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Mazda files patents for a sequential twin-turbo setup

Mazda has a history of interesting engine technologies, from yesterday's rotary engine to tomorrow's compression ignition engine, and new patents show it still may have some internal combustion tricks up its sleeve. The one on display in these patents isn't especially new in concept, though. A sequential twin-turbocharger setup is something Mazda itself used on the third-generation RX-7. But it's something we haven't seen much of lately. It looks like it could have some possible advantages over older sequential systems, and it has some potential advantages for enthusiasts. First a quick and dirty primer for what makes a sequential twin-turbo system distinct from other twin-turbo systems. In many twin-turbo engines, there are simply two turbos that work together as one bigger turbo. They're the same size, and they spool up at the same time. With a sequential setup, at low rpm, a smaller turbocharger is spooled up first at low-rpm for quicker throttle response, and as the rpm and exhaust pressure increases, a valve opens up that allows a larger turbocharger to also spool up and provide high-rpm boost. That's basically how the Mazda design shown above functions. A big flap blocks off the larger turbocharger exhaust inlet, channeling all the exhaust to the smaller turbo. When more exhaust is available at high rpm, it looks like that flap opens up to spool up the big turbo, too. What's interesting here is that the way the turbochargers are packaged takes up less space than past systems. It looks like both turbos are contained in one unit that shares the same exhaust outlet, meaning the exhaust manifold could be kept simple and compact. In fact, the piping for compressed intake air could also be shared, reducing the amount of piping, which would further decrease the amount of materials and possible failure points. There are a number advantages of making this system smaller. The potential applications of the system are much greater, since it could fit in smaller cars with smaller engine bays. Making the system smaller also means that there won't be as much weight, which is important from both fuel economy and performance standpoints. Finally, the smaller setup likely uses fewer materials, which could make the system cheaper and thus easier to offer on a wider range of vehicles, or at least more profitable for Mazda.

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.

How Mazda got Skyactiv-X to work is incredible

"Take everything you know about engines and turn it around," Mazda North America Vehicle Development Engineer Dave Coleman says, patiently and with a look of benevolent pity, as he's quizzed about the particulars of the company's new engine. The Skyactiv-X engine is enigmatic — and deceptively simple in operation. And the bottom line for American consumers is that they'll be able to buy a car (or crossover; we don't know yet what vehicle will first get it) by late 2019 that provides diesel-like fuel economy but runs on regular old gasoline. In between diesel and spark ignition, but it's neither To truly understand it, you have to dive into the contradictions. Take that regular old gasoline: Contrary to common sense, the lower the octane, the better it works. In the lab, the Skyactiv-X engine loves 80 octane. The lowest Americans get is 87, so the engine is tuned for that octane. Go higher and you lose some low-end torque. Coleman was right. It's hard to wrap your head around an engine that thrives just at the point when most gas engines would aggressively self-destruct. It uses a supercharger to pump additional air — but not additional fuel. It uses spark plugs to start a combustion cycle that normally doesn't need a spark. And, quixotically, it's not displacing Mazda's own American-market diesel engine, currently languishing in a seemingly endless hell of regulatory approval. More bizarre: Mazda is a tiny automaker facing real existential headwinds, and gasoline compression ignition is a massive challenge. GM and Hyundai announced compression ignition, or HCCI, projects (full name, homogeneous charge compression ignition) to great fanfare, but they never amounted to a production hill of beans, crippled by reliability issues or horrible vibrations. Worse, they only worked at an unusably narrow range — low RPMs and low loads. HCCI research improved direct-injection gas and diesel engine technologies for these companies, but HCCI itself remains untamed. The benefits of lean combustion Why even try to tame HCCI? The answer is much better fuel economy and lower emissions. Less burned carbon-based fuel, less carbon dioxide released. That's simple. But there are some thermodynamic reasons for the lean combustion you can achieve with compression ignition that are worth explaining. The ideal amount of fuel for a conventional engine to burn is about a 14:1 air-to-fuel ratio. That lets every molecule burn nicely, in theory.