The smart fortwo mhd (short for Micro Hybrid Drive) uses an idle stop system that replaces the conventional starter and generator by an electric setup. The smart mhd cuts the engine when speeds drops below 8 km/h, while you’re slowing down. The eTV team calculated a 9.7% improvement in real-world city driving in the first months of testing, compared to a regular fortwo.
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| smart fortwo mhd (Photo: Matthieu Lambert/Auto123.com) |
The BMW 118d, in a 5-door hatchback body style that’s not for sale in Canada, also figures in the eTV test stable. Its idle-stop and regenerative braking systems combined with a turbodiesel engine provide very low fuel consumption numbers. Based on European driving cycles, the 118d consumes 5.3 L/100 around town and 4.0 L/100 km on the highway.
Let’s do some math. The smart consumes about 5 L/100 km; add the idle stop system (which costs $400, according to the manufacturer), and drive 20,000 km a year. Saving 10% in fuel means 100 litres less (20,000/100x5x0.1) to purchase at, say, $1,20 a litre. That means we save $120 a year. It will take three and a half years to recover the cost of the mhd system in the smart fortwo.
In a truck that consumes 15 L/100 km, the same conditions result in fuel savings of 300 litres (20,000/100x15x0.1), which means the owner would save $360 a year.
Will the Canadian government’s city fuel economy test be updated to give start/stop systems the chance to prove itself in published ratings? Highly unlikely. But as consumers, we must realize that the fuel savings are undeniable, at a cost that won’t break anyone’s bank. What are we waiting for?
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