Yet a further point is that the viscous clutch is no longer within the transmission itself, as it was in the past. Rather, it is now housed on the 911 Carrera 4 in the front differential casing moved far back to the rear of the car, a modification offering the big advantage that the larger differential housing and the viscous clutch apply a bit more weight on the front drive axle. This means even better front-to-rear weight distribution beneficial to the car’s driving characteristics and traction.
Four-wheel drive on the new Carrera 4 ensures that a certain amount of torque is always able to flow to the front wheels at all times. This share of power conveyed to the front varies from 5-40 per cent, depending directly on drive slip on the rear wheels.
Driving Behavior Even Better Than Before. The primary objective in this case is of course to perfect the characteristic driving behavior and the superior driving safety of the Porsche 911, thus reaching a higher standard than ever before. Four-wheel drive conveys the supreme power of the engine to the road even more smoothly and steadily than one drive axle.
Installing four-wheel drive in the floor pan of the Porsche 911 required a number of modifications. The first point is that various body components had to be modified in the region of the front axle in order to accommodate the front differential. This called for a new fuel tank shaped like a saddle and offering approximately the same volume as before. An inevitable result of the more sophisticated drive technology is a slight loss of space in the luggage compartment, which is however kept to a minimum by the folding wheel in flat arrangement on the floor. Luggage compartment capacity therefore remains adequate at 100 liters or 3.5 cu ft. And despite its more sophisticated technology the Carrera 4 remains a light and agile vehicle from the start, the coup? weighing in at 1375 kg or 3032 lb, which makes it only 55 kg or 121 lb heavier than its rear-wheel-drive Carrera counterpart.
Highlights of the Carrera 4
Permanent Four-Wheel Drive with Perfect Power Division. Benefitting from years of thorough experience with four-wheel drive systems, Porsche’s engineers have found a particularly effective solution with the Carrera 4: Variable distribution of drive forces to the front axle via a viscous clutch in the front differential guarantees excellent traction and supreme driving safety on all kinds of roads and under all weather conditions. Porsche Stability Management. The Carrera 4 is the first Porsche ever to feature PSM Porsche Stability Management, a highly sophisticated dynamic control concept serving to stabilize the car in an extreme situation by intervening in the engine management and brake system. Offering supreme stability in this way both in longitudinal and crosswise direction, PSM has been specially tuned to the typical requirements of a Porsche and the Porsche driver, ensuring that the sporting character of the car is not suppressed by premature intervention. The objective in this tuning process was therefore to offer brief but decisive driver support in conjunction with the four drive wheels whenever the car suddenly comes too close to the limits of physics.
Electronic Gas Pedal
A gas pedal incorporating a sensor to transmit electrical signals to the Motronic and an actuator operating the throttle butterfly are the essential features required for dynamic drive control with all the qualities of Porsche Stability Management. The use of such sophisticated electronics pays off not only in extreme situations, since E-Gas, as it is called, also improves the response of the engine to the accelerator and allows a further reduction of fuel consumption by adjusting the throttle butterfly perfectly to the engine control map. A further advantage is the reduction of exhaust emissions and last but not least E-Gas also provides even better cruise control.
Large-Volume Side Airbags Fitted as Standard
Apart from the full-size frontal airbags for the driver and front passenger, Porsche’s new and highly progressive Side Impact Protection System (POSIP) comes as a standard feature. It consists of two side airbags fitted in the doors and additional door lining taking up impact energy. Offering extra-large volume of no less than 30 liters, the two side airbags ensure optimum efficiency throughout the entire seat adjustment range, POSIP thus protecting the driver and his front passenger in all areas around their head, chest, arms and hips, even with the roof down and the side windows fully retracted.
Another Porsche First: Four-Wheel Drive plus Automatic Transmission
The new Carrera 4 is the first-ever Porsche allowing the customer to combine four-wheel drive both with a six-speed manual gearbox and five-speed Tiptronic S.
Exclusive Aluminum Wheels for the Carrera 4
A clear sign of distinction characterizing the Porsche 911 Carrera 4 at very first sight is provided by the 17-inch light-alloy wheels in unmistakable spoke design. Extending far inside to the hub, the spokes become wider towards the rim and merge into the base at the far outside, making the wheels look even more powerful and larger.
Discreet Signs of Distinction
Applying the principle of being “great to look at but even greater inside”, the Carrera 4 does not in any way flaunt its wares. The Carrera 4 model designation stands out in titanium colour on the engine compartment lid and is also to be admired on the black wheel hub covers. Further visible signs of distinction are the special 17-inch wheels and titanium-coloured brake calipers. Like all Porsche 911s in the 1999 model year, the Carrera 4 comes furthermore with modified headlight units, the direction indicators in the headlights and the side indicators now coming in white, while in the rear light clusters they are whitish gray and no longer orange.
