Mercedes B-class (W246)


Debut: 2011
Maker: Mercedes-Benz
Predecessor: B-class (W245)


 Published on 27 Oct 2011 All rights reserved. 


When Mercedes-Benz launched the innovative sandwich platform with A-class in 1997, we thought it could change the automotive world forever. Yes, in terms of space efficiency the sandwich platform was a step ahead of modern FF layout pioneered by Alexander Issigonis' Mini. Its advantage was especially obvious in the presence of stricter crash protection regulations. During collision, the powertrain slid underneath the floorpan rather than towards the passenger cell. This mean it did not need bulky crumple zone to pass crash test. As a result, it was capable of allocating more of its length to wheelbase, hence more cabin space can be extracted from a small package.

Unfortunately, the sandwich platform was too costly to build. Its uniqueness means most critical components – suspensions, engines, gearbox and steering – were dedicated to the platform and could not be used by other (rear-drive) Mercedes, let alone share with other car makers like the case of BMW Prince engine. The low production volume resulted in unusually high unit costs. In the second generation sandwich platform, Mercedes tried to increase volume with the addition of B-class, but even so the combined volume was just 222,400 units last year. This compare unfavourably with the industrial norm which talks about 2 million cars a year on a single platform!



Eventually, Stuttgart has to give up the sandwich platform. The next generation A and B-class are to be based on a conventional FF platform dubbed MFA (Modular Front Architecture). It is not as space efficient as the old one, but it is more flexible, allowing not only A and B-class but also the next generation CLC-class (which will switch to front-wheel drive) and a small SUV called GLC to be derived from it. If the combined production volume is not high enough, you can also count on some Nissan and Infiniti models coming in the future. This is because the MFA is part of the joint-venture agreement between Daimler and Renault-Nissan signed in early 2010. Although its engineering was done purely by Stuttgart, Mercedes is willing to let Nissan take a free ride in order to get the economy of scale it needs.

The first product derived from the new MFA platform is the second generation B-class, codenamed W246. Looking from outside, you can already tell the switch to conventional platform. It gets a longer nose to accommodate the engine and crumple zone. The result is a profile more 2-box than monospace. The car measures 4359 mm in length, some 89 mm longer than the old car. Its width gets a slight increase of 9 mm, but the most change is height, which is reduced by as much as 47 mm to 1557 mm. Despite of the added length, the wheelbase shrank by 80 mm as more space is spent to the overhangs. However, at 2700 mm the wheelbase is by no means short for a 5-seat MPV.



Inside, the change is equally obvious. The gone of sandwich structure means a much lower cabin floor. The driver seat is now mounted 86 mm lower, too, so it offers a more natural and comfortable driving position. The new front seats are also far more supportive than before. The new dashboard is definitely more stylish, with SLS-style circular air vents. Its sporty look is certainly a sharp contrast to the bland exterior design. The dashboard is also made of much higher quality materials. It finally looks and smells like a premium product.

With four passengers on board, the new B-class should feel roomy. Thanks to the lower hip point in relation to the roof, it affords excellent headroom. Knee room is also good, thanks to a rear bench that can slide back and forth for a range of 140 mm. At its rearmost position, the rear seat offers more legroom than an S-class. At the foremost position, luggage capacity is a remarkable 666 liters. You cannot have both, but it is up to you to decide the priority. If rear seat is not in use, you can fold it to expand luggage space further to 1545 liters. Nevertheless, it still fails to match the old car's 1995 liters. Also, the expanded load bay is not completely flat, unlike before.


Unfortunately, the B-class does not accommodate the fifth passenger very well, blame to a prominent tunnel running through the center of the cabin. This is also the key disadvantage of the MFA compared with sandwich platform, which had a flat floor. Theoretically, the front-drive platform does not need a transmission tunnel, so the prominent tunnel is probably introduced to boost chassis strength, or reserve space for a possible 4matic option. Anyway, we found no such thing on most other MPVs. It would be a big minus point when compare with rivals.

Another disadvantage is the lack of long-wheelbase 7-seat version, unlike Ford C-Max, Citroen C4 Picasso or Renault Scenic etc. This could put off many family buyers.

