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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.

Next Mazda MX-5 Miata to weigh a ton(ne), literally

Looking at recent spy shots of the fourth-generation Mazda Miata, it's obvious this sporty little roadster will grow in size compared to the current model, but it's also going on a diet. At the Tokyo Motor Show, Auto Motor und Sport sat down with Mazda executive Kiyoshi Fujiwara, who gave a little more insight into the Miata's redesign.
Fujiwara said that they're aiming for a curb weight of a tonne (metric ton), which is 1,000 kilograms or right around 2,200 pounds, for the next-generation Miata. This would make the roadster at least 300 pounds lighter than the current NC Miata, but still about 200 pounds heavier than the original NA.
There is no indication as to how Mazda will go about removing that much weight from the bigger car, but with as popular as the power retractable hard top (PHRT) model is on the current car, the new Miata may ditch this feature to lose its weight. Improving the power-to-weight ratio appears to be a key goal of the Mazda team, so we also wouldn't be surprised to see a more powerful engine underneath the longer hood.

Autoblog Podcast #396

Episode #396 of the Autoblog Podcast is here, and this week, Dan Roth, Steven Ewing, and Chris Paukert talk about the 2016 Mazda MX-5 Miata, the 2016 Jaguar XE, and the 2015 Lexus RC. We start with what's in the garage and finish up with some of your questions, and for those of you who hung with us live on our UStream channel, thanks for taking the time. Check out the rundown below with times for topics, and you can follow along down below with our Q&A. Thanks for listening!
Autoblog Podcast #396:
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