Ignore the hype: the C3 Stop & Start isn’t the first car to cut its engine in traffic for the sake of economy and emissions. The clever part is that it uses very few components that are different to a standard Sensodrive C3, which means the cost is kept low.
A 2KW reversible alternator performs the functions of both starter motor and alternator, which reduces the noise on start up and the time it takes the engine to fire.
Driving on open roads you’ll notice no difference, but with the brake pedal depressed below four mph the Sensodrive clutch opens, the engine cuts out and a green ‘eco’ indicator illuminates on the dash.
Lift your foot from the brake, the engine starts and the C3 scoots away. The air-con and all electrical accessories still function with the engine off, although the engine will run constantly if the cabin/exterior temperature difference becomes too great for the air-con to cope with, battery power begins to suffer or the engine gets too cool. There’s also a switch to override the system.
The only real drawback is the need to keep your foot on the middle pedal when stationary, even with the gear selector in neutral and the handbrake on, which can be a pain.
Currently this technology is limited to 1.4-litre C3s equipped with the Sensodrive gearbox, but Citroën says that manual transmission and diesel derivatives could follow later, while it’s certain to be offered on other Citroëns and Peugeots.
Prices are yet to be announced but the Stop & Start should cost £200-300 more than the ordinary 1.4 Sensodrive, and it gets parking sensors.
The fuel savings you’ll make in return aren’t startling: six per cent on the combined cycle rising to a more impressive 17 per cent in traffic, but city dwellers should be able to balance the books fairly quickly and the 13g/km CO2 reduction will be useful when next year’s tougher limits push the standard car out of the cheapest company car tax segment.