The smart fortwo mhd (Micro Hybrid Drive) will introduce a hybrid-style eco-start system to the range in Australia, when it arrives here next month. In effect, the new car replaces the current 52kW smart fortwo and will be sold in both 'coupe' ($19,990) and cabrio ($22,990) versions.

The car keeps fuel use low in traffic through an automatic engine stop/start facility. Should the driver wish the engine to remain running in traffic, the stop-start function can be disabled by the driver at will.

Other than the adoption of technical features to facilitate the stop-start operation, the fortwo mhd can't be easily picked from the model it replaces. The engine relies on a single starter/generator unit that is driven by a belt from the engine -- to restart the engine instantaneously and to recharge the battery from the engine.

According to smart, it can restart the engine in a fraction of a second, once the driver lifts pressure off the brake pedal. Conversely, at a speed of 8km/h the system will automatically stop the engine when the driver presses the brake pedal.

The fortwo mhd also saves fuel through revised gear ratios that manufacturer attributes to the new car's fuel consumption improvement of over six per cent (down from 4.7L/100km to 4.4L/100km). Accordingly, CO2 emissions are reduced from 112 to 105g/km. The figures cited by smart are based on combined-cycle testing, so actual fuel use in city driving can be expected to produce different results.

Developed jointly by smart and transmission specialist Valeo, the new system can work in temperatures as low as minus 25 degrees Celsius and the six-rib poly-V belt has been designed for optimum durability and longevity.

This new technology is introduced with the smart fortwo as that vehicle is available with a robotised manual transmission that lends itself -- through its existing electronic control systems -- to incorporating the additional hardware and software to service stopping and starting on the fly.

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