The turbocharger increases engine power by pu<?:namespace prefix = st1 ns = "urn:schemas-microsoft-com:office:smarttags" /><st1:PersonName>m</st1:PersonName>ping co<st1:PersonName>m</st1:PersonName>pressed air into the co<st1:PersonName>m</st1:PersonName>bustion cha<st1:PersonName>m</st1:PersonName>bers, allowing a greater quantity of fuel to co<st1:PersonName>m</st1:PersonName>bust at the opti<st1:PersonName>m</st1:PersonName>al air/fuel ratio. In a conventional turbo, the turbine (4) spins as exhaust gas flows out of the engine and over the turbine blades. This spins the co<st1:PersonName>m</st1:PersonName>pressor wheel at the other end of the turbine shaft, pu<st1:PersonName>m</st1:PersonName>ping <st1:PersonName>m</st1:PersonName>ore air into the intake syste<st1:PersonName>m</st1:PersonName>.
The turbocharger for this syste<st1:PersonName>m</st1:PersonName> has vane position control by the engine control <st1:PersonName>m</st1:PersonName>odule (ECM). The vanes (5) can be opened and closed to vary the a<st1:PersonName>m</st1:PersonName>ount of boost pressure. Thus, the boost pressure can be controlled independent of engine speed. There are 9 controllable vanes in this turbocharger. The vanes <st1:PersonName>m</st1:PersonName>ount to a unison ring (3) that can be rotated to change the vane angle. When the engine is not under load, the vanes are open to <st1:PersonName>m</st1:PersonName>ini<st1:PersonName>m</st1:PersonName>ize boost and exhaust back pressure. To increase boost when the engine load requires it, the vanes are co<st1:PersonName>m</st1:PersonName><st1:PersonName>m</st1:PersonName>anded closed. The ECM will vary the boost dependent upon the load require<st1:PersonName>m</st1:PersonName>ents of the engine.
The turbocharger vanes are nor<st1:PersonName>m</st1:PersonName>ally open when the engine is not under load. However, the ECM will often close the turbocharger vanes to create back pressure to drive exhaust gas through the exhaust gas recirculation (EGR) valve as required. At extre<st1:PersonName>m</st1:PersonName>e cold te<st1:PersonName>m</st1:PersonName>peratures, the ECM <st1:PersonName>m</st1:PersonName>ay close the vanes at low load conditions in order to accelerate engine coolant heating. The ECM <st1:PersonName>m</st1:PersonName>ay also close the turbocharger vanes under exhaust braking conditions.
The turbocharger control syste<st1:PersonName>m</st1:PersonName> utilizes the following co<st1:PersonName>m</st1:PersonName>ponents:
<A name=ss1-1394251></A><?:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office" /> (http://service.gm.com/servlets/BlobShtml?ShtmlFile=1394251&evc=sm&pubid=437&cellI d=133229&mspsdsubkey=3243#ss1-1394251ss1-1394251)
<H5 style="MARGIN: auto 0in">Turbocharger Vane Position Control Solenoid Valve (http://service.gm.com/servlets/BlobShtml?ShtmlFile=1394251&evc=sm&pubid=437&cellI d=133229&mspsdsubkey=3243#ss1-1394251ss1-1394251)</H5>
The vane position control solenoid valve (2) works in conjunction with oil pressure to control the turbocharger vanes. The solenoid valve uses two circuits; a control circuit and a low reference circuit. The ECM uses a pulse width <st1:PersonName>m</st1:PersonName>odulation on the HI control circuit to control the solenoid valve. The ECM will