Fleet News

Stop the engine – start saving cash

CITROEN says its new Stop & Start technology can slash fuel consumption by up to 10%. Adele Burton tests out the claim in London traffic.

The journey

IS there any point to a car whose engine stops every time it comes to a halt? Is it just an eco-gimmick or does it have a genuine place in urban fleets? We decided to find out.

Armed with a stopwatch, a photographer and the new Citroen C3 1.4i 16v Stop & Start, I set off to find if the latest weapon in the war on wasted fuel really works. From our base in Peterborough, we chose to test the car on the motorway and then put it through its paces in London, which suffers some of the worst congestion in Britain despite the improvements the congestion charge has brought.

We were on the A1 for about two hours. As the Stop & Start is designed for city driving, there was no major advantage to using it on flowing dual carriageways. Traffic ran freely and the engine was running for 99% of the time.

Where the car really comes into its own is in the city. Each time it stops, the engine switches off and a green ‘ECO’ sign is illuminated on the dash. I started the stopwatch each time this appeared to see how long the engine lay dormant. Our progress in the capital was hindered not only by volume of traffic but also by traffic lights, which seemed programmed to spend as much time on red as possible. Thankfully, I wasn’t adding to the fog of fumes every motorist has to sit in.

And Citroen believes that the Stop & Start system also helps to improve the quality of life in cities, since drivers and pedestrians benefit from total silence during the times the vehicles are stopped.

It takes time to become accustomed to the eerie silence when the engine is off. It is almost as though the vehicle has stalled, but the technology works perfectly, with the engine re-igniting each time the brake pedal is released.

Citroen opted for the 1.4i 16v petrol engine as petrol engines consume more fuel when idling than diesel and the starter technology is more easily integrated into a petrol engine. When the engine re-starts, it uses the same amount of fuel as if it spent three seconds idling, so for a vehicle waiting any longer than three seconds savings are made, however small.

Citroen has appealed to the authorities to make the C3 Stop & Start exempt from the London congestion charge, but no decisions have been forthcoming. On our whistlestop tour of London, I drove past the Houses of Parliament several times, chugged across Westminster Bridge, stopped at the London Eye, took in Buckingham Palace, then onto the Edgware Road before heading home. In a day of driving, we incurred a £5 congestion charge, covered more than 150 miles and spent a long time in jams, but what savings did we really make?

Stopwatch Statistics

1. On the move: 3hrs 05 mins
2. Congestion: 18.07 mins
3. Traffic lights: 36.43 mins

The technology

PSA Peugeot Citroen launched the Stop & Start system in the UK last November as part of its strategy of developing new technologies. When the vehicle is stationary, the engine is automatically turned off and is in standby mode but starts up instantly the brake pedal is released. Using a combined starter and reversible alternator instead of a traditional starter motor makes the starting process much more efficient and uses less fuel. And the transition is absolutely seamless. No hitches, judders or lurches once the brake pedal is released, just a smooth swift pull away from lights or traffic jams.

Currently, the system is only available with the automated manual SensoDrive gearbox, similar to driving an automatic but without the fuel economy penalties. According to Citroen, the Stop & Start system reduces fuel consumption by 10% for city driving, 6% in a standard combined cycle and up to 15% in heavy traffic.

The alternatives

CITROEN is not the first manufacturer to come up with stop-start technology. Volkswagen used to produce the 1.9D Mark Ecomatic Golf. It was in production from 1994 to 1997 but had limited success.

Honda’s hybrid Insight and Civic IMA go a step further, combining petrol and electric power. Again the engine turns off when stopped, but the engine can also shut down during braking to save fuel. The electric motor boosts the engine’s power to reduce fuel consumption.

The Toyota Prius is another petrol electric hybrid, but the units can work independently. So while the engine shuts down when stopped, the car can also travel at low speeds on electric power only.

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