This Twin-Turbo V12 WRX STI Aims for 1000 Horsepower

Caecey Killian June 27, 2025 2 min read 0

19

Engine swaps come in all forms, but some stand out for more than just shock value. Jonathan Proulx’s 2009 Subaru WRX STI is one of those builds. What started as a wild 2JZ-GTE swap—the first all-wheel-drive 2JZ STI with a six-speed manual and switchable AWD—has evolved into something even more extreme. The latest iteration of the car drops the famed Supra engine in favor of something much more unexpected: a 1GZ-FE V12 from a Toyota Century to make a V12 WRX.

From a 2JZ Swap to Full V12 Madness

Proulx’s 2JZ build once set the benchmark for unique AWD swaps, but eventually the novelty wore off. That led to the pursuit of something even more unique. The 5.0-liter V12, known for its use in Japan’s flagship luxury sedan, isn’t exactly a performance icon in stock form. But that doesn’t matter—Proulx is building the V12 Subaru to deliver “a minimum of 1,000 horsepower.”

Twin Turbos and Street-Strip Ambitions

To reach that goal, the V12 has been heavily fortified with forged internals, including upgraded pistons, rods, and valve springs. Fuel is delivered via 1,000-cc Bosch injectors, and management is handled by a MaxxECU PRO standalone system for this V12 WRX. Twin Garrett G30-770 turbos will provide the boost needed to get the big engine well into four-digit power territory.

Despite the extreme nature of the V12 Subaru build, Proulx still wants the car to be livable. His target? Keep the air conditioning, keep it street legal, and be able to drive it to the drag strip, run a 9-second quarter-mile, and cruise home in comfort. To help make that a reality, a seven-speed DCT transmission from a BMW E9X 335i is being fitted to handle the power and deliver smooth shifts on and off the strip.

A V12 WRX is an ambitious setup, merging reliability, comfort, and race-level performance into one incredibly unique Subaru. With the V12 already in place and the rest of the build underway, we’ll be watching closely to see when it finally makes a pass—and how it sounds doing it.

AboutCaecey Killian

Caecey Killian covers builds, installs, and product features for Car Junkie Magazine. He has spent years on the floor of the garage chasing horsepower across SBC, LS, and modern muscle platforms, and that shop time runs through every article he writes. His current CJM project is Project Street Reaper, a 1976 Camaro built around a fresh SBC 350. He is also known for Project Mighty Mouse, a 1977 Chevy Nova running a 1962 small-journal 327 SBC, with build coverage published across multiple online automotive magazines. His media background spans long-form build documentation, install coverage, and product features across the magazine and the Car Junkie Magazine YouTube channel. He writes the way he wrenches: specific, honest about the mistakes, and grounded in real garage work.