Keith Duckworth, the supreme British racing-engine designer, is known to have had an aversion to supercharging and turbocharging. Graham Robson has made this clear in his fascinating book Cosworth, which MOTOR SPORT reviewed recently. Duckworth made this quite clear soon after the appearance of the first turbocharged F1 car, the Renault V6 RS01 of 1977. Although there were to be Cosworth turbocharged engines, at that time Keith Duckworth saw the turbocharger as different even from a supercharger as a means of taking an unfair advantage in racing. He saw the turbo as a gas turbine sharing its combustion chamber with a piston engine, which is the equivalent of having a two-engined F1 car, which the rules expressly forbid. There may have been mild commercial undertones in this but no-one would question Duckworth’s technical arguments.
The supercharger, he said, was rather different, as although it affected the weight of charge into the cylinder, at the expense of driving the blower or compressor, only the piston stroke did the expansion work. Be that as it may, both supercharger and turbocharger are a means of obtaining more power from an engine without increasing its size. It might be expressed as dodging the old adage that there is no substitute for litres . . . . We know how engineers seeking this line of action looked hopefully at the supercharger, from the days of Chadwick’s experiments in 1908, through the pioneering work of Daimler-Benz who saw forced induction of the mixture as a means of improving the acceleration of production cars, to Fiat’s perfection of supercharged racing engines by 1923, which enabled them to dominate the Grand Prix scene and cause other constructors of such racing engines to follow suit, unless the rules specifically prevented them from so doing.
That was followed by sports car makers such as Austin, Alvis, Lea Francis, Bentley, Bugatti, Stutz and others following Mercedes into blowing their engines, and then followed a spate of tacking belt-driven and chain-driven supercharger sets onto all manner of long-suffering family car engines, even onto flat-twin Jowett, Armstrong Siddeley, Ford Eight and Ten, Hillman Minx and the like, in the hope of endowing them with a little additional urge over and above their normally pedestrian performances. Here I must restrain myself from listing the surprisingly large number of supercharger makes available, beyond the best remembered, such as Zoller, Powerplus, Marshall, Arnott, etc and from discussing which was the better approach, blowing through, or sucking from, the carburettor. . . .
The fact is that in racing, a supercharger (or turbo) gives an artificial answer to a given cylinder capacity limit. A fact which the taxation authorities never took into account, to Duckworth’s amusement. In Grand Prix racing this should be of no moment whatsoever. I have long believed that in the top form of motor racing no limits should be imposed, in the interests of technical advance. That engines of all sizes, and all types, gas turbine, blown and non-blown, should be allowed to compete together, with perhaps certain thoughts in the realms of safety.
When it comes to events divided into capacity classes the position is different. The first anomaly here is in the field of record breaking. A considerable number of capacity divisions are recognised, but what a car achieves remains strictly within the capacity class to which it belongs. A small-engined car may go faster over a given distance/duration than a larger-engined one, but it cannot claim a record in the latter’s class, unless it goes faster than all the cars in all the classes, in which case it owns a World record as well. This was shown up in 1924 when Darracq took records in the 1 1/2-litre category. Alvis had also set records in the then extant Light-Car class, (Class A). Darracq protested in print that Alvis was claiming records which did not belong to them.
To this G Smith-Clarke, Chief Engineer and Works Manager of the Alvis Car & Engineering Co responded, saying that Alvis did hold certain 1 1/2-litre class records but the records Darracq thought they had claimed wrongly were in Class A, for cars of over 1500cc. To attack these records the Alvis engine had been bored out to 1563cc, after which there was a loss of 2.7 mph in top speed. They added that surely Darracq should be the last to expose the matter, because whereas the Alvis engine used for the Class A records was only 64cc above the 1 1/2-litre class top permitted limit, the 1486cc Darracq which had claimed Light-Car class records had taken them during the 200 Mile Race, in which it had run supercharged. Smith-Clarke calculated that if the efficiency of the Roots blower used was 70% it was capable of delivering 2740cc of charge to the cylinders per two revolutions, so that the comparative capacity of the Darracq engine was 2740cc. (This would have put the Darracq into Class D, for cars of over 2458cc and under 2868cc. At the time the 200 mile record in this class was held by a Wolseley, at 88.93 mph, compared to the Darracq’s Light-Car class, under 1500cc record of 102.27 mph). It is interesting that the spokesman for the Darracq Company argued that if a Light-Car class record was broken at a higher speed than a Class A record (their 102.27 mph for 200 miles opposed to Alvis’s 94.67 mph) it should count in both classes. It might have been logical but as explained at the beginning of this discourse, that was not how records were recognised, and the rule holds to this day.
Be that as it may, the advent of the supercharged engine made a mockery of races (and records) to which capacity limits applied. Smith-Clarke calculated that the blown 1 1/2-litre Danacq was the equal of an atmospherically charged engine of 2740cc. When blown (s/c) and non-blown (u/s) cars were permitted to compete together in Grand Prix races from 1938 to 1946 the ratio was set at 4 1/2-litres u/s, 3-litres s/c. This was seen as giving too great an advantage to the forced induction cars and was altered from 1947 to 1953, when supercharged 1 1/2-litre cars were pitted against those of 4 1/2-litres u/s. This worked at first in favour of the big atmospherically charged cars, until the two-stage blown Alfa Romeo Alfettas got into their stride.
