IT HAS taken more than two years, but criticism levelled at BMW’s folding hard-top Z4 when it was launched in Australia in 2009 has finally been addressed, with weight, price and fuel savings coming in the shape of a new downsized N20 four-cylinder engine.

, , In addition to saving weight by reducing the cylinder count, the high-tech 2.0-litre unit employs twin-scroll turbocharging, direct fuel injection, sophisticated valve control and EfficientDynamics features such as idle-stop and regenerative braking, meaning six-cylinder performance is achieved without sacrificing four-cylinder efficiency.

, , BMW has also acted to squeeze out the engine’s maximum potential by offering it with ZF’s wonderful eight-speed automatic transmission for customers who cannot abide the six-speed manual.

, , Those measures combine to earn the Z4 a sizeable luxury car tax saving, and BMW is offering the engine in 135kW or 180kW tune, respectively replacing the naturally-aspirated 2.5-litre and 3.0-litre six-cylinder units.

, , Z4 sales have struggled this year, but things are now looking good for BMW’s re-priced and fully-turbocharged roadster line-up, which is now more competitive against the recently-redesigned Mercedes-Benz SLK.

, , The new engine looks good on paper and the new pricing should give Benz something to think about but can a force-fed four-pot offer the same top-down thrills as the Bavarian brand’s evocative six?