Matters of moment, August 1980

Full circle with FIAT?

” … the phrase, ‘the racing-car is the touring-car of tomorrow’, is none of my coinage . .. I, however, concur in it” – Louis Coatalen, 1924. 

Turbocharging, derived from early high-altitude aeroplanes, is all the rage these days, for increased performance and torque. Renault have followed up their Formula One Turbocharged racing cars with the exciting Renault 5 Turbo (see page 1157) and this development, led by Saab, is now in full spate, with Audi, Alfa Romeo, Aston Martin, BMW, Datsun, Lotus, Ford of America and Porsche among its advocates.

It is possibly significant, however, that Mercedes-Benz, who showed meagre interest in the Wankel rotary engine, have not so far leapt on the turbocharge band wagon (except for their diesel) and that Fiat, although they have experimented with exhaust-driven turbocharging, have also been interesting themselves, as they did nearly 60 years ago, in mechanically-driven superchargers. 

A release from Fiat’s British Press Office in June gave the reasons why the Abarth engineers are now experimenting with positively-driven displacement superchargers. They see possibilities, not only of improving power output and torque, but of actually useing 10% less petrol, by supercharging today’s efficient engines. The advent of effective die-casting techniques has made practical volume-production of lightweight superchargers. Abarth report that a 1.3-litre Fiat engine, boosted with a cast-aluminium Fiat Roots supercharger at from 7.25 to 7.98 lb/sq in, has been giving the same power as a normally-aspirated 2-litre engine of the same type and that the blown power unit saves 10% on fuel consumption at road speeds of 40 to 110 m.p.h., and uses up to 23% less petrol than the non-supercharged 2-litre car when driven with circumspection. Moreover, say Fiat, torque is improved all through the rev-range, a 2-litre supercharged engine blown at 4.8 to 6.5 lb/sq in shows a torque increase of 39%. These experimental Fiat engines have been run on four star fuel, their compression ratios lowered from 9.3 to 1 to 7.8 to 1 to compensate for the forced-induction.

If Fiat decide to standardise their supercharged engines, the great Italian manufacturer will have completed the circle, because in 1923 a· straight-eight 2-litre Roots-blown Fiat became the first supercharged car to win a Grand Prix race, when Carlo Salamano finished first in the Italian GP that September, at 91.06 mph, his team-mate Pietro Bordino lapping at 99.8 mph (the full story of failure, followed by this success, will be found in pages 1203-1206 of Motor Sport, November, 1969). 

From that time onwards, until the outbreak of war, supercharged cars won every International Grand Prix race unless the rules specified otherwise, and for many years after the war supercharged engines were still extremely prominent in racing. Before the war the supercharger was popular for catalogue cars, with Alfa Romeo, Lagonda, Lea-Francis, Austin, OM, Mercedes-Benz, Sa!rnson, HE, Stutz, Alvis, Bugatti, Maserati, MG, Triumph, Frazer Nash, Tracta, Amilcar and others listing supercharged models in their catalogues, and Amherst Villiers doing so with the 41/2-litre Bentley, against Walter Bentley’s wishes. 

At first there had been an obsession with blowing air through the carburetter, with all the accompanying pressurising complexities, so that only Mercedes-Benz, with their impeccable and painstaking engineering, could properly cope, including clutch-engagement of the Roots-blower under accelerator depression. Stutz copied this, but gave the “Black Hawk” driver a lever with which to bring in the supercharger whenever he felt the need of more power. . . . 

By sucking the fuel mixture from the carburetter or carburetters and leaving the engine-driven supercharger, whether a Roots rotor or vane-type compressor, permanently in operation, it became almost simple. Thus the aforesaid manufacturers encouraged to have supercharged models in their catalogues. This was followed by the fitting of superchargers to previously atmospherically-inducted power units, as a simple “hotting up” expedient. This was done to the most improbable of cars, such as Austin 10/4, flat-twin Jowett and Armstrong Siddeley, etc, with a wide choice of proprietary blowers to choose from – Arnott, Berk, Cozette, Centric, David Brown, Foxwell, Marshall, Shorrock-Haydock, Jameson-Gillett, Villiers, Wade, Zens and Zoller, for example.

