The 1932 season would be fought without the German cars from Daimler Benz. It would also be one with an open formula which limited only the length of the races to five hours. Building upon the lessons learned with the P2, Jano created the P3. The P3 Monoposto was the first genuine single-seat racing car in Grand Prix racing. It was powered by an eight-cylinder engine built around two four-cylinder blocks, each fed by its own Roots supercharger. One of the engines major strengths was its low-speed torque. Power to the rear wheels was transmitted through twin driveshafts that allowed for the drivers seat to be placed lower in the chassis. The original leaf spring suspension was replaced in 1935 by an independent Dubonnet front suspension. The complete car weighed in at only 1,545 lbs. and were it not for its cast-iron block engine, it would have weighed considerably less.

Winning its first race out of the box, the P3 went on to win 5 more major races in 1932. With the two best drivers of the day, Nuvolari and Caracciola racing them 1932 was a successful year. Some said that with a Jano designed car and their two great drivers they should not expect anything less. Financial troubles that had come to a head in 1933 saw the factory hand over racing to the Scuderia Ferrari team after going missing at the beginning of the year. Losing some of their initial superiority they still continued to wrack up victories later that year. 1934 found a new formula and new rivals from Germany. In the face of this Teutonic onslaught even Jano's Monoposto could not stem the tide except for one race that has come down through the ages. 

The P3's most famous victory came very late in its career when Tazio Nuvolari beat the combined German might of five Mercedes and four Auto Unions. That race, the German Grand Prix at the Nurburgring, in front of dozens of Nazi officials is considered one of Nuvolari's greatest victories of all time while the car that took him to victory, the P3 is enshrined in the pantheon of great Grand Prix cars.