Last year Mercedes-Benz started replacing its naturally-aspirated 5.5-liter V-8 engine in high-end models like the CL550 with a more powerful, yet more efficient, twin-turbocharged 4.6-liter unit. The new engine delivers up to 32 percent more power than the one it replaces yet it’s 20 percent more fuel efficient, so it comes as no surprise that it has started to filter its way across the rest of the Mercedes-Benz lineup.

For the 2012 model year, it is being made available in '550' variants of the S-, E- and CLS-Class sedans, as well as the E-Class Coupe and E-Class Cabriolet. Depending on which it model it powers, the engine delivers between 402 and 429 horsepower and 443 and 516 pound-feet of torque.

Key features of its design are direct-injection and multi-spark ignition technologies, as well as turbocharging. Mounted on the cylinder heads, the exhaust-driven turbochargers force intake air into the engine at a pressure of up to 13 psi.

Most of the engine is constructed from aluminum, though the crankshaft, connecting rods and valves are made from forged steel.

Even the cooling system is significantly refined in the new engine, beginning with a two-stage flow circuit through the cylinder head. This improved coolant flow results in better heat dissipation, despite lower coolant circuit pressure, so that the water pump uses less engine power.

A three-phase cooling system helps the engine warm up very quickly. When the engine is first started, no coolant is circulating. As the engine warms up, coolant begins to circulate within the engine, but not through the radiator. Only when the coolant temperature reaches 221 degrees F, coolant also circulates through the radiator.

Click here for a more detailed look at Mercedes’ latest V-8 engine design.