TM 5-3895-379-23
THEORY OF OPERATION - CONTINUED
0003 00
ENGINE SYSTEM
1.
General.
a.
The engine system provides power for the roller. The engine combines fuel and pressurized air together and com-
presses it until ignition occurs, creating mechanical energy. The internal explosion from the ignited air/fuel mixture
pushes the pistons down, turning the crankshaft. The crankshaft is connected to a pulley and gear on the front of
the engine and an output shaft on the rear of the engine. The pulley forces belts to turn the alternator which keeps
the electrical system fully charged with electricity. The front gear also turns both the power steering hydraulic
pump and the fuel injection pump. The output shaft turns both of the main hydraulic pumps. A cam lobe operates
the fuel lift pump.
b.
The engine is turbocharged. When the ignited air is pushed out of the engine, it is routed to the turbocharger. The
exhaust from the engine turns the turbocharger which forces high pressure air into the engine intake manifold.
2.
Turbocharger. The turbocharger forces air into the intake manifold. Exhaust gases coming out of the combustion cham-
ber force a rotor inside the turbocharger to spin at a very high rate of speed. This rotor is attached to the intake impeller.
The impeller pulls air in from the air filter and forces it into the intake manifold at a high pressure. The faster the engine
runs, the faster the turbocharger spins and the higher the air pressure it produces.
3.
Cylinder Head. The fuel/air mixture is ignited in the combustion chambers of the cylinder head, located directly over
each piston. The intake ports of the cylinder head route air into the combustion chamber while the injectors supply the
fuel to the mixture. The exhaust ports route burned gases out of the engine.
4.
Cylinder Head Valves. The cylinder head valves open or close the passages in the cylinder head that allow flow from
the intake manifold or to the exhaust manifold. Valve lash must be adjusted periodically.
5.
Combustion Chamber. The combustion chamber is where combustion and ignition occur. Ignition occurs when diesel
fuel or JP-8 is injected into air heated by being compressed by the piston. When the air/fuel is ignited, it pushes down
the piston, turning the crankshaft.
6.
Crankshaft. The crankshaft is an eccentric shaft that changes the up-and-down piston motion into a rotating motion.
The crankshaft uses this motion at the front of the engine to power the alternator, cooling system, and steering and fuel
pumps.
7.
Exhaust System. The exhaust system allows the exhaust gases to be drawn out of the combustion chamber. The exhaust
is pushed out of the cylinder by the piston. It then goes into the turbocharger and makes it spin. The exhaust is then
vented into the air out of an exhaust pipe.
8.
Air Filter. The air filter cleans the air entering the engine. The filter consists of a primary element and a secondary ele-
ment. Air is pulled through both elements to remove particulates that could damage the engine.
0003 00-2
