When Jaguar first started showing off its 2010 XKR and XFR earlier this year, we were pretty excited. After all, both cars would now get 90 extra horsepower stuffed into bodies we already liked for their the handsome British looks.

We weren’t the only ones. Most of the press seemed to latch on to the new 5.0-liter V8 engine and didn’t pick up on the other improvements that make these two R-cars all-around performers. Jaguar has picked up on this and is going across the country to give the XKR and XFR a proper introduction.

It’s a seven-city journey called the Jaguar Legendary Performance Tour. This invite-only occasion allows Jag owners as well as owners of competitor cars to come out to local raceways across the country and put the R-cars through the ringer. Didn’t get your invite in the mail? Don’t worry Jaguar let us smoke the tires on the 510 hp XKR and XFR at Palm Beach International Raceway before the guests had a chance to flog them.

We’ve already spent time with the 2009 versions of the XF and even the XKR, and there are very few cosmetic changes for the 2010 model year. This doesn’t concern us much because the XF was band new in 2009, and the XK is only a few years into the redesign. Besides on the R-cars, it’s what is under the skin that counts.

Both the XKR and the XFR received three main upgrades:

- 5.0-liter AJ-V8 gen III engine Jaguar says it’s all-new, and we have no reason to doubt them. In both cars it’s supercharged to 510 hp. It’s a silky smooth beast; imagine a bull made of wool.

- Active Differential Control Unlike traction control systems that apply the brake or cut power to assist the driver, this rear differential will just shift more power to the wheel that needs it.

- Adaptive Dynamics A computer takes takes readings from the steering wheel, brake pedal and accelerator pedal, and adjusts the suspension accordingly 500 times per second. It keeps the cars from bowing in corners, and more importantly, it keeps the tires more firmly on the road.

All three features were highlighted in two courses Jaguar created at the raceway: a full-length track circuit and a shorter autocross course. The autocross was the first place where Jaguar’s suspension improvements really showed up. Jag set up a 0-60-0 mph test area and had us try out both cars. The V8 puts out a 461 lb-ft of torque, and when that’s summoned from a dead start, the result has the potential to be a tail-wagging disaster. For example, our Dodge Challenger SRT8 had 420 lb-ft at peak, and while we had a fun time, we also had to clear the lane next to us on a hard launch. That’s not the case with Jaguar’s Active Differential Control. When both cars were launched hard, there was just the slightest hint of wanting to go sideways, but before anything happened ‘poof!’ it was gone. No explanation or correction needed, just smiles as the R-cars took off down the track.

The Adaptive Dynamics system started to show itself on the circuit track. The standard “slow in, fast out!” chant of the race driver was interrupted because the weight shift was not as dramatic as expected. The car is constantly analyzing the situation, which means the situation is always ideal -- Taking a corner too hard? The suspension has already adjusted before the driver has to let off the accelerator…Going through a ninety-degree turn? How about a little controlled overseer to bring the car around. Forget sat nav, this is the kind of technology for real drivers.

So Jaguar figured out how to get back on the track, but now these cars are no good on everyday roads, right? Well to our surprise the XKR we took out on the road calmed down and behaved like a regular XK on the roads. No buttons to push or knobs to turn, the car just decided it would go back to the normal softer (but still capable) feel of a standard Jag. Even the exhaust note we enjoyed on the track was calmed down thanks to a noise valve that only open at full throttle. Talk about a sleeper car.

Jaguars new R-cars may just be the new definition of sports luxury. For example the BMW M5 does 0 to 60 in 4.1 seconds vs. the XFR’s 4.7. But as a daily driver, there are plenty of days we’ll gladly trade in the spinal adjustments needed from the M5’s suspension for an extra 0.6 second.

Jaguar, we are impressed.