On the Trail in an XC90
Last week I had the chance to drive Volvo's latest version of its XC90 SUV, a V8 powered model, which will be available after the first of the year. Engineers designed a new, compact V8 to fit within the existing engine compartment in order to preserve the crash impact crumple-zone structure. The vehicle is also equipped with a new 6-speed automatic transmission and improved electronic all-wheel drive system, which delivers 50% more torque and power to the rear wheels in half the time, compared to its predecessor.
Responsiveness of this new drive train was apparent in a test drive along the Apache Trail--a narrow, mostly dirt track, with a few guard rails, climbing the canyon walls around Apache Lake, Arizona. My automotive press driving partner and I started out on the trail from the eastern end at Roosevelt Dam. The paved road immediately reverted to dirt as I headed out of the parking lot. The twisting road was so narrow, in fact, that I wondered if we had missed signs marking it as one way only—a thought quickly dispelled by the appearance of a UPS truck headed toward us! Needless to say, attention and courtesy of those one the trail allowed a two-way flow of traffic that included surprised seniors in big sedans and SUVs towing pontoon boats.
After my partner took over, I was able to enjoy the scenery more. At one point, I looked down over the edge and saw the rusted hulk of a car at least 50 years old that never was recovered. (Back at our hotel we were told of a van that had tumbled off the day before, closing the road for half a day.) But to point out the mettle of the auto press, all of a sudden my partner pulls over at a small overlook to let one of the other XC90s pass. "I'll let her by," he said, as respected journalist and former racer, who I remember watching in the '60s, Denise McCluggage powered past.
As for the test drive, it was transparent to the driver how the electronic power train control system ties the components seamlessly together in negotiating the grades, varying surfaces, and blind hairpins on the trail. Project Manager Johan Tollmén says the CVC (Complete Vehicle Control) software regards the engine and transmission as one unit, tying their separate controllers, via CANbus, to function as one. For example, a specific gas pedal angle will usually result in the same engine torque-- the system figures out the best gear and engine output to effect the result under the vehicle's current conditions. The CVC also balances performance and fuel consumption. For towing, the LDS (Load Dependent Shift) function takes torque, acceleration, and gear inputs to calculate the best shift points.
Finally, while such control functions are the system's main purpose, Tollmén notes about half of the system's code is not for control but unique Volvo-developed diagnostics to monitor and maintain system, and vehicle, "health."
Loading comments... Write a comment