For something so simple in its make-up the Mazda rotary engine is remarkably versatile. Whether you’re talking 13B or 20B, naturally aspirated or force fed, it’s hard to beat the power per cube ratio that these compact little motors generate; which goes some way in explaining why legions of tuners the world over still worship its design more than 40 years after it first broke cover.
Pulse Performance Race Engineering in New Zealand is one of the converted. Warren Overton, its owner, has been toying with rotary engines for more than a decade, and five years ago set up shop and started churning out scratch-built three and four-rotor packages. Now he can add six-rotor to that list—PPRE calls it the “6B.”
“When we came up with the idea for this engine I wanted to build a promotional vehicle [around it] to highlight the skill sets on display to future PPRE customers worldwide,” says Warren. “The owner—my good friend and long-time client Alex Sigley—has had the car since he was 13, and it was his first. It was important to start with an old school ride and this particular car had sentimental value to me in the fact it was the first rotary I ever drove when I was just 14 years old. Alex and I had a shared interest in the finished project so we proceeded to build the car of both our dreams.”
Right from the get-go the idea was to create a truly one-of-a-kind Mazda. “We wanted to keep the original exterior profile of the vehicle looking standard,” says Warren, “but with a tough Pro Street stance to match the power plant.”
Looking at the finished product, it’s hard to argue that they didn’t achieve what they set out to. The RX-4 has never enjoyed the same popularity as its R100, RX-2 and RX-3 siblings, but in this scenario its attitude pulls off a look normally only reserved for V8 muscle cars with ease. The custom-concocted Midnight Blue Pearl paint that’s been laid over the coupe’s perfect steel panels helps the cause, too.
Like the bespoke three- and four-rotor engines the company has gained a worldwide reputation for—thanks in part to the exploits of Red Bull-sponsored Kiwi drifter “Mad Mike” Whiddett and his quad-power RX-7—the 3.9L 6B utilizes a mix of custom tooled or modified parts, as well as off-the-shelf Mazda rotary engine components. “The trick to building the engine lies within finding a solution on how to physically assemble the components together in the correct order,” says Warren. “Coming up with the design for the first custom four-rotor engine certainly helped me find a way to achieve this new goal.”
At its heart is a handcrafted PPRE five-piece eccentric shaft that features a special mechanism designed to support it within factory 13B engine plates. Six FC3S series four RX-7 rotor housings are utilized and fitted out with RX-8 13B-MSP Renesis rotors equipped with PPRE apex seals. On the intake side of the engine a six-deep row of PPRE/EFI Hardware throttle bodies with open trumpets sit on a custom tapered intake manifold. Fuel is supplied through one dozen 550cc injectors supplied from a pair of Bosch Motorsport 044 pumps, and given the squeeze via a Malpassi adjustable fuel pressure regulator. Then there’s the spark, where 12 Bosch Tec coils are used in conjunction with two MicroTech X6 ignitor modules. The setup is much more simple on the exhaust side—a custom fabricated 1.75-inch diameter tubular header running six branches into two, into one single un-muffled pipe that exits just ahead of the rear tire on the passenger side.
It’s angry and very loud. It’s also very powerful, having spat out 813whp on PPRE’s rolling road after tuning through a heavily modified MicroTech LT-16C engine management system. Then there’s the rear-wheel-measured torque curve, which according to Warren starts early with remarkable throttle response, and peaks at 650lb-ft thanks mostly to the engine firing every 60 degrees of rotation.