Porsche Carrera 911 X51 Power kit

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Porsche says the changes allow the X51 Carrera S to sprint from zero to 60 mph in just 4.4 seconds and continue on to a top speed of 186 mph, which is 0.2 second and four mph faste

An exclusive drive in Porsche's 2006 club coupe shows what the new x51 Power kit has to offer

Story by Pete Stout Photos by Rich Chenet

381 horsepower in a Carrera-based 911. According to Porsche, that's one more pony than last year's outgoing GT3 could muster. More impressively, perhaps, it's just 34 less than the twin-turbocharged 2001- 2004 911 Turbo offered. True, the “X51 power kit” option for 2006 Carrera Ss can't match the 415 lb-ft of torque produced by a 996 Turbo, but its 306 lb-ft at 5500 rpm shades the GT3's 285 lb-ft at 5000 rpm.

Any comparisons between an X51-equipped 997S and the no-frills GT3 are difficult, though. The platforms are simply too different. 996 GT3s are “lightweight” 911s intended for hardcore enthusiasts while X51 is offered on the Carrera S — a serious driver's Porsche that happens to have all the luxurious bells and whistles, too. The 997S comes standard with a 355-hp, 295 lb-ft flat six that displaces 3.8 liters. It's an entirely capable motor as-is, but X51 adds 26 headline-grabbing horses and 11 pound-feet of extra twist. The numbers aren't quite as impressive in percentage terms: it's a 7.3-percent gain in horsepower and 3.7 percent more torque. One must also note X51's $16,900 cost, which adds over 20 percent to the $81,400 911 Carrera S's bottom line.

So what is X51? Is it a good option for 997 buyers with a need for speed or the world's most expensive intake, exhaust, and remapped ECU? Before you think it's the latter, know that ticking the box marked X51 adds far more than a pair of new mufflers, a revised airbox, and different spark/ignition tuning. Revised cylinder heads, new exhaust headers, camshafts with more aggressive profiles, a different Varioram intake plenum, and new programming for the Bosch Motronic engine management are utilized to add more grunt to the normal Carrera S's 3.8-liter flat six. So the 26 horses and 11 lb-ft didn't come to Weissach so easily, after all.

Porsche says the changes allow the X51 Carrera S to sprint from zero to 60 mph in just 4.4 seconds and continue on to a top speed of 186 mph, which is 0.2 second and four mph faster than a normal Carrera S. But these differences are probably as academic in the real world as the percentage gains in power that this package offers. The real question, then, is this: Does X51 add something tangible to the driving experience?

To find out, we traveled to Porsche Cars North America's corporate headquarters in Atlanta, Georgia after PCNA offered Excellence the only official road test of its X51-equipped 2006 911 Club Coupe. Even better, it bravely coughed up a 2005 997 Carrera S for comparison purposes. And, as we walk up to the pair of new 911s, we can sense the answer to our power question is close at hand. What we don't know — and won't find out until we hit the superb, challenging mountain roads an hour or so north of Atlanta — is that the 2006 car packs a surprise that's got nothing to do with power.

For the time being, we're left to appreciate a rather pleasant surprise: Azurro California Metallic. It's a one-off hue that Porsche came up with for this special model, which celebrates 50 years of the Porsche Club of America. Just 50 Club Coupes will be made, and all of them will wear this shade of blue that, like the waters off California's coast it's named for, is highly sensitive to changing light. It shimmers mostly blue most of the time but there's more than a hint of green in it, too. It's an attractive color meant to recall 356s of the 1950s. And it does.

Club Coupe buyers get to pick their interior color (this car is bathed in Sand Beige leather) and add some options, but all Club Coupes get the X51 power kit, Sport Design 19-inch alloys, sport seats with nice bolsters, a shifter with a reduced throw, a thicker sport steering-wheel rim, and Sport Chrono Plus. Club Coupes also get a full-leather interior, a center console between the seats that's painted Azurro California Metallic, special door sills, black gauge faces, and a commemorative plaque with the car's build number within the edition of 50. The black gauge faces are an especially nice touch, as they're far more legible than the silver dials that are standard in the Carrera S. Luckily, it's a no- cost option for all Carrera S models, and one we'd highly recommend.

