Mercedes Inline-6 Tops 400 Horses

Daimler AG’s Mercedes-Benz unit is introducing a new turbocharged 3.0-liter inline 6-cylinder engine that will generate at least 408 hp and 369 lb-ft of torque.

The all-new I-6 is Mercedes’ first such powerplant in nearly 20 years. The engine replaces a V-6 that is rated at 333 hp and 354 lb-ft of torque. Carbon dioxide emissions are 15% lower with the I-6, according to the carmaker.

The increased output is attributed in part to the use of a 48-volt mild-hybrid integrated starter-generator. The ISG replaces a traditional starter motor and alternator. Sandwiched between the engine and transmission, the system can help boost power and is able to recover energy during braking to enhance fuel economy.

The I-6 also benefits from the turbocharger’s electric compressor. Mercedes says the system is capable of spooling to 70,000 rpm within 300 milliseconds, virtually eliminating traditional turbo lag.

Mercedes boasts that the I-6 performs like a V-8 with the efficiency of a 4-cylinder engine and the refinement of a 6-cylinder. The layout also provides packaging advantages when combined with the 48-volt electrical system and ISG.

Mercedes will launch the I-6 next year in the S-Class sedan. The face-lifted flagship model also will offer an all-new, twin-turbo 4.0-liter V-8. The engine, which delivers 470 hp and 516 lb-ft of torque, is 4% more powerful and 10% more fuel efficient than the outgoing 4.7-liter V-8.

The I-6 and 4.0-liter V-8 are part of Mercedes’ new $3.3 billion powertrain program. The initiative also includes a new four-banger and I6 diesel.