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.
