In December 2011, the Cross Coupe plug-in hybrid concept vehicle was unveiled at the Tokyo Motor Show. Now, just a few months later at the 2012 Geneva International Motor Show, the all-wheel-drive Cross Coupe is set to make another appearance—this time as a TDI® Clean Diesel-powered plug-in hybrid concept.
The Cross Coupe is based on the Volkswagen Group’s new Modular Transverse Matrix (MQB) and demonstrates the large breadth of variations that can be implemented within the MQB. Already shown with a “conventional” hybrid with two electric motors and a direct-injection turbocharged gasoline (TSI®) engine in Tokyo, this new study of the Cross Coupe incorporates more MQB-specific elements, such as the new EA288 TDI® Clean Diesel engine, seven-speed DSG dual-clutch transmission and MQB-sourced front and rear suspension.
An efficient, fun-to-drive car
The Cross Coupé accelerates from zero to 60 mph in just 6.5 seconds, and its TDI® engine develops maximum torque of 295 lb-ft from approximately 1600 rpm. Nearly instantaneously, the two electric motors deliver 133 lb-ft of torque in front and 199 lb-ft at the rear. During boosting—which involves full use of both motors and the engine—the drive system supplies up to 516 lb-ft of torque.
The Cross Coupe can travel up to 28 miles at nearly 75 mph in pure electric mode. Only the rear wheels are driven in this mode; the turbodiesel and front electric motor are decoupled by disengaging the clutch to the drivetrain, and they are shut off. The clutch on the gearbox side remains closed, and the seven-speed DSG is engaged. The driver can drive for longer stretches in electric mode (provided that the battery has sufficient charge) by simply pressing a button next to the gearshift grip. As soon as the power of the TDI® is needed again, the engine engages and it is once again actively coupled to the drivetrain within fractions of a second.
In pure electric driving, the rear electric motor is powered by an eight-module lithium-ion battery with an energy capacity of 9.8 kWh. Electronics integrated into the front engine compartment manage the flow of high-voltage energy to and from the battery and the electric motors. Meanwhile, the 12-volt electrical system is supplied with power via a DC/DC converter. The battery can be charged either from an external 230V power source or while driving.
The Cross Coupe in Motion
While on the road, the driver can choose from a total of five driving modes: City (ECO mode with minimal fuel consumption); Sport (high dynamic performance); Off road (continuous all-wheel drive); E-mode (pure electric drive); and Charging (via the TDI® engine). The Cross Coupe performs in different operating states, in which the motors/engine and drive axles are coupled or decoupled as a function of driving needs:
Zero emissions: In pure electric mode, only the rear axle is driven. The TDI® and the front electric motor are decoupled from the drivetrain and shut off.
Zero emissions by “coasting”: As soon as the driver lifts his or her foot from the accelerator, both electric motors and the engine are shut off and decoupled from the drivetrain—provided that the battery is sufficiently charged. This is referred to as “coasting”.
Zero emissions in battery regeneration mode: If the driver takes his or her foot off the accelerator or brakes, and the battery is not sufficiently charged, the two electric motors act as generators to feed energy recovered from braking into the lithium-ion battery. The TDI® engine is also shut off and decoupled in this operating state.
Boosting: During enthusiastic, sporty driving, the electric motors give an extra boost of power to the TDI® engine. The Cross Coupe is driven by all four wheels in this mode.
Off road: As soon as the driver chooses to activate “Off road” mode, all four wheels are once again driven. However, in this mode the front electric motor, now supplied with energy by the TDI®, is the sole source of electrical power for its counterpart at the rear axle. This is referred to as an “electric propshaft”, as the energy for the rear electric drive is by wire and does not flow mechanically. Since the TDI® powers the rear electric motor via the front electric motor in Off-road mode, the all-wheel-drive system is fully functional, even if the lithium-ion battery is insufficiently charged.
Driving with the TDI®: When powered solely by the TDI® engine, the Cross Coupe functions as a front wheel-drive vehicle; its battery is charged via the front electric motor. When all of the on-board energy reserves are utilized, the vehicle’s 14.5-gallon fuel tank allows for a theoretical driving range of 800 miles.
A New TDI® for the Cross Coupe
The TDI® used in the Cross Coupe is an engine developed especially for MQB—the 2.0-liter EA288. Low-emitting, fuel-efficient and torquey, this engine is also exceptionally refined and smooth running. Twin balancer shafts with anti-friction bearings are used in the EA288, eliminating system-induced free inertial forces that naturally occur in a reciprocating engine. The toothed belt drive for the oil and vacuum pump and the engine’s encapsulated injection nozzles have a positive effect on acoustics.