HPI Racing Subaru STIs
Snatching racing titles and pushing the limits of street performance, the Subaru Impreza STI has become the dream car of many enthusiasts. The Subaru STI combines the practicality of production vehicles with the performance of true racecars. The result is a potent combination of a high-output turbocharged four-cylinder engine with a road-hugging all-wheel-drive configuration. Subaru STIs can be spotted just about anywhere. Whether it's during a daily commute or it's the car of choice in video games, the STI has gained a cult-like following in the import-performance community.
Competition
One venue that the Subaru STI has proven itself in is Japan's Super Taikyu Series. The Super Taikyu Series is Japan's full-fledged endurance racing series. The Super Taikyu is strictly controlled with competition and technical regulations, which forces race teams to work within the confines of production-based vehicles. Closely resembling their factory counterparts, these highly-tuned vehicles represent the performance and durability of Japan's auto manufacturers. Racing throughout Japan, the Super Taikyu series hits top racing circuits like the Twin Ring Motegi and the acclaimed Suzuka Circuit.
Collaboration
In 2004, HPI Racing joined the Prova Engineering team in their Subaru STI race campaign for the 2005 season. Prova prepped the '04 STI to race in the Super Taikyu endurance racing series. The driver of this car would be Kazuhiro Koizumi, an ex R/C car racer and long time friend of Tatsuro Watanabe, owner of HPI Racing.
Preparation
Staying within the restrictions of the Super Taikyu series, the focus of the build was to deliver excellent handling, moderate power, and long-lasting durability. To this end, the EJ207 engine was left mainly stock. During races however, Subaru Tecnica International offered its assistance with engine support. To elevate the handling characteristic of the Subaru, Prova Engineering shocks were matched to Nova 18kg/mm springs up front and 16kg/mm springs in the rear. The adjustable suspension was used to lower the vehicle onto 17-inch Enkei RS+M wheels, which were wrapped in Yokohama A048 rubber. The performance of the STI was also addressed as a Fujitsubo tubular exhaust manifold and exhaust system were installed. The ignition and fuel maps were optimized with a Prova Super Sports re-flashed ECU. As for longevity, four Bosch 044 fuel pumps were mounted in the trunk to pull fuel from an Aero Tec Laboratories fuel cell to ensure a steady and uninterrupted supply of fuel to the EJ207 engine. Cooling duties were assigned to a custom aluminum radiator and custom oil cooler setup. During racing action, the driver can check vital engine data from a Pi Research data-acquisition system. The driver was also protected with a Prova Engineering roll cage, which surrounds Recaro seats with Sabelt four-point harnesses.
Continuation
The 2004 Prova Engineering Subaru STI sponsored by HPI Racing went on to claim first place for the 2005 Super Taikyu championship along with many other victories. The following year however, Prova decided to once again construct another STI to complete in the endurance racing series. The second car, a 2005 Subaru STI received a facelift to resemble the '06 units and was further refined from the experience gained from the first STI. Some of the changes include a relocated differential cooler with a scoop to channel airflow, a dual titanium exhaust instead of the single exhaust system used on the previous model, and the usage of carbon fiber in place of fiberglass. HPI Racing again united with Prova Engineering for a full sponsorship of their endurance racecar. The initial plan was to race, win, and create replica R/C cars and components; these goals were quickly realized and supported by both the full-size and R/C communities. This program included die cast replicas as well as gasoline-powered reproductions of both racecars.
Realization
Through various partnerships, companies such as HPI Racing and Prova Engineering have been able to fulfill their aspirations. From constructing two championship-winning Subaru STIs or designing R/C cars for the masses, HPI has shown that hard work and perseverance will pay off. For all the enthusiasts out there that have ambitions of owning a high-performance import but are still paying their dues, HPI offers nearly every popular import platform in an R/C version. With features like real all-wheel-drive drivetrains, disc brakes, and high-revving engines, HPI's products can bring you one step closer to your dream car.
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