Force-feeding

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Bill Boddy

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The supercharger is enjoying an Indian Summer on road cars. Bill Boddy recalls when its shrill whine was the biggest noise in Motor Racing.

Superchargers no longer figure in Formula One racing, the regulations now forbidding them. But at one period they were the dominant part of the grand prix scene. This form of power increase dates back to the dim ages of the internal combustion engine. Louis Renault tried blowing air into the carburettor in 1902. Six years later, Lee Chadwick in America used a centrifugal blower on a car that won a hillclimb, ran in important races and, in production form, was said to be the first 100mph sportscar. Sizaire then cottoned on and the celebrated designer Mark Birldgt prepared a pistonpump forced induction Hispano-Suiza for the 1912 Coupe de L’Auto race, but it was not ready in time. Race rules then prevented such experiments on the track, but the war stimulated research into supercharging, to increase the power of aero-engines at high altitudes. At the time our SE5a fighter had a ceiling of 19,500ft compared to that of 20,000ft of the dreaded Fokker Triplane and 22,900ft for the Fokker DDCII. (WWII Supermarine Spitfires with their supercharged Rolls-Royce Merlin engines had a ceiling of 41,000ft.)

Mercedes had been in the forefront of supercharging experiments before WWI and their 1913 and 1914 French GP cars, the latter achieving that great 1-2-3 finish at Lyons on the eve of hostilities, had engines based on their aviation power units. The rules of the race forbade superchargers, but would these cars have had them otherwise? Probably not. But Max Sailer’s supercharged 28/95hp Mercedes finished sixth in the 1922 Targa Florio.

Research in this area had included a three-cylinder radial piston-type blower, a vane-type Wittig supercharger (above) which had proved unreliable, and then a Roots lobe supercharger, which was tried on a Mercedes-Knight double-sleeve-valve engine and, after the sleeves had seized-up, on a poppet-valve power unit. This led by 1921 to a catalogue 15/40hp Mercedes, which used the complicated method of the supercharger pressurising the carburettors, float chambers and fuel tank when in use. A cone clutch drive ensured the supercharger was only in use if the driver fully floored the accelerator, more power thus being developed for acceleration or hillclimbing, but not intended for sustained useage. The car was costly, at £775 for a two-seater in 1925, and not a brilliant performer; but led to a range of impressive Mercedes-Benz sportscars. They continued blowing air into the carburettors for their fabulous grand prix cars until mid-1937.

The supercharger for racing was soon in full spate. Not in 1921, when a Duesenberg won the French Grand Prix, nor in 1922, when Fiat with a sixcylinder Tipo 804 led two Bugattis home, but in 1923, when Fiat used Wittig blowers on the new Vincenzo Bertarione-designed, straight-eight 2-litre Tipo 805s, the first supercharged cars to run in a GP. They used a low boost and the supercharger blew into the carburettor, a flap valve which the mechanics could open cutting down pressure if required. But although these Fiats were the fastest cars at Strasbourg — 15bhp up on the unsupercharged Sunbeams — stones and grit destroyed the blowers and all three retired. Segrave won that historic British victory, but his Sunbeam was virtually a 1922 Fiat, as Louis Coatalen had lured ‘Bert’ from the Turin company to design these cars.

This unfortunate advent of a supercharged GP car was soon rectified. The Tipo 803 supercharged 1H-litre Fiats were driven to Brescia for the 1923 Coppa Florio of 324 miles, which Cagno won, at 80.33mph. Then the 805s, now fitted with Roots superchargers, finished 1-2 in the 497-mile Italian GP at Monza, Carlo Salamano and Felice Nazzaro ahead ofJimmy Murphy’s Miller. The winning car averaged 90.93mph. Both the 1H-litre Fiats, now also Roots-blown, should have walked away with the 1923 JCC ‘200’, for Salamano and Malcolm Campbell had observed the 4500rpm limit round Brooklands. Yet both dramatically retired early in the race, for reasons which Fiat never disclosed.

Such engines became the grand prix norm from then until 1938, when non supercharged 4H litre machines were allowed to compete with supercharged 3-litre machines, and from 1947 with 1H-litre supercharged entries. The result was a series of memorable battles between the big V12 Ferraris and the supercharged, fuel-thirsty (just 1.5mpg in their final form) Alfettas. The Formula One rules for 1954-60 stipulated non-supercharged 2H-litre opposition to blown 750s but no one built the latter, in spire of the success of the MG and A7 racing cars of this capacity, perhaps because it was known that supercharged engines were to be barred from 1961 under a 1Hlitre formula. Prior to that, supercharging had been virtually the only way to go. Roots superchargers sucking through the carburettor(s) were almost universal on grand prix cars, but the high-speed centrifugal blower was used on American board ovals, and the V16 BRMs had this type of blower.

Capt Irving found that the 1923 Sunbeam GP engine would give 1156hp with a supercharger blowing through the carburettor, a system used also on the Vittorio Jano-engineered P2 Alfa Romeos, but 1386hp if it sucked from a Solex carburettor. Its supercharger was driven from the nose of the crankshaft. Albert Lory had experimented with a supercharger on the 2-litre V12 GP Delage but it was not ready until 1925, when it had a suction supercharger for each cylinder bank. MercedesBenz and Auto Union had two-stage supercharging by 1939, and Ma Romeo experimented with this in 1949. In voiturette racing, ERA used a MurrayJamieson twin-lobe Roots supercharger giving 151bs boost, and the 2-litre ERA had a big Zoller vanetype supercharger above the gearbox, straddled by the driver’s legs, giving 251bs boost and 225 bhp.

