Mazda6 Diesel Racer Puts Stranglehold On GRAND-AM's GX Class

July 26, 2013
Story By
Evan Griffey

Like an MMA fighter with his opponent dazed on the canvas, Mazdaspeed and SpeedSource Engineering have pounced on the competition in GRAND-AM’s new GX class and shown no mercy.

The old adage ‘timing is everything’ certainly holds true when looking at Mazdaspeed’s 2013 racing efforts. The convergence of Mazda ending its RX-8 racing program, the emergence of its SKYACTIV design and engineering philosophy, specifically a diesel engine, and GRAND-AM’s creation of a new class that showcases clean, alternate technology vehicles could not have been scripted better.

Despite the Mazda’s trailblazing ‘alternate technology,’ it’s not the first diesel to grace the Brickyard. In 1952, that’s 62 years ago, the Cummins Special shook the rafters by qualifying on the pole of the 500, but a clogged turbocharger forced its early retirement. Heck, the 1951 Special wasn't even the first diesel, nor the first Special; that honor falls to the Cummins Special of 1931, which finished 13th in the ’31 Indy 500…without refueling.

Despite this large advantage, history chose another fuel. This new GRAND-AM GX Class has begun to provide a venue for the exploration and development of alternative technologies. A production car-based division, the GX Class features alternative technologies and alternative fuels. Thirteen cars from 12 manufacturers are eligible to compete in GX. They include the Lotus Evora GX, Porsche Cayman, Mazda6, Audi TT, BMW 1 Series, Chevrolet Cruze, Ford Focus (four door), Hyundai Genesis, Subaru BRZ, Scion FR-S, Nissan 370Z or Altima, and Volkswagen EOS.

The Mazda6 racer has a gaggle of aero enhancements that allows its four-door sedan silhouette to cut through the wind like a knife. An aggressive extended air intake provides improved cooling while a low-projecting lip spoiler improves downforce at the nose of the car. Trick side skirts, aerodynamic side view mirrors and carbon-finished B-pillar treatments reduce air resistance down the side of the car. Out back, an adjustable rear wing and rear under-spoiler creates smooth airflow off the tail of the Mazda. Curb weight checks in at a tossable, class minimum 2,450 pounds.

Beneath the bonnet a 2.2-liter, four-cylinder SKYACTIV-D diesel pumps out the power to the tune of 380 horses. More impressive is the diminutive engine’s torque output of 450 lbs.-ft. The torque comes on low in the rev range at 3,750 rpm, which translates into the Mazda rocketing out of the turns on the track. The new powerplant is a true production-based creation as 51 percent of its parts are stock. The diesel features compound turbocharging where two turbos of different sizes provide the boost. This tag-team consists of a Garrett GTR-3776R and a Garrett GTR-2560R. The smaller 2560R is plumbed into the larger 3776R and the smaller unit provides most of the boost at slower engine speeds and both, wastegated to deliver 55 psi, pressurize the engine as it reaches its 5,500-rpm peak. Engine management is handled by a GRAND-AM -sanctioned Bosch/Motec ADL3 stand-alone system and Mazdaspeed reports converting from its Nippon Denso ECU to the Bosch was one of the biggest challenges of the process. The engine was torture tested with 50 hours of intense dyno testing prior to its debut at the season-opening 24 Hours of Daytona. An Emco six-speed sequential transaxle handles gear changes while Dynamic DSSV dampers and an Alcon/Pagid braking system are tasked with maintaining the Mazda’s contact patch as it attacks the turns. The Mazda6 rolls BBS wheels wrapped with grippy race slicks. Inside we find a sparse yet highly functional cabin with the SpeedSource/Riley chassis and roll cage, Sparco race seat, Schroth harness system and Sparco quick release steering wheel that effects quick driver changes.

Despite running with the precision of a Swiss watch on the engine dyno, the car was caught out by a fuel system snafu in the early stages of the Rolex 24 at Daytona. The root of the Mazda team’s misery was a simple 25-cent nut in the fuel line that had succumbed to vibrations and come loose. This mishap caused a lean fuel condition, which led to dropped cylinders in each of the racers.

MAZDA NORTH AMERICAN OPERATIONS SKYACTIV-D CLEAN DIESEL

After taking a few body shots at Daytona, Mazda fought back and the tide turned quickly for the next two events. Mazda6’s made the podium - taking second and third to their main rivals, BGB Motorsports and its Porsche Cayman. Then the Mazda6 broke through at the Grand Prix of Atlanta in April and since then Mazdaspeed and SpeedSource Engineering have put a whipping on all rivals - tallying wins at Detroit, Mid-Ohio and Watkins Glen.

With seven of 12 events in the books, it’s a toe-to-toe brawl between Porsche and Mazda with Porsche clinging to a scant one point lead in GRAND-AM GX Manufacturers Championship points race. Let the haymakers fly. -Evan Griffey

Mazda6 Diesel Racer Puts Stranglehold On GRAND-AM's GX Class

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