Highlights Of The New 911 Carrera 4/Carrera 4S
Published: 22nd July 2005
Porsche 911
Four-Wheel Drive and Chassis/Suspension - Supremacy at All Speeds
The supremacy so characteristic of the body structure of the new open-air 911 on every road and surface is reflected by the same superiority on the drivetrain: Benefiting from four-wheel drive, the Carrera 4 Cabriolet offers an even higher standard of roadholding and even better grip even in difficult situations than its rear-wheel-drive counterpart.
Thanks to four-wheel-drive technology and the viscous multiple-plate clutch, the front wheels constantly convey a minimum of 5 and, whenever necessary, a maximum of up to 40 per cent of the engine’s drive power to the road. The focus, however, is not so much on pure traction, but rather on outstanding driving qualities and motoring safety at all times.
The multiple-plate viscous clutch is housed within the front axle final drive conveying drive forces to the front axle and setting off any difference in speed between the two axles. Like a multiple-plate lock, the clutch is made up of inner plates connected to the hub and outer plates connected to the housing. Silicon fluid comes in between in a fully sealed-off cavity, power being fed to the front axle as a function of differences in speed via sheer forces between the silicon fluid and the clutch plates.
Four-wheel drive for even faster acceleration
One of the advantages of this four-wheel-drive technology is that even in a fast bend the front wheels will not "push" hard to the outside, the car thus remaining neutral in its handling qualities and behaviour even in extreme bends and on very winding roads. And while the improvement of traction made possible by four-wheel drive is not the most essential point, it is nevertheless noticeable, the viscous clutch responding to even the smallest differences in engine speed.
Should the driver floor the gas pedal while driving dead slow, say, on a snowbound road, with the rear axle being able to convey only some of the engine power into traction, up to 40 per cent of the engine’s torque goes to the front axle without the slightest jolt or unsmoothness.
Four-wheel drive offers the same smooth response under negative acceleration: Even when applying the brakes all-out, there is hardly any distortion or build-up of adverse forces in the drivetrain, the PSM and ABS functions therefore remaining unchanged.
Yet a further advantage, particularly in a sports car, is the low weight of the system, all the specific features and components of four-wheel drive in a Porsche Carrera Cabriolet adding only an extra 50 kg or 110 lb. This makes four-wheel drive from Porsche one of the lightest systems of its kind in the market.
Ideal set-up of both the conventional and active suspension
A crucial prerequisite for converting the inherent benefits of four-wheel drive into superior dynamic driving qualities on the road is excellent suspension. This applies both to the Carrera 4 Cabriolet with conventional suspension and to the Carrera 4S Cabriolet with its active PASM suspension system featured as standard.
The features and qualities of the suspension on both open-air models are the same as on their respective Coupé counterparts. Which means that the springs on the Cabriolet, to take one example, have the same rating, but are slightly longer. The result is greater pre-tension with the springs fitted in position, serving to set off the slightly higher weight of the open-air model. A further modification is the reduction of the spring rate by 10 per cent on the front axle of the Cabriolet with Porsche Active Suspension Management (PASM) (with the exception of the 3.6-litre Carrera featuring Tiptronic transmission), giving the driver the same feeling of comfort as in the Coupé thanks to the modified set-up in conjunction with the higher weight of the car.
A further specific modification involves the stiffer support mounts on the rear axle: The support function is now provided by Cellasto elements connecting the upper spring and damper mounts with the support plate on the body of the car. With these elastomers having a reduced damping effect, the dampers respond to weaker forces and movements than under normal circumstances.
In conjunction with the pre-tension specific to the Cabriolet, this allows Porsche’s suspension engineers to offer two effects in one: First, roll movement of the Cabriolet is more comfortable; second, frequencies potentially making the body of the car tremble are eliminated right from the start.
Porsche 911
Our Porsche 911 Guide lists the full specification of the current UK 911 range, including car prices, fuel consumption, dimensions and other vital data.
Price Range: £63,070 - £131,070
Body Styles:
Fuel:
Models in the range: 13
We have road tested the Porsche 911, to read our in-depth car review:
Porsche 911 Review - Sep 2007
Our Car Buyer’s Guide covers all of the UK’s major new cars and includes CO2 ratings and car insurance groups. Data updated on the 28th Nov 2008
