TM-9-2815-220-34 Direct Support Manual for AVDS-1790-2C and AVDS-1790-2D Engines Download

b. The engine features a fuel injection system and a turbosupercharged air induction system which obtains optimum engine performanc�. The· fuel injection system has a fuel injection metering pump which supplies metered fuel to individual cylinders through fuel injector nozzles. The fuel supply pump assembly (fig. 1-3) located at the front of the engine draws fuel through the primary and secondary fuel systems from the vehicle fuel tanks and deli\•ers it to the injection pump. A tur- bosupercharger assembly (figs. 1-1 and 1-2) is lo- cated on each side of the engine at the rear. 'fhe turbosuperchargers are exhaust-gas driven and increase the ai1· flow pressure entering the air in- take manifolds (figs. 1-1 and 1-2). I c. The Model AVDS-1790-2C and Model A VDS-l 790-2CA engines are equipped with a 28-volt oiJ cooled dc generator (fig. L-1) capable of 650 ampere output over U1e engine operating range. The generator produces an alteating current which i s rectified within the unit to give a direct cuent to t11e output terminals. I d. Th e Mode l s AVD S -17 9 0-20 AVDS-l790-2DR and AVDS-1790-2DA e ngi ne� are equipped with a 28 volt, 300 ampere air-cooled direct cunent generator(figs. l -5, 1-7.l,and 1-7.8). A blower motor mounted on the generator draws cooling air from the crew compartment t hrough the air intake tube which extends along the crankcase below the intake manifold on the right side of the engine. The generator air exhausl tube elbow is connected to the rear of the engine shroud. Generator outlet air is exhausted through the rear cooling n vane. e. The ennes have a 24-volt solenoid operated starter (fig. 1-2). A low voltage sensing module pre- vents starte1· activation with improperly charged batteries. f The engines are lubricated by a forced feed system. The system consists of four circuits; i.e., the scavenge circuit, the main or pressure oil cir- cuit, the leveling circuit, ar;d the make up circuit. These circuits are operated independently by one oil pump which consists of four separale sections. g. The engines arc equipped with two intake manifold heaters (figs. 1-1 and 1-2) which are in- stalled in the air intake systems between the in- take manifold elbows and the turbosuperchargers. The heaters, when opernted, preheat the air enter- ing the cylinders to facilitate cold Wather starting and cold weather idlP operation. h. The enne crankcase is vented by an enclosed crankcase breuther system which is vented through the crankcase breather tube (fig. 1-4) at the left turbosupercharger exhaust pipe. i. The engine primary and fuel/water separator type secondary fuel filters (figs. 1-2 and l -3) both TM 9-2815-220-34 have top mounted bleeder valves to assist in the removal of air from the fuel system. Water is re- moved automatically by a constant bleed orifice in the primary fuel filter and an automatic water drain in the fuel/water separator filter. 1-7. Accessories Refer �o appendix A for information on engine ac- cessones. 1-8. Crankcase The crankcase (fig. 1-1) is a one-piece aluminum casting with forged aluminum main bearing caps. The bearing caps function as an integral part of the crankcase. Each cap is secured on studs with four slotted nuts. 'fwo through bolts clamp the main bearing cap in the tunnel slot of the crank· �ase. With this type of crankcase and bearing cap construction, uniform load distribution in the bear- ing area is obtained making possible uniform dis- tribution of combustion forces over the entire crankcase. 1 ·9. Main Bearings The seven replaceable main bearings are the steel-backed, split type, having copper-lead alloy bearing surfaces. The center main bearing is double-flaned with bearing material to control crankshaft end play and thrust. 1-10. Crankshaft, Flywheel, and Damper NOTE le key numbers sbown below in paren- I theses ref er to figure 1-8. . C1·an kshaft assembly (42) is a nitr-ided steel forging with seven main bearing journals and six crankpins. Each crankpin accommodates two op- posing connecting rod assemblies (46). Flanges are provided on the crankshaft for mounting the nywheel (13) on the rear end and a torsional vibra- tion damper (<15) on the front end. b. AJJ cnkpin bearing jouals are hollow to reduce weight. Holes are drilled diagonally through each main bearing joual and extend through the crank cheek and crankpin to provide a direct passage r oil under pressure to the connecting rod and crankshaft main beari11gs as shown in figure 1-9, c. The crankshaft and flywheel are statically and dynamically balanced. d. The torsional vibration damper (45) is a preci- sion viscous type and is replaceable only as an assembly. 1-11. Connecting Rods and Bearings The connecting rod assemblies (46, fig. 1-8) are ta- pered, I-beam section steel forgings. A bronze- Change 3 1-11