The Bugatti Type 41 Royale’s engine has a displacement of about 12.7 liters.
More precisely, the Royale’s straight-eight engine displaces 12,763cc, or 12.763 liters, which is conventionally rounded to 12.7 liters. The enormous engine was designed for effortless power in one of the most imposing luxury cars ever built, rather than for compactness or economy.
The Type 41 engine used an overhead camshaft, three valves per cylinder, and a 125mm bore with a 130mm stroke. Its monobloc construction made the engine physically huge—roughly 1.4 meters long—and its design originated from an aircraft-engine concept prepared for the French Air Ministry.
Ettore Bugatti intended to sell the Royale to European royalty, but the Great Depression badly damaged the market for such an expensive automobile. Only seven cars were built between 1927 and 1933. Several unused Royale engines later found a second life powering high-speed railcars, an unusual consequence of the car’s limited sales.