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Mazda RX-7 (FD3S) - Hokkaido Dream

This RX-7 became a 4-year build with some of the world's best Time Attack machinery in its crosshairs, but the team behind it is far from a typical group of enthusiasts

Alex Grant
Jun 8, 2017
Photographer: Alastair Ritchie

Though the world of social media has made it easier than ever to keep touch, in car terms there's never really been a substitute for actually meeting up—those evenings spent looking under the hood of your buddy's project, swapping ideas, and laying down plans for whatever comes next. You never know where it might take you.

Mazda rx7 car shop dream fw design rear wing Photo 2/26   |   Mazda Rx7 Car Shop Dream Fw Design Rear Wing

And the guys busily laying still-warm FD RX-7 parts across the floor of the Car Shop Dream Lotas 7 team's pit garage at Sydney Motorsport Park can vouch for that. Four years ago, this same group of enthusiasts was swapping ideas at a meet in their hometown of Kitami in the Hokkaido Prefecture of Japan—ideas that would make them the first Japanese team to take on the Open Class at the World Time Attack Challenge, where we caught up with them.

Fresh from a competitive first outing, and with a 1:32.25 lap time putting them in 10th place being down on power, team driver Kurokawa Tetsuhiro is still visibly excited about reaching that end goal. "It's a very technical high-speed course unlike anything in Japan," he shouts over the brap-brap-brap of a bridge-ported rotary idling a few feet away. "Unless the engine, setting, aero, machine, course capture, and driver skill are not engaged, you cannot win here. But we have learned a lot."

This might be his first time at WTAC, but Kurokawa-san is no novice. He was originally a Nissan works driver in Japan's Super Endurance series, and his career has spanned everything from AE86s to open-wheelers. But he's also built a handful of modern-classic Japanese projects of his own, which laid the foundation for setting up a tuning shop, Car Shop Dream, back in '99.

Mazda rx7 car shop dream lotas 7 team Photo 6/26   |   Mazda Rx7 Car Shop Dream Lotas 7 Team

But the long road to Sydney traces back to Hokkaido Dream Racing, the Kitami-based car club where what's now a 12-man Time Attack team first started talking. Plans had started small with this car; the shop had a near-standard RX-7 in stock and enough connections locally to start building it for track days. As Kitami gets around six months a year of heavy snowfall, there was plenty of off-season time to develop it from a road car to something a little more potent.

It helps that these aren't your average enthusiasts. Kurokawa-san counts ex-Voltex employee Suda Osamu, rotary engine specialist Watanabe Shin, and seasoned drag car builder Yamaguchi Koji among his group of mates. With connections like that on board, ideas started to snowball and, after one season of track days, they set the bar a little higher and slid this sideline project onto the mainline.

Mazda rx7 13b rew engine Photo 7/26   |   Mazda Rx7 13B Rew Engine

"The racing team started four years ago, when we decided to build the RX-7 to compete at Tokachi International Speedway, in Hokkaido," he tells us. "Then we wanted to set a lap time at Tsukuba, with an end goal of competing in and winning the Open Class WTAC. So knowing the right people really helped."

WTAC may be a relative newcomer on the motorsport calendar, but its setting high standards already and competitive times are hard to put down. However, a large amount of power is usually a good place to start, so when winter crept in, Watanabe-san was called in to strip the 13B-REW back to its components, fit bridge-ports to the housings, and swap to FC3S-spec low-compression rotors ready for the huge Trust T88 38GK turbo. It's an unusual setup for a circuit racer.

Mazda rx7 custom front diffuser Photo 8/26   |   Mazda Rx7 Custom Front Diffuser

"Watanabe is Japan's rotary-engine record-holder on the quarter-mile, at 7.4 seconds," Kurokawa san explains. "So the engine is based on a drag racing spec, and it's designed to produce as much power as possible. We haven't had it on a quarter-mile, but it should be capable of 8-second runs."

This isn't a "fit and forget" setup-the engine is stripped after every event and checked for signs of wear, but also to see where further development work is needed. So far it's proved tough enough, and the large front-mount intercooler and mapping by Kumaki Toru of Top Fuel Racing help to avoid event-shortening failures as the Mazda pushes for as-yet-unexplored limits. Kumaki and Watanabe are trackside at every event.

Mazda rx7 bride race seat Photo 12/26   |   Mazda Rx7 Bride Race Seat

The transmission was a familiar setup, too. Tucked in beneath the floorpan is an OS Giken rear differential and clutch, paired with a six-speed Quaife sequential gearbox, and Kurokawa switched to an uprated prop and driveshafts to take the weak links out of the chain.

But it's aero that's separating the top performers at WTAC from the rest of the lineup, and that's been the longest-running part of the project. The RX-7 started shedding its metal panels back in '14 for a one-off kit designed by Suda Osamu's FWDesign workshop. With no full-size wind tunnel, every square inch and each angle was made in miniature and then tested using electric fans before being scaled up to fit the real thing. It's meant everything is bespoke, with a nosecone and fenders that remove in one piece and a rear wing that creates so much downforce that it's tied into the chassis.

