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Why an independent rear suspension for GM's new, full-sized SUVs wasn't easy

A Motor Trend report last month laid out how Cadillac's 4.2-lier twin-turbo Blackwing V8 could be an orphan due to cost concerns in the GM empire. Last-minute chassis changes to Cadillac's new sedans and XT6 crossover led to engine bays that couldn't fit the Blackwing. On the SUV side, according to the report, the new independent rear suspension for big people haulers cost so much to implement that GM ruled out reworking the Escalade to accept the Blackwing. At least one commenter rightly asked how could a suspension swallow that much money. A new piece in Motor Trend has the answer. The excellent Alissa Priddle spoke to Tim Herrick, GM's executive chief engineer for full-size trucks, about why the clean-sheet IRS cost "multimillions of dollars."  First, GM would need to build a new body shop at the Arlington, Texas plant that assembles the automaker's big SUVs to stamp the numerous wholly new parts and panels accommodating an IRS. Then GM would need to design and pay for a new assembly process. On top of those up-front costs, there was the incremental cost of the four-link IRS components being more expensive than those in the trucks' former leaf-sprung solid axles. Herrick endured so many rejections for so long that he remembers the date and time when he got approval for the new unit. He said it came down to a meeting where he told a higher-up, "I'll make you a deal: If we get to the reveal, or if we launch this and you think this was a dumb idea, I'll hand you my badge and let you walk me out." Head to Motor Trend to read the full story. Based on Herrick being on stage to help present the new SUVs to the press, and on our First Ride in the new Chevrolet Tahoe and Suburban at GM's Milford Proving Grounds, it appears this will have a happy ending for all involved. Furthermore, since Herrick worked on the T1 platform that supports the big SUVs as well as the light- and heavy-duty pickups, he understood the demands on the commercial side, too. That could be why when Roadshow asked Tim Asoklis, chief engineer of the Tahoe and Suburban, if the new IRS could endure life in the Chevrolet Silverado and GMC Sierra, Asoklis answered, "Oh, absolutely." Related Video:    

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.

Pony-car sales war: Mustang vs. Camaro vs. Challenger [UPDATE]

Update: An earlier version of this story misstated the 2015 Mustang's weight when compared with previous models. Additionally, we have added comments from Chevrolet in the text. The Ford Mustang has blown past the Chevy Camaro as America's best-selling pony car, and in June, it wasn't even close. The 'Stang outsold the Camaro 11,719 to 8,611 cars. The Camaro remained ahead of the Dodge Challenger, which sold 6,845 units. Even though the Camaro did post an 11.5-percent sales improvement in June, the competition is arguably stronger than at anytime since the 1970s muscle-car era. The Mustang's sales leapt a whopping 53.6 percent, while the Challenger saw a gain of 56 percent. Several factors are weighing down Camaro sales, including its lame duck status. Chevy is launching a new generation of the Camaro this year that's more than 200 pounds lighter, offers a new turbo four-cylinder engine option, and has a nicer interior than the outgoing model. Put simply: wait a few months and you can get a better car. It's also unlikely Chevy will jack up the price much, as it's historically kept the Camaro within reach of everyday enthusiasts. While Chevy fans wait in anticipation for their new sports car, Ford and Dodge have downshifted. The new Mustang, which went on sale last year, is faster and more sophisticated than its predecessor. It also offers a 2.3-liter EcoBoost four-cylinder, which Ford has credited for the Mustang's recent uptick and makes up 36 percent of the car's sales, Ford analyst Erich Merkle said. View 17 Photos June's performance allowed the Mustang to widen its sales gap with the Camaro this year. Through the first five months, Ford sold 68,290 Mustangs, a 54.4-percent increased compared with 2014. Chevy sold 42,593 Camaros, an 8.7-percent decrease. The Challenger – long the No. 3 pony car in sales volume – has seen its sales surge 41 percent this year to 37,011 units. Spokesman Monte Doran said Chevy expected that 2015 would be a "relatively soft year" for the Camaro. "Mustang is taking advantage of years' worth of pent-up demand for an independent rear suspension," he said. "When Camaro introduced an IRS, in 2009, it helped make us the best-selling performance car in America.