Fiat is adding a midlevel model, the 500 Turbo, to its U.S. lineup for 2013. The car will get a turbocharged 1.4-litre MultiAir engine rated at 135 hp and 150 lb-ft of torque. It will have larger brake rotors, sport-tuned springs and shocks and a rear spoiler, and has been developed to address consumer demand for more power and performance in the 500 line.

In addition to many other new features, the monoscroll turbo features electric wastegate actuation for quicker response and better gas sealing. Active control means that it can be opened at part-load, reducing backpressure and catalyst light-off time… The cast turbine wheel is now Inconel rather than MAR steel, and the compressor wheel is milled from solid.

When two turbos were no longer enough, BMW applied three. The outcome – a 2,993cc straight-six diesel with three turbochargers supplying 4bar of boost. The engine generates 740Nm from 2,000rpm, revs to 5,400rpm and, in the M550d, emits only 165g/km of carbon dioxide. The system comprises two small variable geometry (VGT) turbos and a large fixed geometry turbo.

[Source: Automotive Engineering, June 2012]