The Evolution of Supercharging in Motorcycles: GPZ900R Custom

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POWER BUILDER's GPZ900R

Supercharging became common in the motorcycle industry with the introduction of the Supercharged Model Ninja H2 in 2015, but before then, it was a special case. However, in the world of customization, there were already many examples that took advantage of the improved filling efficiency of turbochargers and superchargers, eliminating the disadvantages of lag and sudden power ramp-up through advances in computer technology. Power Builder has also been involved in mechanical tuning and turbo tuning of four-wheeler engines for many years, and they have incorporated their know-how into this Turbo Ninja.

All the supercharger parts, including the piping, are custom-made. The stock Nissan Skyline GT-R (R32) turbine and Toyota injectors were also utilized. The base engine is the Ninja GPZ900R, and the compression ratio was reduced to prevent detonation caused by overcharging. The power output reached 230ps, a level that would be impossible to achieve through mechanical tuning alone, and the torque was measured at 21.5kg-m (both measured at the rear wheel). What's even more astonishing is the bike's ability to handle both city and touring riding without any issues, even with a constant boost of 1 kg/cm2. After reaching the limits of this specification, the shop began working on a 300 hp version. And now, almost 25 years later, the Ninja series continues to push boundaries, including the Ninja (200 hp with mechanical tuning) competing in the TOT Hercules race.

Handle

In addition to the engine tachometer on the left and speedometer on the right, gauges for monitoring the oil temperature, oil pressure, air-fuel ratio, and boost (in the center) have been added. The handlebars have been replaced with a bar type. The front master cylinder as well as the clutch side are NISSIN.

Engine

The engine is derived from the GPZ900R and has been increased to 984cc (from 908cc) using Wiseco φ75.5mm forged pistons designed for the '88-'89 ZX-10. To accommodate supercharging, the compression ratio was reduced to 8.75:1 by enlarging the combustion chamber capacity and utilizing connecting rods from the '86-'87 GPZ1000RX, which were shorter in overall length compared to the GPZ900R.

Intake & Exhaust

The supercharging system is comprised of several components, including a Nissan Skyline GT-R (R32) turbine, TRD injectors with a discharge capacity of 720cc x 4, a custom-made φ60mm throttle body, an HKS intercooler (which cools the hot compressed fresh air and ensures efficient filling), a blow-off valve, a TRUST VVC (Variable Valve Controller), and improved lubrication for the turbine and camshaft. The entire system is controlled by a HALTECH F9 full computing system.

The wheels are Performance Machine aluminum (front is "Chicane" 3.50-17 size, rear is "Solid" custom-made 6.50-17 size), and the swingarm is a custom-made Wheelie wide & 3cm long type. The front fork is a φ41mm upside down type from a GSX-R1100L ('90 model), the outer tube is anodized to match the body color, and the internals are also set up. The rear shocks are Ohlins. Front and rear brake calipers are by Performance Machine.

Gallery

Specifications

Part	Details
Engine	WISECO Over Boa Piston Kit ZX-10R
Exhaust	TSUKIGI ARETE DEXTER Silencer
Frame	WHEELIE 7N01 Swingarm
Brake	PERFORMANCE MACHINE 4 Piston Caliper PERFORMANCE MACHINE Front Brake Disc PERFORMANCE MACHINE 2 Piston Caliper SUNSTAR Custom Rear Brake Disc
Wheels	PERFORMANCE MACHINE CHICANE 3.50-17 PERFORMANCE MACHINE SOLID 6.50-17
Suspension	OHLINS Rear Suspension
Steps	CRAFTMAN Mounting Plate Footpeg Kit for NINJA
Drive System	CRAFTMAN Clutch Release Type-A for NINJA
Electrical	HALTECH F9 Engine Managemnet System
Others	TRUST Variable Valve Controller

About POWER BUILDER

"POWER BUILDER" is a winning tuner in the Taste of Tsukuba, Japan's premier Sunday race for steel-frame bikes from the 80s and 90s. "Power Builder" is a tuner who always wins the Taste of Tsukuba, the most prestigious Sunday race in Japan, where the best bikes from the 80s and 90s compete. Power Builder" is not a restoration company, but rather a company that creates power, a company that is thoroughly committed to creating products that live up to its name.

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Original Source of this Article

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