Decoupling the engine from the driveshaft enables the car to cruise for miles on battery power alone, until it reaches a depletion stage that requires the engine to silently restart.
Engaging clutch in hybrid’s powertrain separates engine from rear axle.
DETROIT – Buyers of the ’13 Mercedes-Benz E400 BlueTec hybrid-electric vehicle in the U.S. and E300 BlueTec in Europe will be able to go “sailing” in their cars.
Both sedans were unveiled at the North American International Auto Show here this week.
A feature of Mercedes’ new HEV technology is a clutch in the powertrain that separates the engine (a 3.5L gasoline V-6 in the U.S. and 2.2L I4 diesel in Europe) from the rear axle.
The driver on a straight road or slight down slope at a cruising speed of, say, 62 mph (100 km/h) can tip a paddle on the steering wheel, take his foot off the accelerator and allow the electric battery to power the 20-kW (27-hp) electric motor to cruise along.
Without this feature, the E-Class decelerates when the driver lifts his foot off the accelerator, regenerating electricity for the lithium-ion battery, says engineer Michael Weiss, strategic project manager-hybrids.
But by decoupling the engine from the driveshaft, the car can cruise for miles on battery power, alone, until it reaches a depletion stage that requires the engine to silently restart, take over the torque responsibilities and generate electricity for the battery.
“The first idea for sailing came up in 1997 or 1998,” Weiss says. But the first Mercedes hybrids, the S-Class and M-Class variants, couldn’t offer it because their architecture was different.
The E-Class has an electric air-conditioning compressor and electric power steering so that even when sailing all comfort and safety features remain.
The new hybrid system was developed to precisely use the same components with either gasoline or diesel engines. “The only difference is the mounting ring that connects to the engine,” Weiss says.
Thus, Mercedes will benefit from higher volume by having the same system for both sets of customers. In Europe, 80% of E-Class buyers prefer diesel, while gasoline is the standard in the U.S.
The diesel E300 BlueTec is rated at 109 g/km of carbon-dioxide emissions, or 57 mpg, on the European driving cycle, while the gasoline-powered E400 is rated at 27 mpg on the U.S. driving cycle.
The controlling electronics and lithium-ion battery occupy the HEV’s engine bay, so the trunk space is the same as the regular E-Class cars.
The packaging means variants of the platform can be made without difficulty. The hybrids are built on the same assembly line in Germany as other E-Class products.
Distribution of the Mercedes E-Class hybrids begins later this year in North America and Europe, and the gasoline version will be exported later to Japan and China.