Wednesday, November 19, 2008

Roadtest: Stopping and starting the Smart mhd

If you're hunting for a Smart that's cheap to run but don't fancy diesel -- such as the Smart cdi -- this car is for you. It's a standard petrol Smart fortwo, but equipped with stop-start technology that flicks the engine off when you stop at light and roudabouts.  When you take your foot off the brake, the engine automatically powers up. The result is 64.2 miles per gallon for this Smart, compared to the 57.6 you'll wring out of the normal Fortwo cabrio.

Driving any car that goes silent when you stop is guaranteed to spook you at first. The mhd is no different, as I discovered during a test-drive today.  Fortunately, by the time your foot's come off the brake and is back on the accelerator, the engine is fully powered-up. Each time the engine splutters back to life, you feel and hear a reassuring judder.

The system felt pretty familiar after 30 minutes of driving. One useful element is a display to the right of the steering wheel, which shows an orange icon when the engine is still warming up and isn't ready for stop-start. It jumps to a green when the engine's ready for stop-start. I found it mostly changed to green in less than a quarter of a mile, though the exact duration depends on the temperature.

The green and orange icons are handy. The new Mercedes-Benz A Class' stop-start system, for example, doesn't have any such visual indicator of when the engine's ready -- you just have to wait for it to kick in. It's worth noting you can also manually switch off the Smart mhd's stop-start system with a button next to the gear stick (pictured below). I can't think of many occasions you'd want to turn it off, aside from when you're parallel parking into a tight spot.

Stop-start really thrives if you're driving in town. Smart says it increases mpg by 13 per cent in urban areas, versus 8 per cent in mixed conditions. I'll admit there's nothing too exhiliarting about those figures and the technology, which has been around since 2004 on several car brands. Still, it will add up to decent fuel economy and cut your carbon footprint. The mhd has emissions of 105g/km CO2 versus the basic non-stop-start model's 116g/km CO2.

Like previous Smart fortwos, this one's fun to drive. It's a five-speed automatic. Read my review of the electric Smart ed for more detail.

The Smart Mhd's just gone on sale in the UK from £7,300; get the lowdown via Smart's site.

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