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Consumer Reports criticizes small turbo engines for misleading performance, fuel economy claims [w/video]

Consumer Reports has taken aim at at small-displacement, forced-induction engines, saying the powerplants don't manage to deliver on automaker fuel economy claims. Manufacturers have long held that smaller, turbocharged engines pack all power of their larger displacement cousins with significantly better fuel economy, but the research organization says that despite scoring high EPA economy numbers, the engines are no better than conventional drivetrains in both categories. Jake Fisher, director of automotive testing for Consumer Reports, says the forced induction options "are often slower and less fuel efficient than larger four and six-cylinder engines."
Specifically, CR calls out the new Ford Fusion equipped with the automaker's Ecoboost 1.6-liter four-cylinder engine. The institute's researchers found the engine, which is a $795 option over the base 2.5-liter four-cylinder, fails to match competitors in acceleration and served up 25 miles per gallon in testing, putting the sedan dead last among other midsize options.
The Chevrolet Cruze, Hyundai Sonata Turbo and Ford Escape 2.0T all got dinged for the same troubles, though Consumer Reports has found the turbo 2.0-liter four-cylinder in the BMW 328i does deliver on its promises. You can check out the full press release below. You can also read the full study on the Consumer Reports site, or scroll down for a short video recap.

GM opens official investigation into C8 Corvette transmission leaks

In March 2020, a month after Chevrolet began customer deliveries of the 2020 C8 Corvette, a GM dealer technician created a Reddit thread about a leaking gearbox in a Corvette with 32 miles. That car hadn't even been sold yet. Since then, as a search of "C8 Corvette transmission leak" shows, it's been tales of woe for some owners. Something in the Tremec TR-9080 transaxle in the back of the mid-engined Corvette doesn't work as it should, the fault able to cause codes that the transmission needs service, or that the driver needs to shift to park. In some cases, the battery would die because of follow-on issues after the initial transmission code, that code preventing the car from powering down. As Autoevolution reports, GM filed paperwork with the National Highway Traffic Safety Administration in August to look into what's going on. Between forum threads and GM's investigation document, there are several issues mentioned. The most common appears to be the dual-clutch transmission leaking fluid due to gasket failures like the one suffered by one owner at 858 miles, and another for an owner currently enduring a second leaking transmission. The Midengined Corvette Forum reported that Chevy engineers redesigned the TR-9080 pan, fitting Corvettes with the new unit at some point in the 2021 model year. The original pan was stamped steel unit affixed to the engine with two studs and 13 bolts, plus "reinforcement plates." The updated pan is said to be a cast aluminum unit affixed with two studs and 17 bolts, omits the reinforcement plates, and gets a new machined new groove around its edge to seat the gasket seal. The GM paperwork now at the NHTSA mentions a P1789 code, and says one reason for it could be "debris on the park position sensor magnet causing an incorrect position reading to the TCM." This might be caused by another issue mentioned in forums, which is clogged transmission filters. GM gives instructions for returning transmission filters to the company, and a poster on one forum said the Corvette tech at the dealer where he bought his Corvette told him the automaker "requires every used transmission filter to be returned to GM."  Whatever's going on, the problems haven't stopped, and they go beyond the P1789 code. Over the weekend, a 2022 Corvette owner posted on Corvette Forums that he got a check engine light on his car after just 850 miles.

'Killing a Duramax' Gale Banks YouTube series methodically tunes a diesel to death

Learning or perfecting a skill by watching YouTube videos is known as attending YouTube University. GM Authority picked up on one of the video site's more fascinating courses, hosted by Gale Banks; in a fair world, he should be referred to as Professor Banks when it comes to diesel engines and truck tuning. A few months after GM introduced the updated L5P 6.6-liter Duramax diesel V8 in the 2020 Chevrolet Silverado HD and GMC Sierra HD that ships with 454 horsepower and 910 pound-feet of torque, Banks decided he wanted to methodically tune the engine to death. The purpose of the resulting series, called "Killing a Duramax," is to push more power out of the engine in order to discover which parts break and when — or, as Banks puts it, force-feed the Duramax "until the crank hits the street and the heads hit the hood." With that knowledge, Banks can figure out all the weak points on his way to building what he calls a "Superturbo," that being a supercharged, twin-turbo race engine with more than 1,000 hp. What makes the series fascinating is Banks' knowledge, paired with the company's comprehensive iDash engine monitoring system that keeps tabs on a glut of parameters every step of the way. So for instance, you get Banks explaining the differences between inches of mercury and barometric pressure, how those are different from the water content of the air measured in grains, then showing those readouts on the iDash, then explaining in detail how they affect the air density in the Duramax system. The stock Borg-Warner variable turbo gets a lot of airtime — Banks accuses it of being "out to lunch" because he feels it's the weakest link on the engine. That turns into a turbo teardown and a deep explanation of performance pitfalls, such as when air pressure on the turbine begins to diverge from the boost pressure coming from the compressor. Banks says he can keep close tabs on where power's coming from, because the iDash monitors the horsepower contribution provided by the ambient air, the turbo, and the intercooler separately. The major changes so far are a stouter Precision 7675 turbo and TurboSmart wastegate (episode 5), a twin intake (episode 6), a custom liquid-cooled intercooler from a marine engine, a new GM oil cooler and synthetic oil (episode 10), and new injectors (episode 11).