One of the world’s most fuel-efficient cars, the smart fortwo mhd (micro hybrid drive), will be in Australia showrooms this December, just in time for Christmas.
This new and ultra-efficient version of the iconic two-seater city car brings with it the same levels of safety, engineering and driving fun as the current model except it will now be offered with further savings in fuel consumption, fewer carbon dioxide emissions as well as reduced levels of urban noise.
Studies have shown that, on average, vehicles come to a stop every 1.3 kilometres in everyday traffic. In line with this, the 52kW smart fortwo mhd uses idling phases to switch off the engine and temporarily completely avoid fuel consumption, exhaust gas and noise emissions when the car is stationary in traffic. In combination with the automated manual transmission already fitted in the production vehicle (known as softip), customers can comfortably use this function with maximum start/stop availability.
Currently, two versions of the smart fortwo are sold in Australia: the smart fortwo coupé and the convertible smart fortwo cabrio. Both come fitted with a three-cylinder one-litre petrol engine producing 52 kW of power, and customers seeking more zap can specify a 62kW turbocharged version of this engine.
The 52kW smart fortwo mhd will replace the current 52kW variant in the Australian smart catalogue. Pricing and specifications will remain unchanged for customers, who will now gain the mhd’s stop-start feature (which can be switched off by the driver at will) at no additional cost.
Powerful belt-driven starter generator
At the heart of the mhd system is a special belt-driven starter generator that supplies the vehicle's electrical system with voltage and has a secondary function as a starter.
It is able to smoothly start up the combustion engine in a fraction of a second as soon as the driver releases the brake pedal. This dispenses with the need for a conventional starter motor that works on the flywheel of the crank assembly.
In conjunction with slightly modified gear ratios, this strategy leads to a combined-cycle fuel consumption saving of over six percent (according to ADR 81/02). The standard consumption is reduced by approximately 0.3 litres per 100 kilometres – from 4.7 litres to 4.4 litres. Depending on the traffic situation (heavy slow traffic), this figure can be improved upon further.
There is also a corresponding reduction in CO2 emissions from 112 grams to 105 grams per kilometre, representing an improvement of more than six percent.
The system was developed by smart in cooperation with Valeo GmbH and the Gates Corporation.
The mechanical assembly comprises the starter generator STARS 137 from Valeo. This generator delivers a torque of 42 Newton metres or current of maximum 120 ampere at 14 volts – enough to guarantee a reliable engine start, even at a temperature of minus 25 degrees Celsius. .
To ensure a low-slip and durable connection of the crank assembly and the starter generator, both components were given wider belt pulleys, as was the water pump that is also driven. A six-rib poly-V-belt from Gates transmits the power.
Belt tension is particularly important because of the changing loads in start/stop operation.
A coaxial spring-and-shock absorber unit that is hinged to the starter generator is supported by the engine block. The starter generator is pivoted so that it can apply the tension force to the belt drive. This ensures that both the belt section pulled by the combustion engine when it is running and the complementary belt section pulled by the starter during the start are able to reliably transmit the torque needed.
Control unit with integrated power electronics
The activities of the system are controlled by a separate control unit with integrated power electronics that is installed behind the battery recess.
This communicates with the vehicle's other control units via CAN databus.
A three-phase cable transmits the generator power of up to 120 ampere. The power electronics regulate the power of both the starter and the generator.
An AGM battery stores the energy for the on-board electrics. The electrolyte is bound in an absorbent glass matt. Its physical properties make it more resistant to varying loaded and unloaded conditions (more cycle resistant) than conventional lead-acid batteries with sulphuric acid electrolyte.
The power electronics of the belt-driven starter generator switch off the combustion engine in idling phases, for example at traffic lights, level crossings or in stop-and-go traffic.
In view of fuel economy and comfort, the electronics switch off the engine at a speed of below 8 km/h when the driver presses the brake pedal, signalling that they want to stop. The engine starts as soon as the driver releases the brake pedal again. This guarantees an immediate response. The start/stop function can be deactivated if required with a switch on the centre console – until the next starting procedure (ignition off/ignition on).
The most important technical data on the new smart fortwo micro hybrid drive at a glance:
smart fortwo: the most cost-efficient car
The smart fortwo is still Germany's most cost-efficient car. This is the conclusion reached by experts from the prestigious market observer EurotaxSchwacke after analysing 16 vehicles in the mini car class.
They confirm previous cost calculations by numerous trade magazines and the ADAC, Germany's largest automobile club. Owners of a smart fortwo micro hybrid drive (mhd) save around €1,700 in running costs compared with the most expensive model in this class.
The smart fortwo tops the ranking of low cost vehicles once again. After auto motor und sport, Auto Bild, Autozeitung and the ADAC, now EurotaxSchwacke GmbH also confirms that the smart two-seater has the lowest running costs in the mini car category.
No other car is cheaper to run in Germany.
In the latest examination the experts compared the running costs of 16 vehicles from the mini car segment. They found that it costs €27.52 to drive a smart fortwo coupé pure mhd 100 kilometres.
For comparative purposes: the most expensive model tested costs €38.88 per 100 kilometres.
With an annual mileage of 15,000 kilometres this means that smart drivers save approximately €1,700 per year.
In addition to tax, insurance and fuel, the complex calculation of the total costs also considered wearing parts, maintenance, repairs and the vehicle's loss of value for an ownership period of 36 months and a mileage of 45,000 kilometres.
"The running costs are also an important factor to consider when choosing a vehicle", says Martin Verrelli, Managing Director of EurotaxSchwacke GmbH.
The EurotaxSchwacke calculations provide impressive real-world proof of the savings potential of smart's micro hybrid drive technology, which has been successfully deployed in production vehicles since 2007.
At a glance: the smart fortwo range in Australia
* according to ADR 81/01
** Prices exclude dealer delivery and statutory charges
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