Duramax. It’s a name and brand that is almost entirely synonymous with the 6.6L V8 diesel engine that you can find under the hood of GM’s 3/4 ton and higher trucks. It wasn’t until recently that Duramax meant more than just the classic 6.6L V8 we all know and love, with GM releasing the 2.8L and 3.0L Duramax over the last few years.
We already made an in-depth article and video talking about the 3.0L Duramax, the pros and the cons, and while you might think the 2.8L Duramax is similar considering they’re separated by a mere 200cc of displacement, they’re actually nothing alike. So, with that in mind, it’s time to a deep dive into the GM 2.8L LWN Duramax.
Where the 2.8L DMAX Came From
The strangest part about this 2.8L engine having the Duramax name, which is a name that is often thought of exclusively with American trucks, is that it’s not even close to being an American engine. Although to be fair, the 6.6L Duramax also isn’t an American engine, as it’s manufactured by Isuzu.
Regardless though, the 2.8L Duramax is actually an older engine from VM Motori, which is a company that is actually now owned by Stallantis which is a company under the Fiat Chrysler umbrella, which is ironically where RAM got their EcoDiesel from. So, in a way, the 2.8L Duramax and the 3.0L EcoDiesel are actually related, as they’re both designed by VM Motori.
The 2.8L Duramax, in particular, it’s based on the A 428 dual-overhead-cam, which itself, is an evolution of the R 428 dual-overhead-cam, which first hit the market all the way back in 2001. So, it’s not like the 2.8L Duramax was a freshly designed engine. In fact, the basis of the engine can be traced back to 2001 or even earlier depending on how deep into it you want to go.
Why Produce This?
GM really began using this engine in their Colorado and Canyon trucks for the same reason that Ford, Ram, and Nissan also developed small diesel engines for their half-ton trucks: which is a gap in the market. If you wanted a diesel engine in your truck, you had no choice but to purchase a 3/4 ton or higher truck.
While those trucks are great at towing, hauling, and generally getting work done, they can also be quite a bit more expensive than half-ton or smaller trucks. 3/4 ton trucks are physically larger, harder to drive, and harder to park, they generally have stiffer suspension for heavy loads which leads to poor ride quality and on and on.
To put it simply, 3/4 ton trucks are generally not great daily driver trucks. While they’re much comfier and better than older trucks, most consumers would prefer to opt for a half-ton truck or smaller, which is exactly where the Colorado and Canyon slot in.
So if you wanted a very small truck and you wanted a diesel engine, you were out of luck, at least here in the US. Overseas, small diesel engines have been popular for decades, but it was never like that here, until GM decided to try to make it happen with the 2.8L DMAX in their smallest trucks.
Although we really saw the earliest versions of this engine back in 2010, it wasn’t until 2016/2017 that we saw it here in the states. This is actually really interesting because Fiat had taken control of the VM Motori company in 2013, but with that, GM somehow kept the rights to rebrand the A 428 dual-overhead-cam engine as the 2.8L Duramax.
Starting with the absolute basics, the 2.8L Duramax is a four-cylinder diesel engine with a 29,000 PSI common rail injection system with solenoid-type injectors. I’d also like to quickly highlight that sources from GM mention the use of piezoelectric injectors and other sources from GM mention solenoid-type injectors, but we’ll get to that later in the article and video.
It uses a grey cast iron cylinder block with a cast aluminum cylinder head. Inside the engine, you’ll find a forged steel crankshaft with forged steel connecting rods. Total power output is rated at 181hp and 369lb-ft of torque,
Because North American emissions standards are different, the engine had to go through a number of changes before it could be launched here in the US, with some of those changes including redesigned pistons with new piston cooling jets.
The Cylinder Head
With the basic overview behind us, let’s take a closer look at the cylinder head and valvetrain. As I mentioned before, the cylinder head is aluminum, which is used for its weight savings but also thermal benefits. You have to remember, that this engine is being used in relatively small trucks, so keeping the total weight low is pretty important for overall performance.
