Volkswagen unveils mid-size SUV plug-in diesel-electric hybrid concept at Detroit Show
14 January 2013
|Powertrain of the CrossBlue SUV PHEV concept. Click to enlarge.|
Volkswagen unveiled the CrossBlue SUV concept at the North American International Auto Show. Developed specifically for US and Canada, the six- to seven-seat midsize crossover CrossBlue is targeted at the rapidly growing mid-size SUV segment, and would sit in the Volkswagen SUV lineup above the Tiguan and below the premium Touareg.
Built off of the MQB Modular Transverse Matrix components set (earlier post), the CrossBlue offers a manufacturer-estimated 35 mpg (6.72 l/100km) combined (37 mpg highway and 33 mpg city), 89 mpge (2.64 l/100km equivalent) in electric mode, and an all-electric range of up to 14 miles (22.5 km).
|The CrossBlue concept. Click to enlarge.|
The CrossBlue plug-in hybrid powertrain mates a TDI Clean Diesel engine with two electric motors, a DSG dual-clutch transmission, an electric all- wheel-drive system that is dubbed “propshaft by wire”, and a 9.8 kWh Li-ion battery mounted in the center tunnel. The powertrain produces up to 306 hp (228 kW) and 516 lb-ft (700 N·m ) of torque: 0 to 60 mph is estimated to take 7.0 seconds.
With a fully charged 9.8 kWh lithium-ion battery, the CrossBlue can achieve an all-electric distance of up to 14 miles in all-electric mode; to achieve optimal driving range, the top speed is reduced from 127 mph to 75 mph. The overall driving range is 661 miles if the 18.5-gallon fuel tank is filled.
The CrossBlue offers a number of driving modes: the default mode is as a classic hybrid. The electric motor is used for propulsive power as often as possible in this situation. The driver can also switch to “Eco” or “Sport” modes by pressing a button to the right of the shift lever.
In Eco mode, parameters such as the throttle map and air conditioning are controlled for minimal fuel and electrical consumption. In Sport mode, the drive system’s maximum power potential is exploited. Other available modes are: offroad, where all-wheel-drive is permanently engaged; charging; and EV mode (E-mode), where it drives as an electric vehicle.
In E-mode, only the 114-hp rear electric motor propels the vehicle and the TDI engine is shut off and decoupled from the drivetrain. Even at speeds of up to 75 mph, the internal combustion engine is not engaged as long as the battery has sufficient charge. As soon as there is a need for TDI power, it is coupled to the drivetrain again, jolt-free, within fractions of a second.
The power electronics unit integrated in the engine compartment operates at a level of around 370V and manages the flow of high-voltage energy to and from the battery and the electric motors. A DC/DC converter supplies the vehicle’s electrical system with the 12V power it needs. The battery can be charged either by external power sources or by the TDI engine while the vehicle is in motion.
The driver can intentionally switch over to a charging mode by pressing another button on the center console. This charges the battery via the TDI engine while driving to store enough electrical energy in the battery for EV operation later in the journey—for example, in an urban area.
There are also a number of other specific modes that automatically come into play, depending on the circumstances:
Coasting: As soon as the driver releases the accelerator pedal, the engine and electric motors are decoupled from the drivetrain, provided that the battery is sufficiently charged. This is referred to as “coasting.” No emissions are generated.
Battery regeneration: Whenever the driver releases the accelerator pedal or applies the brakes, and the battery is insufficiently charged, the two electric motors act as generators and feed energy recovered from the brakes into the lithium-ion battery. In this case, the TDI is also shut off and decoupled from the drivetrain to ensure maximum regeneration.
Boosting: When very sporty performance is required, the electric motors form an alliance with the TDI engine known as “boosting”: in this mode, all four wheels are driven.
Offroad (“propshaft by wire”): All four wheels are also driven whenever offroad mode is intentionally activated. In this case, however, the front electric motor—which is now supplied with energy by the TDI engine—operates exclusively as a generator and a power source for the electric motor at the rear. Since the energy for driving the rear wheels is electrical rather than mechanical, this is referred to as “propshaft by wire”. Because the TDI engine drives the front wheels in offroad mode, the four-wheel-drive system is still operational even when the battery doesn’t have much charge.
TDI only: When the TDI is the sole source for propulsive power, the CrossBlue is a pure front-wheel-drive vehicle.
This vehicle brings together MQB elements that could underpin a future generation of SUVs, such as the front and rear suspensions; the 190 hp TDI diesel engine from the new EA288 family; and a six-speed DSG dual-clutch automatic transmission. These components are combined with electrical parts that are also “made by Volkswagen,” such as the lithium-ion battery in the center tunnel and the 40 kW (54 hp) front and 85 kW (114hp) rear electric motors.
Volkswagen also showed a Cross Coupé compact SUV concept equipped with a similar powertrain concept, showing the extent of the MQB’s modularity. The Volkswagen executives presenting at the reveal hinted very strongly about the production prospects for the mid-size SUV.
The CrossBlue was designed in Germany under the leadership of Walter de Silva (Head of Design, Volkswagen Group) and Klaus Bischoff (Head of Design, Volkswagen Brand), with close coordination with Volkswagen of America.
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