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How GM's grueling 24-hour test gets the kinks out of its performance cars

One of the biggest challenges automakers face when designing a high-performance car is making sure that it is both fast and reliable. For General Motors, any car that might be taken to the track by its owner - like the Corvette, Camaro Z/28 (shown above) and the Cadillac CTS-V, for example - undergoes a rigorous and strenuous 24-hour test by engineers at the Milford Proving Grounds, as pointed out by Car and Driver.
We've posted on this topic in the past - on a video showing the Camaro ZL1 being brutalized, for instance - but this article gives a more in-depth look at what actually happens behind the scenes... including what that poor ZL1 went through. Though the test isn't for 24 hours straight, the cars are pushed as hard as possible by some of GM's best drivers with only the brakes and tires replaced frequently.
We don't want to ruin the fun for you, but it is an interesting article that tells just some of what GM does to develop its sports cars. Check out the full article over at Car and Driver for the rest of the story.

Fullsize GM SUVs have a problem that's making owners sick

Some fullsize SUV owners are getting sick, thanks to a buffeting and vibration problem in 2015 model year examples of the Chevy Tahoe and Suburban, Cadillac Escalade, and GMC Yukon. According to owners' complaints to the National Highway Traffic Safety Administration, the issue can vary from an annoying vibration inside the cabin to an experience so severe that it leads to dizziness and headaches. General Motors is aware of the complaints, but the fix isn't so simple. According to spokesperson Tom Wilkinson to Autoblog, the company "has been tracking this issue for a while." The problem has a fairly low incidence rate, but when it does occur the issue can be "uncomfortable and annoying for owners." There's no precise cause for the issue, Wilkinson claims, and in some cases, simply balancing the tires or changing the door seals can make it go away. However, not all of the fixes are so simple. AutoGuide dug deep into the problem and discovered a GM preliminary information bulletin that advised dealers to remove the headliner and to check the roof's bonds to the bows that go across the vehicle. However, that document included a note that the solution might not entirely eliminate things. According to AutoGuide, adding Dynamat insulation to the roof sometimes helped the problem. A GM spokesperson also told AutoGuide the company fixed the problem at the end of the 2015 model year, and didn't go into any more detail. This roof issue seems linked to some of the worst droning in these SUVs. According to one complaint from a 2015 Suburban owner to NHTSA: "Roof will not remain attached to the roof bows. This causes the buffeting similar to a window being down when all are up. The results span from annoying to painful." A 2015 Yukon owner claims to have another alleged cause for the problem in a NHTSA complaint from February 2015. This person brought their SUV to the dealer seven times over the course of four weeks for vibrations. The dealer replaced the driveshaft, suspension components, and more, but nothing worked. According to an engineer to the service adviser: "In an effort to prevent roll overs, they designed the frame and body mounts too stiff. There are 40 engineers working on issues, they have no solutions that work across the board." Wilkinson told Autoblog that GM is working with customers on an individual basis to rectify things. Since these are newer vehicles, dealers should also fix the problem under warranty.

How Cadillac improved power output in 2016 ELR by 25 percent

Earlier this year, Cadillac announced that the 2016 ELR would come with a big price drop and a powertrain that packs 25 percent more power output. That's a lot more oomph, but it didn't sound like the Caddy engineers made any major changes to the engine or motors. So, what happened? Let's refresh our memories with the numeric details. The 2016 car is 1.5 seconds quicker to 60 miles per hour than the 2014 model (there was no 2015), down to 6.4 seconds. The 2014 put out 295 pound-feet of torque. For 2016, it will be 373 lb-ft. The specific breakdown of the various components in the powertrain has not been disclosed, but from what we can tell, the two electric motors and the 1.4-liter inline-four engine in the new ELR are not that much different than those in the old one. Sam Abuelsamid, senior research analyst at Navigant Research (and former writer here at Autoblog) said that any of the unspecified upgrades would be difficult to tell on a part-by-part basis, but the overall effect will be noticeable. "The changes to the ELR as I understand them are analogous to getting more performance out of a 1965 Mustang with the entry version of the 289 cubic-inch V8. You can replace the carburetor with a larger version that enables more air and fuel to flow into the engine, thus producing more power. The basic engine hasn't changed, but power capability is being unleashed by feeding it more." "Cadillac has changed components in the power electronics to enable more current flow into the motor and thus produce more torque. When you do this in the Mustang, you probably need to replace the rear axle gears and use a beefier clutch to transmit the power to the wheels. Similarly, the ELR probably has some upgraded clutches, bearings, and gears to withstand the increased total output." Cadillac spokesperson David Caldwell told AutoblogGreen in an email that the new ELR does indeed have more than just new lines of code. "One could not 'reflash' a previous ELR to get the performance of a 2016," Caldwell said. "If one only changed software you would not get the performance upgrade fully, as the 2016 creates higher current, more power. So these have been upgraded physically – hardware.