The Dyson name is synonymous with the OZ rotary drag racing scene. and it’s not by chance.
Reading through the spec sheet sent to me by Gold Coast-based driver/car builder Craig Dyson, I couldn’t help but be impressed. This wasn’t a huge surprise. The Dyson name is synonymous with top-notch rotary vehicles, thanks not only to the internationally acclaimed Dyson Rotary workshop, but also to the vehicles the Dysons have produced. Craig’s older brother, Wayne, was the founder of Dyson Rotary, and is known as the godfather of Australian rotary drag racing; he’s been playing with Mazda RX vehicles for just about longer than anyone in Oz. These days it’s Craig who runs the shop, and he’s been associated with dozens of impressive vehicles. Wayne’s son Andrew has also campaigned a highly competitive Series 6 RX-7 and currently has a rotary-powered rail in the build.
Being surrounded by family like this, and having a big hand in building competitive cars for customers, it’s natural that Craig has always had cool toys too. His favourite of the many he has owned is this 1990 Series 4 RX-7. Having owned the car for 12 years now, it’s fair to say Craig and the car have seen their ups and downs. But recently things have only been on the up.
For the last five years the Series 4 has been running 8-second passes. But as we all know, the allure of speed and thrill of the chase almost always require a lot of hard work and money.
In its previous guise the vehicle had been 'rear halved’, meaning that from the driver’s seat forward the chassis rails were intact. For the current build, however, the entire chassis was produced from lightweight chromoly. In an attempt to increase track stability and aerodynamics, the front of the vehicle is now a full six inches longer than standard. Along with major changes to the chassis came the addition of an entirely new engine package. Despite having previously been the fastest 13B in Australia, the old engine has made way for a methanol-fuelled 20B triple rotor.
It’s not only top shelf parts that have gone into producing the highly capable power plant, but two decades’ worth of Craig and Wayne’s combined knowledge as well. The aim for the power plant was to propel the vehicle deep into the seven-second zone, so it’s got all the tricks you would expect in such a package. To limit engine twist the motor has been pieced together with large custom dowels, and is mounted to the chassis both front and rear. The custom porting each housing has received is of a secret specification; Craig’s keeping it close to his chest and well away from the opposition.
With a serious amount of exhaust gas being produced by the three-rotor engine, Craig decided to run with a turbo that would be unfeasibly large for any other combination. The Turbonetics Super Thumper turbo has a 101mm compressor wheel and is so heavy that the custom exhaust manifold is as well braced as a small building. As the turbo builds boost on the start line thanks to its launch control system, the intake charge heats rapidly. The cure for this is a PWR ice-air intercooler that, come race day, is filled with dry ice to produce single digit intake temperatures. The 5-inch intake pipe that exits the cooler is fitted with twin Turbosmart blow-off valves before joining up to the Graphic Skills Racing intake manifold. This larger-than-life intake manifold and its associated fuel system dwarf the engine. Then again, the turbo takes away any attention the engine would receive anyway. Supplying enough fuel for the thirsty engine is a complicated feat in itself. The small, front-mounted aluminium methanol tank is dehydrated by an Enderly mechanical fuel pump, which feeds into five -10 lines. Each line feeds into a custom fuel rail fitted with three 1700cc injectors. That’s a total of 15 massive 1700cc injectors, which equates to a possible 25 litres of fuel being injected per minute from a fuel tank with a maximum capacity of just 20 litres. Completing the mammoth fuel system are a handful of SX regulators, metre upon metre of braided fuel line and a high speed return line. To cleanly ignite the high volume of fuel in each cylinder, six Mercury coils have been installed, one per plug. These feed current through Hurricane leads into NGK plugs, and the resulting combination exits through a 5-inch side pipe. Next to this are twin 2.25-inch waste gate screamer pipes from the twin Turbosmart 40mm Pro Gate wastegates. Both ’gates are regulated through the latest Turbosmart E-boost II boost controller, which works in conjunction with a MoTeC M800 engine management system. The complicated ignition system adds to the electronic trickery by utilising not one, but two MoTeC 4-channel CDI ignition control units. The resulting power produced by the 20B is around 1300hp, yet Craig assures us there is room for even more.
At this level of drag racing every hundredth of a second counts, and that’s why a Lenco CS3 magnesium-cased gearbox was chosen. Not only is the box lightweight and almost indestructible, but it also shifts through the cogs almost instantaneously. This speed is due to the air shift system, which allows Craig to punch a button for each gear he wants to select. Providing the smooth changes are a custom direct flywheel and twin plate slider clutch.
