ACL GTC Porsche 911 R-Gruppe

911 R-Gruppe (physics inspired on the 67' 911R with a S/T Engine and G-model body)

Considering the 911's competition record, it is hard to imagine today that it took Porsche four years to develop the first real racing version of the six-cylinder engined car and then abandoned it after only a handful of examples were built because the sales department feared the 500 examples necessary for homologation could never be sold. Although now forced to run in the prototype class, the 911 R still showed its worth both in rallies and on record runs.

Before creating the 911 R, Porsche did offer substantial support to customers who wanted to take their 911 circuit racing or rallying.

At Weissach, the first order of business was to shed as much as weight as possible from the base 911. The steel shell was retained but all removable panels were replaced by fibreglass examples, the floor boards were extensively drilled and the cockpit stripped from all unnecessary bits including the interior and exterior sound-deadening. Porsche's engineers were well versed in lightening cars and wasted no opportunity; all hinges were cast in aluminium, the door handles were not plated but left in bare plastic and the taillight units were replaced by small circular lights.

Slightly wider five-spoke Fuchs were specified front and rear to deal with the anticipated higher cornering speeds. To clear the 7 inch rear wheels, the fenders were also slightly widened. A more substantial change was the relocation of the oil cooler from the engine bay to the right front fender. The oil lines ran through the rocker panel from the front to the rear of the car. Inside the cockpit, the 911 R boasted lightweight Scheel seats with a ventilated example for the driver. Further changes included a 10,000 rpm tachometer and a Monza steering wheel. The completed car tipped the scales at little over 800 kg compared to 1,070 kg for the production 911.

The 911 R was powered by the Type 901/22 flat six engine, which was closely related to the one used in the 906 and 910 sports racers. The all-aluminium unit featured twin-spark ignition and a pair of triple Weber carburettors. It produced 210 bhp, which was 30 bhp more than the 911 S fitted with the high performance kit. Some cars were also fitted with Bosch mechanical fuel injection. Porsche also experimented with a twin-overhead camshaft flat six, which was effectively one half of the 917 twelve cylinder engine. This Type 916 engine produced 230 bhp and could rev to 8,200 rpm instead of 7,200 rpm.

Further competition success for the 911 R came in 1969 when the Tour de France was re-established and now also allowed prototype cars. Gerard Larousse promptly won the event and later also claimed victory in the Tour de Corse with the same car, equipped with the Type 916 engine. With a pair of Matra prototypes on the entry for the 1970 Tour de France, Larousse urged Porsche on to produce an even lighter car by offering a case of champagne for each kg removed from the 800 kg target. This ended up costing him seven cases yet it still proved insufficient to fight off the 3-litre, V12 engined Matras. Larousse did finish third behind the pair of French prototypes.

For BoP reasons, this version resembles the final iteration of Larousse his car, fitted with the 2.4ST engine producing 250hp and 254Nm, weighting in only 780kg.