1985 Mazda Rx-7 33k Mi on 2040-cars

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This map reveals the cleanest vehicles based on location

Naysayers love to point out how dirty the electricity grid mix is when it comes to charging electric vehicles. Curmudgeons are eager to jump into any conversation about EVs to enlighten the lucky listeners about how plug-in cars contribute to pollution, sometimes even throwing in a dash of climate-change denial for good measure. (Thanks, buddy. Pray, tell me more about the plight of oppressed SUV owners.) Unless someone buys an EV just because they think they're cool (which, yeah, they often are), they probably have at least a passable understanding of their environmental pros and cons. As many EV owners are already aware, location has a lot to do with any particular plug-in car's carbon footprint. Still, there's always more to know, and knowledge is not a bad thing, especially if one uses it to do the right thing. That's why this handy-dandy map from Carnegie Mellon University is so interesting. CMU researchers have compiled information about the lifecycle greenhouse gas emissions of various EVs based on where they're charged, as compared to gasoline-powered vehicles. The researchers looked at the Nissan Leaf, Chevrolet Volt, and Prius Plug-In Hybrid versus the gasoline-dependent Toyota Prius hybrid and the stop-start-equipped Mazda3 with i-ELOOP and compared grams of CO2 emitted per mile. CMU takes into account the grid mix, ambient temperature, and driving patterns. CMU takes into account the grid mix based on county, as well as ambient temperature and driving patterns in terms of miles traveled on the highway or in the city. For instance, if you drive a Nissan Leaf in urban areas of California, Texas, or Florida, your carbon footprint is lower than it would be if you were driving a standard Toyota Prius. However, if you charge your Leaf in the Midwest or the South, for the most part, you've got a larger carbon footprint than the Prius. If you live in the rural Midwest, you'd probably even be better off driving a Mazda3. Throughout the country, the Chevrolet Volt has a larger carbon footprint than the Toyota Prius, but a smaller one than the Mazda3 in a lot of urban counties in the US. The Prius and Prius Plug-In are relatively equal across the US. Having trouble keeping it straight? That's not surprising. The comparisons between plug-in and gasoline vehicles are much more nuanced than the loudest voices usually let on.

Mazda still has a team working on rotary engines

The flame still burns within Mazda to stage a rotary engine revival. Before you start getting excited, it's way too soon to start saving money for the fabled, next-gen RX-7 or RX-8. Still, company boss Masamichi Kogai confirmed to Autocar that the Japanese automaker has an engineering team dedicated to improving the Wankel. This development group has the hard task of trying to make the rotary stack up to modern internal combustion engines in terms of emissions and fuel-economy standards. Neither factor were ever exactly Wankel's strong suits. Kogai described them as working "very enthusiastically" to Autocar. The boss didn't discuss any future RX-vehicles or the size of the team, however, a report from last year indicated that there were 30 engineers in partnership with universities to update the engine's design. After problems keeping up with emissions and fuel economy, Mazda built it's last rotary for an RX-8 in June 2012. Since then, there have been intermittent rumors of a return. One possible solution was a design called the 16X that was supposed to offer more torque and better fuel economy. Another possibility was a small-displacement unit as a range-extender in an electric Mazda2. Rumors of a new RX-7 have been heard for years. In 2013, Kogai clearly said that it wasn't happening. When asked again last year, he reiterated the same point.

Mazda's Skyactiv-X power and efficiency ratings released in Europe

Mazda's long-awaited Skyactiv-X engine is finally headed for production, though not yet for the United States. The Japanese automaker says "various European countries" will get access to the unique engine in the Mazda3 starting this fall. Still, the announcement is relevant to the rest of us because we now have official power levels and fuel efficiency numbers that we can use to compare the Skyactiv-X with other engines offered in the compact Mazda. First, the power. According to Mazda, the 2.0-liter Skyactiv-X makes 178 horsepower and 165 pound-feet of torque. By way of comparison, the 2.5-liter Skyactiv-G engine currently used in the Mazda3 here in the States makes 186 hp and 186 lb-ft of torque. Sure, it's a little less powerful, but note that the displacements don't match and remember that the real reason the Skyactiv-X exists is to reduce fuel consumption. And that brings us to the Skyactiv-X's combined rating of around 53.5 miles per gallon (converted from liters per 100 kilometers). That's around 8 mpg better than the 2.0-liter engine that comes standard in Europe. Before we go any further, it's important to note that these numbers represent official figures for the European NEDC combined cycle, which means they are not directly comparable to the ratings we'll get from the United States EPA. Our official ratings will almost certainly be lower. With that disclaimer out of the way, the 2.5-liter Mazda3 scores a combined 30 mpg here in the States. The obvious unanswered question is when the Skyactiv-X might actually come to America. And the unfortunate answer is that we don't know. Mazda has yet to make an official decision on timing for the U.S market's launch of the engine, but as soon as we know, so will you.