From here, power is transmitted through a custom 4-inch driveshaft with billet ends to a custom chromoly diff. Inside the diff are a Strange Pro Stock centre and 35-spline Strange axles. The tough diff setup is secured and suspended by a custom 4-link suspension arrangement with Koni double adjustable shocks. Mounted to each end of the diff are Wilwood 10-inch discs and callipers. These are hidden in behind the 15×15-inch Max Beadlock rims and 33×16.5×15-inch Hoosier tyres.
Up front, the tyres are at the other end of the scale, at just 4.5-inches wide and 15-inches in diameter. The wheels these are fitted to are ultra-lightweight Aluminstar billet alloys. Holding the front end up are quite possibly the shortest King springs in existence, along with custom lower arms and strut tops built into the roll cage.
With the stretch in the chassis, the original panels could no longer be fitted, so a carbon fibre one-piece nose cone was constructed. The signature Series 4 bonnet scoop has been skilfully moulded in, as has an impressive intake straight into the mouth of the turbo. The roof and rear quarters of the body shell remain steel, while the doors are fibreglass, and all windows have been replaced with lightweight Plexiglass.
The interior of the vehicle is every bit as purposeful as the exterior. Craig is seated in a Kirkey aluminium seat, and all attention is focused on the quick-release steering wheel and centrally mounted shift light.
It’s taken a few years for the vehicle to return to the strip in its new form. But the hard work has already paid off, with Craig running a new personal best ET of 7.45 @ 305kph after just a handful of race meetings. That time is quicker than any import in this country and currently positions the RX-7 as the sixth fastest rotary in Australia. This is up against vehicles that have been campaigning their current setups for years, and with far larger budgets behind them.
And with the car having taken a total of 12 years to build, on and off, Craig won’t be happy until he’s taken back the number one spot.
1990 Mazda RX-7 Series 4 – Specifications
Engine: Mazda 20B 3-rotor, Dyson race porting, doweled, balanced rotating assembly, Guru crank, custom studs, Graphic Skills intake manifold, Turbonetics 101 Super Thumper turbo, 2x Turbo-smart Pro Gate external wastegates, 2x Turbosmart Type II blow-off valves, PWR dry ice intercooler, Enderly 11A mechanical fuel pump, 15x1700cc injectors, 2x SX fuel pressure regulators, 1x high-speed return, 2x MoTeC 4-channel CDI, 6x Mercury coils, Hurricane leads, 5-inch side exit exhaust, 2×2.5-inch screamer pipes, PWR radiator, MoTeC M800 ECU, Turbosmart e-Boost II boost controller
Driveline: Lenco CS3 magnesium case 5-speed gearbox, twin-plate slider clutch, custom direct clutch and flywheel, custom chromoly sheet metal diff housing, full Strange Pro Stock centre, titanium yoke, 4-inch driveshaft, billet ends
Suspension: Koni double adjustable rear shocks, Strange front alloy shocks, King springs, 4-link, custom sway bar, custom track locator, chromoly wheelie bars
Brakes: Strange front callipers/rotors, spindle mount rims, Wilwood 10-inch disc rear
Wheels/tyres: Aluminstar spindle mount rims, 25x15x4.5-inch tyres, rear Max beadlock 15×15-inch rims, 33×16.5×15 tyres
Exterior: 6-inch chassis stretch, Plexiglass windows, carbon fibre nose cone
Interior: Kirkey aluminium seats, quick release steering wheel, air shift, shift light
Performance: Dyno Power — 1300hp, 0-400m —7.45 @ 305kph
Driver Profile – Craig Dyson
Occupation: Rotary mechanic
Previously owned cars: Too many to list
Dream car: This car on a new chassis
Why the RX-7? The love of rotaries and the need to go faster
Length of Ownership: 11 years
Craig thanks: Steven Cockerill, Nick Holmes, Shane, Thunder Road Race Cars, Phill @ Graphic Skills, Drew @ PWR, Roscoe’s Paint Depot, Bryce @ Miller Signs, Pennzoil, Damien @ McKern and Associates Charted Accountants, and of course Dyson Rotary
Words Todd Wylie Photos Quinn Hamill
The compressor turbine draws in a large volume of air, forcing it into the engine by spinning at a very high speed.
Air pressure in the intake builds because the turbocharger’s output exceeds the engine’s volumetric flow — this is called boost.
The speed at which the turbine assembly spins is proportional to the pressure of the compressed air, and the total mass of air being forced into the engine.
