Kompressor

Kompressor is the trade name that Mercedes-Benz applied to its supercharged petrol engines, and the word is simply the German for compressor. It denotes a mechanically driven supercharger rather than any unique design of the firm's own, and it appeared on a badge at the rear of the car to mark out models fitted with forced induction. Mercedes used the name across a broad spread of its range from the 1990s into the 2000s, on everything from compact saloons to sports models, reviving a label the company had used on its supercharged cars before the Second World War.

The engineering behind the badge is the supercharger, a compressor that forces more air into the engine than it could draw under atmospheric pressure alone. Crucially it is driven mechanically by a belt from the crankshaft, so it spins in direct proportion to engine speed. This is the key distinction from a turbocharger, which is spun by the engine's own exhaust gases. Because the supercharger is geared to the engine, it begins compressing air the instant the engine turns, and most Mercedes Kompressor units used a Roots-type or, in some applications, a screw-type blower to do so.

The practical appeal of this arrangement is response. A belt-driven supercharger delivers boost immediately and builds it smoothly and predictably as the throttle is opened, free of the brief hesitation, known as turbo lag, that afflicts a turbocharged engine while its exhaust-driven impeller spools up. The result is strong, linear torque from low revolutions and an eager, immediate feel that suited the relaxed, refined character Mercedes sought. As with any forced-induction engine the compressed air is hot, so a Kompressor installation is paired with an intercooler to cool the charge, restore its density and stave off knock.

The weakness of the supercharger is the obverse of its strength. Because it is driven directly by the engine, it consumes a portion of the engine's own power to compress the air, a parasitic loss that grows with boost and engine speed. A turbocharger, by contrast, recovers energy from exhaust gas that would otherwise be wasted, and so is inherently more efficient. As manufacturers came under mounting pressure to cut fuel consumption and carbon dioxide emissions, that efficiency gap proved decisive.

For this reason Mercedes-Benz progressively retired the Kompressor in favour of turbocharging during the late 2000s and 2010s, and the badge largely disappeared as the company's petrol range moved to turbocharged units that offered comparable or greater output with better economy. The name survives now mainly on older models and as a piece of motoring vocabulary, a reminder of an era when the supercharger's instant response was prized over the turbocharger's thrift, and a useful contrast point to the naturally aspirated engines that need no compressor at all.