beginning, the formula was largely based on pre-World War II regulations defined by engine capacity. The regulation expected to bring a new balance between supercharged and normally aspirated cars. Non-supercharged 4.5-litre pre-war Grand Prix cars were allowed to race against the pre-war 1.5-litre supercharged 'voiturettes', while pre-war supercharged 3-litre Grand Prix cars were banned.

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