Head Bolts
Six 14mm head bolts are used per cylinder. These provide adequate surface pressure for both the bore seal and coolant seal portions. The optimum torque for the bolts was determined by extensive testing.
The head bolts are a torque-to-yield design that cannot be reused once removed from the engine. This technology places the bolt in what is referred to as the plastic range. The theory has the bolt tightened to a desired specification and then with a torque angle gauge installed, turned a prescribed number of degrees. This eliminates the large variation of axial force that occurs with a traditional torque-to-specification head bolt and will guarantee good sealing and little possibility of in-field service issues.
Crankshaft
To cope with the high cylinder pressure of a 300hp diesel engine, the pin and journal diameters of the crankshaft are 2.48 and 3.15 inches, respectively-the 4340 steel forging using a 90-degree plane twist method. The entire crankshaft is also treated to the Tuftriding process for additional strength.
An eight-mass counterweight method was chosen, and a balance weight is added to the crank pulley and the flywheel in order to keep the crankshaft as compact as possible. There is an oil passage from each journal to the connecting rod pin, which lubricates the connecting rod bearing for each cylinder. The journal bearing is a Kelmet design with an overlay. The total thickness, including the steel backing, is 0.98 inch.
Camshaft Drive
Two gears, one for driving the camshaft and another for driving the oil pump, are attached to the front end of the crankshaft. The gear used for driving the oil pump has a 57-tooth disc attached, which is used to generate a pulse for the crankshaft sensor. The flywheel is attached using eight 16mm bolts on a 3.23-inch circle diameter. An axial seal is used for the oil seal at the front and rear of the crankshaft in order to resist deterioration over time.
Pistons
The pistons are made of high-silicon aluminum alloy made through a gravity-casting process. To reduce noise, a cast-in strut is employed. The three piston rings consist of two compression rings and one oil control ring. The top ring is a barrel design. A Physical Vapor Deposit (PVD) is used to put a negative ion plating on the surface of the top ring. This coating provides excellent durability. The second ring is undercut and the oil ring has a backup spring. A ring carrier is cast into the top ring groove, to minimize any wear of the ring grooves. To accept the high thermal load, an oil cooling spray wets the underside of the piston.
Connecting Rods
The piston pin diameter is 1.36 inches, and the connecting rod is made of forged steel. A fractured cap (or cracked cap) division method is used on the larger end of the connecting rod to improve precision in fastening the two parts together. Because this is a structure in which the cap portion is rejoined exactly with the upper section, the shape of the bearing housing has improved accuracy.
Valvetrain
The overhead valve mechanism minimizes friction and wear by using a pair of rocker arms for each set of intake and exhaust valves. Each forged steel rocker arm uses a bridge to operate two valves. The bridge does not have a guide because this component complicates adjustment of the valve lash.
The portion of the rocker arm that touches the bridge has a sintered iron tip, and the bridge has a hardened steel cap at the contact point. This combination has good wear resistance to minimize any changes in valve adjustment.
Camshaft
The steel roller camshaft's surface is induction-hardened and the forged roller tappet is carburized. The pushrod is made of steel tube. Because both ends of a pushrod have a tendency to wear, extra material was added to those areas. Also, lubricating oil is forced through the hollow shaft of the pushrod to help minimize the lash change over time.
Cooling System
The cooling system routes coolant to the back of the engine first and then around the cylinders toward the front of the engine. The coolant goes through a passage in the flywheel housing in the rear of the engine toward the left and right sides of the cylinder block. After coolant flows forward around the cylinders and up to the cylinder heads, it then goes through a tube at the front of each head and to the thermostat housing. Dual thermostats are employed, with opening temperatures of 180 and 185 degrees. The coolant also travels from the water pump to the oil cooler, which is attached to the left side of the cylinder block. This increases the accuracy of temperature control in the engine.
Injection System
The design team decided on a Bosch common rail system that consists of a high-pressure supply (CP3) pump, a function block, and a common rail with a fuel injector for each cylinder. The pump is driven at crankshaft speed. The injection pump has a gear-type feed and a rail pressure control valve. An advantage of this design is that injection pressure can be raised independently of engine speed.
This means the size of the nozzle hole in the injector can be reduced, which, in conjunction with the high operating pressure, makes for better atomization and faster combustion. Pilot injection is used to limit tailpipe emissions and reduce combustion noise.