Miguel Sánchez
Beyond some specific examples relating to Mercedes-Benz sports models produced around the year 2000, the truth is that supercharging by volumetric compressor It has practically disappeared from the automotive map.
Something that has been clearly visible since the eighties, when as a twilight testimony only Lancia with its engines Volumex -derived from the supercharging used in the 037- resisted the generalist attack of turbocharging.
And it is that as the turbochargers were adapting to a more predictable and progressive response - at the same time as the "intercooler"They solved the heating problems - the volumetric compressor was losing points against the advance of a technology that was not only lighter but also powered by waste gases instead of being parasitic on the force concentrated on the crankshaft.
So, talking about issues like the Roots supercharger or the Bentley “Blower"It is something completely linked to the historic automobile; something that only resides in the past. A past whose golden age It is now a century old, thus commemorating the years during which the tracks were filled with this technical element capable of taking on races such as the Targa-Florio or the Mille Miglia.
FROM THE BLAST FURNACES TO THE SKI RUNWAYS
The first compressor with a rotary lobe pump dates back to mid XNUMXth century. At this time, the mining industry was building increasingly longer and deeper galleries, creating many ventilation problems.
Because of this, the invention of this system intended for blow air into In those cavities it was a simple and effective response to ensure a higher level of safety for the suffering miners.
Those who, with their effort and risk, extracted the coal used by the British steel industry in the blast furnaces inherent to the Industrial Revolution; at that time recipients of the first Roots air compressors already in the 1860s, all with the idea of improving combustion by increasing the temperature of the foundries thanks to the forced introduction of more air and therefore more oxygen.
In short, an interesting beginning, to say the least, after which it was only necessary to wait until 1878 to see the first application of the supercharger to an internal combustion engine. This was the milestone from which this technology would first reach airplanes - during the first golden age of military aviation, coinciding with the World War I– and then apply it to cars focused on the performance needs of competition.
1923, FIAT IS A PIONEER WITH ITS 805
In 1922 Fiat was not only one of the main references for the GPs of the time but even amazed the grid with the presentation of the 804. Designed largely by its aviation department, it adapted its mechanics to the new specifications with 2 liters as maximum displacement to mount a six-cylinder block capable of delivering more than 100 HP with which to win the French and Italian GPs.
Likewise, facing the following season, the technical team led by Vittorio Jano doubled the bet by releasing the Fiat 805 with supercharging - initially with Witting vanes, although replaced mid-season by a Roots compressor - in order to produce up to 146 hp at 5.500 rpm.
A giant leap capable of completely dominating the scene, thus forcing the rest of the manufacturers to introduce supercharging in their vehicles as quickly as possible if they really wanted to achieve victories in relation to what was already seen as a new era for GP racing. Without a doubt, a technical revolution on a par with what was seen decades later in F1 with the introduction of the mid-rear engine, aerodynamics and monocoque chassis.
MERCEDES TAKES GOOD NOTE
Focused on mass production increasingly similar to Ford standards, Fiat left competition behind to the chagrin of some members of the Agnelli family and the joy of Alfa Romeo, which paved the way to becoming the dominant Italian company in racing until the arrival of Ferrari after the Second World War.
In any case, the truth is that - as in other matters - Fiat managed consciously or unconsciously to pave the way for the rest of European manufacturers, who saw with greater or lesser pleasure how the application of the volumetric compressor had become an indispensable requirement for the racing field.
A fact that Mercedes-Benz took good note of, which went to great lengths to set another milestone in the golden age of superchargers by acquiring the Targa-Florio of 1924. And not with just any model, but with the PP single-seater, one of Ferdinand Porsche's first works at Daimler, which, thanks to supercharging, managed to go from 68 hp - the power of the naturally aspirated unit sent to Indianapolis in 1923 - to a resounding 126 hp - 150 hp already at the end of the 1924 season.
From here on, the German brand became the European reference for the use of Roots compressors, applying them not only to the SSK saga -with up to 300 hp and 680 Nn to reach 190 km/h- but also to multiple tourism models launched as early as 1924 with the 6/25. Ultimately responsible for paving the way for the street versions derived from the exclusive SSK.
FROM EUROPE TO THE UNITED STATES
Although the volumetric compressor could be especially useful on European circuits - where curves and changes of pace rewarded a good performance - from low revs -, on American ovals it was also well received thanks to its contribution to increasing top speeds.
Because of that Harry Miller -one of the most interesting race designers of his time, with such advanced experiments under his belt as a single-seater front-wheel drive or the first aluminium pistons - was tempted to build his own supercharged option as early as 1924.
And yes, it was something really superb; with an inline eight-cylinder engine of only 1.478 cc it was capable of reaching the 200 CV to 5.000 rpm already in its first versions, reaching over 250 hp if we focus on the units from 1925 onwards offered in both front-wheel drive and rear-wheel drive. Simply wonderful.
BUGATTI AND BENTLEY, FROM DISBELIEF TO BELIEF
Situated at the top of motorsport in both the luxury and racing sectors, Bugatti and Bentley looked at each other closely during the 1920s with beauties on a par with that of Ettore Bugatti calling the vehicles the “Bentley boys" as "the fastest trucks in the world”. And despite their speed, there is no doubt about the enormous size and generous weight of those British designs.
In stark contrast to the small, lightweight Type 35, which was able to win dozens of races across Europe, thus creating one of the most successful careers in the history of any racing car ever introduced. An unmitigated milestone with a relatively extensive mechanical evolution, with the appearance of the 1926 Type XNUMX standing out. Type 35C.
Created in spite of the founder of the brand - who was not particularly in favour of abandoning the strict atmospheric character - this marked a milestone in the trajectory of the model since from it each and every one of the new series of the Type 35 They had units equipped with supercharging.
Of course, the power increase was not spectacular at all. However, the engine's good response at low revs thanks to the action of the Roots compressor - driven by the crankshaft and therefore without turbocharger delays– together with the model’s handling, it formed an exceptional combination; this was undoubtedly a winning option.
AMILCAR, A PROTAGONIST TO TAKE INTO ACCOUNT
Opposite the lightweight paradigm represented by Bugatti's Type 35 was the Bentley "Blower” from 1929; a model so effective on the straights of Le Mans -where it imposed the law of its up to 240 HP in the case of the largest units”tight"- as Certainly clumsy on twisty circuits where its power was useless compared to the meager and rat-like - if we may use the expression - Bugattis.
What's more, even in the later years of its production life the Type 35 easily beat the "Blower” in various GP like the one in France in 1930. In any case, whatever the case, the truth is that this Bentley is one of the great references - if not the greatest - in relation to the popular imagination built around the volumetric compressors of the 1920s.
And it is not surprising, since, although at first its design was denounced by the house itself - actually due to the personal commitment of pilot Tim Birking and engineer Amherst Villiers, capable of subsequently convincing the brand to bring it to series production - the truth is that it has ended up being one of the most famous Bentleys in history thanks to appearing right between the height of success at Le Mans and the immediate absorption of the company by Rolls-Royce.
A ROOTS COMPRESSOR AT THE SERVICE OF LIGHTNESS
However, if we are allowed to introduce a touch of personal preference we would like to crown this brief portrait of the roots compressor During the 1920s, they named an effective, relatively inexpensive and certainly very attractive model: the Hamilcar C6.
Introduced in 1926 by a company founded just five years earlier - with models sometimes so precarious that they did not even have a differential - this model coupled supercharging to its simple block with 1.1 liters to obtain 83 HP on a fast and light frame in curves. And, as we always say, below the most efficient -and obvious- is where the right option is found.
Images: Fiat Historical Centre / RM Sotheby's
