Nitrogen Oxide (NOx) Reduction System
This engine utilizes an NRS system in order to reduce the amount of nitrogen oxide (NOx). The NRS recirculates a portion of cooled exhaust gases in order to lower the combustion temperature. This results in decreased NOx.
The external mechanical NRS system is comprised of the following components:
- Exhaust gas cooler
- Mechanical NRS valve
- Reed valve
- Thermo valve
As the coolant temperature increases the thermo valve opens, and boost pressure of the intake manifold reaches the diaphragm of the NRS valve. The boost pressure acts on the diaphragm. This allows cooled exhaust gases to be recirculated into the intake manifold.
If the coolant temperature is higher, but the boost pressure is lower, the NRS valve remains in the closed position.
The NRS valve is in the open position, and cooled exhaust gases flows into the intake manifold if the coolant temperature is high and boost pressure is high. The reed valve between the EGR valve and intake manifold prevents the intake into the NRS system.
NRS Cooler
| Illustration 1 | g02883026 |
(1) Flange (2) Exhaust gas cooler (3) Mechanical NRS valve (4) Thermo valve | |
Exhaust gas cooler (2) is used to decrease the temperature of combustion gases. The exhaust gas cooler is located between the cylinder head and the mechanical NRS valve
Thermo Valve
The thermo valve controls the boost pressure for the mechanical NRS valve. If the coolant temperature is lower, the thermo valve is closed so that boost pressure does not reach the diaphragm in the mechanical NRS valve. However, if the coolant temperature is higher, the thermo valve is open so that boost pressure reaches the diaphragm in the mechanical NRS valve.
Mechanical NRS Valve
| Illustration 2 | g02971862 |
View of mechanical EGR valve | |
The mechanical NRS valve controls the flow of cooled exhaust gas to the intake manifold. If the boost pressure is low, NRS valve is in the closed position. This does not allow exhaust gas into the intake manifold. If the boost pressure increases, the NRS valve opens and cooled exhaust gas flows into the intake manifold.
Reed Valve
| Illustration 3 | g02970963 |
Exploded view of mechanical NRS valve (4) Mechanical NRS valve (5) Reed valve (6) Reed valve housing (7) Intake manifold | |
| Illustration 4 | g02971056 |
Top view of reed valve (8) Screw (9) Stopper (10) Valve | |
The reed valve is provided at the confluence of exhaust gas after passing through the NRS valve, and intake air. The pressure differential between the inside of the crankcase and the atmosphere. The reed valve also prevents back-flow of the exhaust gas and intake air that is generated by the piston and valves.
Turbocharger
| Illustration 5 | g02973483 |
(11) Lock nut (12) Thrust bearing (13) Snap ring (14) O-ring (15) Thrust sleeve (16) Piston ring (17) Turbine wheel (18) Turbine housing (19) Actuator (20) Compressor wheel (21) Piston ting (22) Oil deflector (23) Bearing (24) Snap ring | |
A turbocharger consists of a centrifugal compressor mounted on a common shaft with a turbine that is driven by exhaust gas. The turbocharger compresses the intake air and forces more air into the engine cylinders. This allows the engine to burn more fuel efficiently, producing more horsepower. When the boost pressure is relatively low, the turbocharger can reduce smoke concentration, concentration in the cylinder, fuel consumption and increase engine performance at elevated terrain. When the boost pressure is high, the turbocharger can provide a large increase in engine output by increasing the amount of air that is forced into the engine cylinders.
