SENR9977 9 Systems Operation Section The turbine wheel and the compressor wheel (3) are installed on the same shaft. Therefore, the turbine wheel and the compressor wheel rotate at the same rpm. The compressor wheel is enclosed by the compressor housing (2). The compressor wheel compresses the intake air (1). The intake air flows into the engine cylinders through the inlet valves of the cylinders. Rocker arms Valve springs The camshaft gear is driven by the crankshaft gear. The camshaft and the crankshaft are timed together. When the camshaft turns, the valve lifters and the pushrods are moved up and down. The pushrods move the rocker arms. The movement of the rocker arms open the valves.
The opening and closing of the valves is timed with the firing sequence of the engine. The valve springs push the valves back to the closed position. The oil from the main gallery of the cylinder block flows through the oil inlet port (5) in order to lubricate the turbocharger bearings (4) and (6). The pressurized oil passes through the bearing housing of the turbocharger. The oil is returned through the oil outlet port (10) to the oil pan. The turbocharger has a wastegate. The wastegate is controlled by the boost pressure. This allows some of the exhaust to bypass the turbocharger at higher engine speeds.
The wastegate is a type of valve that automatically opens at a preset level of boost pressure in order to allow exhaust gas to flow around the turbine. The wastegate allows the design of the turbocharger to be more effective at lower engine speeds. The wastegate is controlled by a diaphragm. One side of this diaphragm is open to the atmosphere. The other side of this diaphragm is open to the manifold pressure. Cylinder Head And Valves The valves and the valve mechanism control the flow of the air and the exhaust gases in the cylinder during engine operation. The cylinder head assembly has two valves for each cylinder. Each valve has one valve spring.
The ports for the inlet valves are on the left side of the cylinder head. The ports for the exhaust valves are on the right side of the cylinder head. Steel valve seat inserts are installed in the cylinder head for both the inlet and the exhaust valves. The valve seat inserts can be replaced. The valves are installed in valve guides. The valve guides can be replaced. The exhaust valve guide has a counterbore in order to prevent the seizure of the valve stem. The seizure of the valve stem is caused by a buildup of carbon under the head of the valve. The inlet and the exhaust valves are opened and closed by the rotation and movement of the following components:
Crankshaft Camshaft Valve lifters Pushrods