Volkswagen Touareg Hybrid Hooked to 8-Speed Automatic Tranny

November 6, 2010/Steve Tackett


American car buyers want gas-fueled vehicles that are also more efficient. Volkswagen offers buyers the 2011 Touareg Hybrid with 7,700 pounds of towing capability and 40 percent better fuel economy over the V-6 gas engine model.
“We want to offer a car for a customer who wants a gasoline car,” explained Touareg hybrid project manager Bernd Stiebels.
But “regular” hybrid designs, of the style typified by the Toyota Synergy system in the Highlander Hybrid, didn’t suit Volkswagen. The Toyota hybrid-style system uses a Continuously Variable Transmission to transmit power to the road, however many demanding drivers dislike the driving characteristics of CVTs. Also, the power they can handle is limited, so CVT-equipped vehicles have reduced towing capacity.
In the case of the Highlander Hybrid, the maximum towing capacity is 3,500 pounds. In this design the electric motor must work for the transmission to function, and hard work will soon overheat the electric components.
Volkswagen — and its technical partner Porsche — opted for a layout that places the electric drive motor between the gasoline engine and a conventional 8-speed automatic transmission with a torque converter. A computer-controlled clutch between the gas engine and the electric motor can disconnect the two, letting the Touareg roll on electric power alone at speeds up to 32 mph on flat ground. It will go as fast as 75 mph in electric mode on downhill slopes.
Press the E-Mode button on the console and the Touareg will whoosh noiselessly around the neighborhood.

Touareg hybrid underhood

The company recognizes that customers want to be able to play with their electric gadget, so adding E-Mode made sense, even if it doesn’t actually contribute to the Touareg’s fuel use because all the energy in its batteries comes from its gas tank at one time or another.
“Part of the reason why people are interested in a hybrid is because it is new technology,” noted Martin Bratzler, product manager for Porsche’s version. “They want to see what is going on so we have E-Mode to help them experience that.”
But more importantly, for tough off-road service, towing, or other heavy-duty use, the gas engine can send power to the automatic transmission with or without some assist from the electric motor, permitting a towing capacity of 7,700 pounds. Maximum total power when the electric motor is boosting the gas engine is 375 horsepower and a very truck-like 428 lb.-ft. of torque.
This power launches the Touareg to 60 mph in just 6.2 seconds while achieving 21 mpg in city driving and 25 mpg on the highway, according to VW’s prediction of the EPA scores. The 2011 Touareg Hybrid is priced at $60,565.
A week of around-town driving confirmed similar results, a stunning turnaround from past gas-powered Touaregs that drank gasoline like they had holes in their tanks. Fuel economy on Touareg’s V-6 SUV are 14 mpg city and 19 mpg highway.
Even if the battery pack is depleted, by say, towing a boat trailer up a long grade, then is this case the supercharged 3.0-liter gas V-6 engine delivers 333 horsepower and 325 lb.-ft. torque to the wheels through a conventional 8-speed automatic transmission, hence the impressive towing capacity.
Programming the hybrid’s computer to know when and how much electric boost to give, or when decelerating how much power to regenerate for the nickel-metal hydride battery pack, was the VW engineers’ toughest challenge, reported Stiebels. That’s because the computer has to manipulate the clutch between the gas and electric motors with the finesse of an expert — a skill that is tough to program. Impossible, actually.
That is why VW gave the Touareg hybrid’s computer the ability to learn a driver’s habits over time, so it can deliver clutch action best suited to the driver’s preferences. A couple days in the car had me wondering if I’d been oversensitive to the Touareg’s hybrid activities, until I remembered that the car was learning as I drove it to tailor its actions to my driving.
The company’s impressive accomplishment illustrates that we remain in the dawn of the electric vehicle era and that there are many technical solutions available. So hybrids like the Touareg and Cayenne can offer dramatically different driving characteristics and capabilities from their competitors to deliver a superior alternative. — Dan Carney, Motor Matters

Copyright, Motor Matters, 2010