TM 5-3805-294-23-1
0003
HYEX THEORY OF OPERATION - Continued
Engine Operation - Continued
The camshaft (Figure 1, Item 2) is timed to the crankshaft (Figure 1, Item 3) through the timing gear train. The
camshaft rotates in honed bores in the cylinder block. There is a bushing in No. 1 camshaft bore. The camshaft
lobes determine the duration and lift of each valve.
Intake and exhaust valves (Figure 1, Item 4) are operated by camshaft followers (Figure 1, Item 5), push rods (Figure
1, Item 6), and a rocker arm assembly. Valve seat inserts in the cylinder head (Figure 1, Item 7) are used for intake
and exhaust valves. The engine has four valves per cylinder, two intake and two exhaust. Each set of intake valves
and exhaust valves is actuated by a single rocker arm (Figure 1, Item 8) using a valve bridge (Figure 1, Item 9).
The crankshaft (Figure 1, Item 3) is a one-piece, heat-treated, nodular-iron or steel forging, which operates in
replaceable two-piece main bearings. The crankshaft is dynamically balanced and machined with undercut and rolled
fillets. Two-piece main thrust bearing inserts are used to control crankshaft end play.
The cylinder liners (Figure 1, Item 10) are the wet sleeve type and can be individually replaced. Liner packing rings
(Figure 1, Item 11) are used at the lower connection between cylinder block and liner.
The pistons (Figure 1, Item 12) are made of high-grade cast aluminum alloy with internal rubbing. The skirt is cam
ground to allow for expansion during operation. The piston crown has a cut-out combustion bowl with a truncated
cone center. All piston rings (Figure 1, Item 13) are located above the piston pin (Figure 1, Item 14). Two compression
rings and one oil control ring are used. The top compression ring is a keystone-shaped ring, located close to the top
of the piston.
The hardened, fully-floating piston pins (Figure 1, Item 14) are held in place by snap rings. Spray jets (piston cooling
orifices), in the cylinder block (Figure 1, Item 1), spray pressurized oil on the underside of the piston (Figure 1, Item
12) to lubricate piston pins (Figure 1, Item 14) and cool the pistons.
The forged steel connecting rods (Figure 1, Item 15) have replaceable pin bushing and bearing inserts.
The engine is equipped with a gear-driven oil pump and full-flow oil filter. A bypass valve in the filter head opens if
the filter element becomes restricted. The engine is equipped with an oil cooler mounted on the right side of the
cylinder block (Figure 1, Item 1). The engine is also equipped with a pressure regulator valve to relieve excessive
pressure build-up in the main oil gallery, and a bypass valve to prevent oil starvation if the oil cooler and filter become
plugged.
The engine has a pressurized cooling system, consisting of radiator, coolant pump, multi-blade fan, and three
thermostats.
Air Intake and Exhaust
During engine cranking, the engine draws fresh air (Figure 2, Item 16) through the intake air filter, turbocharger
compressor (Figure 2, Item 17), which compresses and heats the air (Figure 2, Item 18), through the charge air
cooler, into the air intake manifold (Figure 2, Item 19), through ports in the cylinder head (Figure 2, Item 20) into the
cylinders on the intake stroke of the piston. On the exhaust stroke of the piston, the engine pushes exhaust gas
(Figure 2, Item 21) into the exhaust manifold (Figure 2, Item 22), through the turbocharger turbine (Figure 2, Item
23), through the muffler, and out to the atmosphere.
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