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Inside The 400hp Mazda6 Race Cars - Diesel Speed

An inside look at the Vroom-Vroom

Jason Sands
Mar 5, 2014
Photographers: Jason Sands
Mazda and the Speed Source Race Engineering teams have jumped into the road racing game with both feet, in an effort to show off the company’s new Skyactiv-D diesel engine. The 2.2L inline-four powerplant is slated to hit U.S. shores in 2014 in the Mazda6, where it will be rated at an estimated 175 hp and 310 lb-ft and deliver more than 40 highway mpg. Luckily for us, Mazda decided to show what the 2.2L Skyactiv-D could really do, in the form of two 400hp, 450-lb-ft, diesel-powered Mazda6 race cars we were able to view at Laguna Seca raceway.
While the cars themselves are high-end road racing fare, featuring rear-wheel drive, lift-off carbon-fiber body panels, Lexan windows, and full tube frames, the engine is surprisingly factory. In total, the 2.2L race engine uses 63 percent of the factory parts, including the block, head, and camshafts. More than doubling the horsepower of the engine did involve quite a bit of legwork in the rest of the engine’s systems, however. A custom steel crank was outfitted; new, stronger H-beam connecting rods replaced the I-beam stockers; and a de-lipped and reduced-compression 12.5:1 piston design was incorporated into the engine build.
The airflow and fuel systems were heavily modified to enable the engine to produce the type of power it does. A Bosch Racing stand-alone ECU was used, along with the company’s injectors. The factory turbocharger system was also traded in favor of compound turbochargers. Both turbos are Garrett ball-bearing chargers, the smaller being a GT2560 while the large turbo is a GT3776. Maximum boost through the twin charge-air-coolers is 60 psi.
In addition to the impressive power levels the 2.2L race engine produces, it went through an extremely rigorous testing program, with both dyno testing, and computer modeling. When all was said and done, Mazda had gone through 14 different piston designs, calculated factory crankshaft and connecting rod failure points, made more than 2,000 dyno pulls, and had run 30- and 50-hour endurance tests on the dyno. No corners are cut on race day, either, when live tuning and 70-cetane fuel (as opposed to the normal 40 or 50) are an integral part of competing.
Photo 2/11   |   Mazda fine-tunes its diesel race cars at every race. They run a surprisingly lean 25 to 30:1 air fuel ratio at full boost, which means that when competing, the 2.2L diesel gets literally double the fuel economy of a gas engine at wide-open throttle. s
With this type of commitment to the diesel architecture, it’s no surprise the Mazda6 diesels were able to take out the GX-Class Porsche Cayennes at such prestigious races as the Rolex 24, and to win at Indianapolis Motor Speedway—the only win for a diesel ever. Mazda wrapped up the season with the overall GX Championship, which was a major accomplishment for the program’s first year of racing. With a start like this, we expect the diesel-powered Mazdas to continue to dominate, and we look forward to when the production model finally hits our dealerships.
To cut down on forward weight, the alternator, battery, and starter have all been moved to the opposite side of the driver, behind where the passenger seat would be. The starter and alternator are actually engaged and driven off the driveshaft.


Mazda North America
Speed Source Race Engineering



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