GENEVA -- While rivals are shunning or dropping diesel hybrids because of high costs, Mercedes-Benz is pushing forward with the technology to help boost fuel efficiency and lower CO2 emissions.
Mercedes will introduce in the summer C- and E-class plug-in diesel hybrids with the company's third-generation hybrid technology, marking the first time the brand pairs a compression-ignition engine with a high-voltage electric motor. Currently only technology is offer only in a gasoline version of its S-class flagship badged as the S 560.
Besides reducing CO2 emissions, the system offers a torque boost and improves the cars' climate control equipment because of its extra electrical power.
The 90-kilowatt electric motor adds 440 Newton-meters of further torque. Total system torque is to 700 Nm at just 1,400 revolutions per minute. "That takes us right into performance car territory. With the right technology, the diesel has a future - improving it is better than banning it," Mercedes development chief Ola Kallenius said at the Geneva auto show earlier this month, referring to potential diesel driving bans in German cities.
The high-voltage electrical system supplies the electric refrigerant compressor and the high-voltage heater booster, as well as the powertrain components, allowing customers to quickly cool or heat the vehicle before entry.
The plug-in hybrids can drive for 50 km (30 miles) in emissions-free, all-electric mode, Mercedes said.
Mercedes did not release information about fuel consumption, price or future markets. The two models are currently in the process of undergoing their certification for type approval in Germany.
By switching from a lithium-iron phosphate chemistry to one employing lithium-nickel manganese, Daimler said it could increase the energy density of each cell to 37 ampere hours from 22 previously. This means that the battery pack, built by Daimler in Kamenz, Germany, was able to extend its capacity to 13.5 kilowatt-hours without increasing its size.
Mercedes' previous generation of hybrid battery technology only offered 8.7 kWh, giving models such as the S 500 plug-in that launched in 2014 a range of just 33 km under the NEDC test cycle.
While Mercedes is betting on plug-in diesels, other automakers are avoiding the technology because it is expensive to add a high-voltage drivetrain to an already costly diesel engine, pushing up the car's retail price.
Moreover, the added development, testing and validation costs are high because of low diesel demand in major markets outside of Europe, such as the U.S. or China.
Audi sells the Q7 large SUV as a turbodiesel with a plug-in option
Volvo launched a diesel plug-in hybrid in 2012 in the V60 but is switching its plug-in technology from diesels to gasoline versions with the launch of the new V60.
Peugeot sought to benefit from increased demand for low CO2 cars with hybrid diesel models that were less expensive because they did not have plug-in systems. But sales were low and Peugeot said in 2016 it was dropping diesel hybrids. Instead the automaker will introduce gasoline plug-in hybrids starting next year.
Mercedes, however, expects there will be demand for the cars among its customer base. "We firmly believe in the diesel and we are bringing the diesel plug-in because we are convinced it's a fantastic offer for customers," said Mercedes sales and marketing chief Britta Seeger.