When you picture a Porsche 912, perhaps visions of vibrant, pastel colors, a vintage charm, and a certain understated elegance come to mind. Similarly, the Subaru STi might evoke images of rally-bred performance, a distinctive blue hue, and a raw, energetic spirit. Individually, these cars represent distinct automotive philosophies. However, brothers Mike and Mat Davidson have masterfully blended these seemingly disparate worlds to create something truly exceptional: the Porsche 912R-STi. Built in a condo carport over five years of self-taught wrenching, this project showcases the Davidson brothers’ engineering prowess (Mike in mechanical, Mat in software) and their ability to fuse classic Porsche aesthetics with modern Subaru performance.
My first encounter with this remarkable car, dubbed the 912R-STi, occurred at Luftgekühlt LA. Amidst a sea of meticulously crafted Porsche 911 hot rods, many adhering to established modification trends, the Davidson’s creation stood out as a refreshing and inventive deviation. While many 911s boasted familiar upgrades like wider tires and rally-inspired Cibie lights, the 912R-STi presented a subtler, more intriguing proposition.
At first glance, the 912R-STi maintains a classic Porsche silhouette. It features iconic ATS Cookie Cutter wheels wrapped in performance tires, RS-style bodywork, a purposeful roll cage, and a vintage Prototipo steering wheel complementing plaid bucket seats. Its aesthetic is undeniably handsome and sporty without appearing overtly aggressive. However, beneath this refined exterior lies a beast capable of delivering nearly 300 horsepower in a lightweight, short-wheelbase chassis weighing under 2,000 pounds. Despite its clear modifications, the 912R-STi retains a sleeper quality, hinting at its true potential only when the rear decklid is raised, revealing a substantial intercooler. The story of how this unique machine came to be is a testament to the Davidson brothers’ vision, resourcefulness, and sheer determination, transforming a humble Porsche 912 into a high-performance marvel.
Growing up in the Midwest, Mat and Mike Davidson both developed a passion for cars. After college, Mat moved to the Bay Area, where he began working on a 1975 Porsche 911S project in his spare time. Mike, still in school, dreamt of building a Porsche 914. Initially, Mike had acquired a rusty 1957 Chevy Bel-Air, but after realizing the extent of the restoration needed, he opted for a different starting point. He traded the Bel-Air for a 1967 Porsche 912 located in Monterey. The 912, while also requiring significant work, became the new foundation for his automotive aspirations.
Eventually, Mike joined Mat in the Bay Area. Working on the Porsche 912 in cramped apartment garages with limited tools proved challenging. A New Year’s Day drive in the Santa Cruz mountains revealed the car’s unsafe condition. Extensive rust had compromised not only the bodywork but also structural components. The Porsche 912 was then moved to Mat’s garage in San Jose, marking the beginning of an extensive restoration and modification journey.
Although Mat possessed basic welding and bodywork skills from his own Porsche projects, progress was initially slow due to their full-time jobs and the sheer amount of work required. The first two years were primarily dedicated to welding the Porsche 912 back together. While they didn’t aim for a concours-level restoration, the brothers were committed to quality. They replaced rusted floor pans, front suspension pans, rocker panels, and even a taillight bucket. Demonstrating their dedication to authentic craftsmanship, Mat welded in 1974-’77 Porsche 911 flares and meticulously lead-filled the seams, mirroring factory techniques.
From the outset, the Davidson brothers envisioned enhanced performance for their Porsche 912. Fiberglass body panels were part of the plan, and they acquired bumpers, fenders, and a ducktail decklid from a local racer. These components, like the rest of the car, required considerable preparation. Mat undertook the task of prepping and priming all the panels in his condo’s parking space before sending the shell and ancillaries to a local shop for paint. While Mike relocated to Orange County for work, the Porsche remained with Mat in San Jose as they formulated a plan for the engine. Their initial intention was to rebuild the original 356-based flat-four engine into a high-performance version. However, upon disassembly, they discovered the engine was a Porsche “marine” engine – literally designed for a boat. After three unsuccessful attempts with different carburetor setups, they decided to abandon the original engine.
Shortly after this engine setback, Mat arrived home to find a large wooden pallet in his driveway. It held a motor and transmission sourced from a 2006 Subaru WRX STi. Weeks later, a brand-new TIG welder appeared in the same manner. Mike, recalling his college aspiration to swap a WRX engine into a Porsche 914, proposed the same for the 912. Mike, the mechanical engineer with aluminum welding experience, shipped the TIG welder and the Subaru powertrain to Mat. He then taught Mat the fundamentals of TIG welding, and they embarked on the engine swap.
Utilizing an adapter from Kennedy Engineering, the brothers mated the Subaru STi engine to a Porsche 915 transmission. They sold the Subaru transmission and headers to fund stainless steel exhaust components for a custom, equal-length header system. The TIG welder became crucial for addressing the cooling challenges of a modern turbocharged engine placed in the rear of a classic, rear-engined Porsche. The 912R-STi employs a complex cooling system with three radiators: one in the front bumper and one in each fender. Without resorting to extensive chassis modifications, they engineered a system of aluminum pipes and silicone elbows to maintain pressure and effectively cool the Subaru engine.
Wiring was handled by a harness from iWire. After five years of dedication and perseverance, the project Porsche 912 finally transformed into the road-ready 912R-STi. Today, the Davidson brothers are enjoying the fruits of their labor – a truly unique and compelling car. Their goal was to create a hot rod 912 with a flat-four engine, and their innovative approach exemplifies the creativity that sustains the vibrant community around early Porsche 911 and 912 models.
Now residing in Orange County with Mike, the 912R-STi is enjoyed in autocross events and car shows, prompting enthusiastic inquiries about its origins. Describing the driving experience, Mike shares: “The car itself is a total sweetheart to drive. It starts, idles, and accelerates like a modern Subaru, but steers, shifts, and brakes like an old Porsche. Under 3K RPM it’s as comfortable as any car I’ve driven… Once the engine is uncorked though, 3K and up, the power is savage, and feels almost endless. The motor last dyno’d at around 300hp at the wheels, and it made 265ft-lbs torque. More than enough for a sub-2000-pound car.”
This Porsche 912R-STi is a testament to the Davidson brothers’ vision and skill. They took a Porsche 912 that many would have deemed beyond saving and transformed it into a unique, high-performance machine. It’s a build that respects the Porsche heritage while boldly embracing modern performance, resulting in a truly exceptional automobile. Hats off to their ingenuity and dedication!
