First Drive: 2010 Porsche 911 Turbo

Luckily, I know that the word "seitwärts" in German means sideways, because ask, and ye shall receive. At least five times over the course of two full-opposite-lock laps of the track, I thought we were headed off the track backwards. Judging by the occasional "oops" coming from the driver's seat, so did the he. But no, the Turbo refused it, gradually shuffling power forward and pulling the car through what seemed to be an unsaveable slide. Another new optional feature on the Turbo is Porsche Torque Vectoring, or PTV. This is a predominantly software-based system, unlike other torque-vectoring systems, which use active differentials to shuffle power from one rear wheel to the other. Porsche's system starts with an old-school, passive mechanical limited slip differential, and uses the car's brakes to help rotate the car. Yes, this sounds like stability control, but it's not. Stability control (including Porsche Stability Management, standard on all 911s for quite some time) is an aftertreatment: it helps keep the car on the driver's intended course once the limits of adhesion have been reached. PTV is, on the other hand, a performance-enhancing system that helps to avoid understeer in the first place. It looks at steering angle and lateral acceleration to predict that the car is about to understeer, and intervenes preventatively. If speed is below 100 mph, lateral acceleration is above about 0.8g and the car is about to understeer, the system applies a very light, largely imperceptible braking force to the inside rear wheel. This creates a yaw moment on the car, helping it to rotate and nixing the understeer. The difference was quite obvious on-track: in slippery conditions, where there wasn't enough grip to activate the system, the Turbo understeered. When it was dry, understeer was only very slight. PTV will also intervene on a quick-turn in: if it sees the driver heaving the wheel quickly, it'll activate the inside rear brake momentarily. It's like a friend in the passenger seat yanking the emergency brake lightly as you throw the car into a turn, but only on one wheel, and without the evil laugh or increased risk of death, dismemberment, and dissolved friendships. PTV is a simpler, lighter solution than fully active torque-vectoring rear diffs because it's mostly a stability control software-based system, and requires only a conventional limited slip. While PSM can be fully disabled, PTV remains active, as Porsche sees it as a performance-enhancing system rather than a slow-you-down slap on the wrist. It is, however, disabled when your foot isn't on the gas. Torque-vectoring seems to be a buzzword lately (appearing now in BMWs, Audis, Saabs, Mitsubishi Evos, and of course the original Honda SH-AWD system) but using the term for this system is a little misleading. "Porsche Preventative Understeer Management" (PPUM) would be a more apt descriptor.