When the top limit for non-supercharged engines in F1 racing was reduced to 2 1/2-litres from 1954 the former 3 to 1 ratio of unblown to blown was almost retained, as s/c cars of 750cc were provided for. But as Laurence Pomeroy explained, by this time the 2 1/2-litre racing car engine should have been able to develop 115 bhp/litre at 8000 rpm, equal to an output of 290 bhp. To compete, a 750cc engine would need to be blown at 50 lb to produce a bmep of 520 lb/in. No wonder there were no effective takers. When it came to 2-litre F2 racing in 1947/53 the limit of 500cc for s/c power units was even less encouraging to those who thought in terms of blowers . . . .
Once viable supercharged racing car engines had been used by Fiat in 1923 all capacity limits imposed by officialdom, hopeful of creating more efficient machines that might benefit ordinary car users, or in the interests of reducing the speed of GP cars to an acceptable level, had little meaning. Imposing weight limits, fuel restriction, or what have you, retained into the turbocharging age, were tried; the fact is that after 1923 the 2-litre, GP limits had far less meaning than intended. Sadly, my ideal of a formula libre applied only during the doldrums of 1931/33. It was not until 1961 that the authorities offered a real sop to ordinary cars hoping to gain from racing, by banning supercharging and special fuels.
Supercharging, or turbocharging, dismissed cylinder capacity limits more surely than any other tuning factor on an otherwise standard engine. So how did organisers of pre-war races run on a capacity class handicap system treat s/c and u/s cars? When the RAC ran its first Ulster TT sports car race in 1928 it used class divisions as laid down for International record breaking back in 1925. But it failed to apply different handicaps within these divisions for the supercharged cars. It remained the same in 1929 and 1930, except that the carrying of ballast (246 lb in the case of the larger cars) no longer had to be endured. With no extra handicap on blown cars it was perhaps not surprising that the 1928 TT was won by a s/c Lea-Francis from a s/c FWD Alvis, that in 1929 Caracciola’s blown Mercedes-Benz won, with the next ten places filled by s/c cars, and that the 1930 TT was dominated by the team of s/c Alfa Romeos, and the 4th, 5th and 6th places taken by supercharged cars. I think I can see Keith Duckworth’s wry smile.
By 1931 the RAC had learned its lesson. It decreed that in the up to 750cc class the blown MG Midgets would receive a start of 4 laps and 8 minutes over the scratch 38/250 hp Mercedes-Benz but the lone u/s MG Midget had an advantage of five laps. In the 1100cc class the u/s cars were handicapped at 3 laps 5 min, against 2 laps 8 min 48 sec for a s/c Maserati. The respective penalties for u/s and s/c 1 1/2-litre cars were two laps, 8 min 48 sec for the blown Maserati against Frazer Nash and Aston Martin at one lap, 9 min 18 sec, and in the up to 3000cc class four minutes with no credit laps, against ten minutes. Rather suprisingly, if the blown 4.9 Bugattis with ace French drivers had started, they would have been penalised only two minutes over the u/s 4 1/2-litre Invictas, a slight start indeed from the aforesaid scratch 7-litre s/c Mercedes.
How did it work out this time? Norman Black’s s/c MG Midget won and supercharged cars were second and third. In spite of all this, these pre-war TT’s did produce some very close finishes — but the poor starter, the results officials, and the less knowledgeable spectators would perhaps have deserved our sympathy! The RAC gave up by 1934 and banned supercharged entries from the TT; by then the magic of forced induction was less popular with ordinary sports car drivers than it had been in the late 1920s.
The BRDC was also aware that supercharged cars should go faster than normally charged ones. For example, in its 1931 500 Mile Race round the Brooklands outer circuit Mr AV Ebblewhite had handicapped the lone u/s MG Midget to set off 24 minutes before the gaggle of blown Midgets. Of the 1100cc cars, a blower earned a start penalty of 12 min 4 sec, and the u/s 1 1/2-litre cars were released at the same time. Curiously, an u/s 2-litre straight-8 Bugatti was regarded by “Ebby” as the equal of a supercharged one, and both Bugs left with the u/s 3-litre Roesch Talbots.
But if you were in a s/c 2.3 Bugatti or Alfa Romeo you were held for an additional 3 min 1 sec (trust “Ebby” to resort to a single second in a 500 mile race). In the up to 5000cc class the normally aspirated cars had a start of 3 min and that odd second again, from the Birkin blower 4 1/2 single-seater Bentley. Finally, the heavy metal was assembled, ready to receive the starting flag more than 1 hr 20 min after the first car, that MG, had left the line, and the “Old No.1” 6 1/2-litre Bentley was dispatched on its victorious run. The blower 4 1/2 Bentley and both Mercedes-Benz, would have a further 3 min 1 sec to wait before joining in, the field then complete.
It was perhaps fair enough. The 6 1/2-litre Bentley won, from a Talbot, with a blown MG Midget third. Anyway there were prizes for the best blown and unblown cars in each class. It was left to the ingenious Junior Car Club, with its 250 mile International Trophy races, to devise a means of running a handicap race without resorting to time or credit lap starts. It did this by deflecting cars of different engine capacities into bends, or channels, of varying severity, once per lap of a special course at Brooklands. Thus the spectators could see which car was leading on any given lap, without recourse to calculations or elaborate scoreboards. Clever! How did s/c cars fair, under this system? Well, in the first of these races, in 1933, blown 750s took the same channel as u/s 1500s, blown 1750s that used also by u/s 3-litre cars, and s/c cars of over 1750cc took the same course as u/s unlimited ones, but for some reason all eight-cylinder entries were regarded as in the latter class. By 1936 the handicap channels had increased to five, the categories now s/c 750 and u/s 1100, s/c 1100 and u/s 2000, s/c 1500 and u/s 2000, s/c 2000 and u/s 3000, and over 3000cc cars of either type, a closer call for u/s cars than under F1 and F2 rulings. For readers with a mathematical bent, it should concentrate the mind! WB