The Auto Channel-Sports Car International Magazine

That Ol' Black Magic
Carrera 4

Porsche's latest iteration of its Carrera drives all four wheels and its owners wild.

Driving the new Carrera 4 is a bit like black magic. At normal speeds, the whole experience is very pleasant in the usual Porsche way. Pick up the pace a bit and the seamlessness persists. Then, when you reach the limit, you realize that, unlike many cars whose handling tends to become ragged on the brink, as long as the driver is up to it, the Carrera 4 remains totally composed.

There was a time when a Carrera 4 was unquestionably less of a driver's car than the traditional rear-driven Carrera 2. With the advent of the latest Carrera 4, however, those days are gone forever. For the first time, an all-wheel-drive 911 is unquestionably more fun to drive.

Listening to customer feedback, Porsche has engineered a more neutral handling balance into the Carrera 4. In fact, they have done their job so well that by the first corner it is obvious the turn-in of the new Carrera 4 is now quantifiably superior to the Carrera 2. Power-on balance through a given bend on throttle is more neutral, and its ability to exit bends with a whiff of safe oversteer is quite addictive.

The other point of contention traditionally raised by Carrera 2 aficionados is that of steering feel. In the past, the all-wheel-drive system tended to blunt the massages slightly, adding a veil between the road surface and your fingertips. No more. The steering now talks to you like no Carrera 4 before. While the greater effort required to turn the wheel compared to the latest Carrera 2 may make you initially think otherwise, as you delve deeper into the Carrera 4's abilities, you begin to realize that it is relaying information at a level that 911 purists can appreciate.

Ironically, this is not something that is apparent during the first few miles. In fact, if you were to just drive the Carrera 4 to the local coffee shop, you would not notice it at all. But when the road starts to curve and you commit yourself to finding out just how competent the car is, that is when it shows its true colors. The moment you turn the steering off center, the steering's extra weight is noticeable, as is the fact that it is a little less sensitive in a straight line than the Carrera 2. But press on and you soon learn that the more you turn the wheel, the more the steering loads up in proportion to lateral forces, and the more the road surface communicates, just like on the old non-assisted 911s.

No steering bushings or valves have been changed on the new Carrera 4 compared to its rear-driven brother, but the friction of the added componentry in the all-wheel-drive system has resulted in a steering with more weight. Where the current Carrera 2 has weighting more akin to the Boxster, the Carrera 4 feels as heavy as the older 993 models. Sensitive drivers will argue that in the best driver's cars, all the controls, whether light or heavy, should approximate each other in feel and weight for the car to feel balanced. The Carrera 4 meets this criteria, as the subjective increase in its steering effort is still perfectly in proportion to the chassis' turning rate and balance.

In normal driving, the all-wheel-drive system is totally unobtrusive. But when the road starts to rise, fall and wind through the countryside, the benefits of the system become apparent. The extra grip at the front becomes particularly noticeable when it is slippery and the road cambers fall away. That nasty feeling of the front wheels going light as the car keeps going straight, common to mid- and rear-engined cars, is largely alleviated.

For Uncle Walter Wannabes

There may be only one Walter Rohrl, but an experienced and competent 911 pilot with good car control can look like an ace in the new Carrera 4.

Porsche's interpretation of how electronics can be used to help and not hinder a high performance car is to thank for this.

In the past, the various traction and stability control systems that have been offered by BMW, Mercedes-Benz and others have been quite intrusive in their action. Though helpful to the novice who might get into trouble on a wet roundabout, they cut in at the worse possible moment when an experienced driver is trying to have a bit of fun.

The good news is that Porsche engineers have cracked the problem wide open and come up with the perfect solution. Imagine if you had a system which allowed you to develop quite considerable slip angles and even controlled oversteer on the track, but would cut in and rebalance the car if something untoward happened and you had to lift off suddenly and hit the brakes. Such a system would allow a skilled driver to have a lot of fun, but still be there as a safety net if things went awry. Well Porsche, in collaboration with Bosch, has developed such a system.

Called Porsche Stability Management (PSM), it incorporates Traction Control and Anti-slip Control with the existing ABD Automatic Braking Differential. For the time being, other Porsche models are denied PSM because other engineering changes are required, notably E-Gas, the electronic throttle control system. But there is no doubt that it will come with future model revisions.

Unlike the systems from other makers, the Porsche all-wheel-drive system is viewed as a performance enhancement rather than a traction aiding one. "That is why we don't emphasize the traction aspect of our system," explained Thomas Herold, the Carrera 4 Project Manager.

Development of the new Carrera 4 started in February 1994, shortly after the 996 program began. Although it was run in parallel to the Carrera 2, it was always one step behind the basic car. But by the time the Carrera 2 was summer testing in 1996, the Carrera 4 was alongside it.

The latest all-wheel-drive system is an evolution of the version in the 993, and apportions anything from 5 to 40 percent of engine power to the front wheels. The basic viscous coupling system from the 993 is retained, but the viscous clutch for the front axle is now incorporated into the differential housing. The differential weighs 51 pounds, six of which are made up by the clutch.