Turbos can spin at many tens of thousands of revs per minute, and the speed must be controlled. A wastegate is the most common mechanical control system, and is often further augmented by an electronic boost controller. The wastegate’s main function is to allow some of the exhaust gas to bypass the turbine when the set intake pressure is achieved.
The boost threshold is the minimum engine RPM at which the exhaust is flowing sufficient air to allow the turbo to produce noticeable boost — as they are powered by the movement of exhaust gases, without enough exhaust gas velocity, air cannot be forced into the engine. For example, if you were travelling and the engine was ticking over 1500rpm, and your boost threshold was 2000rpm you would experience a delay between when you pushed your accelerator and the engine revs rising enough to meet the turbo’s requirement to produce boost. This is not lag, this is a result of the engine not revving fast enough to generate boost at all.
Advantages of turbocharging
- More specific power over a naturally aspirated (NA) engine — it means an engine can produce more power for its size. Turbo 1.5-litre Formula 1 engines regularly produced in excess of 1000bhp.
- Reuse of excess exhaust heat (it gets channelled into the turbocharger to increase boost to the engine) means the engine runs more efficiently than NA or supercharged engines.
- A turbocharger is smaller, lighter and easier to fit than a supercharger, and it is more consistent than, for example, a nitrous oxide kit
- Because a small engine can be made to produce the power of a huge NA engine, fuel economy is often better on a per kW basis.
Disadvantages of turbocharging
- Turbo lag, especially on large turbos. A large turbo may give more peak power, but can take more time to spool up.
- Driveability may be compromised, particularly when the boost threshold is approached and suddenly a surge of power is too much for the tyres to cope with, causing understeer/oversteer (depending on which wheels are driven). This reduces the useable power band of the engine, and leads to more wear and tear on the drivetrain.
- Turbochargers are costly to add to NA engines, and add complexity. Adding a turbo can often cause a cascade of other engine modifications to cope with the increased power, such as exhaust manifold, intercooler, gauges, plumbing, lubrication, and possibly even the block and pistons.
Lowering the rotational inertia of the turbo’s turbine will allow it to spool up more quickly, e.g. by using lighter parts that take less energy to turn. Ceramic turbines can help here, but they are limited in their maximum boost and are relatively fragile.
Changing the aspect ratio of the turbine by reducing the diameter and increasing the gas-flow path length, as well as using reduced-friction foil bearings will also reduce lag.
A common method of minimising turbo lag is to clip the turbine wheel. A minute portion is clipped off the tip of each blade of the turbine wheel, reducing the surface area of the rotating blades, and placing less restriction on the escaping exhaust gases. This results in less impedance at low speeds, giving more low-end torque. To counter the negative effects of this, the effective boost RPM is raised slightly higher.
Using two smaller turbos as opposed to one huge one will help. Nissan, Subaru and Mazda have all done this, for example the twin-turbo Legacys (sequential), or the twin-turbo Skylines (parallel). Two small turbos produce the same or more total boost than a large single turbo, but because they’re smaller they have less inertia and therefore reach their optimum boost delivery sooner.
The sequential turbos tend to work with one small turbo being active over the entire rev range, and a larger turbo that comes online at high revs. Early designs had one turbo for low revs and one turbo for high revs which sometimes caused a noticeable drop in power between the boost from one falling off and the boost from the other reaching maximum.
Sequential twin turbos are far more complicated than single or parallel twin turbos because valves and additional piping are required to control the direction of the exhaust gases.
Turbo lag is a delay from when you push the accelerator and when you feel the turbo kick in. This is caused by the time taken for the exhaust system driving the turbine in the turbo to reach the required pressure, and for the turbine to spin fast enough to supply boost pressure.
Older turbo cars were far more susceptible to turbo lag. Modern technology has largely overcome it.
A large volume of air flows between the turbo and the inlet of the engine, forced by the high-revolution turbine in a turbocharger. When the throttle is wide open this air travels into the engine, but when the throttle is closed compressed air flows to the throttle valve and has nowhere to go.
This can cause a surge in pressure that can cause engine damage such as burst induction pipes. Additionally, the compressed air flows back towards the turbo (the only path it can take), slowing the turbo down suddenly. When power is applied again, this speed has to be built up again (causing turbo lag).
A blow-off valve is a vale fitted between the turbo and inlet which allows excess air pressure to escape. This air is usually recycled back into the turbo inlet, but can be vented into the atmosphere.
Venting to the atmosphere causes the signature blow-off valve woosh and it is easier to install because there is no additional plumbing. There is no significant performance benefit through venting into the atmosphere — just a louder, more showy sound.
