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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.

Mazda's new turbo four fits in both the 6 and the 3

Despite the size differences, the Mazda CX-9 shares a lot with its smaller car-based siblings, the Mazda6 and Mazda3. That could allow Mazda to slot its full-sizer's new 2.5-liter, turbocharged four-cylinder engine under the hood of its smaller offerings. Pardon us while we do a happy dance. "[The 2.5-liter turbo] fits in a lot of our cars, and where we're actually going to put it is another question," Mazda North America vehicle development engineer Dave Coleman told Australia's Car Advice. Coleman specified that the turbocharged engine will fit in all the same applications that can accommodate the company's 2.5-liter gas and diesel engines. "Basically, that big space we used for the bundle of snakes exhaust manifold, the turbo is in that space too. They're all packaged to occupy the same space. It's exactly the same clearance as the exhaust manifold of the other engines." This kind of logic – if Engine A is the same size as Engine B, then both should fit in Car C – is what's lead us to imagine a turbocharged Mazda6 since the new engine was announced. In short, it's great news. Mazda's 2.5-liter turbo is a hell of an engine in the CX-9, and it's hard to imagine it'd be worse in a lighter vehicle. But just because it works from an engineering standpoint doesn't mean it's going to happen. At least, not soon. "It fits. I'm not a product planner so I don't get to make that call," Coleman told Car Advice. "It's up to the product planners to decide what they're going to put it in." The most obvious application for a turbocharged engine in the 3 or 6 is as a reborn Mazdaspeed model. But don't get too excited – Coleman said Mazda hasn't even gotten as far as building an engineering prototype with this engine. We're still firmly at the theoretical stage. And that's bad news, because it gels with what we've been reporting – that Mazda will wait a generation for future Mazdaspeed models. We just stopped doing our happy dance. Related Video:

Top Gear recounts the fiery demise of the Mazda Furai

This past September we reported on Top Gear's destruction of the Mazda Furai, one of the finest concept cars to ever grace an auto show stage. It turns out that the Furai, which was burned nearly beyond recognition at the hands of the British magazine, was actually destroyed back in 2008, and that the entire thing had been covered up for five long years.
Now, a few months after publishing that heart-wrenching composite of a half-baked Furai (shown above), the lads at TG have published their account of just what resulted in a priceless concept car being transformed into a smoking hulk on a Suffolk runway. Click over to read the full story about just what happened, along with pictures of the Furai before, during and after the inferno.