Supercharging with such blowers was comparatively simple, apart from the difficulties of maintaining close clearances between rotors and casing or vanes and casing and providing the right amount of lubricant, because double or triple belts from a convenient engine pulley would provide the drive. The idea was exactly the same as with today’s turbocharging, namely, to increase the effectiveness of a production power unit without drastically modifying its internals. 

Apart from lowering the cr by using I.c pistons or, less expensively, a thicker head gasket, there was little else to be done (but you cannot tack on turbochargers that easily), and even mild supercharging was an excellent way of disguising inlet manifold deficiencies, as Lagonda with their twin underhead-camshaft 2-litre, and possibly others, discovered.

So before WW2 the supercharger flourished as readily as the proverbial green bay tree – the writer has very happy memories of exciting runs in the 30/220 Mercedes-Benz and blown 2-litre Lagonda cars as a young man, directly as a result of his interest in supercharging: and less exhilarating recollections of a night spent on the Byfleet side of Brooklands Track while the late Granville Grenfell slaved to put a proprietary blower-set on an SV Ford Ten engine under the eyes of customer Leslie Ballamy …. 

Now that kind of supercharging is as dead as the Dodo and the sprag. The magic word is now turbocharging. However, remembering how exhaust gases (as well as road salt) corrode exhaust systems so that they need early replacement, and the exceedingly high speeds at which turbochargers have to run (100,000 or more r.p.m.), there could be uneasy thoughts about driving a high-speed blower with an exhaust-turbo, apart from the driver’s awareness of turbo-lag when wanting to accelerate. 

To employ gases going to waste to provide increased performance makes sense, but doing so is not entirely free from power loss – in this world, you never get a great deal from almost nothing, although the Government lottery and childbirth are possibly exceptions that prove the rule! In the case of the turbocharger there is exhaust back-pressure to contend with. And if, in the past, engine-driven boost tended sometimes to absorb nearly as much power as it was supposed to produce, Fiat say that their superchargers of this kind, running at 0.85 engine-speed, use only five to six b.h.p. at 4,500 r.p.m. 

So, with modem toothed belts providing a simple, non-slip supercharger drive, blower­-lubrication better understood, and the Fiat light-alloy superchargers weighing a mere 35 lb, there seems to be a good chance of the pre-war system of boosting a production power unit coming back into use, especially as Fiat claim it to cost some 20% less than installing what they call the “complex exhaust turbocharger”. 

Being forward-looking engineers, Fiat will continue to have Weber research turbocharging for them, while doing these other experiments with belt-driven positive-displacement super­chargers. The experiments are being done on the Mirafiori twin-cam range of engines. And as a reminder of just one facet of clever Fiat detail work in this field, the writer has somewhere among what he prefers to call his things of motoring interest rather than “collectors’ items” a sort of plain pre-decimal penny given to him by former Fiat-PRO Alfred Woolf; it is a shim from the valve-gear designed by Aurelio Lampredi (who came to Fiat, as you know, after developing racing engines for Ferrari) so that tappet adjustment can be done without removing the o/h-carnshaft – ingenious! There is a drawing of this in Motor Sport for October 1969, page 1080.

All of which makes us hope that in the not too distant future we may perhaps be able to drive behind the classical twin-cam engine of the spacious Fiat Mirafiori Sport Saloon and behind a supercharger of the good, not-so-old-fashioned pre-war kind, thus enjoying excellent all-round performance while conserving petrol, as with the Type 43 Bugatti all those years ago … . 

Charlie Martin’s Motor Racing – Correction 

In the article commencing on page 1165 the Lagonda which shed a wheel in the 1937 TT while being driven by CC Martin was of course a Fox and Nicholl 6-cylinder 41/2-litre, not a V12 car as stated. – WB.