Inside the head, you’ll find dual overhead camshafts with four valves per cylinder with a finger-follower actuation system. As compared to the international version of this engine, the US version has enlarged exhaust ports, larger water passages, and optimized oil distribution, however, other sources note that it’s identical to the international version, so it’s not exactly clear if the head is the same or not.
One of the big issues I had with the 3.0L Duramax is that it used a timing chain rather than a gear-driven system, and even more annoyingly it was mounted at the rear of the engine.
Unfortunately, the 2.8L Duramax is also void of a gear-driven cam system, this time around it uses a timing belt with a 150,000-mile interval for replacement. It’s unfortunate to see the lack of a gear-driven system yet again, but at least this time around it’s mounted on the front of the engine rather than the rear.
Presumably, they avoided a timing gear system to save cost, but also to reduce total noise, vibration, and harshness, because again, it’s the baby engine. It’s not meant for heavy work and racking up miles like the 6.6L Duramax.
The Intake and Turbo
On the side of the cylinder head, we have a variable geometry turbocharger from Honeywell, which is pretty standard for any modern diesel engine. If you didn’t already know, VGTs work by using movable vanes to effectively change the size of the turbo, which has a big impact on how quickly it spools up and how much boost pressure it can produce at certain RPMs, which simply means you have the benefits of both a small and big turbo in one system.
One of the biggest benefits to using a VGT like the Honeywell unit on the 2.8L Duramax is that it allows for exhaust braking, although reports online highlight that the exhaust brake on this particular engine is pretty weak and lackluster as compared to exhaust brakes on larger diesel engines.
The turbocharger is functionally almost identical to the international engines, but with a modified compressor wheel for improved high-altitude performance.
“The turbo casting is the same as the global variant, but we’ve retuned it (for the USA) with a new compressor wheel. That’s one thing we don’t have to worry about in global markets, but in the U.S., we have higher altitudes, and we have to meet emissions standards at high altitude.”
As with most modern engines, for further weight savings, the intake manifold is composite, as it doesn’t appear to have any internal flaps for a variable-length system, which is something we did actually see on the 3.0L Duramax, as it’s a great solution for improving power output throughout the rev-range.
The Block and Internals
Moving down to the cylinder block and the internals of the engine, we have a grey cast iron block with a 94mm bore and a 100mm stroke to bring total displacement to 2.8L. The head, block, crank, and camshafts are all assembled in Thailand at the VM Motori facility down there.
Which again, this is in stark contrast to the 3.0L Duramax which uses a cast aluminum block for weight savings and thermal efficiency, so it’s certainly strange to see the 2.8L Duramax using cast iron. That being said, cast iron can be cheaper on the manufacturing side and it’s also really strong, but in this application, I don’t think the extra strength is needed considering the power output.
As I mentioned much earlier in the article and video, the pistons on the 2.8L Duramax were actually redesigned compared to the international version of the engine for emissions purposes. But, that being said, they’re nothing special. They’re a traditional deep-dish piston for your normal three-ring design.
“We recently, for 2014, made a global upgrade co-designed for the North American market and it includes new pistons specific to meeting emissions in North America.” – Yackley. Strangely enough, the addition of oil jets was part of the change, as the international engine doesn’t feature piston oil squirters.
And because the 2.8L Duramax is a four-cylinder engine and four-cylinder isn’t inherently very smooth, on top of this engine being massive for a four-cylinder, it’s quite buzzy even for a diesel engine. So, to help smooth this out the engine uses balance shafts. In fact, the balance shaft, oil pump, and vacuum pump are all gear-driven off the crankshaft.
The Injection System
That takes us to the injection system, where there is a lot of conflicting information online. The entire system is supplied by DENSO, which is the same injection system supplier for the LM2 Duramax as well as the L5P. It’s a common rail injection system that peaks out at 29,000psi, although some sources list the maximum pressure at 26,000psi, but as far as I can tell it’s actually 29.
