratings: 850 hp (635 kW) at 2,300 rpm and 1,000 hp (735 kW) at 2,300 rpm. Both ratings meet the requirements of EPA Tier 3, IMO II, the EU Recreational Craft Directive and EU Stage IIIA regulations.