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Re: Thermal Index of Efficiency Formula

To: Chris Thompson <cthompson@rrinc.com>
Subject: Re: Thermal Index of Efficiency Formula
From: Victor Hughes <hughes@scides.canberra.edu.au>
Date: Mon, 21 Jan 2002 09:11:55 +1100
Chris

Thanks for this formula, I have always wondered about it.  I am now also
wondering about the source of the editorial comments, some of which don't quite
fit the facts.

> 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.

Le Mans started in 1923.  The Index of Performance was introduced in 1925 (the
year a Sunbeam came 2nd outright), long before WW2 at a time when French cars
were still winning the race outright, as they did in '23, '25 and '26. Although
a Bentley won in 1924, the Bentley era really started in 1927, the Alfa era in
1931.

> 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 Index of Thermal Efficiency was introduced in 1959.  Between 1949 (first
post war Le Mans and 1959, Porsche won a single Index of Performance, (1955),the
same number as Ferrari, Aston Martin, Lotus and Osca. French Panhard cars won 6
(1950 was a tie between the Aston and a Panhard).  Between 1965 and 1971 (when
the IP was discontinued), Porsche did win 5 IPs (Alpine Renault 2) but that was
after the ITE came in.

>
> 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!

The ITE was discontinued in 1975 but resurfaced as late as 1981 - that's hardly
"soon"

Although the IP and ITE were thought of as giving small cars a chance of winning
something, both Indexes were won several times by the outright winner (IP 7
times, ITE twice including once by the 7 litre Ford GT40 in '67).  In 1961 two
1.2 litre Lotus Elites and a 0.85 litre Fiat Abarth completed more laps than the
Proctor/Harper Alpine.

LeMans results can be found at: http://user.tninet.se/~aiq291w/index.htm

I also put the formula into a spreadsheet, and it is clear that both speed and
fuel economy are 'rewarded'.  A linear increase in either, results in an
exponential increase in points calculated.  This is how it should be as the
relationship between speed and fuel economy is exponential rather than linear.

Cheers

Vic Hughes

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