Will GM’s New 2.7-Liter Turbo Gas Engine Pull Stronger Than Its 2.8-Liter Duramax Diesel?

[Gorehamj]

John Goreham
Contributing Writer, GM-Trucks.com
5-22-2018

The recent news that GM will be introducing a new four-cylinder 2.7-liter turbocharged gasoline engine tuned specifically for truck duty is exciting news for those seeking a new entry-level, affordable, and fuel-efficient option. Coupled with the many technological advances the new engine brings, the 2.7-Liter gas turbo caught our eye for its unusually low torque peak coupled with such an unusually high torque value. As Zane Merva already pointed out in his detailed technical overview of the new engine, it does have comparable specs to some not-so-old Chevy V8 engines installed in Silverados. We wondered if it might, in fact, be more capable than the Duramax diesel engine GM produces in partnership with Isuzu and makes optional in the Colorado and Canyon midsize trucks.

GM’s original press release materials didn’t include detailed torque curves for the new engine, but when asked by GM-Trucks.com, quickly responded with the curves so we could check out the torque and compare it to the Duramax 2.8. 
Above is the curve for the Duramax first. The 2.8-liter Duramax has a peak torque rating of 369 lb-ft of torque. As you can see from the curve above, it hits that peak at about 2,000 RPM (and that is what GM confirms). The peak torque is maintained for roughly five or six hundred RPM and it then drops off pretty steeply at about 2,500 RPM. It is still at 300 lb-ft as the engine’s speed hits about 3,500 RPM. Not bad at all. 

However, the new 2.7-liter gas turbo engine has a different profile, and one folks who tow might want to look closely at. Notice that the new gasoline turbocharged engine hits its peak torque sooner than the Duramax Diesel does. Peak torque of 348 lb-ft comes at just 1,500 RPMs in this new engine. Practically right off of idle. Torque is then maintained at that peak for a full 2,500 RPM (five times longer than the diesel’s peak is maintained) all the way up to 4,000 RPM. 
Although the Duramax diesel does have a slight edge in peak torque (369 vs. 348) of about 6%, that advantage only occurs from roughly 1,900 RPM to about 2,700 RPM. The 2.7-liter gasoline engine has a broader peak torque curve that is much more constant over a significantly wider range of engine speeds. 

The gasoline engine also produces dramatically more horsepower than does the Duramax diesel. And that power appears to be much lower in the rev band than the power of the diesel. Few of us rev our trucks to redline, but we all use the 3,000 RPM range pretty frequently. Looking at the curves, the new 2.7-liter engine produces about 200 hp at this point, and the Duramax produces about 170 hp by our reading of the curve. (note that the diesel curve shows hp along the right side of the graph, the gas engine uses the left for both torque and power.) Chevy is promising a sub-7-second run to 60 mph. That is quicker than the smaller Colorado can sprint to 60 mph with the Duramax.

GM has not yet released fuel efficiency ratings for the new 2.7-liter gasoline engine. Even after it does, it may be hard to draw a perfect comparison of the fuel efficiency and fuel economy between the two engines if they appear in different trucks and have different transmissions. However, with gasoline’s national average cost per gallon substantially lower than the average cost for diesel, GM’s new 2.7-liter engine may not only have more pulling power in real-world use, it may also prove to be more fuel economical in real-world operation. 

[newdude]

The big difference is the HP.  That 2.7 Turbo gas makes near double the HP of the 2.8 Duramax.  The 2.8 is a sweetheart of a powerplant, but as you break 3000rpm, she starts to steam off due to the torque loss.  The 2.7 Turbo peaks its HP near double the RPM, and has near twice the HP.  To me that alone shows its faster, and would probably be faster at yanking a similarly weighted trailer around.  The 2.8 Duramax though would probably eat it in mileage with and possibly without a trailer.  I've never ran less than 24mpg per fill up, and that includes winter time idling.  I'm on 28.5mpg on my current tank, 150 miles into the tank. 

