Guzzi's Supercharged Four

Another supercharged motorcycle, this Carlo Guzzi’s 1931 Quattro Cilindri, photographed by Phil Aynsley. It was a case of something old, something new, something borrowed (but nothing blue). The Cozette rotary supercharger was positioned above the gearbox, which sat vertically behind the crankshaft as on modern sportsbikes. The very oversquare layout, at 56mmx50mm, was also something today’s engineers would recognise as good practice in an engine designed for outright power. The four individual cylinders lay almost horizontally, mimicking the Guzzi singles, justified in terms of packaging and cooling. Yet the pushrods driving overhead valves and the hand change three-speed gearbox seemed old fashioned ideas in 1931. It was also surprising that there was a rigid rear frame, Moto Guzzi have practically been alone in developing and proving the worth of rear suspension. The Quattro weighed close to 165kg (365lbs) so, despite producing 40bhp at 7,800rpm, it seems the power and weight would have proven more of a liability than an asset on all but the smoothest race track. The Quattro’s only race was at the Nations Grand Prix in 1932 where three of them were entered. Terzo Bandini rode to great effect, challenging the winning Norton for the lead for much of the race. Yet all three Quattros failed to finish and, despite the considerable extra power they offered compared to the competition, they showed no great promise in the race. The Norton International that won was a new long-stroke design that produced just 29bhp. In theory the Moto Guzzi’s 30% horsepower advantage should have allowed riders to pull out uncatchable leads along the straights, but there were mitigating circumstances. Firstly the Nations Grand Prix wasn’t held at Monza, Moto Guzzi’s home track, from 1932 and 1934. Instead it was hosted at Rome’s airport, the Pista del Littorio. This was a much shorter, slower circuit than Monza, although the winning rider still averaged 170km/h (105mph). That the winning rider was Piero Taruffi also meant Bandini had nothing to be ashamed of. Perhaps this was the reason Carlo persevered with Quattro until the end of 1932 when the project was quietly dropped.

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