Walking around the Club Coupe, one might think the big X51 tip-off is the staggered sizing of the four tailpipes. But any 997S ordered with the optional Sport Exhaust system shares the same tips — so there are only two ways to be sure you're looking at an X51-equipped 997. The first is to pop the decklid and take a peek at the engine. Do so and you're confronted by a real carbon-fiber airbox in place of the black plastic item in plain Carrera S models. The X51 airbox uses two snorkel-like intakes that mate up with the engine lid when it's closed — instead of the lone snorkel used by the regular 3.8. Buried further back, but still visible, is the bare-metal intake plenum, which is noticeably different than the standard plastic unit. The other way to spot an X51 is to get down on your hands and knees; an X51 997S will be wearing sexier, beautifully bent exhaust manifolds to the Carrera S's utilitarian pipes.

Far more important, though, is whether or not the difference is noticeable from the driver's seat. So it's time to fire up the Club Coupe. It's a special thing to put No. 01 of 50 through its paces, and twisting the ignition the key clockwise and waking the enhanced 3.8-liter flat six is no disappointment. Hitting the “Sport” button ahead of the shifter activates the sharper throttle setting as well as more aggressive mapping for both the PSM stability management and PASM variable shock absorbers. It also alters this car's exhaust system for a sportier sound. Past experience dictates hitting the button to the left of “Sport” with an icon that looks like a shock absorber. Doing so keeps the Sport- mode throttle and PSM while using the softer suspension setup; the stiffer setup is generally too hard for anything but trackwork.

Trundling through a quiet Atlanta suburb on a Sunday morning, the first thing that's obvious is this: intake and exhaust noise are both noticeably altered from that of a normal 997S. Through the gears, it's a bit less grainy, a tad more refined. Even at 25-40 mph, this is hands-down the best voice in a 997 yet. Aggressive down low — without relying on the “flatulence” that plagues a normal Carrera S — the new sport exhaust system is a winner. It's hard to imagine an enthusiast who wouldn't love this 911's sound.

With the fluids properly warmed and a long onramp just ahead, it's time to put the X51 engine through its paces. In second gear and at full throttle, acceleration is strong — but then the same can be said for any Carrera S and even the 3.6-liter Carrera. The latest 3.8-liter 997s are powerful enough leave one wondering if there's much development potential left in the normally-aspirated flat six.

X51 answers that question convincingly, with a 997 Carrera S-like powerband that's as linear as it is strong. It offers good torque from just off idle all the way up to redline, but it can't match the GT3's top-end fervor. It feels slightly more “workhorse” to the high-strung GT3's thoroughbred. But, in a 911 more likely to be used every day than most GT3s will be, that's a good thing. The X51 3.8 offers tractable power everywhere, with plenty of good noises and enough zing to keep things interesting as it reaches for redline.

Does it feel faster than a plain Carrera S? Yes and no. No because it's tough to feel a seven percent power increase in a car that weighs more than 3,000 pounds and claims more than 350 horsepower. But informal roll-on tests in third and fourth gears later in the day saw the Club Coupe pull away from the 2005 997S slowly, but surely. It was exactly the difference you'd expect from a 26 hp/11 lb-ft advantage. Importantly, X51 gives up nothing across its powerband to the regular 3.8. Though its peak power and torque figures come 600 and 900 rpm later, the X51's powerband never dips below the 3.8's. Even from 1500- 2000 rpm, it has a useful, 15 lb-ft advantage.

People after the best horsepower-per-dollar equation might be happier spending their $17,000 on the aftermarket, but X51 has two edges that must be considered: (1) it maintains the factory's full warranty and (2) there's a sweetness to this engine that can't be quantified. The throttle response in the X51-equipped 2006 997S was plain superior to the 2005 997S we tried. The revised motor sings through its powerband with an alacrity one wouldn't know the standard engine is missing — unless he or she tried an X51. Gear after gear, pull after pull to its 7300-rpm redline, the X51 engine is considerably more satisfying than the normal 3.8 — which itself is no slouch.

Leaving the Insterstate and turning onto the superb driving roads around Cleveland, Georgia, the X51 motor continues to impress with its seamless power delivery, stunning flexibility, and willing character. Between the noise, power, and responsiveness, the thought Weissach might have designed the X51 setup first and then detuned the 3.8 for the plain Carrera S is inescapable. The production-line plastic used for the regular 3.8 liter's intake plenum suggests otherwise, but this flat six really is happier as an X51. It breathes more freely — as if it's been liberated and is ready to rock.

