Highly Turbocharging a Flow Restricted Two Cylinder Small Engine - Turbocharger Development

This paper describes the turbocharger development of a restricted 430 cm 3 odd firing two cylinder engine. The downsized test engine used for development was specifically designed and configured for Formula SAE, SAE’s student Formula race-car competition. A well recognised problem in turbocharging Formula SAE engines arises from the rules, which dictate that the throttle and air intake restrictor must be on the suction side of the compressor. As a consequence of upstream throttling, oil from the compressor side seal assembly is drawn into the inlet manifold. The development process used to solve the oil consumption issue for a Garrett GT12 turbocharger is outlined, together with cooling and control issues. The development methodology used to achieve high pressure ratio turbocharging is discussed, along with exhaust manifold development and operating limitations. This includes experimental and modeling results for both pulse and constant pressure type turbocharging. The engine completed extensive static and transient testing with no turbocharger issues after initial development. Peak values of 25 bar brake mean effective pressure (BMEP) were recorded while running on pump gasoline.