With dynamically controlled four-wheel drive, new chassis, optimized aerodynamics and new 3.6 litre twin plug 250 hp engine the Porsche model program from 1989 expanded with the all-wheel drive version of the 911.

New in the Porsche program: Porsche 911 Carrera 4

Leusden, January 10, 1989 - The new 911 Carrera 4 with four-wheel drive is the most powerful version of the 911- model series. Presented on the occasion of the 25th production anniversary of the Porsche 911, the C4 is not intended to be the successor to the rear-wheel drive 911 Carrera. The newly developed, dynamically controlled four-wheel technology of the Carrera 4 is the result of years of Porsche experience with variable four-wheel drive in passenger cars, all terrain vehicles and racing cars. For the first time this drive system from the Porsche 959 has been made accessible to a larger circle of buyers . Eight years of it technical development and trials have preceded the introduction :

1981	Presentation of the all-wheel study of the 911 Convertible at the IAA in Frankfurt.
1984	René Metge's Porsche 4WD Carrera wins first sports car the super heavy rally Paris-Dakar.
1984	First successful participation of the Porsche 959 with electric-hydraulic controlled four-wheel drive at the Pharaoh Rally in Egypt.
1986	Double victory and 6th place out of the three participating Porsches 959 at the Paris-Dakar rally.
1987	Production start of the exclusive Porsche series 959 in street version.
1988	Production of the Porsche Carrera 4 began with "Porsche dynamic all-wheel drive" and with further developed variable four-wheel drive.

Advantages for traction and driving stability: "Porsche dynamic all-wheel drive".

Compared to drive on only two wheels the four-wheel drive basic advantages:

• Full utilization of the front vehicle weight transmission of the driving force.
• Distribution of driving dynamics active drive influences (driving forces) over front and rear axle (driving stability).

These advantages apply to a greater or lesser extent with respect to all forms of two-wheel drive. The advantages of this are a lower weight and less technical complications. The cons of two-wheel drive for traction and driving stability differ according to the mode of drive (front wheel drive, rear wheel drive, mixed drive).

Already during the four-wheel study for the Cabrio in 1981 Porsche combined with a normal sports car the four-wheel drive with the rear-wheel drive concept: from the gearbox on the rear axle guides an additional drive shaft to the front axle. The shaft turns a tube, which is a fixed one connects the front and rear axle (Transaxle). This construction was developed in all on the basis of the 911 4WD vehicles maintained.

Compared to the other types of two-wheel drive rear-wheel drive offers the greatest benefits to the traction. Rest with the unladen vehicle at a standstill most of the vehicle weight on the driven wheels. The occurring during acceleration with each vehicle change in weight distribution (dynamic axle load displacement tsing) puts an extra load on the rear wheels with him. For this reason arises even when powerful motorized rear-wheel drive vehicles such as the Porsche 911, when starting and accelerating only extremely rarely the phenomenon of over-running of the driven wheels.

However, the experiences at the Paris-Dakar rallies delivered proof, that extra drive of the front wheels, also with the sports car with rear engine, to clear improves traction. This improvement also arises, when on a slippery surface (wet road, ice, snow) must be driven away or accelerated.

The second principal advantage of four-wheel drive, the greater driving stability due to the distribution of the driving forces over both axles, is reflected in driving straight ahead and when cornering. When driving straight ahead the spinning of one or more wheels, which means the course stability of the car, by a correspondingly regulated four-wheel drive reliably. At the cornering is controlled by a driving dynamics all-wheel drive the steering behavior (oversteer, understeer, load shift responses) to positive ones affected and thus increased driving safety.

There are additional influencing options for a sports car the driver is desirable and these are provided by Porsche for it first in electronically controlled variable four-wheel drive of the "959" realized in an exemplary way. In a further developed form it is now called "Porsche dynamic four-wheel steering" in the 911 Carrera 4 for one made more accessible to buyers.

Thanks to the new catalytic converter exhaust system and partial casing the most powerful 911 suction motor to date.

