In order to deeply analyze the influence of continuously variable valve lift(CVVL) system on the fuel economy of a turbocharged gasoline direct injection engine(TGDI)

the effects of variable valve lift and variable valve timing(VVT) on brake specific fuel consumption(BSFC) were experimentally compared and analyzed at four typical working conditions of 0.2 MPa and 1.2 MPa at 2 000 r/min and 5 000 r/min. The results show BSFC at low load conditions decreases linearly with the advance of intake VVT and the delay of exhaust VVT. Reducing intake and exhaust valve lifts and increasing the throttle opening can further advance the intake VVT and further postpone the exhaust VVT. This forms the Miller cycle and BSFC is further reduced. At high load conditions

BSFC at the maximal intake valve lift is lower than that at a smaller lift

and BSFC decreases with the advances of intake VVT and exhaust VVT.