When you think Subaru, you probably picture rugged WRXs or reliable Outbacks but buried deep in Subaru Motorsport’s vault is a one-of-a-kind beast: the EG33 Flat-12 prototype. Born from fusing two flat-6 EG33 engines, this monster was an audacious push toward creating a naturally aspirated supercar engine that could have redefined Subaru’s performance limits.
The EG33 itself, a 3.3-liter flat-six used in the SVX, was no slouch, boasting dual overhead cams and smooth boxer architecture. But Subaru Motorsport had a far wilder idea slot two EG33 blocks side by side, synchronize them with individual throttle bodies, and pump out between 550 and 600 horsepower with a dry-sump oiling system under the hood. Imagine a flat-12 boxer, revving high, naturally aspirated and raw.
Though the engine represented the pinnacle of engineering with a complex intake setup and twin-cams across 12 cylinders it never raced or reached production lines. Its sheer width, complexity, and Subaru’s strategic priorities meant the EG33 Flat-12 remained locked away, a fascinating “what if” example of what could have been.