Recycling the compressed air back into the turbo reduces this noise, and also keep the turbo spinning more effectively, particularly between gear changes.
Blow-off valves are usually operated by engine vacuum.
They are sometimes called dump valves.
The Mazda Furai concept car which made its world premiere at the NAIAS in Detroit, Michigan, celebrates 40 years of Mazda’s rotary engine and international motorsports heritage. The raciest interpretation of NAGARE design language to-date, Furai is the latest car in Mazda’s award-winning and highly acclaimed series of concept cars.
Nagare (pronounced 'na-ga-reh’), is the Japanese for 'flow’ and the 'embodiment of motion’.
Furai (pronounced 'foo-rye’ — Japanese for 'sound of the wind’) is the sort of car that could only come from a company that incorporates the 'Soul of a Sports Car’ into everything it builds, but with an eye toward the future and the environment through the use of renewable fuels. Consequently, Furai is initially tuned to operate on 100 per cent ethanol, while research with partner BP into other future fuels, including ethanol/gasoline blends like E10, continues.
On any given weekend, there are more Mazdas and Mazda-powered cars road-raced in North America than any other brand of car.
The 'Nagare’ ethos is how Mazda’s future production models will sustain the Zoom-Zoom spirit by exhibiting their strong affinity for motion.
Manufacturers commonly showcase concept cars and design studies with little or no intention of actually using the theme presented. Mazda’s approach is the opposite: all of the Nagare concepts, including Furai, help evolve this evocative surface language for future use. Nagare is how this celebration of motion will be portrayed on interior and exterior surfaces in future models. Instead of form following function, the two merge as one.
Franz von Holzhausen, Mazda North American Operations’ (MNAO) Director of Design and the person who led the team that created the Furai, explains the thinking behind the concept, “We were looking for a way to bridge the gap between Mazda Motorsports and the production vehicles in our lineup. The mindsets of road-car and racing car fans are quite different, so the purpose of Furai is to find a meeting point for these disparate interests.
“Furai achieves this by purposely blurring boundaries that have traditionally distinguished the street from the track. Historically, there has been a gap between single-purpose racecars and street-legal performance models commonly called supercars that emulate the real racers on the road. Track cars are, by their competitive nature, ill-suited for practical highway use, as well as generally far from road-legal. While some supercars visit the track on occasion, they are primarily road cars not properly equipped for racing. The aim of Furai is to bridge this gap,” continued von Holzhausen.
However, Mazda neither intends to race Furai, nor is it a supercar the company plans to build and sell in the near future. Rather, Furai is a design study that lives between those extremes. Without the restrictions imposed by serial production models, and with the freedom of an autoshow environment, Mazda is using the opportunity to evolve the company’s Nagare design theme one more step closer to reality.
Instead of mimicking racecar components and design elements in a road car — the strategy preferred by supercar manufacturers — the 'Mazda way’ was to begin this project with the real McCoy: a Courage C65 chassis that earned its stripes during two seasons of LMP-2 endurance racing in the American Le Mans Series (ALMS). This sports car was successfully campaigned under the MAZDASPEED Motorsports Development banner by B-K Motorsports during the 2005 and 2006 seasons. Drivers Jamie Bach, Guy Cosmo, Elliott Forbes-Robinson, and Raphael Matos piloted the car to one victory and a total of nine podium finishes in 15 ALMS events. B-K finished third in championship standings both years; while Bach and Cosmo were co-Rookies of the Year in 2005 after their first season of ALMS racing.
“Anticipating future rules changes in the ALMS, we created a new closed cockpit which would be more appropriate for a future production model,” said von Holzhausen. “The major element we did not change is the 450-horsepower RENESIS-based R20B three-rotor rotary engine that provides the Furai’s ample Zoom-Zoom. The ultimate Mazda in our minds is rotary powered; as a company, we have no intention of abandoning that valuable asset. When people think of the very best production sports cars in the world, the rotary powered Mazda RX-7 is always on that list.”
The Furai concept serves as a turning point in the Nagare developmental process. While the four previous concept cars explored different ways to express Mazda’s emerging design philosophy and to explore an aesthetic, this one is all about function — every last texture and detail serves some functional purpose. In essence, the Furai creative process boiled down to guiding air over and through the body in fruitful ways. To prove that this concept goes far beyond static aerodynamic analysis, Mazda’s design, motorsports and R&D teams worked together to construct Furai as a 180 mph rolling laboratory to demonstrate its functional capabilities on demand.