With a conventional architecture, the mechanical package is easily predictable. It rides on suspensions consisting of MacPherson struts up front and a new multi-link setup at the rear – the latter contrasts to the old car's torsion-beam. Steering is now assisted electromechanically rather than hydraulically to save fuel. Engine can be either a 1.6-liter turbo petrol or 1.8-liter turbo diesel, both have been downsized. The petrol engine is finally up to date, with twin-cam 16 valves, variable valve timing and direct injection to insult the old 8-valver, although we would have liked the addition of twin-scroll turbo like its BMW rivals. It produces either 156 hp / 184 lbft or 122 hp / 147 lbft, depending on state of tune. The common-rail diesel offers 136 hp / 221 lbft or 109 hp / 189 lbft. Both engines are equipped with fuel-saving automatic stop-start facility and brake energy regeneration alternator – a must these days. Transmissions have been upgraded as well, with the choice of 6-speed manual or 7-speed twin-clutch gearbox. Finally, the new B-class has a class-leading drag coefficient of 0.26, benefiting fuel economy.



On the road, the new B-class is definitely better to drive than the old car. Its chassis controls body movement better and resists understeer stronger, thanks to the more sophisticated suspensions and a center of gravity 20 mm lower than before. The electromechanical steering is also satisfying, with consistent, natural weighting and good response. Unless you opt for sport suspensions, 18-inch wheels and low profile tires, the ride quality is much more compliant than the old car. However, the Mercedes chassis is not as well engineered as Ford C-Max. It never feels as light and agile as the latter around tighter bends.

The powertrain also gives a mixed impression. The 1.6 turbo petrol works smoothly but it needs rev to keep its turbo spinning, even though the spec. shows peak torque arrives at just 1250 rpm. The diesel engine is better, offering stronger low-end punch and demanding less effort from the driver. The paddle-shift gearbox responds well to manual shift, but in auto mode it does not work as smoothly as it should. Overall, the dynamic aspect of the car is satisfying rather than outstanding.

Unquestionably, the new B-class is less compromising than the old car, mainly owing to its abandonment of sandwich platform. However, compare with many mainstream compact MPVs, especially the class-leading Ford C-Max, it is not good enough to justify its premium prices. Poor accommodation for the 5th passenger is its biggest flaw. Some other areas like interior flexibility, cargo space and an average petrol motor are also slightly underwhelming. For a car wearing a three-pointed star badge, we have to admit a slight disappointment.
Verdict: 
Specifications





Year
Layout
Chassis
Body
Length / width / height
Wheelbase
Engine
Capacity
Valve gears
Induction
Other engine features
Max power
Max torque
Transmission
Suspension layout

Suspension features
Tires
Kerb weight
Top speed
0-60 mph (sec)
0-100 mph (sec)
B200
2011
Front-engined, FWD
Steel monocoque
Mainly steel
4359 / 1786 / 1557 mm
2699 mm
Inline-4
1595 cc
DOHC 16 valves, VVT
Turbo
DI
156 hp
184 lbft
7-speed twin-clutch
F: strut
R: multi-link
-
205/55R16
1350 kg
137 mph (c)
7.9 (c)
-
B200CDI
2011
Front-engined, FWD
Steel monocoque
Mainly steel
4359 / 1786 / 1557 mm
2699 mm
Inline-4, diesel
1796 cc
DOHC 16 valves
VTG turbo
CDI
136 hp
221 lbft
7-speed twin-clutch
F: strut
R: multi-link
-
205/55R16
1430 kg
130 mph (c)
8.7 (c) / 9.4*
28.8*
B250
2012
Front-engined, FWD
Steel monocoque
Mainly steel
4383 / 1786 / 1557 mm
2699 mm
Inline-4
1991 cc
DOHC 16 valves, DVVT
Turbo
DI
211 hp
258 lbft
7-speed twin-clutch
F: strut
R: multi-link
-
225/45R17
1390 kg
149 mph (c)
6.5 (c)
-




Performance tested by: *Autocar





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