Therefore, the repositioning of the IGV at the inlet of the turbine (just after the exhaust manifold) defines a new equilibrium point of the engine which corresponds to a different boost pressure of the air entering in the cylinders. Fig. 8 illustrates the boost pressure increase due to the HRVG inside the intake common manifold for the operating conditions analyzed.
Fig. 8. Boost pressure in the two cases for the operating conditions examined (50% of the maximum engine load).Figure optionsDownload full-size imageDownload as PowerPoint slide
This behavior is, however, so complex: at low engine speeds the boost pressure LY2109761 quite the same in both cases (with and without HRVG presence), while at higher engine speeds the system turbine-compressor increases the boost pressure of the engine, restoring the air mass inside the cylinder when the engine back pressure tends to grow up. This is confirmed by the value of the position of the VGT actuator (“rack”): till to 1800 RPM the VGT is fully closed and vasopressin is not influenced by the presence of the HRVG (Fig. 9); therefore, the higher back pressure, due the HRVG, leads to a lower turbine specific power, slowing the turbocharger group (Fig. 9). On the other hand, at higher engine speeds, the VGT is more closed, when the HRVG is present, and turbocharger is accelerated (Fig. 9), producing a significant boost pressure increase (Fig. 8).