In August of 2005, competitive drifting had finally returned to its roots of street driving with the introduction of the D1 street legal series. No longer was the field of competitors filled with D1-spec vehicles sporting tube-framed chassis, sequential transmissions or high horsepower engine transplants. The D1 committee was determined to level the playing field between both pro and amateur competitors as strict D1SL rules required all drivers to enter with fully sanctioned street legal vehicles and compete in more "streetable" machines. The pure competitive nature of drifting was no longer handicapped with who possessed the most tricked out vehicle or the most horsepower as amateur drifting enthusiasts were given the opportunity to wet their feet and compete in an evenly competitive field of drivers to see who would reign supreme.
Guts, a large pair of brass balls, and the willingness to take your vehicle to the limits are prerequisites when entering the competitive world of drifting. If a little bit of craziness was all it took to find the perfect driver to suit the D1 street legal series, BOMEX found a perfect candidate by the name of Naoya Yamano. Yamano's resume was overflowing to the brim with plenty of motorsports experience, such as the All Japan championship Gymkhana series and Integra One Make Race in 2005. In 2006, Yamano held on to become series champion in Super Taikyu class 4 piloting an Integra DC5. This year brings new challenges to the young superstar as he once again campaigns in Super Taikyu in class 1 series for the Euro Mevis/Macau/Advan Porsche team and currently holds third place in the rankings. With such a robust background in racing, it was no surprise that Yamano welcomed the sport of drifting as it brought forth a whole new challenge to a man who seemingly done it all.
With driver packed down tight, the Bomex team moved forward in finding a reputable shop, able to build the perfect engine for their Silvia. Red Matsuda Tuning shop of Osaka, Japan was commissioned to fully assemble the BOMEX S15's SR20DET engine from top to bottom. Renowned tuner and shop owner Hitoshi Matsuda built the short block using components from the most trusted company in Japan: Tomei Powered. A set of 86.5mm Tomei forged pistons, with a compression ratio of 8.4:1, replaced the factory slugs and topped off with a set of Tomei titanium-coated piston rings. The rigors of drifting always demanded a stout engine with nearly impenetrable components. A set of beefy Tomei forged H-Beam rods stuffed into the SR20DET block spins to the tune of 8500 rpm with the aid of specially treated Tomei micro-finish main and rod bearings. Each bearing undergoes a special treatment process that's been proven under scientific data to outperform and outlast the factory bearing under full engine loads.
With the bottom end buttoned up and built for endurance, the next stage in the game turned towards creating additional power under a newly revised cylinder head. Tomei Powered engineers porting and reshaping the bowls while installing a full aftermarket valvetrain of Tomei valve springs, retainers and valve guides. Tomei Poncams with 256mm duration and 11.5 intake and exhaust lift were installed to help improve midrange and top end response. A front-mount ARC intercooler chills the inlet charge leading into the intake manifold, while exhaust gases pulse through a Tomei Extreme exhaust manifold before making its way into the Tomei ARMS B7652 turbine. Equipped with a 76 trim turbine wheel and T25 turbine housing, the B7652 turbo has been proven to outflow and outperform the factory S15 turbo while delivering superior response-an ideal setup for the BOMEX S15. Spent gases are huffed out the tail section using a 5Zigen Border III exhaust system.
Using a Tomei metal head gasket to sandwich both upper and lower halves of the engine together, the newly built engine was christened with a set of Tomei 740 cc/min side feed injectors. A Nismo fuel pressure regulator maintains adequate fuel fed through a Bosch fuel pump system, complete with a custom surge tank setup. Looking to remedy engine overheating problems associated with the S15 Silvia, an ARC 3-row aluminum radiator helps maintain stable temperatures on the track as large portions of air are ingested though a RUN MAX air intake cleaner. Feeding the brains of the operation is a Tomei Reytec engine control system. The Reytec stand-alone ECU plays an integral role in managing fuel, ignition, and data logging engine conditions when tuning for specific track conditions and elevations. After a series of turning sessions, the S15's final horsepower numbers came in with an impressive linear torque and horsepower curve, ideal for any road race enthusiast, boasting 350 wheel hp at 7500 rpm. Not impressed, you say? Consider the fact that this car is still boosting on the streets of Osaka through its catalytic converters and easily passes Japan's government-controlled emissions inspections. It's a drift car folks! Not a drag car.