Hopefully John can tell us the source of the story and editorial comments.
Le Mans the Fuel Efficiency category
When the French invented the Le Mans 24 Hours race in the 1920s, cynics
said the event was specifically designed to show off the worth of French
sports cars, but the British Bentleys and Italian Alfa Romeos soon limited
that aim.
Then, after the Second World War, there were no more large and fast French
sports cars, so the organizers invented a further competition, a complicated
Index of Performance event, which theoretically allowed small-engined cars
(of which France had many) to compete against the big cars on a handicap
basis. Even this was not always a guaranteed success for the French
(Porsche was outstanding in this category), so the organizers tried again,
this time with yet another category, to be known as the Index of Thermal
Efficiency.
The classification was complex, for it not only included the average speed
achieved by a car, but its scrutineered (chris - this was the best I could
read) weight, and the actual fuel consumed during the race.
The thermal Efficiency Cup was run for the first time in 1959, when a French
DB-Panhard beat a Lotus Elite and the two race-winning Aston Martin DBR1s.
The French were delighted. They were not pleased in 1960, when the best of
the DB-Panhards was soundly beaten by two Lotus Elites.
Then came 1961, when the works Sunbeam Alpine of Peter Harper and Peter
Proctor won the Category, beating a Lotus Elite and the fastest of the
DB-Panhards. No wonder the French soon decided that this Category might as
well be abandoned!
In 1961, incidentally, the Thermal Index was calculated according to a
fiendishly complex formula. I can do no more than quote from a translation
of the regulations:
The Thermal Efficiency Index is based on the relationship between the cars
engine capacity, weight and quantity of fuel used during the 24 Hours. The
calculations are as follows, the Thermal Efficiency Index being IR:
IR=Em/Er
Where Er is the actual fuel consumption of the car in litres-per-100km, and
Em is calculated from the following formula:
Em = (P-300)/100 + V/25 + ((V-95)**2)/600 + ((V-140)**3)/21000
(note: ** indicates to the power of, as in **2 means squared, **3 means
cubed)
V being the average hourly speed of the car for the 24 hours (in kph), and P
being the weight of the car in kilogrammes (1kg = 2.2 lb)
Apart from producing the most fuel-efficient engine, and the most
wind-cheating body style, it was almost impossible, and certainly
impractical, for a team manager to prepare his entry with a view to winning
this category. In any case, in the days before computers, it took far too
long to work out all the combinations and possibilities.
No wonder Rootes were as surprised as anyone when they won the Index award
in 1961!
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