“Diesel Chevy truck” sounds as American as John Wayne watching Jackass on a phone while he’s eating a hot dog and picking a fight at a baseball game. But even though the four-cylinder Duramax rumbling in the new Colorado and GMC Canyon has been around since 2011, it wasn’t actually fit for the U.S.A. until now.

As you may or may not feel comfortable accepting, General Motors does indeed sell vehicles beyond our nation’s impermeable borders. Some of those international markets include places that actually buy small, cheap, utilitarian vehicles instead of just commenting about them on the internet.

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For example; the Chevy Colorado. Which went on hiatus here but still sold in South America, Asia, and Australia with the 2.8 liter four-cylinder Duramax diesel engine we’re only just now getting to enjoy here in the homeland.

This engine was always in GM’s plan for the Colorado’s return to the American mid-size truck market, it just took a few years to work out the coughs and clatters that the company figured would scare off American buyers. It was also dirtier than that used diaper you watched a rat eat in the subway station.

Colorado Assistant Chief Engineer Scott Yackley saw quite a few tweaks to make the truck’s little diesel emissions-legal and bearably quiet, which he walked me through last week. Here’s a breakdown of the specific changes that were made to Americanize the Duramax 2.8.

Development

The new bodystyle Colorado was designed to have a diesel variant from day one, which is why there are hardly any differences between trucks with different engines.

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The 2.8 Duramax inside was all-new for global markets in 2011, but work commenced to adapt it to U.S. standards in secret almost immediately after its initial release. Yackley said the conversion effort alone was a “three or four” year process.

Emissions

Trucks rated to three-quarter ton or larger (the ones that have 2500s and F-250s and bigger) fall into a different category of emissions regulation. Basically, they’re allowed to pollute a lot more than cars. Not really the case with the Colorado though, which is much smaller and subject to tougher regulations.

In a post-VW Dieselgate world, public scrutiny is hot on automotive emissions and “diesel” is dangerously close to becoming a dirty word. “Ours is completely EPA compliant,” I was assured by GM’s marketing lackeys.

What do you want me to tell you? I sniffed it, seemed okay. Of course I’ve fallen for that before and I paid dearly for snarfing down those expired meat slices, so maybe we better take a closer look at the pollution-curtailing technology at work here.

The first phase of emissions control is an exhaust gas recirculation (EGR) valve. Basically, that’s exactly what it sounds like; some of the exhaust gases are sucked up and run back through the engine. This is supposed to reduce NOx significantly.

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Right after the turbocharger, emissions gases go through a diesel oxidation catalyst which uses chemicals to break down the fumes to reduce their toxicity. This means less hydrocarbons out of the tailpipe.

Then the Selective Catalyst Reduction goes to work. That’s where the blue fluid you may have heard called urea or DEF gets injected into the truck’s exhaust stream. That blue stuff is basically ammonia mixed with binding agents, which converts noxious NOX into harmless nitrogen and water.

Finally, exhaust is routed through the diesel particulate filter. This device collects all that black crap coming out of the engine and periodically burns it off. It’s the main thing standing between your Colorado and rolling coal. Please do not remove it.

Noise

With all that plumbing in place to clean up the truck’s emissions, a muffler becomes redundant so the Colorado doesn’t have one.

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But diesel engines are inherently noisier than ones that burn gasoline, even if you’re standing in front of the tail pipe. To counteract that the new Colorado has three acoustic absorbers on top of the engine, extra steel up front, and even more noise-softening material below the balance shaft in the bottom of the engine.

Assistant Chief Engineer Yackley told me the engine’s fuel map was specifically designed to be quieter than its international counterpart as well, timing fuel injection to minimize noise while maximizing performance.

Vibrations

You can’t have a rumbly engine splashing the Big Gulp all up and out of your cup holder, so keeping the Duramax’s shakes off the Colorado’s body starts with hydraulic engine mounts. These act as little shock absorbers between the engine and the truck.

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Moving the oil pump down to run off a balance shaft, and refining said shafts, is also supposed to have calmed the engine’s vibrations significantly.

But the most far-out sounding piece of tech I heard about was also one of Yackley’s favorties; the Centrifugal Pendulum Absorber (CPA). Here’s an illustration of how a CPA works, this is in the transmission:

This definitely real and not made-up component is manufactured by an outfit called LUK, and as you can see in the diagram above it’s basically just a little mechanical piece that smooths out a lot of vibration as it passes through the transmission.

Survivability

The 2.8 Duramax has timing belt scheduled to be replaced at 150,000 miles, but the engine’s supposed to last a whole lot longer than that. Even though the engine’s all covered in plastic, it’s supposed to be relatively easy to work on as far as modern mills go.

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To improve starting in cold conditions, the engine uses a ceramic tip glow plug in each cylinder to pre-heat the combustion chamber, a larger output starter, and a bigger battery. For extreme frozen scenarios, you can plug-in a block heater to your house.

I didn’t realize that was still a part of modern diesel engines, but the engineer told me it’d only be necessary in continuously exceptional cold. And not just a couple nasty days in New York; we’re talking about –30ºF.

Performance

All those emissions and noise caps do affect the Duramax’s output; the U.S. spec engine makes 181 horsepower versus the global market’s 197. But peak torque is the same, and Yackley promises it comes on lower in the rev range.

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The Honeywell turbo spins up to 35-40 psi of boost under max load. That’s a fast snail!

Yes you’ll probably be able to pull some of those filters off, slap a tuner on this thing, and squeeze any number you want out of it. But think about how hard Scott and his team worked to make this engine efficient and emissions-friendly!

I mean, I don’t want you to egregiously ruin the air. But I really want to see how much power one of these little guys can churn out. Start paying attention next month with the aftermarket bros all bonk heads in Las Vegas at the Specialty Equipment Market Association (SEMA) show.

Images via GM, FLAG Program/Flickr. CPA gif via Volkswagen Inside.


Contact the author at andrew@jalopnik.com.