With the U.S. such a key market for the 3 Series, accounting for more than half of all the BMWs sold in the U.S. since its introduction in 1976, BMW used the occasion of the North American International Auto Show in Detroit 9 to introduce the sixth generation of the 3 Series sedan and ActiveHybrid 3, dubbed the first full hybrid compact sport sedan in the premium segment.
The sedan has been stretched 93 mm (3.7 in) in length, creating 15 mm (0.6 in) of extra legroom for rear seat passengers and 8 mm (0.3 in) of additional headroom.
“To make the car longer was primarily interior space [reasons], especially in the rear,” said Udo Hanle, BMW Product Manager for the 3 Series, told AEI on the show floor Jan. 9. “In the [fifth-generation 3 Series], some people had problems getting into the car, having enough room for their seat for their knees. And so to increase the comfort of getting into and out of the car, we wanted to increase legroom, and that’s one reason for making the car longer.”
Significant changes were also made to the vehicle’s suspension.
“Our goal was to combine driving dynamics and comfort," Hanle explained. "Therefore we made changes in the suspension system in the way the suspension increases the force, and added special mounting points with increased stiffness in the rear and the front.
"Due to the stiffness, the suspension works also at small displacements. That’s one of our biggest steps against the E90. By changing the suspension and changing the mounting area to the body, this was one of the major things that we increased compared to the E90. We also have the adaptive suspension system in this car as an option.”
The ActiveHybrid 3 combines a six-cylinder gasoline engine and an electric drive to offer 335 hp (250 kW) and 450 N·m (332 lb·ft) of maximum torque as standard, while achieving 37 mpg.
Described by BMW as “not an ordinary hybrid,” the ActiveHybrid 3 offers 390 L (13.8 ft³) of cargo space, providing hybrid customers with full functionality.
BMW worked with A123 Systems on the battery and selected AHR32113 cylindrical cells due to their high power and excellent life under demanding duty cycles.
“It’s designed for lots of cycles—microcycles—because they’re constantly charging and discharging as you let off the gas or apply the gas,” said Jason Forcier, Vice President of Automotive Solutions Group, A123 Systems. “They’re designed for very high cycle life, short bursts of power. They don’t have that long energy capacity that you find in an EV. It’s definitely designed for power, fuel efficiency.”
Dr. Herbert Negele, Project Manager for ActiveHybrid 3, explained why A123 Systems was selected as supplier of the lithium-ion cells: “The A123 cells fit best in the space that we had available for integrating the battery without compromising trunk volume. We have a very tight package of cells. In that part of the car it also has to be very safe because it’s not too far away from the rear end. We were able, with the cylindrical cells, to get a very good crash performance with this battery. The chemicals of the A123 cell are a bit safer than the other suppliers.”
There was also no compromising when it came to maintaining engine performance despite the added weight of the hybrid system.
“You have additional weight with a hybrid system—about 140 kg—and the additional power from the electric motor helps us to equalize it,” Negele said. “So the driving performance is comparable to the 335i automatic. In some situations it is even better because we can fill when the combustion engine is not performing so good."