It’s true what car commercials say: Vehicles have personalities. Minivans are sensible, red Italian sports cars are sexy, and S.U.V.’s are intimidating. And their identities aren’t just conveyed by boxy or curvy lines, practical or flashy paint jobs, but in the way they drive and handle. After all, you wouldn’t expect a Buick to have the same taut feel as a BMW.
 
Then there are cars whose personalities can almost magically morph.

In the early 1990s, G.M. created the Corvette ZR-1 coupe, which put out a then-impressive 375 horsepower in the hands of the owner. But when operated by a parking attendant (or teenager), the aluminum V-8 engine was effectively sedated, with half its valves and fuel injectors shut down. Some cars come with a “valet key” that locks out the trunk or glovebox. The Corvette’s locked out part of the car’s power.

While that trick is still a novelty, today a handful of manufacturers, including Bugatti, BMW, and Subaru, are in the multiple-personality game. And, as the fast growth in microelectronics gives automakers more power to control more functions, expect to see more of them.

Microprocessors stuffed with carefully crafted software now control every facet of a car’s on-road performance. The engine, transmission, suspension, and other systems have their own digital brains, intensively programmed to deliver the right blend of performance, economy, and safety. Computers can adjust the suspension to make a bumpy road feel smoother; they can override a driver’s steering if it will put the car into a skid. But more than that, each model in a modern carmaker’s lineup has different software to make the car conform to its personality—powerful, fast-braking, cushy. So why not combine different options in one vehicle?

As one engineer for an American carmaker said to me in passing a few years ago, “Just by changing the software, I could make a Ferrari drive like a 20-year-old minivan with a bad spark plug.”

But multiple-personality cars mostly offer more, not less, performance. Take the $1.4 million Bugatti Veyron. A button allows the driver to switch it to Handling mode, which drops the car’s body closer to the ground, reducing drag. (Between 135 and 230 miles per hour, the Veyron automatically goes into Handling mode.) More dramatic is what happens when you stop the car, insert your key into a slot on the floor near the driver’s seat, and visually confirm all the car’s changes against a prelaunch checklist. The result: Top Speed mode, which lets the car go more than 235 miles per hour—assuming you have lots of road, and lots of insurance.

Then there’s the M6, BMW’s sportiest coupe. A steering-wheel button marked M lets drivers toggle among several preset performance profiles, from standard to aggressive. The owner can also use the car’s iDrive menu system to program his or her own combinations, mixing three settings for engine power and throttle response, 11 for the transmission, and several others for additional variables.

Subaru, meanwhile, is the first to bring such a system to the mass market. The BMW M6 costs roughly $100,000, whereas the Subaru Intelligent Drive system, or SI-Drive, will appear in almost every car it makes—starting below $20,000. It’s a standard fitting on three models this year, and more will follow next year.

Subaru has always been something of a Jekyll and Hyde company: Its prosaic, sensible, all-wheel-drive Outback wagons sit in showrooms alongside the blindingly fast, road-holding WRX sedans developed through years of off-road rallying. Now its sensible-car owners can have the acceleration and handling of the sportier cars—when they want it.

Twist a rotary dial on the console to choose one of three modes: Intelligent, Sport, or Sport Sharp. Depending on which you opt for, the software revises settings for the engine control, automatic-transmission shift points, and throttle response.

Intelligent mode cuts maximum power by roughly 20 percent, and gives a smoother feel, ideal for navigating a commute. It also improves real-world fuel mileage by as much as 10 percent, Subaru says. (Federal mileage tests can’t handle cars with multiple personalities, so Subaru’s claim hasn’t been independently verified.)

Sport mode sharpens throttle response to favor acceleration and power. This one’s meant for freeway and suburban driving, or hilly terrain. Finally, the Sport Sharp mode gives you instant power. It’s useful for passing—and, presumably, for drag racing. The mileage? Not so good.    

It’s not simple to design multiple personalities for cars. The challenge for Subaru engineer Toshio Masuda lay in the fact that offering three performance profiles requires three times as much software development. Each mode had to be carefully tested for anomalies—the lurches, rough shifting, engine hiccupping, and other strange behaviors that could spoil the driving experience. But with a foundation built, the company plans to adapt it to other functions, like adaptive cruise control, which keeps the car a safe distance from the vehicle ahead. Intelligent mode might have you follow at a conservative distance, while Sport Sharp could keep you closer for easier passing.

Actually, software hacking to improve a car’s performance is hardly new. The back pages of car magazines are brimming with ads for replacement chips that can change engine-control software. They all invalidate a car’s warranty; some also violate emissions laws. But they sell well to a generation of hot-rodders that’s as comfortable with electronics as with wrenches.

Carburetors? Distributors? Manual gearboxes? Ha! Welcome to the digital driving future.