Highlights Of The New 911 Carrera 4/Carrera 4S | Part Eight

Porsche 911

Porsche 911

Wider track on the rear axle for higher lateral acceleration

Up front, the four-wheel-drive cars have the same wheel and tyre dimensions as their rear-wheel-drive counterparts: 8J x 18 wheels running on 235/40 ZR 18 tyres on the open-air 911 Carrera 4 and, respectively, 8J x 19 wheels with 235/35 ZR 19 tyres on the Carrera 4S Cabriolet. 19-inch Carrera Classic, SportDesign, and Carrera Sport wheels are available as an option.

As with the four-wheel-drive Coupés, the Cabriolets clearly focus on the rear axle when it comes to the tyres and wheels: The open-air Carrera 4 runs on 295/35 ZR 18 tyres, the rear tyres on the Carrera 4S measure 305/30 ZR 19. Since these wider tyres are combined with rims with reduced hump depth, rear track measures 1548 millimetres or 60.9". This is attributable above all to driving dynamics, the tyre/road contact points moved further out providing better body support with a smaller roll angle and, as a result, enhanced lateral acceleration. The bottom line is an even higher standard of driving behaviour for even faster speeds in bends.

PASM suspension with two damper programs

Launched together with the new Carrera model series, Porsche’s PASM suspension is naturally one of the highlights on the new four-wheel-drive Cabriolets. Lowered by 10 millimetres or 0.39", this active suspension is standard on the Carerra 4S and comes as an option on the Carrera 4.

PASM offers the driver two different programs: PASM Normal or PASM Sports. The normal set-up provides a more comfortable basic suspension with the dampers switching over to a more sporting mode as the driver’s style of motoring becomes more dynamic. The advantage for the car’s occupants is a significantly higher standard of motoring comfort particularly on long trips on the Autobahn, PASM quite simply absorbing minor and medium bumps on the road even better than the standard suspension. The Sports Program, in turn, activates a harder damper control map for a very agile and dynamic style of motoring quite comparable to the features of an all-out sports suspension.

Porsche’s active PASM suspension is made up of adaptive dampers with continuous adjustment of damper forces, two accelerometers determining vertical movement of the body, and the PASM control unit relating the signals from the two accelerometers fitted on the damper domes front right and rear left to the car’s lateral acceleration, steering angle, road speed, brake pressure, and engine torque. Taking this data provided by the CAN-bus, the system then determines the optimum damper control line and sets the appropriate level of damper control individually on each wheel.

Engine and Transmission - Power and Even More Power

Like all model variants in the new-generation Carrera line-up, the Carrera Cabriolet with four-wheel drive is available with two different engines: The 3.6-litre flat-six in the 911 Carrera 4 Cabriolet develops maximum output of 239 kW or 325 bhp at 6800 rpm. The even more powerful engine in the Carrera 4 S Cabriolet displacing 3.8 litres churns out maximum output of 261 kW or 355 bhp at 6600 rpm.

Apart from the model designation on the rear lid, the two engine variants can be distinguished most clearly by the different design and paint finish of the intake system: The air collector and intake manifold on the 3.6-litre engine are finished in black, the same units on the larger engine come in silver. A further sign of distinction is the exhaust tailpipes, the 911 Carrera 4 featuring two individual tailpipes in oval design, the 911 Carrera 4S coming with two dual tailpipes.

Even the "basic" engine features all the technologies required to combine superior power with equally superior economy, reliability and environmental friendliness: Four-valve technology, a two-stage resonance intake system, cylinder-specific knock control, individual coils with solid-state high-tension distributors, and dual oxygen control ensure a very good cylinder charge cycle and combustion process.

The key technology providing these qualities is Porsche’s VarioCam Plus valve management system made of camshaft adjustment and valve lift control on the intake side. This valve lift control system consists of two interacting, switchable cup tappets on the intake side of the engine operated by two cams of various size on the intake camshaft.

VarioCam Plus offers optimum engine power and torque, on the one hand, as well as further improvement of fuel economy, emission management and motoring culture, on the other.

Manual six-speed gearbox or Tiptronic S as an option

The six-speed manual gearbox combining low weight with supreme gearshift quality and precision is also the same as in the other 911 models. Particularly the precise synchromesh and gearshift offers the driver the advantage of short shift travel with shift forces reduced to a minimum. For the purposes of four-wheel drive, the gearbox comes with an additional output drive unit leading to the front axle drive shaft.

Tiptronic S automatic transmission with five speeds is available as an alternative. In this case the electronic transmission management (ETM) comprises a wide range of gearshift strategies extending from highly comfortable cruising all the way to an extremely sporting and dynamic style of motoring, the gearshift points adjusting infinitely to the driver’s style of motoring and the particular profile of the route he is taking.

Tiptronic S also offers a manual mode: All the driver has to do is flip the selector lever from the automatic gear lane to the left side of the transmission box, then shifting gears manually via paddles in the spokes of the steering wheel. The transmission will then respond quickly and with virtually no interruption of pulling forces to the driver’s gearshift commands.

The driver also has the option to use the gearshift paddles in the automatic mode, should he wish to spontaneously shift back while overtaking or use the brake power of the engine when entering a bend. An engine braking effect based on the transmission shifting back is activated automatically as soon as the system detects a downhill gradient.

continues... | Part Nine
Published 22 July 2005 Melanie Carter

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