The new small car range has been designed for front- and all-wheel-drive models and to be as future-proof as possible, paving the way for hybrid, electric and fuel-cell derivatives.
The sandwich chassis pioneered in the outgoing A-Class and previous B-Class has gone, replaced by what Mercedes-Benz calls an "energy space" in the floor which can be used to store batteries and hydrogen fuel cells. But the company says it won't stop using sandwich construction and is already using it for fuel-cell prototypes. The sandwich structure made the previous A- and B-Class cars especially strong but it was expensive to make and didn't help interior packaging.
The lower, more conventional floor improves cabin room and gives the car a lower centre of gravity, up to 30mm.
Overall, the B-Class is slightly wider and longer than the outgoing model but its height has been pulled down by a significant 47mm to 1557mm.
The seat height in relation to the road is also down, by 71mm, but the seats themselves are more upright - a request, apparently, from customers.
The ergonomic change helps head and legroom front and back. Indeed, rear passengers get what Mercedes-Benz says is class-leading legroom, only 12mm less than that offered by the company's standard flagship S-Class.
The B-Class is much more agile and energy-efficient than the old one, as Mercedes-Benz sets out on a new direction in the compact segment with turbocharged four-cylinder petrol and diesel engines with stop-start, seven-speed automatic gearboxes and a host of technical innovations.
"No model change in the history of Mercedes-Benz has ever seen so many new developments introduced in one fell swoop," said the carmaker's chief research and development executive, Dr Thomas Weber.
"Future B-Class customers will benefit from this quantum leap in terms of exemplary low fuel consumption and CO2 emissions combined with driving pleasure, plenty of space and the highest standard of safety that has ever been available in this class," he said.
Three B-Class variants carrying the company's BlueEfficiency label went on sale in New Zealand this week: the petrol-powered B180 ($49,990) and B200 ($56,900), and the diesel B200 CDi ($56,900).
The B180 and B200 use a boosted 1.6-litre four-cylinder engine in different states of tune. The unit in the B180 delivers 90kW/200Nm and the B200 puts out 115kW/250Nm. The 1.8-litre turbo-diesel is a smaller version of the 2.2-litre unit in the C-Class range and develops 100kW/300Nm.
Mercedes-Benz claims the new range of east-west mounted engines are 21 per cent more fuel-efficient than the outgoing units.
It claims town-and-around fuel economy of 6.1l/100km (46mpg) for the two petrol models and 4.7l/100km (60mpg) for the diesel. CO2 exhaust emissions are rated at 141g/km for the B180 and B200 and 122g/km for the B200 CDi.
The carmaker says it expects the new B-Class range to lure first-time Mercedes-Benz buyers, although it admits the vehicle will have a number of competitors, including the BMW 1 Series.
A 200km round trip on a mix of roads north of Melbourne on Wednesday revealed much about the new model. There is less body roll through corners and more overall stability, thanks largely to the lower centre of gravity. The electro-mechanical steering is one of the better such systems on offer, too.
The ride is particularly impressive, helped by a new multi-link rear suspension designed to fit with future all-wheel-drive variants. Vision from the upright front seats is excellent and the switchgear is a vast improvement over the old model.
The confusing aspect of such a front-drive car is the transmission tunnel that restricts foot space for a middle passenger in the rear. It is there to accommodate future all-wheel-drive mechanicals.
So what is the B-Class, exactly? Hard to categorise. It's a small MPV/five-door hatchback/crossover with plenty of interior room, six optional packages ($1600-$3800), class-leading safety equipment - including Pre-Safe collision prevention technology - and state-of-the-art infotainment.
This includes an upcoming unit that integrates an Apple iPhone to give "the Facebook generation its natural home on four wheels". It was revealed in the A-Class at the Geneva show and will reportedly go into the B-Class later in the year.
The new in-car system features an app, developed in-house, that allows access to all content from the iPhone via the large screen mounted atop the instrument fascia and operated from a control dial on the centre armrest.
The Digital DriveStyle app can be downloaded free from iTunes. It allows access to the internet, radio, navigation software with real-time traffic updates and a "car finder" that displays the car's location on a smartphone - should you forget where you parked it.
'Baby' expands B-class family
A four-door coupe, a "baby" CLS if you like, is one of the five variants based on the B-class platform. I
t will be unveiled at this month's Beijing motor show and in Los Angeles and go on sale next year. Reports say front- and all-wheel-drive versions will be available.
Power will come from a range of petrol and diesel engines mated to seven-speed dual-clutch and six-speed manual transmissions.
