The Mercedes 2.1 OM611 engine is the four-cylinder version of the diesel engine series that includes the OM 612 and OM 613 with five or six cylinders, respectively. All three are in-line engines with common features. They have the same cylinder capacity, and are equipped with the same injectors, pistons, connecting rods, valves, and other components. All the engines are built with cast-iron blocks and feature aluminum cylinder heads with four valves per cylinder.
Produced from 1997-2006, the OM series engines feature common rail injection with Bosch injectors. In the Mercedes CDI Series II cars, the injection system uses a mechanical fuel feed pump, a pressure control valve, a flow control valve, and a fuel temperature sensor to manage the high pressure. The 2.2 CDI OM611 Engine produces from 82 to 143 hp and is rated to last 600,000 km (over 372,000 miles).
Mercedes installed the 2.1 OM611 engine in the C-Class W202, W203, CL203, E-Class W210, V-Class W 638, and Sprinter W901. Mounted in a 1997 Mercedes C 250 Turbodiesel, the five-cylinder OM 612 diesel connected to a five-speed manual or automatic transmission produces 148 bhp at 4,400 rpm and 207 lb-ft of torque at 1,800 rpm. The BMW with a curb weight of 1,480 kg accelerates to 62 mph in 10.2 seconds and reaches a top speed of 126 mph and has an estimated fuel economy of 35.3 mpg.