Now this is more like the kind of result we’d like to see from the hit BBC series, The Apprentice, we can just picture Lord Sugar setting the challenge – “your task is to build a muscle car from a Mercedes-Benz B-Class…”

According to a report in this week’s Autocar, Mercedes-Benz is planning to enter the hot hatch market in 2012 with a 320bhp AMG-badged A-class, meanwhile workers at the Mercedes-Benz Rastatt plant in Germany came up with the idea of squeezing the 5.5-litre 382 bhp V8 from an E550 into a diminutive B-Class.

The challenge

After finding a B200 CDI that had been sacrificed to training, Plant manager Peter Wesp and his team set about the replacing the oil-burner with one of Stuttgart’s finest propulsion sources.

The idea came from the Rastatt plant manager, Peter Wesp. He gave some of his staff the task of creating a very special vehicle using the B-Class as its base – leaving it to their creativity to decide what and how. Andreas Würz, a foreman in the technical vocational training department, immediately took up the challenge.

Foreman, Andreas Würz, thought that it should be possible to fit a V8 into the engine compartment.

He took a close look at this large compact model, enlisted the aid of a tape-measure and came up with an idea that not only surprised and delighted his boss and colleagues, but also the trainees: “Actually it should be possible to fit a V8 into the engine compartment.” Together with his fellow-foreman Matthias Rieger from the electrics/electronics installation section, he assembled a team of twelve second-year and third-year trainees specialising in production mechanics and automotive mechatronics.

A technical specification was created and a build plan was formulated based on the following assumptions; the B-Class was to remain a recognisable B-Class, on the inside and outside. The interior was to be upgraded in line with the more premium class being aspired to and the resulting car was to be suitable for day-to-day driving.

The build process

HR manager Martin Spicale promised financial support, which made the project a feasible proposition in the first place. And a “victim” (Würz) for the conversion was also soon found: a B 200 CDI which had been donated to the workshop for training purposes.

While the trainees completely disassembled the B 200 CDI, Würz went in search of a suitable engine and found what he was looking for. The 5.5-litre V8 developing 285 kW (382 bhp) and 530 newton metres of torque was transplanted into the B-Class together with a seven-speed automatic transmission and the engine control unit. The latter proved to be quite a headache later on, as it had to be reprogrammed only to process signals from the driven rear axle.

Würz: “The V8 power unit fitted amazingly well, and we were even able to use the original engine mounts.” There were serious problems with the steering, but here too, harmony was restored with a number of modifications.

The exhaust system was a clever combination of various replacement parts and took the form of a twin-pipe system emerging at the centre of the rear valance. This is where the one-off B 55 gets its typical V8 burbling sound – once the ignition key has been turned, all heads in the vicinity are guaranteed to turn in the direction of this very special B-Class.

The B 55 could be described as a subtle conversion, that is until the ignition is turned and the engine started.

Intensive perusal of Mercedes parts catalogues solved the second major transplant challenge, namely the rear driven axle. It emerged that the rear axle of an older W 210 series E-Class would be a very good geometrical fit. Plant manager Wesp gave the go-ahead to obtain one, and Würz and his colleagues designed a subframe, which with extensive forming and welding work enabled it to be integrated into the B-Class bodyshell. Elegantly concealed within the sandwich floor, the propshaft of the E-Class also fitted into the B-Class with no further modifications. Neat eh?

For the brakes the team also struck gold within the replacement parts catalogue, this time donated from the C32 AMG listing. Perforated and internally ventilated disc brakes in 345 x 34 mm dimensions were fitted at the front, with perforated and internally ventilated disc brakes in size 300 x 30 mm at the rear.

The system was combined with striking 8.5 x 18 AMG sports wheels in a five-spoke design shod with 235/40 ZR 18 Y tyres at the front and 9 x 18 wheels with 255/35 ZR 18 Y tyres at the rear. The maximum steering angle at the front axle was mechanically restricted to avoid fouling the wheel arches. The team stepped outside of Mercedes parts catalogue for the suspension, turning to coil-over suspension specialists K&W.

Finishing touches

Where the interior was concerned, friends from the training workshop in Sindelfingen were able to help, providing Alcantara linings for the A, B and C-pillars as well as a roof liner in the same luxurious material. The seats in a leather/Alcantara combination were provided by the specialists at Johnson Controls, who are also located on-site in Rastatt.

The finishing touches were added to the B 55 in the paint shop. In trendy white with dark-painted radiator louvres and smoked headlamp lenses, the B-Class cuts an imposing figure but only gives a discreet indication of the power plant concealed beneath its bonnet, assuming of course you’re not within earshot of its burbling V8.

The project team headed by foreman Würz are particularly proud that at 1620 kg, the weight of the B 55 is only around 180 kg greater than that of the original car. Which means that impressive performance figures can be expected…

Würz: “We have not made any measurements yet, but we should manage a sprint to 62 mph in under six seconds. “Plant manager Wesp is equally proud of the result: “The team of trainees has done a superb job, and placed a spotlight on the sporty genes of the B-Class that nobody could have imagined.”

Training manageress Manuela Rascher is likewise very pleased: “The B 55 shows what our training workshop can do. It clearly demonstrates that we not only offer young people high-quality professional training, but also highly unusual and exciting project work.” Could it be that further projects of this nature are planned for the future?

Rascher: “We may have some surprises in store…”


And the great thing about reading this online is that you can also listen to it. It’s cars like this which show why V8’s are the most charismatic of powerplants to fit in a car.

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