With more air flow, the supply of gasoline is also increased to ensure the correct composition of the working mixture.
On the left in the engine compartment of the 110 kW turbo engine you can see the charge air cooler (1) and thick air hose (2) from the turbocharger to the charge air cooler.
Sectional model of a turbocharger
- 1 - impeller on the exhaust gas outlet side;
- 2 - turbocharging shaft;
- 3 - impeller on the suction side;
- 4 - vacuum box of the turbocharging regulator.
Boost pressure adjustment
The selected design data of the turbocharger has the pleasant property of supplying charge air to the cylinders even at relatively low engine speeds. It follows that too much air may be introduced at high speeds. The pressure in the boost system could rise to levels that would be detrimental to engine longevity.
To prevent this is the job of the boost pressure regulator. By opening the valve, it allows only part of the exhaust gases to pass through the blower impeller. As a result, the boost power is reduced and the pressure cannot exceed the maximum value.
Rigid adjustment in this case is unacceptable, since in some driving situations you need either more or less air. The charge pressure control is therefore influenced by the Motronic control unit. electropneumatic valve, «boost pressure control solenoid valve», by means of a vacuum box controls the boost bypass channel (boost pressure control valve). When the bypass opens, the boost pressure decreases.
Height sensor connected to Motronic control unit (installation location: electronic unit in the engine compartment). Thanks to this, the boost pressure control is able to equalize the change in air density when driving in mountainous areas.
Thinner air for the same power supply (i.e. with the same amount of injected fuel) would cause a supersaturation of the fuel-air mixture. This is prevented by increasing the boost pressure and thus the increased air supply.
Therefore, the engine power and the composition of the exhaust gases with a turbo engine remain constant under any driving conditions.
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