Four Turbos Are Better than Three in New Bimmer Diesel

BMW AG is introducing a new diesel engine with four turbochargers that kicks out 394 hp and 561 lb-ft of torque. Both figures are up about 3% over the carmaker’s outgoing tri-turbo diesel.

Billed as the industry’s first quad-turbo diesel for a mass-production model, the new engine will debut in Europe with the 2017 750d xDrive version of the carmaker’s 7 Series flagship sedan. Eventually, the powerplant also will be available in the X5, X6 and X7 crossover/SUVs and next-generation 5 Series car.

As with the previous tri-turbo unit (pictured), which was introduced in Europe four years ago, the new diesel is a 3.0-liter inline-six. BMW hasn't said whether the engine will be offered in the U.S.

The quad-diesel teams two low-pressure turbochargers for low-end torque with a pair of high-pressure units to handle the rest of the rev range. By comparison, the tri-turbo design featured two high-pressure units and one larger low-pressure turbocharger.

The larger diesel is about 5% more fuel efficient and less expensive to produce than its predecessor, according to the carmaker. The weight of the two engines is comparable.

In the 750d xDrive, the new diesel will be mated with a ZF 8-speed automatic transmission. BMW says the engine itself is capable of generating even more torque but is limited by the transmission.

The all-wheel-drive 750d xDrive can sprint from zero to 62 mph sprint in about 4.5 seconds on its way to a top speed of 155 mph.