2008 Chevrolet Suburban Z71 on 2040-cars

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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.

Watch Evo pick its 2015 Car of the Year in this epic video

With just a few days left in 2015, it's the perfect time to check out Evo's annual Car of the Year test to determine the greatest performance vehicle of the last 12 months. The writers' picks for the 11 finalists spanned a breadth of engaging models and included: Peugeot 208 GTi by Peugeot Sport, Lamborghini Aventador SV, Seat Leon Cupra Sub8, McLaren 675LT, Porsche 991 GT3 RS, Porsche Cayman GT4, Honda Civic Type R, Ferrari 488 GTB, Chevrolet Camaro Z/28, Lotus Evora 400, and Mercedes-AMG GT S. For the venue to test the mettle of these performance machines, Evo stuck close to home this year and visited the twisting roads at the beautiful north coast of Scotland. Racing brothers Marino and Dario Franchitti also came along for the ride to provide two more voices in the competitive challenge to determine a winner. Evo's video explains why each model deserves to be among such rarified company but doesn't gloss over their faults either. There can be only one winner, though. We don't want to spoil it, so check out the clip for magnificent views of these performance machines through the Scottish countryside.

Frustrated GM investors ask what more Mary Barra can do

DETROIT — General Motors Co Chief Executive Mary Barra has transformed the No. 1 U.S. automaker in her almost five years in charge, but that is still not enough to satisfy investors. Ahead of third-quarter results due on Oct. 31, GM shares are trading about 6 percent below the $33 per share price at which they launched in 2010 in a post-bankruptcy initial public offering. The Detroit carmaker's stock is down 22 percent since Barra took over in January 2014. After hitting an all-time high of $46.48 on Oct. 24, 2017, the shares have declined 33 percent. In the same period, the Standard & Poor's 500 index has climbed 7.8 percent. Several shareholders contacted by Reuters said GM could face a third major action by activist shareholders in less than four years if the share price does not improve. "I've been expecting it," said John Levin, chairman of Levin Capital Strategies. "It just seems a tempting morsel to somebody." Levin's firm owns more than seven million GM shares. Barra has guided the company through the settlement of a federal criminal probe of a mishandled safety recall, sold off money-losing European operations, and returned $25 billion to shareholders through dividends and stock buybacks from 2012 through 2017. GM declined to comment for this story, but the company's executives privately express frustration with the market's reluctance to see it as anything more than a manufacturer tied mainly to auto market sales cycles. GM's profitable North American truck and SUV business and its money-making China operations are valued at just $14 billion, excluding the value of GM's stake in its $14.6 billion Cruise automated vehicle business and its cash reserves from its $44 billion market capitalization. The recent slump in the Chinese market, GM's largest, and plateauing U.S. demand are ratcheting up the pressure. GM is one of the few global automakers without a founding family or a government to serve as a bulwark against corporate raiders. In 2015, a group led by investor Harry Wilson pressed GM to launch a $5 billion share buyback, and commit to what is now an $18 billion ceiling on the level of cash the company would hold. In 2017, GM fended off a call by hedge fund manager David Einhorn to split its common stock shares into two classes. Einhorn, whose firm still owned more than 21 million shares at the end of June, declined to comment about GM's stock price. Other investors said there were no clear alternatives to Barra's approach.