Our theoretical look at the comparative speeds of leading cars from 100 years of GP racing. Part 2: the 1930s supercharging unleashes a power spiral. Words: Mark Hughes. Photography: LAT
1927 Delage 15-S-8
Index figure: 129
Virtual lap time of the current Spa circuit: 3min 33.7sec
A car that attained immortality by taking Robert Benoist to victory in all four Grandes Epreuves of 1927. At its heart was a hugely efficient supercharged straight-eight. Despite the loss of 500cc to the new regulations, it was still quicker than the 1925 2-litre V12. The car’s chassis lacked torsional rigidity, but the abolition of the riding mechanic in ’25 meant there was space to offset the transmission and engine, so the driveshaft ran alongside the driver. The chassis was also much lower, reducing both drag and centre-of-gravity height.
1928 Bugatti T35B
Index figure: 127
Virtual lap time of the current Spa circuit: 3min 35.7sec
A large-scale withdrawal from grand prix racing by manufacturers left the scene dominated by privateers. By far the most popular piece of hardware for them was the T35 Bugatti, introduced in 1924. The abolition of any engine formula allowed the use of the 2.3-litre supercharged variant of the single-cam straight-eight introduced in 1926 for libre racing. Giving just 130bhp, it was a less advanced, less efficient engine than the 1927 Delage.
1929 Alfa-Romeo P2
Index figure: 130
Virtual lap time of the current Spa circuit: 3min 32.7sec
Like the Bugatti, this design dated back to 1924 and had been continuously developed since. Also like the Bugatti, it was a traditional two-seater, high-chassis car harking back to the early-20s Fiat, and technologically inferior to the ’27 Delage. But Vittorio Jano’s 2-litre supercharged twin-cam straight-eight was sufficiently over-engineered to easily withstand big power increases brought by new alcohol fuel brews. Privateer owners Varzi and Brilli-Peri were enjoying 175bhp by 1929, 40bhp up on the original.
1931 Maserati 8C-2800
Index figure: 135.5
Virtual lap time of the current pc:i circuit: 3min 26.9sec
The 8C was the Maserati brothers’ response to the libre GP regulations. Introduced in 1930, in 2.5-litre form it was no faster than the revitalised Alfa P2. But the Maser got into its stride with the 2.8, which won on its debut with Fagioli at Monza. The straight-eight, supercharged, twin-cam, two-valve-per-cylinder design was installed in an equally conventional chassis, still with two-seater dimensions; but it was potent — with close to 200bhp at 6000rpm.
1932 Alfa-Romeo Tipo B
Index figure: 140
Virtual lap time of the current Spa circuit: 3min 22.3sec
The first pukka single-seater GP car, the tight-fitting, drag-reducing narrow body enclosed an innovative mechanical layout. Twin superchargers fed the 215bhp, 2.6-litre alloy-block straight eight. But the best bit was how the designer managed to get the driver sitting lower than the transmission without using the spare seating space as the ’26/7 Delage did. Whereas the French car offset the whole transmission and engine, in the Tipo B (also known as P3) the driveline was split. The diff was moved to the centre of the car (next to the gearbox) and drove two propshafts, taking drive to each rear wheel via bevel gears. The driver sat between these shafts. Nuvolari helped Alfa to a dominant season.
1934 Auto Union Type A
Index Figure: 150
Virtual lap time of the current Spa circuit: 3min 11.9sec
The 750kg formula was a soft target for the two Nazi-subsidised German teams. Professor Porsche came up with a radical solution for Auto Union. The advantages of the mid-engine layout and four-wheel independent suspension were each amplified by the immense power and torque of the new V16 supercharged 4.4-litre engine. With no propshaft to clear, the driver sat low. It was a monster, but a very fast one.
1935 Mercedes W25B
Index figure: 153
Virtual lap time of the current Spa circuit: 3min 08.8sec
More conventional in layout than the rival Auto Union, but more sophisticated in detail. The front-engined Merc was developed from the original ’34 car. The independent suspension of the German cars made massively more powerful motors feasible — by late ’35, this was producing 462bhp, its traction aided by a rear-mounted gearbox. Extensive use of light alloys kept the weight in check.
1936 Auto Union C-type
Index figure: 158
Virtual lap time of the current Spa circuit: 3min 03.6sec
Ostensibly the same design as the ’34 original, but now with six litres and 520bhp. Torsion-bar springs at the rear had replaced the leaf springs of ’35. The use of a ZF limited slip diff for 1936 gave it much better traction than the Mercedes, helping Bernd Rosemeyer to the European championship.
1937 Mercedes W125
Index figure: 163.4
Virtual lap time of the current Spa circuit: 2min 58.0sec
A longer-wheelbase version of the W25, with a 5.7-litre evolution of the original straight-eight. Once they’d put the supercharger after the carburettor, as per the ’24 Sunbeam and most others subsequent to that, this was the most powerful GP engine until the early 1980s, with 646bhp. The previous box-section chassis was replaced by a tubular frame.
1938 Mercedes W154
Index figure: 160
Virtual lap time of the current Spa circuit: 3min 01.5sec
A new 3-litre formula replaced the 750kg one, with sliding maximum weight limits according to engine size. Mercedes took the W125 design and installed in it a new 60-deg V12. Its 468bhp at 7800rpm represented a big increase in engine efficiency. The engine was skewed to run the propshaft alongside the driver (finally bringing this aspect up to date with the ’26 Delage). It was noticeably lower than the W125.
1939 Mercedes W154/M163
Index figure: 165
Virtual lap time of the current Spa circuit: 2min 56.3sec
Twin-stage supercharging upped the power to 485bhp and a more streamlined body further increased the straight-line performance. At 800kg, it was almost 100kg lighter than the W154. Interestingly, this car’s lap time is roughly halfway between that of the original 1906 Renault GP car and the F2002 Ferrari, the fastest current-era Fl machine.