The P3 was powered by a supercharged eight-cylinder engine. Despite using a cast iron engine block, the car was remarkably light for its period, weighing just over 1,500 lb (680 kg). The single-seat configuration was a meaningful departure from the two-seat convention that had defined Grand Prix cars since the early racing era. The car's agility and structural efficiency would prove to be recurring advantages across multiple seasons and engine specifications.
The P3 was introduced partway through the 1932 European Grand Prix season, making its debut in June. Tazio Nuvolari won the car's first race, and by the end of the year the P3 had secured six victories, with Nuvolari and Rudolf Caracciola sharing the winning drives. Those six wins included all three of the season's major Grands Prix in Italy, France, and Germany.
Financial difficulties hit Alfa Corse in 1933, and the decision was taken to withdraw the P3s from competition. The cars were locked away while Enzo Ferrari was compelled to run his breakaway works team, Scuderia Ferrari, on the older and less effective Alfa Monza. Alfa Romeo procrastinated until August, missing the first 25 events of the season. Only after extended negotiations was the P3 released to Scuderia Ferrari. Despite the delayed start, the cars then won six of the final 11 events, including the Italian and Spanish Grands Prix.
New regulations for 1934 mandated larger bodywork, prompting Alfa Romeo to bore the engine out to 2.9 litres to compensate for the additional weight. Louis Chiron won the French Grand Prix at Montlhery in a P3, but the German Silver Arrows — Mercedes-Benz and Auto Union — dominated the other four rounds of the European Championship. Even so, the P3 won 18 of the 35 Grands Prix held across Europe that season, reflecting the depth of the international calendar beyond the headline championship rounds.
By 1935, the P3 was comprehensively outpaced by the German factory teams in European Championship events. Yet the car produced one final, defining victory. For the German Grand Prix at the Nurburgring, Nuvolari's P3 was bored out to 3.2 litres. Running in the heartland of Mercedes-Benz and Auto Union, Nuvolari punctured a tyre early while leading and dropped back. After his pit stop he carved through the field, and on the final lap Manfred von Brauchitsch, whose Mercedes-Benz W25 had been leading, suffered a tyre failure. Nuvolari crossed the line to win in front of an estimated 300,000 stunned spectators. Across the full 1935 season, the P3's versatility enabled it to win 16 of the 39 Grands Prix held.
1932: Tazio Nuvolari, Rudolf Caracciola, Giuseppe Campari, Baconin Borzacchini
1933: Louis Chiron, Luigi Fagioli, Giuseppe Campari
1934: Achille Varzi, Louis Chiron, Guy Moll, Brian E. Lewis, Carlo Felice Trossi, Gianfranco Comotti
1935: Tazio Nuvolari, Raymond Sommer, Louis Chiron, Comte George de Montbressieux, Richard Shuttleworth, René Dreyfus, Vittorio Belmondo, Mario Tadini, Antonio Brivio, Guido Barbieri, Pietro Ghersi, Renato Balestrero
1936: Raymond Sommer, Charlie Martin, José Padierna de Villapadierna, Giovanni Battaglia, Clemente Biondetti, Austin Dobson
The Alfa Romeo P3's significance extends beyond its race record. As the first purpose-built single-seat Grand Prix car, it established a configuration that would define the sport's machinery for decades. Designed by Jano and refined across four competitive seasons, it remained a formidable weapon even as the German manufacturers poured factory resources into rendering it obsolete — and it produced arguably the most celebrated upset victory in pre-war Grand Prix racing at the 1935 Nurburgring.