The proliferation of supercharging in racing convinced a surprisingly large number of manufacturers that there was scope for supercharged sportscars. If I try to list them all I shall miss some, and get letters! They include the Cozette carburetted and blown Ulster A7, its power raised from 16H to 27bhp, Birkin’s blower-4H Bentleys with a Villiers supercharger between the front dumb irons, fed from twin SU carburettors, and the Cozetteequipped Hyper Lea-Francis.

‘Fiats were the fastest, but grit destroyed their blowers’

Mercedes-Benz had those splendid 33/180, 36/220 and 38/250hp cars with the aforesaid complex supercharger system, preferring large lazy engines which could be made aggressive by bringing in the supercharger. An SSKL 38/250 in race trim was timed at 147mph at Avus, using the biggest ‘Elephant’ supercharger delivering 1216 boost. Mercedes used two-lobe Roots superchargers, with Pallas carbs mounted vertically at the front, beside the engine of the 45/280hp straight-eight. In the USA, Stutz on its 1929 Le Mans Blackhawk also had a Roots supercharger which the driver could engage or disengage by use of a lever, and Franklin made use of the fan on his air-cooled engine to also mildly pressurise the cad) on the 1932 Altman model.

The front-wheel-drive Alvis was supercharged, and Lagonda found supercharging a palliative for the tortuous inlet manifolding on their 2-litre using an SU-fed vertical Zoller at 10-121bs, boost coming in at 800rpm, and later a Cozette-fed Powerplus supercharger. The big 1933 Duesenberg had a centrifugal blower above the cam cases, running at six times engine speed or up to 26,200rpm; it drew from a Schebler carb and blew at up to 8lbs.

The smaller MGs leant themselves to supercharging. A racing C-type, with gear-driven No7 Powerplus supercharger and special fuel devised by Dr Porsche, gave about 52bhp at 6400rpm with 12113 boost; a J4 on 181bs boost produced 73bhp.

An oddball was the 1½-litre sidevalve HE with Cozette blower beside the engine, a £75 extra and, if Frazer Nash customers asked loudly enough, they too could have Cozettes bolted to sidevalve and overhead-valve engines. Lubrication of the supercharger involved mixing oil with the fuel or, more usually, by providing a separate oil tank and pump feed, especially for vane superchargers. The 2.3 OM had a 3½1bs ‘smoother’ boost, for reliability.

The Ulster TT regulations banned this power aid from 1934 onwards, after supercharged cars had won all but one race since 1928. But for other forms of racing it remained almost universal, until recent times. WO Bentley and Georges Roesch never liked supercharging, but Ettore Bugatti eventually got round to it.

The general acceptance of supercharging caused individual makers of blowers to spring up. Laurence Pomeroy, with Arnold Zoller, ET White and BY Roche, had formed Forced Induction Ltd, to sell Zoller vane superchargers and patented their application. They were against cheap solutions, but could supercharge your car for £60. The great racing driver and record man Capt GET Eyston, FG Schreiber and C McNeil started Superchargers Ltd to promote the Powerplus model and, in Derby, Michael McEvoy was agent for the McEvoy-Pomany systems, priced at £75 to £85. Later in the 1930s the Jameson-Gillett vane supercharger with cam and link action was made in Leatherhead (prices from £33 6/8d), the Arnott was used on Atalanta cars, and from Paris came the Zens, with fluctuating rotors, a sort of Wankel effect. Foxwell ofCheadle offered Roots boosting for £10 to £15, Glenville Grenfell at Brooldands fastened the well-known vane Centrics to ordinary engines, and Pressure Vac of Bradford made the Berk as early as 1926, used on Capt Waite’s racing A7, the Halford Special etc, and the Hurst with single concentric rotor and rotary valves appeared as late as 1966.

‘Superchargers were adapted to bread-and-butter motors’

In London, at Penbridge Mews, JW Marshall made his well-liked Roots device, able to run at 10,000rpm, and David Brown was in on the act, after Dr HE Merrett had designed for him a supercharger which used die-cast light-alloy rotors and patented seals to stop fuel or oil escaping. The Shorrock-Haydock supercharger had six sliding vanes and was said to need less power to run it than rival makes. Tom’ went to Germany to meet Zoller, once asking me to accompany him until his train left; I assumed he was lonely, but perhaps he was hoping a young writer might provide publicity!

Supercharging had by then been adapted to bread-and-butter motors. Granville Grenfell bolted these on at his Brooklands depot, watched by Leslie Ballamy, who later did this too, right up to a 30hp Ford V8 which repaid him by running a big end on an Edinburgh Trial. Any engine could be, and was, boosted. Austin, Morris, Ford, Singer and Riley etc, and even a 7hp Jowett’s ‘Little engine with the Big Pull’ was provided with more pull, from a beltdriven Centric.

I drove such cars and usually the supercharging worked. But there could be problems, if a belt slipped or a driving chain broke, and overheating and knocking would result if the compression ratio had not been lowered. But a neat Centric layout was contrived for the P-type MG, and another of these superchargers made to fit snugly beside a Lancia Augusta’s engine, rotation by a slim belt, boosting at a sensible 4lbs.

Centric used a supercharger oil pump (no messy mixing oil with the petrol) fed from an auxiliary tank, but said their supercharger would tolerate 12 hours with no oil; they charged £30 to £40, plus £2 for the bolt-on which some car owners attempted themselves. Maurice Platt of The Motor had a small Zoller supercharger on the bulkhead of an Alvis Speed 20 Follett Van den Plas tourer (A)(Y 323), which reduced its standing-start ¼-mile time by 3sec, for a weight increase of half a cwt.

There we have the supercharger age which, as far as ordinary cars went, died out after the war for many years. Turbocharging had its vogue in the 1980s, but in more recent times Lancia, Fiat and VW revived the mechanically-driven blower, and currently Jaguar, Mercedes and Aston Martin have supercharged production cars in their catalogues.

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