At eight liters of displacement, Bugatti's W16 is the largest engine on this list by volume, and it packs more cylinders than any other. Four turbos help the mill produce 1,479 hp (1,103 kW).
The Bugatti might not be the record holder forever, though. If it ever hits the market, the Devel Sixteen's V16 could produce 3,006 hp (2,242 kW) in daily driving configuration and over 5,000 hp (3,728 kW) in the maximum level of tune. A video proves that at least the engine of this actually exists.