The OS Giken Story


Engineering Engines
The first stop on our tour took us to the engine division, where we met the chief engineer of engine development, Tohru Takemasa. Clearly, OS Giken did not stop with the L28 engine. OS Giken embraced Nissan’s next great engine, the RB26DETT, producing a number of upgrades from camshafts to complete RB30 and RB31 engine kits that increase the displacement of the RB engine from 2.6-liters to 3.0-liters and 3.1-liters, respectively. However, as had happened with the older engines, power output had surpassed the capacity of the clutch options of the time, prompting OS Giken to begin the development of clutch solutions to handle the increased horsepower.
Improving The Middle Man
The next stop on our tour was the clutch engineering division. Surrounded by walls lined with flywheels, baskets, clutch discs and covers, chief engineer Hiroyuki Yamagata showcased the latest clutch development project, the twin carbon-disc Street Master clutch. Although it is still in the prototype stage, OS Giken is confident that this clutch will perform well on street applications without the usual chatter associated with multi-plate clutches. Okazaki also directed our attention to a release bearing and fork kit in development that features an adjustable slave cylinder rod and a fork return spring. OS Giken’s grasp of power transfer solutions inevitably led to the next component to fall short, the transmission.OS Giken is testing out carbon clutch discs on prototype Street Master clutch systems. If put into production, OS Giken states that it should perform flawlessly in day-to-day traffic and occasional weekend track days without the noisy multi-plate clutch chatter.
Geared Up
Below the second story main office, we were led to the transmission shop where we were greeted by engineer Ryosuke Sasaki. He had on display another of OS Giken’s original designs, the OS-88 sequential six-speed transmission for the powerful RB-powered Skyline GT-R. On the shelves were numerous gears and shafts for short ratio transmission kits offered for a variety of other platforms as well. He shared some insight with us about the process of transmission development and ways that the OS Giken gear sets improved upon the factory design. The OS-88 remains one of OS’s finest creations capable of handling up to 1,500 horsepower.The famous OS-88 sequential transmission for the Skyline GT-R features helical gears with dog engagement and a power capacity of 1,500 horsepower.
The Lock Up
With engine, clutch and transmission solutions in place, the next obvious driveline component that OS Giken would invest in was the differential. In the 90’s, horsepower development was on the rise, leading to numerous broken driveline parts, including differentials. Once again, dissatisfied with the offerings that were available, OS Giken channeled its energy into developing one of the finest limited slip differentials on the market. Head engineer Takuya Tomimatsu explained the differences between the stock and aftermarket differentials compared to OS Giken’s Super Lock differential. After studying the various designs, a clutch-pack style differential that featured a stronger housing, thinner pressure rings, more discs than any on the market and a 100-percent locking mechanism was born.OS Giken engineered the Super Lock LSD with a revolutionary locking system, thinner pressure rings and more friction discs. An LSD dyno tests each LSD design to ensure a positive lock.
Cranking Them Out
After visiting all of the engineering divisions, we were led into the one building we hadn’t yet seen, the manufacturing facility. Although OS Giken does not have a foundry on the property, the manufacturing division managed by Yukiharu Izumori runs non-stop, with lathes and CNC machines constantly grinding and cutting metal. From pistons and differential housings to transmission bell housings, many of OS Giken’s products were seen in various stages of refinement.Coming Full Circle

Watch for our OS Giken Shop Tour video coverage and exclusive interviews with Okazaki and the OS Giken staff in DSPORT DVD #27.
DSPORT would like to thank Mark Mendoza of Toyota Tsusho/OS Giken USA and Tom Oathoudt for assisting us with interpretation during our visit.