Superior Driving Safety, Outstanding Driving Qualities
The springs, anti-roll bars and dampers are all specially tuned and modified to reflect the dynamic driving qualities of the four-wheel-drive model. Consistent adjustment of axle geometry to four-wheel drive and re-tuned elasticity on the front axle ensure neutral behavior all the way to extreme limits, allowing the driver to safely approach the highest possible speeds in a bend without losing control of his car.
Superior Crash Safety
Carefully defined deformation of the steel bodyshell keeps the loads acting on the car’s occupants in an accident to an absolute minimum. Throughout the entire process of developing the new Carrera, passive safety was consistently enhanced to an ever-increasing standard, the results of numerous crash tests confirming the conviction of Porsche’s engineers that they have created one of the safest high-performance sports cars in the world.
Air Drag and Lift Forces Reduced to a Minimum
The Porsche 911 offers a low drag coefficient compared with other sports cars. And at 0.58 m2, the product of drag coefficient and the frontal area of the car is also very low and therefore advantageous on the road. A further, particularly important factor is the minimization of lift forces on the 911 Carrera, the Cfa lift factor on the front axle being a mere 0.08, while rear axle lift, thanks to the spoiler automatically coming out at speed, is even lower at 0.05.
Water-Cooled Boxer Engine
An efficient cylinder charge ensured by four-valve technology and stable thermal conditions guaranteed by water cooling make Porsche’s flat-six power unit a genuine performance machine. Displacing 3.4 liters, the engine of the 911 Carrera 4 develops maximum output of 300 bhp or 221 kW. Top speed is 280 km/h or 174 mph. A further point is that the horizontally-opposed engine, through its concept alone, offers decisive benefits in the construction of a sports car: Compensation of mass forces is perfect, dimensions are kept to a minimum, and the short, stiff crankshaft allows high engine speeds.
Aluminum Suspension
All track control arms on the suspension and the two axle subframes integrated in the body are made of light alloy. In its design and dynamic driving characteristics, the front axle has been modified in accordance with the car’s four-wheel drive technology.
Four-Piston Monobloc Brake Calipers
Following positive experience in motor racing, the Porsche 911 Carrera 4, like all other Porsche models, comes with four-piston monobloc brake calipers made of light alloy. A particular advantage of this technology is the high standard of safety ensured at all times and minimum fading even under extreme conditions.
Litronic Headlights with Dynamic Range Control
The 911 Carrera 4 is available as an option with Litronic headlights, special gas-discharge units illuminating the road ahead far more brightly and thoroughly and thus significantly improving safety at night. A further contribution to your extra driving safety is the dynamic headlight range control considering not only the load the vehicle is carrying, but also any change in body angle due to dynamic driving conditions. The halogen bulbs for the high-beam headlights are surrounded by a particularly efficient free-space reflector. Whenever the driver activates the high beams, the low-beam headlights remain switched on and also move their own beam up by way of headlight range control in order to improve illumination of the road ahead. A further feature of the Litronic headlights, finally, is the headlight cleaning system.
Individual Sports Features
It almost goes without saying that the Carrera 4 can be enhanced to an even more sporting standard as an expression of the customer’s personal taste. Features available individually are sports seats with reinforced side support, 18-inch turbo-look wheels measuring 225/40 ZR 18 at the front and 265/35 ZR 18 at the rear, and – as on the coup? – a sports suspension with even firmer and shorter springs, harder dampers and reinforced anti-roll bars.
Race series
On 23rd February at 21.12, factory driver Bob Wollek started the six cylinder turbo engine of the Porsche 911 GT1 in Weissach, year 1998, for the first roll out. The third generation of the Gran Turismo, first used in 1996, is the most innovative hitherto. Although its predecessors still had the front car of the standard vehicle, project manager Norbert Singer used a carbon fiber monocoque in this case. Thanks to this made-to-measure production and other details, it was possible to lower the weight of the new 911 GT1-98 to around 950 kilograms. Other benefits of the new monocoque: greater rigidity and, as regards the shape, optimal harmony with the requirements of aerodynamics and wheel suspension. For designing the carbon fiber body and the underbody, the Racing Department spent many weeks and weekends in the two wind tunnels owned by Porsche in Weissach. The result is an even better optimized shape, which distributes the negative lift on the vehicle in the best possible way, at 4.89 meters in length, 1.99 meters in width and 1.14 meters in height. The 100 liter safety tank is now situated between the rear wall of the cockpit and the engine. At the beginning of the year the 911 GT1 passed the necessary EU crash tests for approval for use on the roads.
The drive unit: 3,162 ccm cubic capacity, four valves per cylinder, aluminum engine block and cylinder heads, water cooling. With two KKK turbochargers, limited by 33.9 millimeter restrictors in the air intakes, output approximately 550 hp at 7,200 revs. Maximum torque: 630 Nm at 5,000 revolutions. The power reaches the rear wheels via a sequential six-speed gearbox.
The wheel base of the double transverse control arm