The Birth of Group C

It is 1982.  Group 5 Special Production Cars are getting out of hand.  FIA was becoming increasingly concerned with the engine output of vehicles in this category.  After introducing it in 1976, manufacturers continued to do what they did best.  Take the inch given to them in the FIA rulebook and turn it into a mile through ingenuity and exploitation of technical loopholes.  Porsche was enjoying more sports car success with its 935 in this division.  While a regulation had been applied to BMW racers for the 1978 season that involved cutting the floor to accommodate the exhaust of the front engine, Porsche went a step further and removed the entire floor pan of its rear engine 935 which allowed for a lower ride height.  Coupling the increasingly radical aerodynamics that exploited omissions in the rulebook, and larger capacity engines that chucked out well over 800 horsepower, and the top level Group 5 racers were leaving Group 6 prototype cars in their dust down the Mulsanne straight at Le Mans.    

 Group 5 sports cars circa 1982

Group 5 sports cars circa 1982

The FIA took halting measures to this progression by introducing a new class under the name Group C.  This class was aimed at closed cockpit sports prototype vehicles that were to be designed as purpose built racers, and not homologation specials.  The FIA imposed a fuel consumption limit – 100L maximum fuel tank capacity, and a maximum of 5 refueling stops per 1000km of race distance traveled.  Essentially, Group C cars were allowed to guzzle 600L in a 1000km race.  This concept had been introduced by the ACO at Le Mans in the late 70’s to try and revamp the prototype classes by forcing manufacturers to look beyond engine development as the main source of performance advantages over the competition, and the FIA intended to do the same.  Of course the fuel consumption based regulations on paper seemed like a boldface disregard for full power driving and outright performance, but manufacturer support for the new regulations and for good reason.

If I may, I would like to quickly discuss the topic of forced induction versus naturally aspirated engines.  There is a point to this engineering lesson which ties into the early development of Group C racers.  I promise.

Engines run on fuel which has two components to it; liquid fuel, and air.  Fuel enters the engine through controlled injectors, the air, enters via one of two methods.  In a naturally aspirated engine, the air is brought into the combustion chamber at atmospheric pressure.  It travels through a series of ducts and filters before it enters through the intake valves.  However, there is an important fact to keep in mind.  That is, the more air you can fit inside the combustion chamber, the hotter and more powerful the explosion will be.  The same way one might try to stuff a few extra protein bars into their gut to build muscle faster, a turbo achieves the same effect.  A forced induction motor (turbocharged or supercharged or both, but let’s leave the Lancia Delta S4 Stradale out of this) is fed air through a mechanism which sucks more air into the engines lungs and crams it in the combustion chamber at as high a boost pressure as possible.  Turbos in particular use exhaust gas to spool up a turbine which pulls air in at very high pressure to achieve incredible power figures.  Just look at today’s Formula One cars.  They are achieving nearly 700hp out of a 1.6 liter engine but among other things, turbocharging it.  But if Spiderman taught us anything, it is that great power comes with great responsibility.  The more you turbocharge a car, the more boost pressure the engine must deal with, and so many internal components must be beefed up and made from exotic materials to cope with the immense stress.  This drives running and maintenance costs through the roof, and prices many smaller outfits out of competition in the racing world.

And so we circle back to the FIA fuel consumption regulations.  With the rules set as such, it became theoretically possible to run larger displacement naturally aspirated engines competitively against the smaller forced induction motors.  This gave the manufacturers options, especially those that hadn’t had years to hone a successful forced induction motor like Porsche had with its 935.  Additionally, the race format for all events was modified to a 1000km race distance minimum to put a greater emphasis on actual car and driver endurance.  As a result, the 1982 season saw a growth in the number of unique manufacturers competing that season, including the likes of Aston Martin, Peugeot, Ford, and of course Porsche.

 Porsche 956s lead the field of Group C prototypes at Imola in 1983

Porsche 956s lead the field of Group C prototypes at Imola in 1983