To most, an engine boasting 300 horsepower and 303 lb.-ft. of torque is more than adequate. However, there are certain folks for whom those seemingly lofty figures simply won't suffice. For them, Jaguar offers the 2007 XKR. Using the XK's 4.2-liter, 32-valve V8 with variable-valve timing and dual overhead cams, the XKR adds an Eaton supercharger boosting horsepower up to 420 at 6,250 rpm with torque climbing to 413 lb.-ft. at 4,000 rpm. A six-speed manually-interactive automatic transmission with a sport mode and plastic paddle shifters delivers the goods to the rear wheels. Weighing in at 3,671 pounds (154 pounds lighter than the previous XKR), Jaguar claims the XKR coupe will reach 60 mph in 4.9 seconds; the 3,781-lb. convertible (220 pounds lighter that its predecessor) barely lags behind, screaming to 60 in five seconds flat. More important, at least for anyone who drives outside the confines of a drag strip, are the supercharged XKR's improvements over the normally-aspirated XK when accelerating at speed: 60 – 90 mph is achieved 30 percent quicker and 50-70 mph is achieved 25 percent quicker. Top speed is electronically limited to 155 mph, though pedal-to-the-aluminum runs suggest such a figure relegates gobs of velocity to the unavailable reserves.

Standard Dunlop rubber reads 240/40R19 up front and 275/35R19 on the rear, backed up by larger ventilated discs designed to increase effectiveness and fade resistance. Aiding in the effort are ABS, electronic brake-force distribution, and electronic brake assistance systems, while revised traction and stability control technology works in conjunction with a sport-tuned suspension to keep the XKR's four feet planted on terra firma. Compared to the relatively tame XK, the 2007 Jaguar XKR's front and rear springs are 26 and 38 percent stiffer, respectively, the shocks are 25 percent stiffer, the anti-roll bar grows in circumference by one millimeter, and a rear structural brace is positioned behind the seats. The XK's adaptive variable suspension has been retuned for XKR use, as has the Servotronic rack-and-pinion variable-assist steering system.