As it's gradually made its way from sexy grand tourer to ferocious performer, the Jaguar XK's learned some lessons from the sportscars that live across the English Channel--and even across the Atlantic. First it got the body structure it needed in its 2007 redesign; then in 2010, it adopted (some say it engineered) a new 5.0-liter V-8 with some strong resemblances to the one in today's Ford Mustang that changed its tone entirely, from polite to a lot more urgent.
The base XK convertible and coupe keep that normally aspirated, "5.0" for the 2013 model year, carrying over its 385 horsepower and 380 pound-feet of torque, sending the force through the rear wheels via a six-speed ZF automatic transmission with paddle-shift controls. It's a vocal, jolting powerplant that has a distinct American rumble in its exhaust and an authoritative snap off the line--some of the credit for which goes to the gearbox, the workhorse of luxury cars everywhere. You'll befuddle a bunch of Shelby fans when you brrrap by in the XK, and get addicted to its muscular thrusts to 60 mph in a stated 5.2 seconds. Top speed is pegged at 155 mph. The shifts happen quickly, about as quickly as a dual-clutch unit, Jaguar says, and snow- and sport-shift modes are calculated into the 'box's selectable shift models. Stay in normal to avoid some twitchy responses in town, and the XK will feel alternately serene and snarly.
It's still delightful to drive, even as its dynamic capabilities have grown. The ride's controlled, with the right give for highway cruising and the tight reflexes, flat cornering and neat tracking needed for hard charging. That's due to the Adaptive Dynamics suspension, a set of adjustable shocks that do yeoman's duty honing down the worst of the road's surface irregularities, without sending too much reverb into the body structure. The XK's steering is reasonably quick and somewhat light; the brakes are exceptionally easy to modulate and let the driver know exactly what's left in them.
Throw some heat on that equation--well, really, a supercharger--and you're talking about the XKR, the 510-hp relative of the XK. With 461 lb-ft of torque and most of the same mechanicals, the XKR's 0-60 mph times drop to 4.6 seconds, and the jaw factor drops a couple more degrees. It's a stunningly quick grand tourer with supreme loafing capability at 2500 rpm, and bracing acceleration at any engine speed. Its adaptive suspension is tuned more firmly, and though it's shod with 20-inch wheels and tires, it feels always ready to overpower them to the point of electronic intervention. Top speed is 155 mph, but with an optional Dynamic Pack, it rises to 174 mph, while it also gets aero add-ons like front and rear diffusers, a rear spoiler and side sills, as well as the even more specific suspension tuning of the next model up in the ladder. To call it all out, the Dynamic Pack XKR gets red-painted brake calipers and its own 20-inch "Vulcan" wheels.Need more? Then sample the limited-edition XKR-S, the Jaguar that goes where no Jaguar has gone before. With the XKR coupe's kit as a starting point, Jaguar tweaks fuel delivery and lifts some of the restrictions on the exhaust system to lift total output to 550 horsepower. New estimates put 0-60 mph times at 4.2 seconds, and top speed at 186 mph. The adaptive suspension is reprogrammed for more damping in dynamic mode, along with quicker shifts and sharper throttle response, while spring rates are up 28 percent. The active differential modulates power between wheels as traction needs arise, and this version gets its own steering geometry for claimed improvements in steering response and precision. Finally, the Jaguar four-mode stability control is remapped for more wheelspin, a complement to the exhaust valving that gives this XK a roaring motorsports soundtrack. Top speed is 186 mph.
If you thought the XKR was the incomparable peak of power, wait until you hear the XKR-S bellow through its mostly unrestricted exhaust. We're not sold on the steering changes--it's very fast but also very light--but the unflappable XK chassis feels even more so in this very exclusive edition, vaulting it into collectible status just as quickly as it catapults off the line. We've smoked tires around the most treacherous sunny-then-shady California switchbacks in one to find out the truth: You'll choke at your own price limits before you exhaust the ones that bind the XKR-S to the street.