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GM patent reveals new two-stage turbocharger

Modern turbochargers may be some of the best ever made, but performance is something that engineers are always trying to improve. According to GM Inside News, General Motors (GM) is hoping to alleviate some of the negative aspects of a two-stage turbocharger setup with a newly-patented design. The patent, that was filed on May 19, 2016, reveals a clever bypass system that allows the engine, a four-cylinder unit, to optimize both the low-pressure and high-pressure inlets for its respective functions. According to the filing, a conventional two-stage turbocharger setup is engineered to allow both turbines to operate simultaneously at low and mid engine speeds. At high engine speeds, only the low-pressure turbine works. The setup can't isolate either the low or high pressure side, which can impair low-end performance. GM's new two-stage turbocharger setup looks to eliminate this by linking the high-pressure turbo to the exhaust manifold through the high-pressure inlet duct. The low-pressure turbo is attached to the high-pressure turbo by a low-pressure inlet duct, which is linked to a connecting channel. A single actuator that is housed in the exhaust manifold creates a bypass that can opens the high-pressure inlet or close the connecting channel. Depending on what the engine load and speed is, the ECU guides the actuator—a single rotating spindle with discs corresponding to flanges on the high and low pressure sides—to isolate one of the two turbos. Isolating the turbos allow the respective inlets to be engineered for the best possible fluid dynamic performance. The setup should increase performance and decrease lag. There's no word on what car this setup will make an appearance on, but it will most likely be used in premium vehicles before trickling down to the rest of GM's vehicles. Related Video: News Source: GM Inside News, AutoGuide via GM Authority Cadillac Chevrolet GM Technology Sedan turbo patent engine turbocharging

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.

GM recalls 2022 Cadillac XT5, XT6 and GMC Acadia for suspension issue

General Motors is recalling a relatively small number of 2022 Cadillac and GMC crossovers to address the potential for missing or loose rear suspension hardware that is being blamed on a lapse in quality control at the company's Spring Hill facility. The campaign covers 223 examples of the Cadillac XT5, 159 examples of the Cadillac XT6 and 354 examples of the GMC Acadia. "General Motors has decided that a defect, which relates to motor vehicle safety, exists in certain 2022 model year Cadillac XT5, XT6, and GMC Acadia vehicles," GM said in its defect report. "A fastener in the left-rear suspension toe link in some of these vehicles may not have been fully tightened during suspension assembly. After an assembly process was moved to a new area, error proofing equipment was not initially set up properly, which allowed a window where the operator might miss tightening certain fasteners without the failure being flagged." The issue was discovered by a quality engineer at the Spring Hill facility in March of this year, at which point GM conducted an audit to determine which and how many vehicles may have left the factory with improperly torqued or missing fasteners, narrowing down the recall population to the above 736 vehicles. No incidents associated with the defect have been reported in customer vehicles.  Related video: Recalls Buick Cadillac GM Ownership Safety