Experiments were conducted for a typical R134a compact European automotive air conditioning system equipped with an internally controlled variable displacement compressor, minichannel condenser, TXV, and minichannel evaporator. A "drop-in" R1234yf system was tested together with two modified R1234yf systems with the primary goal to document some laboratory results and their analyses which could prove useful in aiding manufacturers and researchers by indicating "minor" system modifications which could be implemented in existing air conditioning systems, with the aim to achieve with R1234yf similar capacity and efficiency as modern R134a systems. Since the experimental results indicate that, for a given cooling capacity, R1234yf systems present lower performance than the baseline R134a, numerical simulations were used to investigate the effects of "major" system modifications, such as, the use of an enhanced condenser and/or an enhanced evaporator. (C) 2011 Elsevier Ltd. All rights reserved.