Some engine and exhaust combos sound better than others. For many, the wide-open scream of the NSX's C30A V-6 at 9K rpm is heaven. For others, a Nissan V-8's instant crack from idle raises the neck hairs. But the distinctive sound from the turbocharged 1.3-liter rotary engine and proprietary exhaust system in this Knight Sports Mazda RX-8 can't help appealing to everyone.
It's almost like a siren as the revs build up, announcing that something earth-shaking is about to happen. After reading this, go to YouTube and search "Knight Sports RX-8 / Power Run", and fast-forward to about 0:55 to understand what we're talking about.
Knight Sports is a Tokyo-based company that specializes in rotary engines and has been in business for more than 30 years. Our contact for this car, chassis code SEP3, is Hidefumi Nakamura. Now 57, he's had the motorsport bug since high school, when he went to see a race at Fuji Speedway. Since then, he has peered into the deepest nooks and crannies of rotary engines, and his cars have occasionally kicked the butts of Japan's fastest. So when he advises people who are thinking of undertaking a similar project to "take it one step at a time," it would be a smart thing to listen.
This RX-8 is an out-and-out track car, built in gradual phases and tested on the circuit to be sure that each addition, subtraction, or tweak can make the car go faster for longer. Knight Sports makes a lot of its own stuff, including the body kit. This takes in a Type II front bumper and lip, side skirts, and a rear bumper/valance. A custom-made hood has been designed to help bring cooling air into the engine bay while a KS GT-style rear wing helps outside air create downforce.
Going from outside to in, there isn't much left of the standard car-a bit of dash and steering column, and that's about it. Instead, there's a custom-made roll cage, pimp Defi Super Sports Cluster, an NGK air/fuel and boost meter, and an HKS EVC-5 (electronic valve controller) boost manager. The driver sits in a Knight Sports bucket seat and twirls a Nardi Torino steering wheel.
Then he will mash the throttle and bring the big guns to the party. In this case, a 13B-REW twin-rotor, fitted with a Turbonetics 60-1 trim/0.84 A/R turbocharger. This is connected to a Knight Sports manifold, while an HKS blow-off valve and GT-II wastegate perform their duties. Nakamura also had the housings ported and changed the lubrication to a race-standard dry sump system. An A'pexi Power FC stand-alone engine management system talks to NGK Racing 11.5 spark plugs via an Accel 300+ digital ignition unit. These guys set fire to gasoline supplied by 550cc/min primary injectors and 850cc/min secondaries, regulated by an HKS pressure regulator, and fed by a pair of Bosch pumps via an Arias fuel rail.
Making sure the Fahrenheit is on the money and not about to cost money (a job that's even trickier with a rotary) is an intercooler and piping made in house, accompanied by an all-aluminum radiator-with both arranged in a V-mount setup (that vented hood was a giveaway, wasn't it?). And let us all give thanks for the Samco Sport hoses and Setrab oil cooler. Amen.
That siren sound is the accompaniment to the engine making 440 hp with boost levels at 14.7 psi (1.0 bar). Up that figure to 17.4 (1.2 bar) and there's 480 hp to play with. Or 500 hp with 18.6 psi (1.3 bar) of boost. All this from a displacement of 1.3 liters . . . isn't technology wonderful?
Not only was the native RX8 transmission swapped for the RX-7's Getrag when the 13B originally went in, but even that was replaced with a Hewland SGT six-speed manual gearbox, upgraded with an Exedy twin-plate clutch and flywheel. Not that Knight Sports can't knock together some impressive hardware itself; the company claims to have made the suspension here, fitting 14kg springs up front and 8kg springs to the rear in an adjustable coilover setup. The front anti-roll bar measures 29mm and its counterpart at the other end is 19mm in diameter. Even the bushings are sourced in-house.
But why mess around with brakes when Brembo already does such a great job? Hook up some stainless steel braided lines from Aeroquip and move on. In front of the anchors are Yokohama Advan RS racing wheels, sized 18x9.5 with a +38mm offset at each corner, dressed in sticky Yokohama R-compound rubber.
