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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:    

GM tells owners not to use SUV wipers due to fire risk

General Motors is recalling 31,685 examples of the 2016 Buick Enclave, Chevrolet Traverse, and GMC Acadia because a short circuit in the windshield wiper motor can potentially lead to a fire. Due to the danger, the company is asking owners not to use the wipers until the problem is fixed, according to The Detroit Free Press citing the Associated Press. A manufacturing defect in the wiper motor cover means that the electrical terminals can come into contact and cause a short. The part could "melt, smoke, or catch fire," according to a statement from GM. The company will get them fixed immediately, and dealers will replace the cover. If there's bad weather at the time the owner specifies to get the recall work completed, the automaker will come pick up the crossovers. Depending on parts availability, the automaker will supply a rental car for customers, as well. The issue was discovered at the factory. According to the company's statement, only 6,405 actually made it to customers, and they were notified immediately by overnight letter. The rest were in dealer stock. The affected crossovers carry build dates between August 18, 2015 and September 24, 2015. Of those, there are 29,295 in the US and 1,073 in Canada. GM Statement: General Motors has told the National Highway Traffic Safety Administration that it will recall approximately 29,295 2016 model year Chevrolet Traverse, Buick Enclave and GMC Acadia SUVs in the U.S. because the front windshield wiper motor may overheat when in use because of a manufacturing defect. In some cases, the front windshield wiper motor cover may melt, smoke or catch fire. The approximately 6,405 customers who have taken delivery of these vehicles were notified by overnight letter and are urged to contact a GM dealer as soon as possible to arrange a service appointment. These customers should not use the front windshield wipers until they have been repaired. If weather conditions prevent driving the vehicle without using the windshield wipers, GM will arrange to pick up the vehicle for servicing. If repair parts are unavailable, GM will provide a rental car at no cost until parts become available. The total population, including Canada, Mexico and exports, is approximately 31,685. About 25,280 of these vehicles are in dealer stock and will not be sold until repairs are made.

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