 

To me, the Silverado's secret weapon might be that 3.0 Inline Duramax, providing they give it some strong tow rating numbers.  The 2.7 is a potent and technologically sophisticated base engine, that packs quite a punch, but will it pack that with potential customers?    

Edited May 22, 2018 by newdude

[Daly]

The 2.7 looks like it'll be a nice little engine. Doubtful I'll ever own one in a full-size, call me old school (I'll gladly take that moniker by the way), but full-size trucks should have v8's IMO. But if I were looking at midsize trucks and the 2.7 was an option, I'd strongly consider it, I think it would be a nice addition to the Colorado/Canyon platform.

[Colossus]

Which engine will hold up to abuse and hard work better? 

[Grumpy Bear]

I'm going to bet the gas motor will be plenty durable. This isn't a motor that was converted from a lower service but a clean sheet design with this kind of cylinder pressure in mind from the get go. Anyone remember the Olds diesel? Dedicated blocks made killer gas blower motors. Just saying, it has all the right bits and pieces to succeed. 

[Epsilon Plus]

The 2.7 should be in future ZR2s. The diesel and it's sub 200hp and meh torque has been a disappointment from the beginning.

[Colossus]

I wonder if we'll see it kill off the 4.3 v-6..

[newdude]

16 hours ago, Epsilon Plus said:

The 2.7 should be in future ZR2s. The diesel and it's sub 200hp and meh torque has been a disappointment from the beginning.

I drive one every day.  Wouldn't call it a disappointment at all. 

[2018GMC]

1 hour ago, Colossus said:

I wonder if we'll see it kill off the 4.3 v-6..

4.3 is the standard for fleet trucks. I bet it will stick around for a long while filling that role. 

 

The 4.8 v8 (paired with 4l60e) was the standard engine in lower trim GMT800 and GMT900 trucks and SUVs 1999.5 - 2013. 

 

It then disappeared in 2014 when the new 4.3 v6 had much better hp and torque numbers than before. 

[hizzo3]

Having driven the older LNF (2.0 turbo, ~22 psi boost) engine with a tune... I'd say yes... I almost went with a Ford Ecoboost except they still don't have the valves sorted.

Either way, the days of old with the turbos sucking at gone. Once they figure out homogeneous combustion (Mazda has an idea on this, and it's with forced induction) these engines will make the small block obsolete. I wouldn't be surprised to see them start adding lead to the front of the trucks just to get weight there for towing.

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[Grumpy Bear]

8 minutes ago, hizzo3 said:

Having driven the older LNF (2.0 turbo, ~22 psi boost) engine with a tune... I'd say yes... I almost went with a Ford Ecoboost except they still don't have the valves sorted.

Either way, the days of old with the turbos sucking at gone. Once they figure out homogeneous combustion (Mazda has an idea on this, and it's with forced induction) these engines will make the small block obsolete. I wouldn't be surprised to see them start adding lead to the front of the trucks just to get weight there for towing.

Sent from my XT1585 using Tapatalk
 

Mazda HCCI motor looks interesting. Anything that is over 50% thermally efficient gets my attention. 

Edited May 23, 2018 by Grumpy Bear

[Grumpy Bear]

2 hours ago, Colossus said:

I wonder if we'll see it kill off the 4.3 v-6..

In your dreams. 10 million hours invested in that platform. 

[Daly]

6 minutes ago, Grumpy Bear said:

In your dreams. 10 million hours invested in that platform. 

So... How many hours were invested in the straight six motors before they were dropped? Or the small block, or big block, or any other engine that has gone by the wayside... Even the almighty LS was dropped eventually. 

[hizzo3]

With turbo and homogeneous combustion, expect most engines over 4L to disappear. The great thing is those can still move the same amount of air, let's say of a 6.3 or bigger, when they need it. It's not uncommon for moderate boost turbos to move almost an equivalent of 20-50% more air than their NA competition. That means a 3.4 can be as powerful as our 5.3.... with better torque numbers. That is what makes a tuned Ecoboost so much fun.

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[SnakeEyeSS]

People want Diesel for low and flat torque curve, but this turbo gas engine makes it look like a moot point. Put that thing in a new Equinox Sport.