This 4Motion system will also be the only drivetrain offered in the U.S.; there will be no two wheel-drive variant and we will not get the more-capable 4XMotion drivetrain offered elsewhere in the world with its heavy-duty transfer case. While 4Motion isn't as capable off-road, Volkswagen says most of its U.S. buyers won't know the difference and the Touareg Hybrid will be just as capable off-road as the non-hybrid variants.
The beauty of the Touareg Hybrid's powertrain really comes from the computer that controls it. Because the electric motor can fully decouple from the gasoline engine, the Touareg Hybrid can leave from a stop and operate under EV power up to 31 mph thanks to a 288-volt, 1.7 kilowatt-hour Nickel-Metal Hydride battery that replaces the under-floor storage in the cargo compartment. As the electric motor reaches its limits, the torque converter between it and the transmission begins to slip, allowing the electric motor to spin up and act as a starter for the gasoline engine by closing the dry clutch. Once the gasoline engine is started, the dry clutch closes and the torque converter slowly locks back up to meld the two motors seamlessly. In normal driving, the whole process takes just 0.7 to 0.8 seconds, though it can be done in as little as 0.4 to 0.5 seconds when Sport Mode is engaged.
Because the gasoline motor can be restarted so quickly, the computer can shut it down any time it's not being used. While many hybrids will only shut off the gasoline engine at stops, the Touareg Hybrid will shut its engine down whenever possible, even while you're driving down the road. Volkswagen calls this a "coast" mode, and it typically activates whenever you take your foot off the gas. The electric motor will bleed off a small amount of power to keep the vehicle's electrics going, then fire up the gasoline engine again as soon as you put your foot back on the gas. This allows the engine to shut down long before you reach a stop sign or red light, or even just while slowing down for traffic, maximizing efficiency. Volkswagen says the coast feature will even work at speeds up to 99 mph, though using Sport Mode will reduce its operation to speeds under 44 mph.
Far more impressive than the drivetrain's engineering, is how smoothly it goes about its business. Around town, the shut down and restart of the gasoline engine is barely detectable-- usually only noticeable at all when accelerating from a stop, where we found it typically occurred around 13 mph under normal driving. Out on the highway, the only way to tell if the gasoline engine is on or off is to glance down at the tachometer, its engagement and disengagement from the drivetrain is completely unnoticeable. Even more exciting is the fact that this technology is easily scalable, so Volkswagen will have little trouble adapting it to other models. Indeed, the Jetta Hybrid prototype uses the same technology in a transverse layout.