Here's How GMC's Huge New Hood Scoop Works Without Sucking In Water

GM added two significant items to the Chevy Silverado HD and GMC Sierra HD for 2017: a more powerful 6.6-liter diesel engine and a giant flared nostril of a hood scoop that feeds it. So how does that thing work without drowning the truck every time it rains? Check out what’s underneath.


I finally got to drive the new Duramax diesel-powered GMC Sierra HD in Colorado and Utah this week. There, GM’s engineers were keen to make sure I understood that the scoop is “functional” and “patent pending!” Or maybe they have the patent by now.

Regardless– I wouldn’t think you’d need a patent for a vent. Until I realized the opening was about the right size to accept and play a VHS tape. So wouldn’t it also be sucking down snow and rain and small-to-mid-sized birds, too?

It’s tough to miss. (Image Credit: Andrew Collins)
It’s tough to miss. (Image Credit: Andrew Collins)

It might, but GM’s engineers have a solution: a centrifugal separation chamber which pulls engine-damaging debris out of consumable air.

Basically, air flows through a box that’s shaped in such a way that forces heavier things like water and stones to fall through the bottom. Meanwhile, the lightest thing in the equation (air) proceeds out, through another filter and on into the engine. Debris then falls out of a valve at the bottom of the separator box and gets dumped harmlessly along the side of the engine onto the road.

I asked an engineer if it was anything like a salad spinner, and he seemed reasonably satisfied with the analogy. Water gets pushed away, air gets sucked down deeper. So there you have it- there’s just a little more to making a hood scoop than taking a slice out of the sheet metal and running a pipe into the engine.


GM says the new 6.6-liter Duramax engine gets about “half” of the air it needs to run from this scoop, with the other half coming in from a fender-mounted inlet like most trucks have. Apparently, the advantage of the hood-mounted intake is that it can grab colder, denser air in the highest ambient temperatures. That would theoretically allow the engine to make more power and potentially hit a higher towing capacity rating.

Or maybe GM just needed a quick way to make its heavy duty diesel trucks look a little more badass before the next big redesign.

Jalopnik Staffer from 2013 to 2020, now Editor-In-Chief at Car Bibles



You answered my question. Thanks. Anyway, I remember hearing another engineer talk about the scoop when asked how much power it adds answer (paraphrased) “none, it prevents power loss with increased ambient temps, so you get the same power all the time.”

Makes sense, just levels out the spikes in inlet temp a little.