Posted by Mark Williams | July 30, 2014

We know the target for the 2015 Ford Power Stroke was to beat the horsepower and torque ratings of the 2014 Ram Heavy-Duty HO Cummins and the overall performance characteristics of GM's current 6.6-liter Duramax V-8 (offered in both the Chevy and GMC three-quarter-ton and one-ton pickups). But it looks like GM is getting ready to fight back, specifically with a newlytuned Duramax for its 2016 or 2017 HD pickups. Here's what our hot-weather-loving spy shooters have to tell us:

"We caught GM engineers testing several prototypes outfitted with an upgraded version of its Duramax turbo-diesel V-8 engine. We don't have any performance specifications at this time, but the goal must certainly be to bump the current 6.6-liter Duramax turbo-diesel's horsepower, torque and and towing capacity to counter Ford's recently upgraded 6.7-liter Power Stroke V-8 turbo-diesel. Ford's revamped 6.7-liter diesel currently outguns GM's 6.6-liter units — the Ford generates 440 horsepower and 860 pounds-feet of torque versus GM's 397 hp and 760 pounds-feet of torque of the Duramax.

"We don't know exactly what internal changes are in play on these latest GMC and Chevrolet HD prototypes, although our sources have reported that a more potent turbo and software upgrades are on tap for the 2016 model year. This fits perfectly with the evidence now spotted undergoing severe hot-weather testing in the California desert."

Deeper Breathing to Add Power

"We can clearly see that part of GM's strategy is to feed more air into the engine, via a new functional hood air-intake designed into the trucks' redesigned hoods. The new airduct sits prominently near the leading edge of the hood — the GMC gets a circular mesh intake grille while the Chevy appears to get a diamond-shaped interweaving mesh grille insert."

Definitely a Diesel

"You may be wondering how we can be sure that these prototypes were powered by GM's Duramax turbo-diesel engines. Here's how: We caught some of the prototypes tanking up and it was definitely diesel being dispensed into the truck. We also managed to zoom in tight on the fuel door, and it read 'Ultra Low Sulfur Diesel Fuel Only.' It's also worth noting that the test group had a Ford F-350 on hand as a benchmark vehicle, fitted with the 6.7-liter PowerStroke turbo-diesel V-8.

"We're hearing that more changes may ultimately be in store for GM's full-size trucks, with some additional, modest changes to the trucks' front fascias joining the redesigned hood spotted on these prototypes."

We'd also note that the diesel exhaust fluid tank, clumsily mounted underneath the front passenger door, looks like it has some bulky padding protecting or hiding something. This is the main piece of information regarding this camouflaged vehicle, meaning GM has tried to make it look like it's keeping the exposed tank in that location when we predict it will be moved to a less-exposed location. We're calling this box a decoy. Also, given the fact that there is no instruction or explanation about DEF on the fuel filler door, we assume GM will keep the filling spout underneath the hood in the engine compartment. We're also guessing GM will want to take the horsepower ratings above 420 and torque to the low-to-mid-800s. We'll know more later.

KGP Photography images