Nakamura started work on this car in spring 2009, with a goal of running at Macau the following November. It wasn't just a case of stripping everything out and bolting on choice parts. For example, the front hub assemblies and suspension uprights were deemed not man enough for trackside punishment. So a redesign and bespoke build was called for. After something like $90,000 was spent, it was time to head to the Road Sports Challenge Race in the aforementioned most famous street circuit in Asia. And guess who became the B-class winner. Nakamura tells us he intends to field this car again in 2010, and we're thinking we could make some money on a little wager here . . .
Behind The Build
Hidefumi Nakamura/Knight Sports
Tuners, race prep
Approximately nine months
Knight Sports Mazda RX-8
Output: 500 (max.)
Engine 13B-REW; Turbonetics 60-1 trim/0.84 exhaust turbocharger: Knight Sports turbo manifold, radiator, intercooler, piping, rotor-shaped catch can, clear brake and clutch fluid reservoirs, modified intake manifold, "Rotor Tail" turbo-back exhaust; HKS blow-off valve, GT-II wastegate, EVC-5 boost controller, fuel pressure regulator; A'pexi Power FC engine management; Accel 300+ digital ignition; NGK Racing 11.5 spark plugs; SLR manifold, radiator, radiator diversion panels; Samco Sport hoses; Setrab oil cooler; Run Max oil filter relocation; Earl's stainless lines, aluminum fittings; Bosch fuel pump (x2); Arias fuel rail; 550cc/min primary injectors; 850cc/min secondary injectors
Transmission Hewland SGT six-speed gearbox; Exedy twin-plate clutch, flywheel
Suspension Knight Sports coilovers, springs (14kg/mm front, 8kg/mm rear), anti-roll bars (29mm front, 19mm rear), bushings
Wheels 18x9.5 +38mm offset Yokohama Advan RS wheels; 250/660-18 Yokohama Advan competition tires
Brakes Brembo brakes; Aeroquip stainless steel braided lines
Exterior Knight Sports Type II front bumper, front lip, vented hood, side skirts, rear bumper, rear valance, GT wing
Interior Knight Sports bucket seats (front), roll cage, fire suppression system, carbon fiber door panels; Sabelt four-point harnesses; Sparco window netting; Defi Super Sports Cluster-03; A'pexi FC Commander; Nardi Torino steering wheel; Defi gauges; NGK AF boost meter
The rotary engine natively in the Mazda RX-8 is called the Renesis. It's a kind of hybrid word. The R and E refer to rotary engine (duh), while the rest alludes to the word "genesis". But it's not so much a genesis as a resurrection.
Previous rotary engines (or Wankels, after the original designer Felix Wankel, a German engineer) were never known for their meager thirst or low emissions. The Renesis brought the design up to date, making it able to meet the more stringent emissions demands now in place.
Like the 13B-REW of the FD3S RX-7 before it (and the FC3S RX-7 even earlier), it has two rotors, with each combustion chamber displacing 654cc. But unlike its predecessor, the Renesis reaches a peak output of 250 hp at a screaming 8,500 rpm and maximum torque of 159 lb-ft at a similarly lofty 5,500 rpm-with no forced induction.
Where the 13B-MSP Renesis gains its real advantage is in the port configuration (MSP stands for multi side port). In older 13Bs, exhaust ports used to line up peripherally with the rotor. The new layout has them off to the side, eliminating the carrying over of any spent gases into the next combustion cycle. There's even an added bonus now of having increased intake and exhaust port area compared to previous engines. The result is more stable combustion, better efficiency, lower emissions, and greater power (a 49-percent improvement over its immediate predecessor).
Incidentally, much of the Renesis is assembled by hand. A possible second generation of Renesis (called the 16X), powered by hydrogen, was in Mazda's Taiki concept car. With a bit of luck, the rotary engine may not die when the RX-8 ceases production, which is slated after the 2011 model year.