Hiroki Sakamoto may have possibly built, not only one of the fastest, but also the cleanest RX-7 in Japan to date. With a best time of 55.801 around Tsukuba, and a 2’14.399 around Suzuka it can definitely hold it’s own among the frontrunners of Japanese time attack.
Hiroki has taken a different approach aesthetically to this build from that of the majority of FD’s on the grid. Absent are the obtrusive canards, projecting from the front bumper, and a very regulated size front splitter moderately pokes out from the underside of the car, leaving the RX7 with a very conservative appearance. However, the low-key look of the car is no indication of it’s performance, or that of Hiroki’s knowledge of the chassis and Mazda’s rotary engine in general. With over 20 years of hands on racing experience, Hiroki has taken his accumulation of knowledge and used it in launching Sakamoto Engineering; a rotary centered tuning shop in Tochigi.
Hiroki Sakamoto’s story started out in a similar fashion to that of other shop owners in Japan. From a young age, he had become captivated by the world of motor sport. When he was 18, under the guidance of mentors, he pursued a line of work in the automotive field that eventually led to him opening his own garage. Despite being observant of the nuances of road racing, there was a part of him that was always drawn to time attack:
“Although pursuit of speed with rival is certain course, tense feeling applied to 1 lap is pleasant.“
This climactic feeling is not lost on those who have personally experienced the turbulent energy associated with a time attack event. Whereas in traditional wheel to wheel racing, you may have the opportunity to make up for minor mistakes throughout the course of a race, in time attack this is not the case. In many cases, car owners or teams will attend an event in hopes of getting just one or two perfect laps in, and if they aren’t executed flawlessly, they are for not. This is the excitement of time attack, and what draws many people like Hiroki to challenge themselves in such a medium.
The most prominent feature of the car is the chassis mounted GT wing affixed at the rear. This is a recently upgraded piece from it’s previous iteration of a street car, and one of the many changes as Hiroki transformed the car into a dedicated track car/demo car. You can also see the Super Now lower control arms; one of several Super Now parts underneath the chassis. Dampening is taken care of by a set of custom valved Bilstein Ennepetal coilovers matched with 20k front and 19k rear HyperCo springs.
The now 1030kg car has been reduced in weight dramatically by utilizing a good amount of carbon throughout the body. The roof, rear window and hatch, doors and dash have all been replaced with composites. The interior has also been stripped of all amenities to further benefit performance on track.
The profile view of the car gives us an idea of just how simple the car is in comparison to others in the field. The RE Amemiya full body kit adds a touch of similarity to the FD that we’ve grown accustomed to in RX-7’s throughout the world. There really is nothing without substance on this build, and the more I look at it, the more I sense an almost mature quality resonating about it.
18×10″ Advan Racing GT Premium Version wheels in Titanium Blue contrast the bright white of the paint, and do well to match the teal of the Project Mu big brake kit hiding behind them. 295/35 Advan A050’s are the tire of choice for Hiroki.
The rear bumper has been cut to make way for a one-off diffuser that’s tucked above the custom center exit exhaust. You can see the one -piece carbon hatch is removable via a set of aerocatch pins to gain access to the trunk where the fuel system is housed.
Not to be outshone by the exterior of the car, the engine bay holds the same simple cleanliness as the rest of the build; in fact, this is by far one of the immaculate rotary motor displays I’ve seen in a race car.
The 13B has been assembled to Sakamoto Engineering’s secret specs, and has undergone a Side Port, Cross Port, and Peripheral Port. The current adaptation utilizes a Trust T88-38GK, but depending on need Hiroki swaps the unit for a TD78-29D or T88-34D. The one-off V mount setup uses a Trust Intercooler and radiator. Also aiding to cool the setup is a oil, differential, and transmission cooler. The car is tuned with a Vi-pec V88 stand alone ECU and makes a healthy 500ps at the wheels. Knowing the abuse race motors go through, you can tell that Hiroki has really done all he can to ensure reliable performance from the motor.
It really is one of the cleanest rotary engine bays I’ve seen – actually not just in a race car, but in RX7’s in general. By keeping things as simple as possible, and eliminating waste, Hiroki reduces the time needed to diagnose and fix issues that arise at track.
The interior of the FD leaves little to the imagination with only the essentials remaining. The carbon dash houses the Motec ADL3 dash unit, and a simple ignition switch panel. Safety is provided by a custom 13-point roll cage, welded into a fully prepped chassis which also helps stiffen the older car up a bit. A Juran Tanida bucket seat and a deep suede Momo wheel make up the rest of the cockpit.
You can see the shifter for the HKS 6 speed sequential transmission rising from the carbon bezel on the transmission tunnel. The transmission works in collaboration with an ATS Carbon Twin-Plate Clutch and OS Giken Super Lock LSD to get the power to the ground.