M266

The A-Class was built around a sandwich floor: a double bottom with the drive unit sitting on a steep incline above it, so that a frontal impact pushes engine and gearbox underneath the passenger cell rather than into it. Mercedes-Benz held patents on the arrangement, and it dictated the engine. The M266, which took over from the M166 when the W169 A-Class arrived in October 2004, had to be short, had to be narrow, and had to run happily at an angle no ordinary four-cylinder would tolerate. It also had to be cheap, which is why it has one camshaft and eight valves in an era when sixteen-valve heads were routine in the class.

Four versions came off one 83 mm bore — 1.5, 1.7 and 2.0 liters naturally aspirated, and a turbocharged 2.0 good for 193 PS with 280 N·m from 1,800 rpm. That last one made the A 200 Turbo and B 200 Turbo genuinely quick cars in a body shape nobody expected it from, and both A- and B-Class shared the whole range. The A 200 Turbo was dropped in 2010 and the W169 finished in April 2012. Its replacement, the M270, was designed for a conventional platform: the sandwich floor went out with it, and so did the reason the M266 was shaped the way it was.