The powerful 3.6 liter engine with twin ignition and a maximum power of 250 hp (184 kW) at 6100 rpm. It is the most powerful to date in the 911 model series as standard built-in motor and at the same time one for the future orientated new version of the classic six-cylinder boxer engine: through a partial covering it becomes engine noise outwards and inwards effectively muffled. For all countries with unleaded fuel, the engine supplied as standard in catalytic converter version. The version without catalytic converter has the same performance. The combination of high power and catalytic converter technology required a completely new exhaust system. It became combined with newly constructed heat exchangers, which provides the new heating system with heat, which is quickly available after the cold start. The double ignition is the result of experience in Porsche aircraft engine technology. She is a further contribution to clean and environmentally friendly combustion. That is also the case for the anti-knock control, which controls the fuel sensitivity of the engine is reduced to such an extent that the refueling of fuel with an octane rating lower than the prescribed none can cause damage. Ignition and injection are through Hotronic electronically controlled. In the back of the Carrera 4 the familiar art but neither more powerful, with a lower noise level and a better exhaust gas quality.

The torque has been increased to 310 Nm, which already at 4800 rpm. is achieved: the combination of high permeability and sporty turning characteristic remains a 911- characteristic. The partial encapsulation does not change the with nothing to compare "sound" of the air-cooled boxer engine. At the same time, the smooth surface makes the soil dynamics improved. And it contributes to it that the engine stays clean. The Carrera 4 has one of the engine compartments best protected against pollution, which so far are built. At the top it is used by the new spoiler shape ensures that the intake air and cooling air even under unfavorable conditions in a clean and environmentally friendly quality are available.

Bodywork: aerodynamic changes, smooth finish bottom and fold-out rear spoiler, no upward pressure.

Already in the zero-series stage, the Carrera 4 sees in the new Zuffenhausener bodywork factory is born. From the normal 911, it differs in structure from the base plate, which is adapted to the space needs of the four wheel drive. This has a larger center tunnel and changed spatial conditions in the front section as a result. More striking are the innovations of the body shape: integrated front and rear sections modify and harmonize the contours of the vehicle without it change its character. With the elastic plastics manufactured spoiler bumpers use the bee the 928 experiences gained. The multiple interchangeable elements existing and yet appearing as a unity segments are painted in car color, the fog lights are incorporated into it. The rear fog lights are also in the rear sections integrated. The classic round headlights are not changed in shape, the new rear light section is placed obliquely. An important thought behind the optical changes is the aerodynamics. This one is with the 911 van traditionally tuned not only to air resistance, but likewise on the upward pressure.

The reduction of buoyancy by front and rear spoilers as well as through provisions on the bottom of the car is of great importance for driving safety at large speeds. With the Carrera 4 the air resistance value is (cW) reduced from 0.395 to 0.32. With ignoring one possibly even more favorable cW value was simultaneously increased buoyant pressure (cA) is so effectively reduced that it is currently close to zero. This combination of low air resistance and virtually absent buoyancy underlined the high aerodynamic quality of the Carrera 4. Among the measures to the bodywork forms, in addition to the smooth-lying windshield and the smoothly placed rain gutter, worth to mantion is the cladding of the undercarriage. This is because, by integrating the hood and the exhaust system up to the rear of the car, one smooth surface. While the current rear spoiler the silhouette of the 911 changes and therefore only on request, the Carrera 4 will receive an extra stationary unobtrusive, expandable rear spoiler. This new development aimed to add the classic line from the 911 to the rear and optimal airflow conditions and keeping the air drawn in clean the engine. No extra was added for this solution body part required, but one already present body segment is moved out. In doing so, the air inflow area almost doubled. The spoiler is coming from 80 km / h automatically upwards and will be at 10 km / h withdrawn again. This arrangement ensures that the spoiler is always extended at high speeds, it also becomes unnecessary moving in and out at low speeds.

New for the 911 optics are also the aerodynamic smooth aluminum disc wheels with enlarged ventilation openings at the front to enhance the brake cooling. They come in sizes 6 inches (front) and 8 inches (rear) x 16 inches made of cast aluminum. For the carrera 4, there is only this rim version, which on the space requirement of the four-wheel drive and the standard built-in ABS is tuned. The tire sizes 205/55 ZR 16 front and 225/50 ZR 16 rear are adapted to the handling characteristics and weight distribution.

