Analysis of 1993 Grant Touring regulations
Regulations for the 1993 Grand Touring car category have been finalised by FISA and by the Automobile Club de l’Ouest, and unfortunately they differ in so many respects that entrants will be put to considerable trouble and expense in preparing for Le Mans.
The ACO’s classic event on June 19/20 will remain the focal point of the season, though, and serious entrants will have to go through with the exercise.
Specifically, in preparation for the big event they’ll need to shed as much weight as possible to get down to the 1000 kg baseline, change the inlet air restrictors, install a 120 litre fuel tank (instead of 100 litres), reduce wheel widths, change the rear wing, change the exhaust system, even install a new differential with sophisticated controls. Afterwards the car will have to be put back to standard in preparation for the next FISA approved race!
In a nutshell, if you want to win the GT class at Le Mans you find (or make) a road-legal sports car that weighs 1000 kg and is powered by a nice big turbo engine! The category seems to have been designed around the Schuppan 962CR, except in one important respect: the maximum wheel width is 12 in, therefore favouring a four-wheel-drive car.
The ACO has made it virtually essential to install a turbocharger, specifying larger size air restrictors on turbos (45mm single, 32mm twin) than on naturally aspirated cars (40mm and 28.5mm). It looks like a mistake, but the ACO confirms the figures.
FISA will soon announce a calendar of about six 1000 km/six-hour races, and the diameters of the inlet restrictors will be established any day now.
The curtain rises on the FISA GT series at Daytona on January 30/31, followed by the Sebring 12 Hours on March 20. The IMSA organisation has decided to go with FISA after studying the two sets of regulations, and Toni Walkinshaw Racing is hard at work right now preparing two Jaguar XJ220s for their debut in Florida.
It looks as though the FISA regulations, prepared by Tom Kean, are much better thought-out than the ACO’s rules which are, admittedly, only a part of a much bigger plan. In particular, FISA does offer a class for almost any type of homologated GT car based on power-to-weight ratios, while the ACO has a simple 1000 kg base which is too heavy for a few, much too light for the majority.
Specifically FISA aims for a target of 2.5 kilogrammes per horsepower, but the equation strongly favours entrants with large capacity engines. We have to bear in mind that FISA’s target is with catalytic converters installed, though with modern technology the penalty is not likely to be greater than five per cent off the peak of the power curve.
I have added the target power outputs in the accompanying tabulation below, based on 2.5 kg/hp, and it transpires that a three-litre car needs to develop 113 bhp per litre (340 bhp) to hit the baseline, but six-litre cars such as the McLaren F1 V12, the Jaguar XJ220 or the Porsche 911 Turbo 3.6 (with equivalencies of 1.7 applied) need only 87 bhp per litre.
TWR has consistently obtained more than 100 bhp per litre from the Jaguar V12 engine, and on FISA’s scale a six-litre version would be rated at about 2.15kg/hp. Also, of course, the larger engine always has a major advantage on torque, and this is never overcome by a rest rictor.
Taking another make close by in the alphabet, TVR’s S3C could scrape in at the bottom of FISA’s scale. It is powered by a Rover three-litre V8 engine nominally rated at 168 bhp, but might be persuaded to yield 350 bhp when fully tuned. The TVR weighs 1050 kg, though, and would need to have 200 kg pared off.
Nearer the mark is the new TVR AJP8 project, an aluminium 4.2-litre engine capable of producing 505 bhp in race tune. Installed in a Tuscan weighing 1,075 kg, the Blackpool car would be spot-on for the FISA series, and a grid of 20 might be assembled for the price of one Jaguar XJ220!
The introduction of the FISA/Simtek ‘black box’ in 1994 would change all the parameters overnight, if this wondrous device actually reaches production. Although it is capable of doing so, the device would not impair a car’s performance while on the track, but would measure hundreds of bits of performance and enable FISA to handicap the car before the next race.
The danger of this is that excellent preparation might not be rewarded. We do not want to see a V12 powered McLaren F1 disappearing over the horizon at the start of every event, it is true, but the best-prepared cars should always have the advantage.
FISA needs to bear in mind that spectators go to the big races to cheer the Jaguars, Mercedes, Pcrsches or Ferraris, and not to see their favourites slowed down and swallowed up in some mysterious way.
We hear very little from FISA about Porsche, but inevitably these cars will form at least half the grids. The latest Turbo 3.6 will be rated as a six-litre car in FISA’s listing and will have to weigh 1300 kg, almost 200 kg more than the Group 4 (GT) Porsche 934 back in 1976.
Even then the drivers sweated and wrestled with their cumbersome cars, and although the modern chassis and other developments will make the Turbo 3.6 much easier, it won’t like the weight penalty.
The 3.6-litre Carrera 2 would be a much better bet at 1000 kg, while the Turbo 3.6 would be better reserved for Le Mans, where the 1000 kg weight will be fine and dandy; the 1976 Porsche 935 started out at 970 kg, and we didn’t hear any complaints about that.
Conversely the Jaguar XJ220 is down to 1150 kg in Group B trim and will be ideally suited to the FISA formula. The car has been announced with a 2940 cc version of the V6 twin-turbo, designed to fit the five-litre class with the 1.7 factor applied.
There will always be some jokers in the pack, and some are thinking of making a Lola T92/10 or a Spice eligible. Clearly Group C cars can be made road-legal, witness the Schuppan 962CR, but the modern variety which started life at 750 kg would be heavily ballasted and stressed to make 1000 kg at Le Mans, and much of their advantage would be lost.
The Spice would have to be re-engineered to run at 1000 kg, but it would be a rewarding exercise and plenty of them exist. Even with a five-litre Chevrolet V8 installed the Lola would be marginal at 1,000 kg… and somehow the 12 in wide rear wheels might not seem a good idea at three o’clock in the morning!
These way-out projects might be better off in FISA’s camp, if FISA would accept them as GT models. A road-legal Spice, powered by a plain three-litre DFV, would do well in the 850 kg category, and that bracket might suit the Lola T92/1 best too. With the proviso, though, that someone would have to go to the expense of putting the exhaust through a catalytic converter.
Considering that FISA and the ACO are not on speaking terms, it’s surprising that their regulations are as close as they seem to be. However the gulf is quite deep and FISA’s rules are more attractive to a wider cross-section of potential interests (manufacturers and private entrants).
They all want to be at Le Mans, for all the right reasons, and we can only hope that reason will prevail and the ACO will open a class for FISA GT cars, even at the expense of their own.
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