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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

GM recalls Chevy Impala, Cadillac XTS for braking problem

Back in April, General Motors launched an investigation into braking issues affecting the 2014 Chevy Impala. Now there's a recall of both the Impala and the Cadillac XTS with which it shares its Epsilon II platform.
The issue apparently revolves around the electronic parking brake, which may not properly disengage. As a result, the rear brake pads could rub the rotor even while the vehicle is in motion, causing "significant heat, smoke and sparks." The earlier investigation had been launched following a complaint regarding the forward collision avoidance system, which is now either appears to have been unrelated or possibly a symptom of this larger issue.
The recall affects 2013-15 XTS models manufactured between February 14, 2012, and August 22, 2014, as well as 2014-15 Impalas manufactured between January 15, 2013, and August 22, 2014. The total number of affected vehicles reported by the National Highway Traffic Safety Administration comes to precisely 132,921 units, while The Detroit News reports a higher total of 205,000 units - the difference potentially coming down to the scope within the US and more broadly across North America. Dealers will contact owners to update the software in order to fix the problem.

Autoweek divulges details on Presidential limo

Ever since the latest presidential limousine, also known as The Beast, debuted in 2009, we've wondered what's underneath that black Cadillac body. We already know a few details, like the fact it isn't a Cadillac at all, but a very heavy duty truck chassis from General Motors with a body that resembles a super-sized Caddy. Autoweek, however, has managed to extract new details from veteran Secret Service agents about the closely guarded presidential limo. Their methods, of course, are classified.
Designed to be a rolling office, bunker and escape pod all in one, the current presidential limo is far different from previous presidential state cars, which were heavily modified production vehicles. As we would expect, The Beast uses thick, military-grade body armor (eight inches on the doors), an armored fuel tank, special run-flat tires with Kevlar lining, an encrypted satellite phone, a fully sealed cabin with its own oxygen supply and a trunk full of weapons and medical equipment that includes a supply of the President's blood type (in case the car gets cut off from the ambulance that's always present in the President's motorcade).
The Beast also comes with a Halon fire-suppression system, night vision and is powered by a V8 engine, which we already knew runs on gas and not diesel, that returns an EPA-unfriendly estimated 3.7 miles per gallon. The Secret Service operates a fleet of 12 limos and each Beast costs $1.5 million. Lastly, AW estimates that the 18-foot-long state car weighs 15,000 pounds, and each Secret Service agent that drives the car must be specially trained to maneuver such a massive vehicle.