Now this is special and surrounded by anomalies and unknowns – not least why did Porsche build it?. In 1991 Porsche’s customer sport department at Weissach released the Carrera 4 Lightweight. Henry Rasmussen in his ’92 book “Porsche Six Cylinder Supercars” quotes ’89 as the start of these cars. He’s writing about car number 1 and in the picture it’s got old style RSR seats and he says 7&8 x 16 Design 90 wheels. Later road tests show Nomex clad Recaros and 7&9 x 16 wheels, and even standard Cup 1 wheels. Ludvigsen gives production as starting in the winter of ’90. In April ’91 Christophorus (after the RS was announced) there was a short paragraph describing the car. In it the car is described as a ”heavily ‘dieted’ Carrera 4 built for racing customers. By eliminating all interior trim the car turns out some 100kg lighter than a Carrera RS, despite all wheel drive”.
Whenever production began, some 22 Lightweight’s was built, all of these being sold to special customers at a cost of around $190,000. They weren’t originally legal for road use in any country but neither were they homologated for a GT racing category. Aimed at ‘the serious club racer’ as Jurgen Barth put it, the Carrera 4 Lightweight’s came issued with special six digit VIN’s ranging from 964001 to 964020 (another anomaly here if 22 were built).
They were based on the M003-optioned RS shell albeit now with four-wheel drive. The bodyshell was lightened significantly with sliding plexiglas side windows, aluminium doors, an aluminium front lid and an engine cover fabricated in fibreglass. One visual clue to the identity was in the re-adoption of the external oil filler, just in front of the right rear wing, this was previously used only on the ’72 911S.
Steering was power assisted, as on the stock Carrera 4, the braking system getting dual master cylinders with an adjustable balance bar for fine-tuning the front/rear bias. Underneath, a thin coat of Cosmoline was sprayed on for rust proofing. Very little was done to what was effectively a stock RS engine, but with no catalytic converter and token silencing, these cars were probably realising close to 300bhp. The real ‘trick’ bit though was the use of a Rally gearbox, essentially the one used on Porsche’s old 959 Paris-Dakar contenders. It featured two switches on the centre console that allowed the driver to adjust the torque split of the centre and rear differentials.
A fixed spoiler similar to the type used on the 911 SC/RS was installed along with faired wing mirrors and retaining pins for the front lid and engine cover. In the cockpit, no carpeting or soundproofing was applied, Porsche equipping each of these factory hot rods with an aluminium roll cage, racing seats, a small three-spoke steering wheel and Halon fire system. Tipping the scales at precisely 1100kg, the Carrera 4 Lightweight’s extremely short gearing meant it was typically good for around 130mph and 0-60mph in less than 4.5 seconds. Most of these cars were finished in white – though yellow and silver cars have turned up in road tests. They remain the least known and most enigmatic or the RS variations.