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Mazda Skyactiv-D racer first diesel to run at Indy in 60 years

While it may not be touting the old "Win on Sunday, sell on Monday" axiom we all know and love, Mazda recognizes that racing can only improve its cars. And so it's no surprise that the Japanese automaker is testing and refining its Skyactiv-D diesel engine by sending it out on various race tracks around the country - notably being the first diesel ever to compete at Daytona and the first to notch a Grand Am win at Road Atlanta.
Next up? Indy. It has been over 60 years since a diesel-powered machine ran at the Indianapolis Motor Speedway, and the Cummins-powered racer that competed in the 1952 Indy 500 with a 6.6-liter inline-six-cylinder oil-burner was a fast and brutal machine that set a new lap record in qualifying leading up to the race. Though that car was withdrawn with turbocharger failure 71 laps in, its diesel powerplant left an indelible impression on the racing community, and that's something Mazda hopes to accomplish once again.
Mazda says that the diesel engine in its race car is pretty darn close to stock - 51 percent stock by parts count, and 63 percent stock by weight - which means the way it performs in competition is at least a somewhat meaningful way to the stock engine's durability in the real world. Check out the image of the Mazda6 Skyactiv-D racer posing alongside the 1952 Cummins above (click to enlarge) and feel free to peruse the press release below for the rest of the details.

Mazda Miata 'fathers' Hall and Case offer a tour through the roadster's history

The original Mazda Miata broke onto the automotive scene in 1989 and was a huge success. However, the convertible's genesis goes all the way back to the early '80s. Bob Hall and Dean Case were among the inside men of the program on the US side, and they were on hand at Mazda Raceway Laguna Seca during the recent MX-5 event there to tell some of their stories about the project's beginning.
Hall was on the Miata project from very early on, and one of his most fascinating stories is how the convertible got its shape. The droptop wasn't necessarily going to be a rear-wheel drive roadster. There were both front-wheel-drive coupe and mid-engine concepts being considered. In fact, the classic look of the NA generation was the least favorite of the three at the sketch stage.
Hall comes off as a jokester hiding a genius mind. He has a fountain of information in his head about what a Miata should be, but it all comes down to "less is more." However, he admits that it's easy to conceive that idea, but it's much harder to actually execute it well.

Mazda Skyactiv-X Review | The revolution begins with a squeeze-bang

The matte black Skyactiv-X prototype looks like a rough Mazda3, perhaps reconstructed after a bad wreck by an over-enthusiastic owner of a spot welder and lots of gaffers' tape. Ribbed ducts poke out of the dash sending two breaths of conditioned air to no one in particular. Even its revolutionary engine, the thing we're here to experience, is entombed in a massive, nondescript cover to mask its unseemly noises. It's a wild, strange way to meet a very unconventional vehicle that promises diesel-like fuel economy, a wide torque band, and an exotic method for burning less gas than ever before. It takes a few hours for Mazda's engineers to explain the fundamental principles of operation. For more detail, read our Skyactiv-X Spark Controlled Compression Ignition explainer, but here's a very brief overview. Skyactiv-X marries some traditional gasoline engine characteristics with a novel form of compression ignition called SPCCI. The key for Skyactiv-X is to use very high compression in the cylinder and an extremely lean fuel-air mixture. Squeezed right to the cusp of getting hot enough to blow up all on its own (which is very hard to predict), a squirt of extra gas and a spark interject to cross that compression-ignition threshold in a controlled and predictable manner. See the animation below: That takes a few essential components to get just right. One is a massive amount of computer processing power and some pressure sensors in the individual cylinders, because the ambient conditions change how and when these things happen. Skyactiv-X uses a clutched supercharger to pump in additional air when needed to nail the mixture precisely, and high-pressure injectors to get the low ratios of fuel to disperse properly in the chamber. And since it operates like a conventional gasoline engine sometimes, it uses valve timing to lower the very high compression ratio so it doesn't reach combustion ignition in that mode. In practice, the Skyactiv-X runs in compression ignition mode most of the time. In practical terms, that means it drives like a torquey gasoline Skyactiv engine. The torque curve is broad and flat — diesel-like in that respect. That also means it can get away with using a six-speed transmission and a lower final drive for better response. There's enough grunt and economy together that Mazda can let the engine spin faster — at 60 mph, it's running at roughly 1,000 more RPM than a similar gas engine, with greater efficiency.