Moving the viscous clutch into the front differential has enabled Porsche to use the same clutch, irrespective of gearbox. This new arrangement enables the Tiptronic automatic gearbox to be used with the all-wheel-drive system for the first time. The five-speed Tiptronic gearbox is physically larger than the six-speed manual and there would not have been room otherwise, so two engineering problems were killed with the proverbial single stone. Porsche expects 30 percent of Carrera 4 sales to be Tiptronics.

So where do the extra 11 pounds come from? The 993 Carrera 2 was actually a Carrera 4 with the all-wheel-drive components removed. However, the 996 Carrera 4 was designed the other way around, as the new 911 was designed to share as many parts as possible with the higher volume Boxster. The numbers are something like 30,000 Boxsters and Carrera 2s against 5000 Carrera 4s, so it made sense to make the compromises on the low volume model.

The underbody is new from the bulkhead forward. The chassis rails are the same as the Carrera 2's, but the Carrera 4 uses all the space between them for the fuel tank, differential and axle shafts. Thus, the fuel tank had to be reshaped and the luggage compartment floor is higher, sacrificing space. Luckily, the reshaping of the fuel tank had no affect on its capacity, though it now overhangs the new folding space saver spare tire that lies flat on the bottom of the trunk floor.

Brakes are the same as the Carrera 2's, as are the spring and damper rates. But the suspension geometry has undergone a fundamental change to accommodate the front differential and driveshafts. If you were to look at the Carrera 2 front struts, they are precisely where the driveshafts would be on the Carrera 4, so the MacPherson struts have now been inclined rearwards. A positive effect of this inclination is improved anti-dive geometry. The springs, previously concentric on their dampers, have been offset and decoupled from the struts to compensate for the angular velocity applied to the front suspension by this radically different geometry. The turning circle remains unchanged.

One of Porsche's objectives was to retain the handling balance of the Carrera 2, but in practice, they have actually improved upon it. The weight increase is mostly in front and this has improved the balance of the car slightly by taking the front/rear weight distribution from a tail heavy 38/62 to 40/60. Yet the extra weight in the nose has not increased understeer, a bugbear of the original Carrera 4 of 1989.

Visually, distinguishing features of the new Carrera 4 are limited to the titanium painted brake calipers, silver Carrera 4 badges, redesigned 17-inch alloy wheels and the Carrera 4 script on the door sill plates. The clear indicator lights are now standard on all 911s starting from around the time you read this.

The Carrera 4 uses the new 3.4-liter water-cooled flat-six, with 296 hp at 6800 rpm and 258 lb/ft of torque at 4600 rpm. Zero to 60 mph takes 5.1 seconds, 0-100 mph occupies 11.6 sec and top speed is 175 mph.

The Hofingen Highway

It was bone dry and the sun was shining when we set off for the Malmsheim proving ground midway between Porsche's Zuffenhausen plant and the Weissach Research Center. The country roads here are open, fast and have some demanding bends. The most demanding, and one of the stretches used by Porsche test drivers, is just after a town called Hofingen. Here, as the road dives up and down through the surrounding farmland, is a sequence of tight bends connected by short straights. Bumps and off-cambers complete the challenge.

In a fast car, you can hit serious speeds on the short straights, so the brakes and the car's ability to turn-in crisply are at a premium. The bumps and off cambers are a test of a suspension's poise, control and ability to use available grip.

Powerful front-wheel-drive cars are scary in this sequence of bends because the front wheels, which are also the driving wheels, leave the ground simultaneously! On this road, 911s are quick because their inherent tail bias is actually more of a help than a hindrance, unless you get it very wrong.

Here, the Carrera 4 is supreme. The compliant suspension of the latest-generation 911 soaks up the bumps, while the all-wheel-drive system deploys just the right amount of power to the front wheels to help them claw the car around bends when you apply throttle.

One section that separates good cars from great ones contains a bump which coincides with a right turn at the top of a crest. In the Carrera 4, the tail stepped out, but with the power on and some opposite lock dialed in, the car seemed to correct itself and blasted out of the bend without raising a bead of sweat. Further runs up and down this road revealed that, strange as it may sound, the Carrera 4 is more neutral with the PSM system on than off.

On the test track, high speed handling tests confirmed this, as well as the fact that the system is not in the least intrusive if you drive smoothly and deliberately. Saw at the wheel though, and the electronics cut in, keeping you and the car out of terminal trouble.

One has to be very careful with superlatives, because each time we test a new variant of Porsche's living classic, we end up saying that it is the best 911 ever. This time, however, the leap forward is objectively quantifiable as well as just subjectively.

A car with electronic handling aids can be fun, though just a few short years ago, such a statement would have been considered a contradiction in terms and would have elicited derisory remarks from enthusiasts. But Porsche's new Carrera 4 shows that it is possible to engineer active handling aids that really act as the servant and not the master. In this respect, the new Carrera 4 is a great step forward in the art of the sports car.

Send questions, comments, and suggestions to
Editor-in-Chief@theautochannel.com