Reducing the transient specific fuel consumption of a turbocharged i.c. engine having an electronically controlled turbine inlet flow control device

摘要

A method for reducing transient specific fuel consumption of an engine is disclosed in which a turbocharger inlet flow control device 44 is controlled so as to reduce pressure upstream from a turbocharger 14 and improve specific fuel consumption. In particular, when the pumping mean effective pressure (PMEP) exceeds a calibratable limit, a minimum closing limit is applied to the inlet flow control device 44 so as to prevent closure of the inlet flow control device 44 beyond this limit thereby minimising increases in upstream exhaust gas pressure and reducing pumping losses. The current value of PMEP may be determined using a virtual sensor produced by (a) accelerating the engine with the electronically controlled inlet flow device set to a predetermined position; (b) recording PMEP and pressure ratio for acceleration between idle speed and normal engine speed; (c) repeating (a) and (b) over a range of opening positions; (d) repeating steps (a) to (c) for a number of acceleration rates and (e) recording the generated data in a look-up table referencing PMEP values, pressure ratio values, engine acceleration and engine speed.