Mazda rx7 car shop dream lotas 7 team Photo 13/26   |   Mazda Rx7 Car Shop Dream Lotas 7 Team

Optimized airflow over the top is matched to a calculated program of weight loss and chassis stiffening. An interior stripped of anything soft and filled with rollcage, the metal-on-metal is interrupted only by its single Bride seat and Racepak instruments on the dash bar. The roof is dry carbon, which sheds pounds and lowers the center of gravity, and the doors are fiberglass-reinforced polymer. Not that you'd know-once the testing was complete, almost all of the bodywork was re-painted with the original Mazda Innocent Blue Mica.

Bespoke bodywork also offered plenty of space for more rubber. The WTAC's Advan A050 control tire is wrapped around a set of square 19-inch TE37SL wheels, in turn home to a D2 big brake kit and bolted to a fully adjustable Endless coilover kit. Just enough to take advantage of the Mazda's naturally balanced chassis.

Mazda rx7 fwdesign carbon fiber hood Photo 14/26   |   Mazda Rx7 Fwdesign Carbon Fiber Hood

"I've always liked the RX-7, particularly the FD, and I knew it had potential as a Time Attack car," he says, and he's not wrong. The team took the rear-wheel-drive turbo record on their first event at Tokachi in '13, then broke it in '14. As every run is data logged, improvements come in strides. So the RX-7 began 2016 setting a 56.0-second lap at the Tsukuba Time Attack Championship, coming in second in its class, before setting another record at Tokachi's full-length circuit by more than a second. The previous record-holder was Nob Taniguchi in the HKS-tuned CT230R Evo.

Unfortunately, for all that potential, nothing quite prepared the team for the climate change they met when the car landed in Australia for WTAC '16. Though they got around Kitami's ability to limit on-track time, most of the mapping had been done in much colder temperatures than Sydney's spring heat. It meant the team had to run with the boost turned down a notch to avoid breaking things on track, costing them power and robbing the RX-7 of its spot at the top of the class.

Mazda rx7 13b rew engine Photo 18/26   |   Mazda Rx7 13B Rew Engine

Not that it's bothered Kurokawa-san: "The build has brought together an amazing team of passionate rotary people and given us the opportunity to compete in Australia and meet some amazing rotary drivers, builders, and fans," he says with a smile.

"Once we get the settings right, the car should be able to get to the top of its class. We just need to understand what's missing and fix it. But the biggest task is the engine-I want to make it tougher and get a better understanding of working with E85 fuel. So we're looking to add a bigger cooling system and possibly change the porting."

Mazda rx7 car shop dream lotas 7 team Photo 19/26   |   Mazda Rx7 Car Shop Dream Lotas 7 Team

With the same group that inspired the project all loudly comparing notes in the pit lane as we talk, there's no doubt that those early plans are already beginning to form. The conversations that turned an idea at a local meet some 5,500 miles away have gotten them this far. How they progress with another 12 months of workshop time will make this car's return to WTAC worth looking out for.

Mazda rx7 car shop dream lotas 7 team Photo 23/26   |   Mazda Rx7 Car Shop Dream Lotas 7 Team
By Alex Grant
14 Articles
Mazda RX-7 (FD3S) - Hokkaido Dream
Tuning Menu
Owner: Kurokawa Tetsuhiro
Hometown: Kitami, Hokkaido, Japan
Occupation: Owner, Car Shop Dream
Engine: 13B-REW; Watanabe bridge-ported housings, special FC3S low compression rotors; E&J seals; custom stainless steel exhaust; Trust T88 38GK turbo; front-mount intercooler with custom stainless pipework; Turbosmart Race Port blow-off valve; K&N air filter; RUN-MAX magnetic oil filter; fuel cell
Drivetrain: Quaife six-speed dog sequential gearbox; OS Giken triple-plate clutch, flywheel, pressure plate, limited-slip differential; uprated driveshafts, axles and tail shaft
Engine Management: Link ECU mapped by Top Fuel Racing
Footwork & Chassis: Endless adjustable dampers; Swift springs; Cusco sway bars
Brakes: D2 eight-piston front, four-piston rear calipers, 380x32mm two-piece front and rear rotors, Circuit spec pads; Wilwood brake bias adjuster
Wheels & Tires: 19x10" Volk Racing TE37SL wheels; 295/35R19 Yokohama Advan A050 tires
Exterior: Car Shop Dream/FW Design original aero including custom-made front diffuser and canards, louvered front fenders and rocker panels, rear wing and diffuser; OEM Innocent Blue Mica metallic paint; dry carbon roof and under panel; FRP side doors; rear bumper removed; FWDesign carbon-fiber hood; Slimline racing mirrors
Interior: Momo Trek steering wheel; Bride race seat; Racepak digital instruments, custom rollcage, wiring loom
Thank Yous: Mr. Aoki from Ready Go Next, Lotas Club, JU Kitami City, Joycal Japan, Broadleaf, Hiranaka Car Dealership, Bold, Takumi, Kashimakohan, Auto Sanrin, Zeroyon Factory, Kitami Suzuki Dealership

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