“The basic proportions of contemporary race cars are every designer’s dream,” enthused von Holzhausen. “Furai is less than 40 inches high (1000mm) but nearly 80 inches (2000mm) wide.”
While Furai strikes an incredibly strong presence, the real beauty of the project — and it’s most valuable asset as a real-world test-bed — is in the details that von Holzhausen and his team incorporated:
- The body surface provides ample opportunity to feature core design elements such as aggressive headlamps and Mazda’s unique five-point grille.
- The headlamp trim pieces function as guide frames to help cancel aerodynamic lift.
- High-pressure zones just above the front wheels are relieved to serve the same end.
- The air flow package takes air moving under the front of the car and guides it inside the body to the engine-cooling radiators.
- Nagare textures incorporated in the side surfaces feed air to the rear brakes, the oil cooler and the transmission cooler.
- An under-car diffuser that begins rising aft of the cockpit helps draw the volume of air flowing through the radiators and engine bay, out the rear.
The Mazda design and R&D teams worked closely with Swift Engineering to refine the aerodynamic characteristics, assuring that Furai remains glued to the ground at high speeds. Through its existing relationship with Swift Engineering, forged through development of the Mazda/Cosworth-powered Champ Car Atlantic single-seater chassis, the team used complex Computational Fluid Dynamics (CFD) software to tune various Nagare design elements to function at a high degree of efficiency. Drag, downforce, lift and overall aesthetics were all key considerations.
Sourced straight from the race track, the Courage carbon-composite tub is essentially intact under the new Furai body, including the right-side driver’s seat. Instead of the stark interior typical of race cars though, this cockpit is finished with more comfortable but still highly functional surfaces. An electronic display screen and gear-change shift paddles are built into the steering wheel.
In the chassis’ original racing configuration, the passenger seat is filled with electronic gear, so those components were relocated elsewhere to provide adequate space for two occupants. The greenhouse is somewhat wider than the original cockpit to provide adequate head and shoulder room and adequate visibility. Doors attached with butterfly hinges provide a very efficient means of entering the cockpit. In this instance, the design team followed an approach that has proven very effective during years of endurance racing.
“One thing we learned from CFD studies is that we don’t need much rear wing to balance the down force created by the front splitter and the Nagare features we’ve sculpted into the body,” observed von Holzhausen. “Combustion air is provided by a variation of the Turbo Tongue device that Swift developed for Indy car use a decade ago. It rises slightly higher than the surrounding roof surface to ingest clean air above the boundary layer. Our final design works so well that we applied for a joint patent with Swift. Of course, it helps that it’s a real piece of art, too, and one we had to incorporate into the design.”
The Irvine, California-based Aria Group was responsible for creating new composite panels and they worked hand-in-hand with Mazda North American Operations’ own in-house fabrication team to mate them to the Courage chassis. The dark matte finish with red and orange accents harkens back to the livery worn by Mazda’s legendary 787B when it won the Le Mans 24 Hours in 1991, making the company the first — and still only — Japanese company to ever win the endurance classic.
Furai not only probes future design possibilities, it also ventures ahead with an alternative fuel. Consistent with the Mazda’s recently announced 'Sustainable Zoom-Zoom’ initiatives, the Furai’s three-rotor powerplant has been tuned to run powerfully on 100-percent ethanol (ethyl alcohol) and ethanol/gasoline blends. There are exciting advances being made in renewable fuels, from current blends like E10 (10% ethanol/90% gasoline) with research ongoing into making ethanol from cellulostic materials, to future renewable gasoline components like Butanol — a 'higher order’ alcohol which is fungible with gasoline.
John Doonan, Mazda’s manager of motorsports team development in the USA, explains the thinking behind Furai’s use of alternative fuel, “One of our key technical partners in motorsports, BP, helped facilitate our use of E100. In 2007, ALMS required use of E10 and E100 is now the only acceptable fuel in the Indy Racing League, so we’re projecting ahead with this application to gain experience and to improve Mazda’s environmental profile.
We are proud to partner BP which is a string leader in renewable fuels and recently announced a US$500 million investment in the Energy Biosciences Institute. BP also has a very green focus in the marketplace, and it’s Mazda’s intention to sustain its Zoom-Zoom performance image on and off the racetrack. While Mazda’s rotary has proven readily adaptable to various alternative fuels, including considerable work with hydrogen fuel, this is the first time it’s been engineered for other ethanol blends. The Mazda rotary engine is unique in its ability to run well on multiple fuels.”