1 - turbocharger; 2 - thrust and boost pressure regulator lever; 3 - boost pressure regulator; 4 - intake manifold high pressure hose.
The turbocharger consists of 2 discs with blades located on the same shaft. Engine exhaust gases pass through one of the disks, which increase or decrease the shaft speed depending on the engine speed. The second disk, located on the same shaft, directs the intake air under pressure into the combustion chambers, which increases the efficiency of the diesel engine. The high pressure fuel pump regulates the amount of fuel supplied. This is done by injection into the forced air (depending on boost pressure) more or less fuel (this is described in more detail in the section Diesel injection system).
Boost pressure regulator
The type of turbocharger under consideration is good in that it supplies air under pressure to the cylinders even at relatively low engine speeds. From this it follows that at high speeds the amount of air injected can be much more than necessary. The pressure in the compressor system would then rise to a value that could adversely affect the life of the engine. In order to prevent this, a boost pressure regulator is installed. It ensures, by closing the valve, that only part of the exhaust gases pass through the turbine blades of the compressor. Due to this, the compression ratio is reduced, and the pressure in the compressor system does not rise above 1.26 bar.
Purge valve
The safety valve in the event of a damaged or overloaded boost pressure regulator prevents the boost pressure from rising above 1.26 bar. This valve is located directly in the intake duct and removes air at excess pressure through the air filter.
Recommendation: turbocharged diesel is equipped with an additional electric pump that circulates the coolant when the turbocharger overheats and also when the engine is stopped. It is contraindicated for a turbocharger to immediately stop the engine after a long trip at full speed «gas». This can lead to premature coking of bearings and compressor lubrication channels; the bearing of the turbine wheel shaft can then become so hot that all the oil in the bearing burns out and sinters. Clogged oil passages lead to compressor failure. Therefore, after a longer drive, at full load, let the engine idle for a while before turning it off. Before replacing a faulty turbocharger, check the following causes of malfunctions: start of air supply; fuel supply, peak load limiter, turbocharger system pressure, air filter and possibly existing leaks in the intake and exhaust pipes.
Cleanliness must be observed when working on the turbocharger. Therefore: thoroughly clean the joints before dismantling; lay the removed parts on a clean surface, cover with a piece of clean cloth, install only clean or new parts, do not work with compressed air in the work area and do not move the car.
Air blade
At relatively low engine speeds (diesel) its efficiency depends on the good filling of the cylinders with combustion air. To do this, air is forced into the cylinders by a turbocharger, which is installed in the intake tract and is driven by exhaust gases. However, before the air enters the swirl chamber, it passes through the radiator, as the temperature of the air in the turbocharger rises significantly.