Body and Roof - Open-Air 911 with Outstanding Stiffness and Stability
The four-wheel-drive Cabriolet develops its specific fortes and qualities particularly on winding roads and serpentine routes. The name of the game in such situations is superior body stiffness minimising the rattling noise and trembling effect so typical of an open-air car on bad roads and surfaces. In the interest of extra stiffness and stability, the body-in-white of the 911 Carrera 4 Cabriolet comes with additional sill reinforcements and components with twice the usual panel thickness. These components are primarily reinforcement plates integrated in the sills as well as three-dimensional junction plates added at the connection points leading from the sills and the door hinge column/A-pillar to the rest of the car’s body.
The car’s high level of structural body stiffness is ensured in particular by spot welding and bonding connecting the side panels and the floor assembly. In other words, the components are not just welded to one another at a large number of points, but are additionally bonded together in order to significantly strengthen the connections from one component to another.
The longitudinal arms or "chassis legs", to use the colloquial term, are a particularly important feature: To acheive the same standard of passive safety as in a Coupé while at the same time maintaining the lightweight structure so typical of a Porsche, the front and rear longitudinal arms are tailored blanks, fine panels made of high-strength and ultra-high-strength steel of varying thickness welded together by laser technology. This combines supreme strength and stability with minimum overall weight.
As a result, the body of the new Cabriolet not only fulfils the significant demands made by Porsche of a sports car in terms of stability, but rather outperforms all safety requirements in both Europe and the USA: The new 911 Carrera 4 Cabriolet easily passes the offset crash test at an impact speed of 64 km/h or 40 mph in Europe, just as it complies with the US 100 per cent overlap impact test at a speed of 35 mph or 22 km/h.
With the body of the 911 being adapted for four-wheel drive, the load-bearing and support structure at the bottom of the luggage compartment responsible for crash safety had to be modified accordingly: Instead of the horseshoe-shaped carrier plate featured on the rear-wheel-drive models, Porsche’s engineers have given the four-wheel-drive models a self-contained, triangular carrier structure made up of aluminium profiles establishing an additional load path in the middle. In the event of a crash, therefore, forces generated at the front of the car are fed back like in the 911 Carrera 4 Coupé both to the wheel arches at the sides and to the front axle final drive.
Wide rear end also on the Cabriolets
The body of the new four-wheel-drive Cabriolet offers an extremely attractive combination of Cabriolet and four-wheel-drive design features. The folding roof and the particular contours of the engine compartment lid typical of the Cabriolet, for example, further accentuate the characteristically wide track of Porsche’s four-wheel-drive models: A total of 44 millimetres or 1.73" wider at the rear than the rear-wheel-drive Cabriolet, the new open-air 911 offers ample space for the extra-large and voluminous wheels and tyres.
The body structure is in principle the same as on the two-wheel-drive Cabriolets. Significant features and components at the front end of the car have however been re-conceived in order to accommodate the final drive at the front as well as the larger tank: Apart from specific modifications of the body-in-white around the front-end final drive, the bulkhead made up of several components has been moved further to the front. The complex shape and design of the fuel tank, in turn, is characterised by the split tank sections to the right and left of the final drive unit. Fuel is pumped out of these two recesses by an intake extraction pump on either side. Useful tank volume is 67 litres or 14.7 Imp gals, that is three litres more than on the 911 Cabriolet with conventional drive.
Offering capacity of 105 litres or 3.68 cu ft, the luggage compartment is able to accommodate two suitcases. Instead of a spare or emergency wheel, the new generation of the 911 comes with a tyre repair system comprising a tyre pressure compressor, a tyre sealant, a towing hook, the on-board toolkit, and wheel bolt adapters. This Mobility Kit is housed conveniently in the floor of the luggage compartment in between the body carrier structure.
The big advantage of the new luggage compartment design is however not just the extra volume of five litres compared with the former four-wheel-drive Carreras, but also the extra loading depth serving to conveniently accommodate the usual crates for drinks and beverages.