910103-0825 Tohatsu BOLT

Illustration 1 g00328150
Air Inlet And Exhaust System Schematic (1) Air inlet. (2) Turbocharger. (3) Air inlet choke. (4) Aftercooler. (5) Main gas supply. (6) Cylinder head inlet port. (7) Precombustion chamber gas supply. (8) Precombustion chamber. (9) Spark plug. (10) Exhaust valve. (11) Exhaust. (12) Inlet valve. (13) Exhaust bypass control valve.The components of the air inlet and exhaust system control the quality and the amount of air that is available for combustion. The inlet manifold (air plenum) is a passage inside the cylinder block. This passage connects the aftercooler to the inlet ports in the cylinder head. The camshaft controls the movement of the valve system components. Air Inlet And Exhaust System Components
Illustration 2 g00328151
Air Inlet And Exhaust System (1) Exhaust manifold. (2) Aftercooler. (3) Air choke. (4) Exhaust outlet. (5) Engine cylinder. (6) Air inlet. (7) Turbocharger compressor wheel. (8) Turbocharger turbine wheel. (9) Exhaust bypass valve.Clean inlet air from the air cleaners is pulled through air inlet (6) into the turbocharger compressor by the turbocharger compressor wheel (7) . The rotation of the turbocharger compressor wheel causes the air to compress. The rotation of the turbocharger compressor wheel then forces the air through an elbow to the aftercooler (2) . The aftercooler lowers the temperature of the compressed air before the air enters the air plenum. This cooled and compressed air fills the air plenum. The air fills the inlet chambers in the cylinder heads. Air flow from the inlet chamber into the cylinder is controlled by the inlet valves. Fuel (gas) flow into the cylinder is controlled by the gas admission valve.There are five valves in each cylinder head. There is one gas admission valve (refer to System Operation, "Fuel System" ), two inlet valves and two exhaust valves for each cylinder. Make reference to "Valve System Components". The inlet valves and the gas admission valve, open when the piston moves down on the intake stroke.The camshaft controls the opening of the valves. The cooled, compressed air is pulled into the cylinder from the inlet chamber along with the gas that is supplied through the gas admission valve. The gas admission valves and the inlet valves close and the piston starts to move up on the compression stroke. When the piston is near the top of the compression stroke, the rich air fuel mix in the precombustion chamber has been leaned to a combustible mix and is ignited by the spark plug. The force of the combustion pushes the piston down on the power stroke. When the piston moves up again the piston is on the exhaust stroke. The exhaust valves open and the exhaust gases are pushed through the exhaust port into the exhaust manifold (1) . After the piston makes the exhaust stroke, the exhaust valves close. The cycle (intake, compression, power, exhaust) starts again.Exhaust gases from the exhaust manifold cause the turbocharger turbine wheel (8) to turn. The turbine wheel is connected to the shaft that drives the compressor wheel. Depending on the speed and the load requirements of the engine, exhaust gases are directed either through the exhaust outlet to the turbocharger or through the exhaust bypass valve.An actuator controls the position of the exhaust bypass (wastegate) valve (9) . The wastegate actuator provides the desired inlet manifold air pressure. This is based on a command signal that the actuator receives from the ECM. The ECM determines the command signal. The command signal is based on the difference between the actual air/fuel ratio (or average combustion burn time) and the desired air/fuel ratio (desired combustion burn time).The position of air choke (3) is controlled by an actuator. The choke actuator provides the desired inlet manifold air pressure during part load operation. This is based on a command signal that actuator receives from the ECM. The ECM determines the command signal based on the engine speed (rpm) and the engine load (calculated value based on pressures and temperatures that are measured on the engine). Aftercooler
Illustration 3 g00485390
Air Inlet And Exhaust System Components (1) Coolant outlet connection. (2) Coolant inlet connection.The aftercooler is located on the left rear side of the engine at the rear opening of the plenum. The aftercooler has a coolant charged core assembly. Coolant from the water pump on the left side of the engine flows through coolant inlet connection (2) . Coolant circulates through the core assemblies. The coolant then exits the aftercooler through the coolant outlet connection (1) .Inlet air from the compressor side of the turbocharger flows into the aftercooler housing. The inlet air passes the fins in the core assemblies. The aftercooler core lowers the temperature of the air. The cooler air is directed into the air plenum. The cooler air is directed up and through the inlet ports of the cylinder heads.Lowering the temperature of the inlet air will increase the density of the air (per volume). The increased air density will result in more efficient combustion and in lower fuel consumption.Turbochargers
The turbine side of the turbocharger is connected to the exhaust manifold. The compressor side of the turbocharger is connected to the aftercooler. Both the turbine (exhaust) and compressor (inlet) are connected to the same shaft and rotate together.The exhaust gases go into the turbocharger through the exhaust inlet adapter. The exhaust gases push the blades of the turbine wheel. This causes the turbine wheel and compressor wheel to turn.Clean air from the air cleaner is pulled through the compressor housing air inlet by the rotation of the compressor wheel. The action of the compressor wheel blades causes a compression of the inlet air. This compression gives the engine more power because it makes it possible for the engine to burn additional fuel with greater efficiency.The bearings in the turbocharger use engine oil under pressure for lubrication. The oil comes in through the oil inlet. The oil goes