Interior and instruments are unchanged in terms of design remained, but contain many functional improvements. The operation of the fully automatic controlled system is new heating and ventilation, whose capacity and constant temperature in combination with air-cooled engines a novelty. The optional air conditioning is integrated into the installation and offers several options for mixing fresh and warm air, as appropriate the need. The Carrera 4's round instruments are in fluorescence technology performed: symbols and texts are only visible, if this is for driver information is necessary.

Gearshift, center console and storage compartments are more ergonomic fitted and the light switch is under the standardization carried out as a rotary switch (until now pull switch). The trunk space in the front has also been redone designed. However, she still offers the option several small pieces of luggage or one large suitcase in this categorize under. This means that the Carrera 4, just like the normal Carrera to the few sports cars, which next folding rear seats and additional separate trunk space to offer. Fuel capacity has been reduced from 84 to 76 liters. There the consumption thanks to the improved aerodynamics could be reduced, the range changes hardly any.

With "intelligent" differential steering and course-correcting rear axle: all-wheel drive and chassis from the Carrera 4.

In the Carrera 4, Porsche introduces a new form of the four-wheel drive, which is derived from the further developed technology of the "959", a "differential slip-controlled" drive of all four wheels. The drive system is standard with an in-house developed anti-lock braking system combined, that until the car comes to a stop constantly remains fully functional. The specially constructed chassis is tuned for four-wheel drive and ABS. The front wheels are changed with a changed axle geometry (negative steering roller radius) separately by means of triangles and struts. The standard power steering ensures excellent road contact and a light and accurate control. The new rear suspension features spring damping elements, the inner diagonal guide arms have a course-correcting effect in the event of lateral forces and thus increase driving stability varying load in bends and when changing direction.

The four-wheel drive with intermediate differential divides the drive force consciously with the accent on the rear axle, that is say in a constant ratio of 31 percent to 69 percent behind in order to ensure good controllability when cornering reach. Slipping of one or more wheels detected by "intelligent" electronics and by hydraulically controlled blockages prevented. This takes one fast switching system, which in terms of response speed of the solenoid valves is similar to the anti-lock braking system for the brakes and also contains elements of the ABS.

The speed of the wheels are determined via the ABS sensors and continuously compared in the on-board computer.

Already due to extremely small slip differences from 0.8 km / h blockages can be activated.

The threshold values, which trigger the entry into force, are variable, however: at high speeds the system leaves greater differences than at low speeds. Over there influences such as different tire diameters or deviations in the tire pressure can lead to speed differences without any slip, become "learning" modules that recognize such special circumstances and take this into account. The through the differential controlled distribution of the driving power between the front and rear rear axle becomes slippery due to the action of the blocking changed: the shaft, which at that time can have more force transfer is allocated the largest share. because of this an automatic adaptation of the system to the driving conditions. The traction and driving stability driving straight ahead, cornering behavior, as well as reaction load changes are continuously optimized. As a rule, the most heavily loaded rear axle gets it most of the driving force, so that still the basic sporty characteristics are retained. The advantages in particular with regard to driving dynamics right on a dry and rough road surface.

This Porsche dynamic based on experiences with the Porsche 959 four-wheel steering "reflects the latest development state of four-wheel technology. For the first time an electronically controlled four-wheel drive with "intelligent" control for a wider circle of buyers made accessible. In the year of the twenty-five year old anniversary of the "911", Porsche once again proves the predecessor role of the "911", as far as the automotive technical progress.

Technical data of the Porsche 911 Carrera 4

Body:	two-door self-supporting all-steel body, Coupé, optionally with sliding roof
Engine:	air-cooled six-cylinder four-stroke engine with opposite lying together cylinders (boxer engine)
Bore:	100 mm
Stroke:	76,4 mm
Displacement:	3600 cc
Compression ratio:	11,3 : 1
Output:	184 kW (250 hp) at 6.100 r.p.m.
Max. torque:	310 Nm at 4.800 r.p.m. (31.6 mkg)
Power Transmission:	engine and gearbox in the back, combined by means of a connecting pipe to one rigid drive unit between rear wheel and front wheel drive
Brakes:	hydraulic two circuit brake system with four internally ventilated brake discs. brake booster, standard with ABS
Weight:	empty weight 1.450 kg Max total weight 1.790 kg
Performance:	acceleration from 0 to 100 km/h in 5,9 sec., maximum speed 260 km/h