What you should know before anything else is that the B55 is not a regular Mercedes-Benz model. Nor is it being considered for sale--not now and not at any time in the future. That's unfortunate because this wild take on the German carmaker's wholesomely conservative B-class is an absolute riot.
As its name suggests, the superbly constructed one-off prototype is well removed from the standard B-class. Having started life as a humble European-market B200 CDI, it has been liberated from its standard turbocharged 2.0-liter four-cylinder diesel engine. Shoehorned into its place and other extremities of the engine bay is the 5.5-liter V8 unit packing 383 hp and 391 lb-ft of torque.
How the engine fits under the heavily sloping hood within the tight confines of the compact car--using the original mounts and without any modification to the standard steel body structure--remains somewhat of a mystery. But with polished-chrome inlet plumbing and other visual tweaks, it certainly looks the goods.
And it sounds it, too. Turn the key and you're treated to a deliciously throaty soundtrack thanks to a new exhaust system created from various replacement parts that does without the usual silencers and back-pressure-reducing trickery. If you didn't know, you could be forgiven for thinking it was the product of AMG, which apparently had no direct input into the new car.
The engine is not the only highlight. Mercedes' trainees also ditched the B-class's front-wheel-drive layout for rear-wheel drive, running a propshaft from its new seven-speed automatic gearbox under the flat floor toward the rear, where it mates with an axle from the old E430 Estate. To cope with the increased performance, it also adopts the brakes from the decade-old C32 AMG with discs up front and at the rear. Because of the limited development, though, there's no traction control or stability program to corral the engine's reserves.
The result is a driving experience quite unlike any other B-class--unlike any other Mercedes-Benz, for that matter. Without registration for road use, we used Mercedes-Benz's Rastatt test track to determine that the B55 is more than mere show. It also possesses surprisingly mature dynamic properties. With extra weight over the front axle, distribution definitely favors the front end. But there is sufficient balance and grip to allow you to attack corners with real gusto.
Apart from a lack of self-centering with the steering, whose packaging has been compromised by the need to give up so much space to the engine and thus runs a smaller hydraulic pump than perhaps is required, the B55 also steers accurately, rides with impressive comfort and is free of any obvious vices.
It is decently quick in a straight line. Andreas Wurz, a foreman in the technical-vocation-training department who is largely credited with the idea behind the new car, reckons it should be good for 0 to 62 mph in less than six seconds when he finally gets around to strapping some measuring equipment to it. He's lying, of course. This thing will easily run in the low five-second bracket.
The B55 looks rather striking. As you can see, Mercedes-Benz's team of trainees managed to package the new engine and driveline without any obvious changes to the standard B-class body--a remarkable achievement given the major driveline modifications that took place underneath. But with a lowered ride height, 18-inch wheels shod with 235/40 (front) and 255/35 (rear) profile tires and two centrally mounted chrome tailpipes, it possess a much more aggressive stance than its standard sibling.
Sadly, though, it'll never progress beyond this prototype. But with a new, second-generation B-class due out at the Frankfurt motor show in September and likely to be sold in North American, it is a fitting way to send off the first-generation of Mercedes-Benz's popular compact.
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