“The History of Kansai Service Mukai’s Second Generation GT-R Tuning” A prestigious milestone–the first domestic car to achieve over 200 mph
Published : 2019/10/30 13:47 Modified : 2019/10/31 17:18
Toshiyuki Mukai Reflects on the Trajectory of RB26 Tuning
Kansai Service’s breakthrough and growth since the arrival of the second generation GT-R
The dawn of RB26 tuning. Kansai Service actively worked on Yatabe max speed tests, as well as other 0 – 300 km/h (about 186 mph) tests.
(Yatabe: high-speed test road of the Japan Automobile Research Institute)
The foundation of the current Kansai tuning was surely built during this time. This included turbine test balancing, exhaust pressure, exhaust temperature, intake air volume, and ignition timing. In this article, we would like to reflect on the trajectory since the appearance of the second gen GT-R.
In 1988, Kansai Service’s 3.1L + TO4E twin-turbo MZ20 Soarer became the first domestic car to achieve over 200 mph. It marked 323.159 km/h (about 200.801 mph) at Yatabe’s max speed test. The BNR32 Skyline GT-R appeared the following year. At that time, the max speed tests of cars such as the Supra, Soarer, Z, etc. were thriving. Then, the BNR32 came into the picture, which shook Japan’s tuning scene. It boasted a Group A-conscious package–including a 2.6L straight 6 twin-turbo, 4WD system.
Kansai Service started its development with a two-unit system. They ran it on Yatabe with a boost-up specification right away and began turbo tuning from the genuine bolt-on twin. At the same time, they advanced with the single turbo test. And by 1989–the release of the BNR32–the TO4S turbine specification had already surpassed 300 km/h (about 186.411 mph).
At that time, the president of Option Magazine, Daijiro Inada (aka Dai), was the driver for the Yatabe test. Many highlighted max speed tests as power contests, but Mukai’s setup theory begged to differ. “The extent of Dai-chan’s confidence to keep driving this will lead to the best results,” he commented.
By the way, in the Golden Era, Mukai commuted from Nara to Yatabe in Ibaraki four times a week. They conducted tests early in the morning, and all-nighters were a given. Mukai recalled that “the gradual build-up of driving data greatly boosted the machine’s potential.”
The appearance of the 4WD GT-R greatly began to change the testing methods at Yatabe. Until then, the spotlight was on max speed. However, with the introduction of Ono Bit, the focus shifted towards 0 – 300 km time trials. To show the strengths of 4WD sports, a focus on acceleration performance from zero start to 300 km began.
Kansai Service made a major shift during the process. Instead of just the engine, they began to emphasize the total package–the clutch, transmission, underbody, and LSD. To shorten its time, it was necessary to operate the front appropriately, and thus, they developed the Atessa ET-S controller. In addition, they made a wide-variety of arrangements. For example, they used a tension rod bushing to suppress geometric changes while driving for smooth, lossless acceleration.
Regardless of the power increase, the BNR32’s distance between fourth and fifth gear was clear. This caused a loss in acceleration when shifting to fifth gear for the 0 – 300 km/h test. For this reason, Kansai Service developed and commercialized an original close-ratio transmission. With this missing puzzle piece, their time shrank greatly.
Mukai tuned the BNR32 as “the car to spend your life with.” This was eventually produced as the T. MUKAI Edition. He pursued smooth revs and good acceleration in order to minimize discomfort, even after a decade of use. This edition used Kansai Service’s original LC turbine. It was a mix of a genuine exhaust housing and a compressor housing–a size similar to that of an N1. Although it was a temporary product, many often request for the production of this turbine once more.
More parts from other manufacturers became available for the BNR32. Alas, the tuning scene of the GT-R was very well in its maturity. After the BCNR33-type debuted in 1995, there was a growth in tires and wheels with larger diameters and higher performance. This was a response to the need of increased weight and power. The 2.8L engine was originally common for the BNR32. But in consideration of durability, attacks with the 2.7L with expanded bore diameter became the norm. To increase power, it became established that one needs to secure strength that can withstand high boosts.
The BCNR33 appeared in 1996. At the same time, Central Circuit opened in Hyogo prefecture. Its home straight also served as the Zeroyon (quarter-mile drag race) course. Zeroyon became widely popular in Kansai, and Kansai Service also rode that wave. They seemed to emphasize the max speed tests that required durability at Yatabe, more than Zeroyon that risked blown engines.
The BNR34 that followed could aim for max speed, but the weight increase was an acceleration handicap. Due to the trend of circuit attacks, Kansai Service also shifted its focus to testing on the circuit. Max speed tests of heavier loads required not only power, but also durability. Undeniably, Kansai Service’s experience and expertise became a strong foundation for the R35 tuning that we know of today.
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1080 Oguracho, Nara City, Nara Prefecture, 074-384-0126