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'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).

GMC Sierra spied with ZR2-style off-road modifications

A few months ago, the 2022 Chevy Silverado ZR2 was revealed with a bunch of off-road goodies to help it achieve a little more parity with trucks like the Ford F-150 Raptor and Ram 1500 TRX. But GM has another full-size truck, the GMC Sierra, and it would seem silly to us if the company didn't share those parts. Based on these spy photos, it seems GM agrees. Though thoroughly camouflaged, we can tell this truck is a GMC Sierra thanks to the sheetmetal on the doors and the distinct shape of the wheel arches. Under the wrappings, we can see that this Sierra features a very different front bumper to the current king of Sierra off-road models, the AT4X. The bottom edge is much higher for better clearance, particularly on the sides in front of the wheels. This is the same type of change applied to the Silverado ZR2's front end. It does appear to be missing the ZR2's skid plate, though we suspect that's a temporarily missing component on this prototype. One other off-road upgrade this Sierra features is a pair of rock rails to protect the rocker panels on the cab. What we can't see are the shocks installed on this truck. If this is a GMC version of the ZR2, it should have the spool-valve shocks from Multimatic. They're some of our favorite suspension components on any vehicle. Other components it should have are locking front and rear differentials, 33-inch tires and a standard 6.2-liter V8. Since the Silverado ZR2 is already revealed and ready for production, we would expect to see the GMC version soon. A good bet would be for a reveal in time for the 2023 model year. As for a name, it's hard to say, since we've already had AT4 and AT4X. It could be named something completely separate from the AT4 line. Related Video: This content is hosted by a third party. To view it, please update your privacy preferences. Manage Settings.

Chevy and GMC trucks get CNG option pricing

Chevrolet and GMC have clued us in to pricing of the bi-fuel option for the 2015 Silverado and Sierra 2500HD CNG and 3500HD CNG pickups: it starts at $9,500; we're still missing the rest of the pricing inferred by the word "starts," however. If you remember from the Chicago Auto Show introduction, the 6.0-liter V8 puts out 360 horsepower and 380 pound-feet of torque when drinking gas, 301 hp and 333 lb-ft when inhaling CNG.
Chevrolet figures that a bi-fuel Silverado HD is worth $2,000 in savings if driven 19,500 miles on CNG and 7,500 miles on gasoline in the span of a year, a recoup rate easily attainable to high-mileage fleet owners. It can be specced on double- and crew-cab pickups with single rear wheels, not on dualies.
The 2015 Chevrolet Express and GMC Savana short-wheelbase passenger and cargo vans also get CNG options, starting at $10,825 for the three-tank system, and $12,090 for the four-tank system that can only be had on the cargo hauler. You'll find a bit more info on all of the permutations in the press release below.