Sterling, John Anthony2014-03-142014-03-142009-06-22etd-07132009-192300http://hdl.handle.net/10919/33996Rotordynamic instability is present in most or all automotive turbochargers. High subsynchronous amplitudes can cause a variety of problems in areas such as mechanical failures, emissions regulations and rotor design. Self-excited vibrations from sources of damping can lock in at lateral natural frequencies causing dangerously high vibration levels. The resulting high-amplitude conical and bending modes can be reduced in order to achieve a more robust system. This research focuses on the relationship between synchronous and subsynchronous amplitude levels. It is theorized that an increase in unbalance could cause a reduction in subsynchronous vibration amplitudes. Through the use of a custom turbocharger, a series of unbalances were applied to both the turbine and compressor wheels and the resulting amplitudes were recorded off a modified compressor nut. The resulting data were reduced and are presented at the end of this paper.In CopyrightTurbochargerInstabilitySubsynchronousUnbalanceThesishttp://scholar.lib.vt.edu/theses/available/etd-07132009-192300/