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Chevy's 6.6-liter Duramax is pretty much all new

To say there's a heated battle in heavy-duty pickups is an understatement, with Chevrolet, Ford, and Ram constantly trading blows of increased torque, horsepower, and towing capacity. The latest salvo is the revised, more powerful turbo diesel 6.6-liter Duramax V8 in the 2017 Chevy Silverado. It has 910 pound-feet of torque, an increase of 145, putting it nearly level with the Ford Super Duty. Here's a closer look at where those gains come from. How exactly did Chevrolet add all that torque plus 48 horsepower? The automaker essentially took a fine-tooth comb to the entire engine. Chevy says it changed 90 percent of the V8, and the cumulative effect of those small changes adds up to big increases. As you might guess, the turbocharger is updated. The larger unit features electric actuation of the variable nozzle turbine (VNT), and what Chevy calls a double axle cartridge mechanism that separates the VNT moving parts from the housing. That helps with heat performance as well, with a claim that the exhaust side of the turbo can run continuously up to 1,436 degrees Fahrenheit. Helping that cause are six exhaust gaskets made of Inconel - an nickel alloy that contains chromium and iron – and upgraded stainless steel for the exhaust manifold. Despite having the same cast iron cylinder block, albeit with some minor enhancements, the engine has new cylinder heads, pistons, piston pins, connecting rods, and crankshaft, which have all been upgraded to handle 20 percent higher cylinder pressures. Alongside the increase in pressure, Chevrolet also increased the cylinder head's structure with a honeycomb design. The pattern features high-strength aluminum with dual layer water jackets that not only improve strength, but also optimize water flow for better cooling. For 2017, the cylinder head also benefits from integrated plenum that aids the engine in getting more air under heavy loads. The cylinder head isn't the only component to get a minor update, as the pistons have a larger diameter pin for improved oil flow. The same detailed improvements has been bestowed to the humble connecting rods (second in our hearts only to the inanimate carbon rod). The new design has the bolts oriented roughly 45-degrees to the rod instead of parallel. The angle split design, as it's called allows for easier passage through the cylinder.

2020 Chevrolet Tahoe, Suburban and GMC Yukon all spied with production lights

One of our spy photographers just caught a smattering of full-size GM SUVs out testing, including the Chevrolet Tahoe, Suburban and GMC Yukon. Previous spy photos of the next-generation of these big GM SUVs have revealed that GM is going with an independent rear suspension design, and these shots confirm the news once again with our best look at the hardware yet. Check them out from the rear, lined up like ducks in a row to see the beefy control arms down there. This will undoubtedly give the big SUVs a more compliant ride, and should bring it back into touch with the refinement from the Ford Expedition and Lincoln Navigator. The new bits we get to see with these shots are production headlights and taillights that are shaping up to look pretty neat. Most distinguishable are the GMC Yukon's LED DRLs. These look a lot like the C-shaped LEDs outlining the headlights on the Sierra, but they have an extra LED strip on top of the C. The parts of the taillights that we can see look significantly different than that found on the Sierra, showing GM is planning on having a great deal of differentiation there. We can sort of see through the mesh covering the grille to what appears to be a classic horizontal bar style front opening. Chevy is predictably dialing the crazy LED strip design back for the Tahoe and Suburban. The parts that are lit up look a whole lot like the headlight fixtures on the 2019 Silverado. That truck uses a stack of lights with the actual headlights separated from the DRLs. We can see the same thing going on here, with the headlight up top and curved LED DRL strip sitting below. It's tough to say if the designs are exactly alike, but we expect to see an extremely Silverado-esque look once all the camouflage comes off. Chevrolet's taillight design differs from its donor truck like the GMC, showing off a curved, vertical series of LEDs out back. Once production lights start popping up like this, we know the vehicle is moving closer to its end game. A reveal sometime later this year could be in the cards for GM's next batch of full-size SUVs. It certainly needs them quick, as Ford rockets ahead with increased Expedition production announced earlier this week.

Race Recap: Rolex 24 at Daytona was fast and feisty

Let the record show that victory at the 2015 Rolex 24 at Daytona went to the No. 02 Chip Ganassi Racing with Felix Sabates Target/Ford EcoBoost Riley DP driven by Verizon IndyCar drivers Scott Dixon and Tony Kanaan and NASCAR drivers Jamie McMurray and Kyle Larson. The winner did 740 laps to cover 2,634.3 miles in 24 hours and 57.667 seconds. That's a statement to this year's pace in spite of 18 cautions, two more than last year: the Michael Shank Racing Ligier got pole with a time of 1:39.194, slower than last year's pole time of 1:38.270; however, the winning car last year only did 695 laps. The fight for top honors was shaved to a four-car battle over the first third of the event. The No. 02 Ganassi car took the lead on the first lap, swapping it well into the night with the No. 01 Ganassi car, the No. 10 Wayne Taylor Racing Corvette DP, and the defending champion No. 5 Action Express Corvette DP, all of them staying within about 20 seconds of one another. The Action Express car had a fuel connector come loose and lost three laps getting towed back to the pits to have it reattached, but was back in the lead 18 hours in. The No. 01 Ganassi car dropped out with recurring clutch problems 22 hours in, retiring not long after. A race-within-the-race is where the concluding action happened, a seven minute, 30-second dash from the end of the last caution to the checkered flag. During the penultimate pit stops with an hour to go, Dixon was in second place followed Jordan Taylor in the Wayne Taylor Racing DP into the pits but beat him out, taking the lead. The Action Express car was in third. In the last pit stops of the race, Dixon gained even more time, getting a four-second advantage over Taylor. Then a full-course caution came out twenty minutes before the finish when a Prototype Challenge car hit the wall and caught fire, bunching up the field. That closed the pits, but the Wayne Taylor Racing car had to pit during that yellow because of a miscalculation of driver time. No driver can be behind the wheel for more than four hours in a six-hour period but Jordan Taylor was going to go over, so he came in to swap out for brother Ricky. That cost the team any chance of second place, since they took an additional drive-through penalty for entering closed pits. When the track went green again, Sebastien Bourdais in the Action Express car stayed all over Dixon for the final five laps but couldn't get around him.