The e-booster is marketing-speak for a capacitor, which can dump its electrical charge much faster than a battery for engine restarts in 0.04sec. This, and the starter that's connected to the engine by a belt, allows the C4's engine to be shut down and started at low speed, not just when stopped.
CO2 emissions are currently 109g/km, with 99g/km promised on future variants. Overall fuel consumption is only a few drops over 4 litres per 100km. A Toyota Prius emits 89g/km and has an overall fuel consumption rating of 3.9 litres per 100km.
Citroen's claiming smooth restarts and a good overall driving experience from e-Hdi cars, but none were available to try at the C4's Australia-New Zealand launch last week.
E-HDi technology will be rolled out on most Peugeot and Citroen models powered by their 1.4-litre and 1.6-litre diesels; parent company PSA reckons that by 2013, some 30 per cent of the group's diesels will be e-HDI. That represents about a million cars.
Gimmick-free newcomer turns on the style to attract the ladies
Built on the latest version of the Peugeot 308 floorpan, the Volkswagen Golf-sized C4 hatch is one of Citroen's most important models worldwide. The previous version is credited with revitalising the make in many markets, attracting younger buyers and more women.
Locally, Citroen's hoping the C4 will do well in a segment that it has identified as increasingly ticking style as the most important factor, followed by cabin roominess, comfort and cargo space. At 380 litres, the boot is class-leading.
All models in the range perform well and offer good fuel consumption; partly the result of a weight-saving campaign that left no part examined and, if possible, trimmed.
When its working life is done, the car is said to be 85 per cent recyclable.
Culling the fixed-hub wheel underlines another achievement; the new C4 is largely gimmick-free - an exception being able to choose your instrument light colour.
New Zealand gets two petrol engines, the 1.6-litre with 88kW and a turbocharged version producing 115kW. But after a day of driving around Sydney, the flexible 82kW Hdi diesel emerged as Driven's favourite.