PORSCHE 911 CARRERA 4

Carrera 4: high performance, all-wheel drive

The 911 Carrera 4 is Porsche's high performance all - wheel - drive ( AWD ) sports car. The Carrera 4 was introduced in early 1989 , a year before the Carrera 2 , and embodies much of the AWD technology developed for Porsche's ultra - exotic , limited - production 959 .

Porsche showed an AWD 911 Turbo Cabriolet concept at the 1981 Frankfurt auto show . This show car led directly to an AWD racer based on the 911 body shell , and to the legendary 959 , first shown in 1983. The AWD technology was made available on the Carrera 4 in early 1989 .

Electro-hydraulic differential system

The Porsche 911 Carrera 4 uses a sophisticated electro - hydraulically controlled drive system . The engine output is distributed between the front and rear axles by a center differential . The torque split , nominally fixed at 31 percent for the front axle , 69 percent for the rear axle , preserves much of the traditional rear - drive sports car feel that is a Porsche hallmark . The center and rear differentials incorporate electronically controlled multi - plate clutches to manage the engine power flow to the tires .

Lockable differential for extreme situations

The electronic control unit modulates hydraulic valves to lock the differentials , thereby diverting engine power to the tires with the most grip . The driver never notices the system at work , only that the Carrera 4 has incredible grip under all conditions . For extreme situations , such as starting up on glare ice or climbing steep snow - covered driveways , the driver can temporarily lock both differentials by means of a switch on the center console to gain added traction .

AWD offers superior traction under all conditions . Even on dry pavement , AWD offers benefits in a high - powered sports car . Strictly speaking , the acceleration of a car is limited by how much force can be transmitted by the tires - the traction of the tires . If one attempts to put more force through the area with which the tire contacts the road , the tire will break free of the road surface and spin , and spinning tires have little or no traction .

But one can also apply the engine power to all four wheels , instead of just two . This distributes the force through four tire contact patches , and , therefore , offers superior grip to two - wheel drive under dry conditions but especially in wet and slippery conditions . AWD also offers improved stability under straight - line acceleration .

Improved stability and higher grip

AWD advantages are not restricted to straight - line acceleration or slippery conditions . In cornering at the limit , the Carrera 4 is less sensitive to power changes than a rear - drive car . As such , the horsepower will be more usable even by drivers less familiar with the traditional Porsche rear - drive sports car concept .

Because of physical constraints of the AWD system , the Carrera 4 is available only with a five - speed manual transmission .

For more details:

• 911 Carrera 2
• 911 America Roadster
• 911 RS America