UENR4490-01 17 Engine Operation When the load on the engine increases, more fuel is injected into the cylinders. The combustion of this additional fuel produces more exhaust gases. The additional exhaust gases cause the turbine and the compressor wheels of the turbocharger to turn faster. As the compressor wheel turns faster, air is compressed to a higher pressure and more air is forced into the cylinders. The increased flow of air into the cylinders allows the fuel to be burnt with greater efficiency. This produces more power. Crankcase Breather The engine crankcase breather is a filtered system.
The crankcase breather system consists of two main elements, a primary separator in the valve mechanism cover and a filtered canister that is mounted on the cylinder head. The gases exit the engine through the valve mechanism cover. The gases then pass through the primary separator. The primary separator removes most of the liquid oil from the gas. The liquid oil is then returned to the engine. A wastegate is installed on the turbine housing of the turbocharger. The wastegate is a valve that allows exhaust gas to bypass the turbine wheel of the turbocharger. The operation of the wastegate is dependent on the pressurized air (boost pressure) from the turbocharger compressor.
The boost pressure acts on a diaphragm that is spring loaded in the wastegate actuator which varies the amount of exhaust gas that flows into the turbine. The gas then passes through the filter element before exiting to atmosphere in an open breather system or back to the induction system in a closed breather system via the breather vent pipe. Any liquid oil that is captured by the filter drains from the bottom of the canister. The liquid oil is returned by the drain pipe that runs from the bottom of the canister back to the crankcase. A valve connects the drain pipe to the crankcase. This valve prevents the bypass of gas past the filter and oil from passing up the drain pipe.
The wastegate regulator (15) is controlled by the engine Electronic Control Module (ECM). The ECM uses inputs from a number of engine sensors to determine the optimum boost pressure. This will achieve the best exhaust emissions and fuel consumption at any given engine operating condition. The ECM controls the wastegate regulator, that regulates the boost pressure to the wastegate actuator. A pressure relief valve is located in the rear of the canister in the integral mounting bracket. Under normal operation of the engine, this valve will not operate. If part of the system becomes blocked the valve will open at a pressure of 8.5 kPa (1.2 psi).
The open valve will allow gas to bypass the filter and the pipes for venting. When higher boost pressure is needed for the engine performance, a signal is sent from the ECM to the wastegate regulator. The wastegate regulator reduces the pressure in the air inlet pipe (14) that acts upon the diaphragm within the wastegate actuator (12). The filter element can be accessed by removing the top cap of the canister. Refer to Operation and Maintenance Manual, “Engine Crankcase Breather Element - Replace” for the correct procedure. The spring within the wastegate actuator (12) forces the wastegate valve that is within the turbine housing to close via the actuating rod and lever.
When the wastegate valve is closed, more exhaust gas is able to pass over the turbine wheel. This results in an increase in turbocharger speed and boost pressure generation. NOTICE The crankcase breather gases are part of the en- gines measured emissions output. Any tampering with the breather system could invalidate the engines emissions compliance. When lower boost pressure is needed for the engine performance, a signal is sent from the ECM to the wastegate regulator. This causes high pressure in the air inlet pipe (14) to act on the diaphragm within the wastegate actuator (12). The actuating rod (13) acts upon the actuating lever to open the valve in the wastegate.
When the valve in the wastegate is opened, more exhaust gas from the engine is able to bypass the turbine wheel. The exhaust gases bypass the turbine wheel results in a decrease in the speed of the turbocharger. The shaft that connects the turbine to the compressor wheel rotates in bearings (4) and (6). The bearings require oil under pressure for lubrication and cooling. The oil that flows to the lubricating oil inlet port (5) passes through the center of the turbocharger which retains the bearings. The oil exits the turbocharger from the lubricating oil outlet port (10) and returns to the oil pan.