Looking at the injectors, again, there is a lot of conflicting info, with some sources claiming the 2.8L Duramax has piezo injectors and some sources saying it’s a solenoid type injector, and again, as far as I can tell, it is in-fact a solenoid type injector. And this is kind of weird considering how popular and effective piezo injectors are, but solenoid-style injectors have gotten much better in recent years, and they’re really using these injectors to the max.
“We’re going to have a multi-injection strategy, pre and post, even multiple-post injections, a broad response we’re still dialing in, but very broad for emissions and performance.” The computer controlling everything comes from Continental, which is the first time ever a GM diesel engine has been paired with a Continental ECU.
The Emissions Systems
And that takes us to everyone’s least favorite part of any diesel engine, and that’s all the terrible emissions components that absolutely ruin reliability and make these engines much more expensive to run in the long term, shoutout to the EPA.
And to make this short, the 2.8L Duramax has every single emissions component you’d expect on a modern diesel engine, including a diesel oxidation catalyst, diesel particulate filter, selective catalyst reduction, and exhaust gas recirculation.
And as a quick run down on these systems and what they do, the EGR system basically just diverts some of the engine exhaust gas and routes it back into the intake, which ultimately lowers combustion temperature.
The diesel particulate filter captures excessive exhaust soot and burns it off through a regeneration mode, and the selective catalyst reduction uses diesel exhaust fluid to reduce tailpipe emissions output, at least in theory.
It’s a little too soon to know how these emissions will fair in the long term, but looking at other examples, I’m pretty confident these systems will become reliability issues down the line.
Outside just the scope of the engine, we should take a look at the transmission behind it, which Hydra-Matic 6L50 six-speed automatic transmission in the Canyon and Colorado, however, with the Express and Savanna you’ll actually find the 8L90. The issue I have with this is that the 6L50 is really not the transmission for the job.
And for reference, in GM’s gas-powered trucks and SUVs, you’ll find a bunch of different transmissions. My Tahoe SSV, for example, has a 6L80 to back up the little 5.3L gas engine, so why do these trucks have the 6L50 behind a diesel engine? Sure, in stock form, the 2.8L Duramax doesn’t make any crazy amount of power and is well within the 6L50’s power rating, but what about a modified 2.8L Duramax in a truck that tows a lot? That transmission is very quickly going to become the weak point.
The 6L50 is the same transmission you’ll find in the V6 Camaro from 2010 to 2016, the Cadillac SLS, STS, SRX, and CTS. You can also find it in a handful of other Chevy applications and Holden applications. My point is, that it’s quite literally a car transmission behind a diesel engine in a truck. Granted, these little trucks aren’t meant for big towing loads, but a car transmission isn’t really meant for any towing loads at all.
My point here is that the 2.8L Duramax in Colorado is backed up by a literal car transmission that is completely lackluster. I’m not quite sure why GM decided to use this transmission other than potentially cost savings, but it would’ve been much better to see them use one of their existing truck transmissions instead.
But again, the trucks equipped with the 2.8L aren’t really meant for doing heavy work. This is reflected in the towing capacity numbers, where a 2009 Tahoe can have up to an 8500lb towing capacity compared to the 2.8L Duramax Colorado’s 7700lb towing capacity, which is pretty underwhelming for a diesel truck. Albeit a small diesel, still, that’s pretty underwhelming.
Another note that’s a little strange is Scott Yackley claiming that the “(The 2.8-liter) follows the same validation and testing as the bigger Duramax engines. Also, this is a truck-specific engine. It’s for trucks, not designed for a car.”
I have two points to counter this. One, very few changes were really made to the base VM Motori engine this is based on, so clearly they didn’t have to do all that much validation and testing, which really makes me think that their testing parameters are not as high-standard as they make them say. And two, if this is a “truck-specific” engine, why is backed up by a transmission used almost exclusively in GM cars rather than something from their existing truck parts bin?