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Chevy's 6.6-liter Duramax is pretty much all new

To say there's a heated battle in heavy-duty pickups is an understatement, with Chevrolet, Ford, and Ram constantly trading blows of increased torque, horsepower, and towing capacity. The latest salvo is the revised, more powerful turbo diesel 6.6-liter Duramax V8 in the 2017 Chevy Silverado. It has 910 pound-feet of torque, an increase of 145, putting it nearly level with the Ford Super Duty. Here's a closer look at where those gains come from. How exactly did Chevrolet add all that torque plus 48 horsepower? The automaker essentially took a fine-tooth comb to the entire engine. Chevy says it changed 90 percent of the V8, and the cumulative effect of those small changes adds up to big increases. As you might guess, the turbocharger is updated. The larger unit features electric actuation of the variable nozzle turbine (VNT), and what Chevy calls a double axle cartridge mechanism that separates the VNT moving parts from the housing. That helps with heat performance as well, with a claim that the exhaust side of the turbo can run continuously up to 1,436 degrees Fahrenheit. Helping that cause are six exhaust gaskets made of Inconel - an nickel alloy that contains chromium and iron – and upgraded stainless steel for the exhaust manifold. Despite having the same cast iron cylinder block, albeit with some minor enhancements, the engine has new cylinder heads, pistons, piston pins, connecting rods, and crankshaft, which have all been upgraded to handle 20 percent higher cylinder pressures. Alongside the increase in pressure, Chevrolet also increased the cylinder head's structure with a honeycomb design. The pattern features high-strength aluminum with dual layer water jackets that not only improve strength, but also optimize water flow for better cooling. For 2017, the cylinder head also benefits from integrated plenum that aids the engine in getting more air under heavy loads. The cylinder head isn't the only component to get a minor update, as the pistons have a larger diameter pin for improved oil flow. The same detailed improvements has been bestowed to the humble connecting rods (second in our hearts only to the inanimate carbon rod). The new design has the bolts oriented roughly 45-degrees to the rod instead of parallel. The angle split design, as it's called allows for easier passage through the cylinder.

These are the 'Greenest' and 'Meanest' cars in 2015

As has become tradition, the American Council for an Energy-Efficient Economy (ACEEE) has come up with a ranking of what it refers to as the "greenest" cars of 2015, and, by way of contrast, a list of the so-called "meanest" cars, so those who value eco-friendliness over all else can choose which vehicles they should or should not consider buying. As you may expect, electric cars make up the majority of the greenest cars on the list, but, perhaps surprisingly to many, the Tesla Model S didn't make the cut. It's worth noting, too, that where the electricity an owner uses to charge their electric vehicle has a big impact on its overall environmental impact. "A car that is charged using electricity generated from natural gas or renewables is going to have significantly less impact on the environment than one charged on a coal-heavy grid," says ACEEE lead vehicle analyst Shruti Vaidyanathan. The ACEEE's list for 2015 looks very different than it did in 2014. It's an interesting collection, though – and we're sure this goes without saying, really – we'd recommend doing a bit more research into each vehicle and how it might fit into your daily life before making any purchase decisions. Click here to see the ACEEE's list of the Greenest and Meanest vehicles sold in the United States in 2015. Green Bugatti Chevrolet Fiat GM GMC Mercedes-Benz Nissan RAM smart Toyota greenest greenest cars

Top horsepower-per-dollar cars in 2017

Bang for the buck. That quasi-scientific statistic is bandied about by motor heads everywhere from classrooms to barrooms, though the truth of the matter is that it's exceedingly complex to measure. A fair performance-per-dollar index would include something like cross-referencing MSRP (Manufacturers Suggested Retail Price) with point-to-point times on a track or driving route, which is obviously hard to do comprehensively. But, for the sheer joy of talking about cars and playing with a big spreadsheet, there's always the horsepower-per-dollar index, which is more straightforward, albeit hilariously flawed. There are vagaries even with this simple formula, of course: MSRP for vehicles can change at a moment's notice, to say nothing of the bottom-line shifting that happens with local deals or showroom negotiation. For this list we're running with the straight MSRP wherever possible, and as recently reported as we can get it. All the vehicles on this list are 2017 models, and all trims are reported where the lowest price and differing power levels intersect. Some choices were made for personal preference and some for sanity, avoiding things like all 48 trim levels of the Ford Transit, all with the same horsepower). If this list were a simple top ten, or even a top fifty, you'd be bored to tears with all the red, white and blue that is represented. Following perfectly with conventional wisdom, American cars really do lead the world where hp/$ is concerned. So, for the sake of variety (and the sheer joy of seeing a minivan 'win' one round of this thing) I've sorted out some top five and bottom five lists for broad power categories. Let's dive in. Less Than 100 Horsepower Okay, okay, this is hardly a category we'll grant you. But we've often tried to click off all the sub-100-hp cars on sale in the US, and making this list gave us an excuse. It also illustrates that none of these smallish vehicles bring cheap horsepower to the table - for that you'll need a motorcycle. The segment-leading Chevy Spark (above) asks just over $139 for each hp, and that Smart Fortwo Electric Drive has hp on sale for about the same price as its very distant family cousin, the Mercedes-Benz SL65 AMG (insert your favorite Smart joke here... we know you want to).