First Test: 2014 Mercedes-Benz CLA45 AMG

AMG's engine laboratory in Affalterbach would probably impress NASA's top tinkerers. The impeccable workplace sits adjacent to the building housing the division's famous "one man, one engine" production line. "How's the new turbo four-cylinder coming along?" I bluntly asked a powertrain engineer during my laboratory tour. At the time -- last October -- the engine was a rumor. So too was the car it supposedly would power in the States. The car that would eventually become the Mercedes-Benz CLA45 AMG. He smiled and looked around like a gossiping schoolboy, then whispered, "You'll be amazed at what's coming: its power, efficiency, and, yes, its sound." He smiled and shot me a thumbs-up. Could a four-cylinder AMG be a real AMG? AMGs are about torque on top of torque with a side of torque. They're dealers of tire destruction. They're autobahn annihilators.



One year later, I got my first crack at the final product, a 355-hp, 332 lb-ft of torque, 2.0-liter turbocharged four-cylinder codenamed M133 that's packed neatly inside the nose of the CLA45 AMG 4MATIC. The division's first engine with fewer than six cylinders is also the most powerful inline-four to ever propel a production car. It's a gem of a mill that's constructed to the same meticulous standards as AMG's mighty V-8s and V-12s, though it's done in Kölleda, Germany. Color me amazed. At just 2250 rpm, every pound-foot is first routed through a newly developed seven-speed dual-clutch gearbox, then directed to the brand's 4MATIC all-wheel-drive system tuned for AMG duty. The setup uses a two-part propeller shaft to route torque to the rear wheels via a multi-clutch rear differential when slip or hard cornering is detected. It's a front-wheel-drive car in normal circumstances for fuel economy sake, but can ultimately split torque 50/50 between the front and rear axles. I began questioning the engine's claimed power output as I cruised through some of Virginia's suburbs. For more than 350 horsepower, it's superbly calm. However, instances of powertrain confusion were created by jumping onto the throttle too quickly in fuel-sipping ECO start/stop mode. The gearbox and engine hiccupped, but they usually recovered quickly with a surge of smooth, hefty pull. If the pull wasn't enough, instantaneous -- almost imperceptible -- shifts and beautiful BRAAP BRAAP noises from the quad exhaust clearly indicated that the 45 means performance business. Few turbocharged cars of this caliber possess a gearbox that can match the hustle and silkiness of the CLA's.