The goal of building "RX-7.0" was simple: create a reliable daily driver that can outperform any production street car available while offering the driver an engaging and challenging experience. This meant starting with a light, compact rear-wheel-drive chassis that features double wishbone suspension, a low center of gravity, an aerodynamic shape, and plenty of room for wide tires. The Mazda FD3S (93-95 RX-7) was the perfect choice with a curb weight well under 3000 pounds, a 50/50 weight balance, and room for 18"x10" wheels on all four corners. The correct build process will produce an blisteringly fast sportscar that it's just a point-and-shoot drive.
The first challenge was the drivetrain: the FD3S features a 1.3 liter (13B) twin turbo Wankel rotary engine. While the rotary is a very clever and elegant design, reaching over 350 RWHP required a tough decision: push the stock twin turbos to their absolute limit, retaining their excellent throttle response but suffering reduced reliability, or move to a single turbo and deal with lag and driveability issues. Since the requirement was a daily driver that worked equally well in stop-and-go traffic and on the track, the rotary engine quickly became a major bottleneck.
To hit the power, driveability, and reliability targets a new drivetrain was needed. A hybrid GM/Ford drivetrain offered huge increases in power and a very broad torque band. An 427 cubic inch (seven liters, hence the "7.0" moniker) LS7-based all aluminum V8 puts out over 500 horses at the rear wheels, and weighs only about 40 pounds more than the original rotary engine. The stock 5-speed was replaced with a 6-speed unit built to handle 600 ft-lbs of rear-wheel torque. The rear end features a durable torque-sensing differential with a driveshaft and axles built to handle more than double the FD3S's original power and torque.
To handle this massive powertrain upgrade, the entire chassis was modified to ensure durability and enhanced driver control. The brakes were more than doubled in their thermal capacity. A custom-valved set of adjustable coil-overs were added to achieve a blend of comfort on the street and chassis control at the track. A Racelogic traction control system offers driver-selected levels of torque reduction and does so through progressive cylinder shutdown. The factory ABS and airbag systems were retained, and a four-point roll cage was installed with additional cross bracing. Removable Formula One style 6-point harnesses are used to hold the driver securely in place in the case of track incident, while the factory 3-point system is still available for street driving.
All of the original amenities of the cabin were either retained or augmented. The factory gauges are supplemented with a trio of SPA digital gauges with configurable alarms to enable the driver to instantly slow pace in the case of warnings. A column-mounted set of RPM lights enables optimum shifting under racing conditions. The climate control system provides heat and air conditioning. The audio system features a touch-screen interface and iPod support with a dock hidden in the glove box. In short, the driver is comfortable and well-informed of the condition of the vehicle.
The result is a vehicle that runs on 91 octane pump gas, still has a 50/50 weight balance, gets over 25 miles per gallon on the freeway, tips the scales at 2900 pounds, goes 0-60 in well under four seconds, can be driven in any weather, and is faster around the track than any Porsche, Lamborghini, or Ferrari under a few hundred thousand bucks. With street tires (Michelin PS Cups) and Hawk DTC brake pads this car runs solidly in the 1:30's at Laguna Seca—a lap time that is competitive with many purpose-built race cars like the Ferrari F430 challenge or the Viper ACR.
The difference is: I don't trailer my car to the track. I drive it. With the A/C on, and my iPod tunes playing—because the RX-7.0 is not a race car for the street. It's a street car that runs really, really fast at the track.
 |
 |
 |
 |
 |
 |
 |
 |