Paired with the stunning chassis that is the basis of every 997, this engine is well-suited for the work of devouring these Georgian roads. As challenging as some of the very best roads California has to offer — but with far better pavement — these twisty two-lanes carve their way up, down, over, and around the hills and mountains north of Atlanta. The 911 Club Coupe shines brightly on them.

As always, the mechanical, variable-ratio steering is pin-point accurate and makes dialing in the apex a nearly telepathic experience. Body movements are well controlled, and there's an organic feel to every input. As the realization that the 2006 Club Coupe's handling is nothing short of incredible filters in, another realization comes up: This 997 has PASM. It's a system Excellence and Autocar have criticized pointedly in 2005 997s. Our concern revolves around a disturbing mid-corner lurch in the rear end of PASM-equipped 997s — something that's just not there in this car.

Then we realize this is the first 2006 997 with PASM we've driven. Porsche AG will probably never admit a change has been made, but we suspect a revision to the rear suspension bushings. Olaf Manthey, a well-respected Porsche tuner based at the Nürburgring, says that the 997's PASM “lurch” can be eliminated by turning selected rear suspension bushings — meant to be hard in one direction and soft in another — 90 degrees. Porsche's solution is probably a better fix. We'll need to spend more time in 2006 997Ss — but, for the time being, our reservations about PASM and 997s appear to be obsolete.

Between the massive mechanical grip offered by 19-inch wheels and tires, the strong stopping power applied by the standard-issue Carrera S brakes, and the endless, addictive torque of the 3.8-liter X51 engine, the Club Coupe is flat fantastic. The torque out of turns is better than that of any modern, normally-aspirated 911 we've driven, and the ability to use all of it through the 295-mm wide rear tires makes us wonder why anyone would opt for a 997 Carrera 4/4S — unless they need to regularly deploy the 911's considerable power in inclement weather.

The Club Coupe demonstrates how good the current 997 Carreras can be. That might upset a lot of people because all 50 examples are already spoken for, but everything besides the Azurro California Metallic paint is available on any 2006 Carrera S. And a 997S with X51 might be the most satisfying 911 on sale right now — just as the 996 Carrera 4S was in many ways the driver's pick of the Carrera line in 2003 and 2004. We'd definitely add the thicker sport steering wheel ($800) and we'd strongly consider the PCCB ceramic-composite brakes ($8,150). Also attractive: Sport Chrono Plus ($920) and the adaptive sport seats ($3,055).

Less appealing is the normally optional short-shift kit ($765) in this particular Club Coupe. Maybe it's a fluke; the action is less precise than any factory short-shifter we can remember — and this car had only 135 miles on its odometer when we left PCNA's headquarters. Notchy comes close but doesn't quite describe its dissatisfying feel. There's an element of “rubbery” there, too. To be sure, the lever always finds the gate you're looking for, but it moves slightly sideways after getting into some gates. The standard shifter in the 2005 997S we sampled had longer throws, but they weren't excessive and the effort and precision were superior.

The only stumbling block to X51 is its high price. $16,900 is a lot of money to part with in order to get a Carrera S with an engine that's significantly sweeter but only marginally more powerful. Add that amount to the 2006 Carrera S's base price of $81,400 and you come up with $98,300 — and that's before adding the extras we've listed above plus the inevitable color, trim, and other options a buyer might want. In this light, then, all 50 of the $99,911 2006 Club Coupes are something of a giveaway.

That becomes painfully clear when we add up the 997S we described just a paragraph or two ago. Ignoring any other extras or color/interior options and adding only these performance-oriented bits, the MSRP swells to $110,915. Then there are gizmos that wouldn't be bad to have, like a factory fire extinguisher ($140), a rear-window wiper ($360), and the excellent, 13-speaker/325-watt Bose surround-sound system ($1,390). We'd probably better stop here, because — any way you cut it — this is a lot of coin for a Carrera-based 911.

So, in the end, it all comes back to the numbers. For sensitive drivers without a budget, the X51 package is currently the best path to a more satisfying 911. For those who are on a budget, there are certainly options within the 997S order guides that offer better value. There's also the $71,300, 3.6-liter base 997 Carrera, which is sweet straight out of the box with no options added. So we're fairly certain that X51 will remain a rare and exclusive option — which may be how Stuttgart and some of its 911 customers want things.

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