35490-ZY6-003 Honda SWITCH ASSY., OIL PRESSURE

AIR INDUCTION AND EXHAUST SCHEMATIC
1. Air cleaner element. 2. Exhaust manifolds. 3. Aftercooler. 4. Turbocharger turbine wheel. 5. Turbocharger compressor impeller. 6. Exhaust outlet. 7. Intake manifolds.This engine has an exhaust driven turbocharger and an air to air aftercooler (3) to provide dense compacted air to the cylinders.Filtered air from the dry-type air cleaner goes to the turbocharger compressor section where air is compressed and directed to an aftercooler. Aftercooler (3) is mounted inside the radiator guard on the right side of the radiator core. Air from the turbocharger is cooled as it passes through the aftercooler. This increases the air density providing more oxygen per unit at the inlet valve ports.When engine load increases, more fuel is injected into the engine cylinders and the volume of exhaust gas increases. This causes the turbocharger turbine wheel (4) and compressor impeller (5) to rotate faster. The increased speed of the impeller increases the quantity of inlet air. As the turbocharger provides additional inlet air, more fuel can be burned; hence, more horsepower produced by the engine.Camshafts, Valves And Valve Mechanism
There are four in-head valves for each cylinder; two intake valves and two exhaust valves. The valves are actuated by overhead camshafts and rocker arm assemblies, located in a housing mounted above each cylinder head. No push rods or lifters are used. The rollers of the rocker arm assemblies act directly on the cam lobes.Correctly adjusted valves operate for many hours before they need to be reconditioned. Eventually, however, the valve faces and seats can become pitted, causing some loss of compression. The cylinder head contains valve seat inserts which can be replaced when the seats have been ground to the maximum limits.The right bank camshafts are driven by the rear-mounted timing gears and the left bank camshafts are driven by the front-mounted timing gears.
VALVE MECHANISM
1. Exhaust camshaft. 2. Rocker arm assemblies. 3. Inlet camshaft. 4. Roller. 5. Rocker arm shaft. 6. Valve spring. 7. Valve rotator. 8. Valve retainer and locks. 9. Valve (exhaust). 10. Valve (intake). 11. Valve seat insert.Fuel System
The fuel system is a pressure type with a separate fuel injection pump and injection valve for each cylinder. Fuel is injected into a precombustion chamber, not directly into the cylinder.
FUEL SYSTEM SCHEMATIC
1. Bypass line. 2. Priming pump. 3. Fuel injection valve. 4. Fuel injection pump. 5. Pump housing manifold. 6. Supply tank. 7. Bypass valve. 8. Pressure gauge. 9. Primary filter. 10. Transfer pump. 11. Filters. 12. Reservoir. 13. Vent valve.A transfer pump supplies fuel to a manifold in the injection pump housing. Before fuel is delivered to the manifold, it is filtered by a primary filter that removes dirt particles and by a final filter that removes more minute particles.The transfer pump can supply more fuel than is required for injection, so a bypass valve is built into the system. The valve limits the maximum pressure to the injection pumps.The injection pumps receive fuel from the manifold and force it under high pressure to the injection valves. The injection valves spray atomized fuel into the precombustion chambers.An air vent valve in the system permits removal of air. Air is removed by opening the valve and pressurizing the fuel system. The system can be pressurized by using the priming pump. The vent valve must be open until a stream of fuel, without air bubbles, flows from the vent line.Fuel Injection Pump Operation
The injection pump plungers (5) and the lifters (8) are lifted by the cam lobes on the camshaft and always make a full stroke. The lifters are held against the cam lobes by springs (6).The amount of fuel pumped per stroke is varied by turning the plunger in the barrel. Action of the governor moves the fuel rack (7) which turns the pump gear segment (4) on the bottom of the pump plunger.
FUEL INJECTION PUMP HOUSING
1. Fuel manifold. 2. Inlet port. 3. Check valve. 4. Gear segment. 5. Pump plunger. 6. Spring. 7. Fuel rack. 8. Lifter. 9. Camshaft.Speed Sensing Variable Timing Unit
The variable timing unit, couples the fuel injection pump camshaft to the engine rear timing gears. As engine rpm increases, the variable timing unit advances the timing from 11° BTC at low rpm, to 19° BTC at high rpm.
LOW RPM POSITION
1. Power piston. 2. Power piston cavity. 3. Control valve spring. 4. Power piston return spring. 5. Oil inlet passage. 6. Drain port. 7. Control valve. 8. Flyweights. 9. Shaft assembly.During engine low rpm operation, the flyweight force is not sufficient to overcome the force of control valve spring (3) and move control valve (7) to the closed position. Oil merely flows through the power piston cavity (2).As the engine rpm increases, flyweights (8) overcome the force of control valve spring (3) and move control valve (7) to the closed position, blocking the oil drain port (6). Pressurized oil, trapped in power piston cavity (2), overcomes the force of spring (4) and moves power piston (1) outward. This causes the fuel injection pump camshaft to index slightly ahead of the shaft (9) portion of the variable timing unit. Any outward movement of the power piston increases the force on the control valve spring. This tends to reopen the control valve, letting oil escape from the power piston cavity. As oil begins flowing from the cavity again, return spring (4) moves the power piston inward.
HIGH RPM POSITION
1. Power piston. 2. Power piston cavity. 3. Control valve spring. 4. Power piston return spring. 5. Oil inlet passage. 6. Drain port. 7. Control valve. 8. Flyweights. 9. Shaft assembly.At any given rpm, a balance is reached between the flyweight force and the control valve spring force. The resultant position of control valve (7) will tend to maintain proper pressure behind the power piston. The greater the rpm, the smaller the drain port opening, and the further outward the power piston is forced.As the power piston is moved outward, the angular relationship of the ends of the drive unit change. As the power piston moves forward in the