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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.

Junkyard Gem: 1990 Mazda 929 S

In the late 1980s, Toyota, Nissan, and Honda were cleaning up in the American market with the Cressida, Maxima, and Legend, respectively. Mazda wanted some of those dollars, so the HC-series Mazda Luce was modified for the US market and sold here as the 929. It had rear-wheel drive, a powerful V6 engine, and lots of luxury features, but not many were sold. Here's a rare '90 that I spotted in a San Francisco Bay Area self-service yard. In 1990, the sporty 929S version got 190 horsepower from its DOHC 3.0-liter V6. Unfortunately for Mazda, American buyers associated the marque with sensible econoboxes and screaming rotary engines, not luxury machinery, at the time. For the 1990 model year, American-market cars were required to have either a driver's-side airbag or automatic seat belts. The 929 had the automatic belts, the less said about the better. The Luce-based 929 became the Sentia-based 929 for the 1992 model year. Meanwhile, the new luxury brands from Honda, Nissan, and Toyota were kicking the crap out of 929 sales; Mazda had planned to launch the Amati brand in the United States, but didn't have the resources to follow through. The last 929s were sold in the United States for the 1995 model year. Related Video: Featured Gallery Junked 1990 Mazda 929 S View 16 Photos Auto News Mazda

Sorry, rotary fans, Mazda's RX Vision probably won't happen

Mazda is doing a lot of things the right way in this age of beige-ness. It just crammed a turbocharged inline-four into the improved CX-9, a bold move unto itself, and one that should also be heartening for Mazdaspeed fans. Wouldn't that engine make for a swell Mazdaspeed3 or Mazdaspeed6? There's a reasonable ray of hope there, but not necessarily a guarantee. The RX Vision, though, is a pipe dream. Mazda is smart to keep the rotary dream alive. It's smart to keep developing it in back rooms and to keep the idea on the public's mind. Credit where credit's due: Mazda has solved some of the stickiest issues the rotary engine has, through savvy engineering and perseverance. We've seen promising patent filings for the Skyactiv-R engine, which is supposed to be found in the RX Vision concept. Mazda uses every opportunity to remind us that development is continuing and that the company would love to bring a rotary-powered sportscar to production. I believe it. But the RX Vision is just a design study. And there are some harsh realities about rotary engine emissions and fuel economy standards that are difficult for modern piston engines to achieve without expensive componentry. Emissions and fuel economy are both bugbears of the rotary, in case you've forgotten. And that explains Mazda's interest in running rotaries on hydrogen, but down that road lie infrastructure challenges as daunting as making a gasoline-powered rotary burn as clean as one of Mazda's Skyactiv piston engines. All this is meant to put Mazda's recent comments to Top Gear in context. Mazda's design director, Kevin Rice, spoke to TG at the Concorso d'Eleganza Villa D'Este, and was waving Mazda's rotary flag quite enthusiastically. "In the back rooms at Mazda, we're still developing it," Rice said, "and when the world's ready to buy another rotary, we'll be ready to provide it." I'd like that to be a comforting statement, but given the realities of fuel economy and emissions regulations and Mazda's position in the market, it seems like a hollow platitude. "When the world's ready" is just another way of saying "when we solve the fundamental issues with this engine layout, and there's an unambiguous market study that shows we can build these cars and make a profit, we'll consider it." That seems like a lot of "ifs". Perhaps Mazda does have a clean-burning, efficient, cheap-to-produce rotary running on an engine dyno in Hiroshima, and it's prepping an RX-9 for the next auto show.