SPOOL 5433730 - Caterpillar

Engine Description
Ignition System
G3406 Engines use the CAT Digital Ignition System.G3412 Engines use the CAT Digital Ignition System or the Electronic Ignition System.Digital Ignition System
The digital ignition system includes a timing disc, a speed sensor (timing), a timing control, and wiring harnesses. The sensor monitors the rotation of the timing disc in order to sense a reference position of the crankshaft. The sensor sends a signal to the timing control. The timing control calculates the correct ignition timing. The timing control initiates the ignition by providing a pulse to the transformer of the proper cylinder.Electronic Ignition System
The system provides dependable firing and low maintenance. The system provides precise control of the duration of the spark and the ignition timing.The system also provides diagnostic capability that enhances troubleshooting. The primary ignition wiring is routed internally through the engine.The engines are equipped with protection from detonation. A detonation sensor is located on each side of the cylinder block. The ignition timing is retarded when excessive detonation is sensed. If the maximum retarded position is attained and detonation continues to occur, the ECM shuts down the engine.Inlet Air and Fuel System
G3406 Engines are available with natural aspiration or turbocharged with separate circuit aftercooling.G3412 Engines are turbocharged with separate circuit aftercooling.Inlet air is filtered by an air cleaner.For turbocharged engines, the inlet air is compressed by the turbocharger. The turbocharger is driven by the engine exhaust. The air is cooled in an aftercooler before the air enters the carburetor. The air becomes more dense from compression and cooling. This provides more oxygen for combustion.Air is mixed with fuel in the carburetor before combustion. The throttle is controlled by a governor. The governor efficiently maintains the engine rpm that is selected by the operator.The valves and the valve mechanism control the flow of air and exhaust gases in the cylinder during engine operation. Each cylinder has two inlet valves and exhaust valves. The camshaft actuates the rocker arms and valves through mechanical lifters and pushrods.Lubrication System
The engine lubrication oil is supplied by a gear-driven pump. The oil is cooled and the oil is filtered. A bypass valve provides unrestricted flow of lubrication oil to the engine parts if the oil filter elements become plugged.Cooling System
The jacket water coolant is circulated by a gear-driven centrifugal pump. G3406 Engines have one temperature regulator. G3412 Engines have two temperature regulators. The 90 °C (194 °F) temperature regulators regulate the temperature of the coolant. Heat can be removed from the coolant by a radiator or a heat exchanger.For engines with a Separate Circuit Aftercooler (SCAC), the air is cooled by a heat exchanger. The water that cools the air in the heat exchanger is in a circuit that is separate from the jacket water. The aftercooler coolant is pumped by an auxiliary water pump. The SCAC is required to operate at 32 °C (90 °F) or 54 °C (130 °F). The operation temperature depends on the engine rating and the application.Generator Description
The SR4B brushless generator can be