A veteran of the Tohoku 660 championship

The popular “Tohoku 660 Series” is a race contested exclusively by kei-cars. We would like to introduce the machine of veteran driver Mr. Takeshi Otsuka, who competes in the Tohoku 660 Championship, which is contested by cars equipped with the new NA (naturally aspirated engine) standard. We will be looking at the secret of his machine makeup, in which he uses parts from vehicles other than mini-cars.

The skillful makeup of the machine shines through

This class 1 is the pinnacle of the Tohoku 660 championship, where many drivers with official race experience and pro-shop owners participate, and the range of modifications that can be made is wide. The 2024 season has seen several young drivers step up to the plate, and the class is more exciting than ever before.

One of the veterans waiting to take on these challengers is Mr. Takeshi Otsuka of the pro store Auto Modify Taku. Active in one-make races with Toyota Starlets and Vitzes, he first competed in the Tohoku 660 Championship in 2015, starting in the 2nd class, and moved up to class 1 in 2018.

His skilled race management based on his abundant experience and safe driving to avoid contact, as well as his thoroughly detailed race car, have made him a target for many entrants.

The engine is an early model called VE1 (KF-VE type), which is considered to be highly durable, and the interior is composed only of parts diverted from the original factory parts following the regulations. Noteworthy is the one-off intake system that he fabricated himself. While it is common in other classes to hear about the construction of pipes, Otsuka’s attention was drawn to the SR20 turbo throttle used in Nissan’s Silvia and other models. The diameter of the SR20 turbocharger is 50mm, which is much larger than the 42mm diameter of the stock Esses, so Otsuka made his adapter and managed to dock the two together.

The greatly increased intake airflow forced us to change the air cleaner, and through repeated trial and error, we created a whopping five sets of piping. By determining the position and size of the air reservoir, and then narrowing it down to a tapered shape, the flow velocity was increased, and air was efficiently fed into the engine.

Naturally, the muffler, which is the outlet, was not a commercially available product. The main pipe is φ50mm and the outlet is φ60mm, and as thin as possible was used to reduce weight. To meet the exhaust emission standards set by regulations, a catalyzer for motorcycles was installed in front of the silencer.

The control system is a Link ECU, and although he was using HKS F-CON V-Pro when he first entered the first class, he has learned from the ground up to increase the options for customers, not only for light cars, and now even his competitors in class 1 are asking him to set theirs.

One of the major weapons in his arsenal is the transmission: the first and second gears are stock, the third and fourth gears are genuine Storia X4, and the fifth gear is the RS Mach, which has been discontinued and is almost impossible to find used. Although it depends on the outside diameter of the tires, he believes it has the most fighting power against the current rev limit of 9,000 rpm, and can bring out the potential of the engine.

Lightening of the body has drastically changed the driving

The major change from the 2023 season is the body. The hood and rear gate had already been replaced with lightweight types, but when a relaxation of vehicle regulations made it possible to change the rear doors under certain conditions, Otsuka immediately introduced FRP doors made by Heartbeat. He was able to lose 20 kg on both sides.

Before the shakedown, he was concerned that the front-rear balance of the weight would be upset, but when he drove the car on the circuit, he was surprised to find that the suspension settings were the same as before, and the behavior of the rear, which had been nervous at times, was much more relaxed.

At the end of the back straight where hard braking is required at Sportsland SUGO, and entering the final corner where the car will stall if the speed is not raised to the very limit, he says that the stabilized rear end makes it much easier to drive than with the stock doors.

The changes Mr. Otsuka felt were reflected in his performance, and the opening round of this year’s season, he did not give up the lead in practice, qualifying, or the race, and his overwhelming speed was enough to secure a pole-to-win victory. It is safe to say that he has taken a big step toward the championship in the first class, which he has yet to achieve.