We Slide Behind the Wheel of the All New 2018 GMC Terrain DIESEL
This 2018 Terrain is far better looking. Sleek, muscular, and brashly bolder, 2018 brings a sophisticated layered look to the midsized CUV. In front a signature octagonal grille is anything but subtle and brightwork surrounding both the main air intake and lower are used to project power forwards. We like the boomerang headlamps, LEDS in the Denali and HIDS elsewhere, both shapes are echoed by LED taillights. All models feature automatic liftgates as an option or standard for Denali. Overall it is far better looking than its predecessor.
Where you cannot see, the 2018 Terrain body itself is improved, now 34 percent stiffer in construction. Though it wasn’t mentioned, we assume this is through extensive use of both advanced computer modeling and high strength steel in critical areas. Another way stiffness and interior quietness was improved was extensive use of structural adhesives. A borrowed aircraft technique, adhesives both join and better prevent flex at joints. Diesel specific, there’s an acoustic dash mat to dissipate sound from the engine, a first for GM.
Inside it’s all about luxury. Steering wheels are leather wrapped; contrast stitching creates premium appearance for the seats and dash panel, and trim is real aluminum. The difference is perceptible. Driving in traffic for hours we found the seats very comfortable. We didn’t try the heated or ventilated seats, but we trust that they function as designed and heat or cool your backside as needed. Note that the second row and front passenger seat fold flat to create an eight-foot load floor. Kayaking holiday anyone?
Available in FWD and AWD, the AWD Traction Select system uses rotary control to suggest options for highway, mountain, and towing. We did
t this year's North American International Auto Show in Detroit GMC released the all-new GMC Terrain and we were somewhat surprised (but happy) to hear that it would feature a 1.6L diesel engine. However, GMC sales in North America, Canada, and the Middle East have risen dramatically; making GMC a profit center for GM. Offering a diesel option for Terrain is surely a way to capture sales that might have gone to European automakers who have abandoned diesel in North America.
no off-roading nor dirt-play so cannot say anything other than the AWD system was transparent. There are many other features we were unable to test, or simply forgot to try. Those included automatic park assist, surround vision, low-speed automatic braking or lane keep assist with lane departure warning. We did back up, so used the rear camera. We’ll just leave most of the other technology for another story and perhaps more in-depth review.
What we questioned was the innovative console mounted shift buttons. We’ve seen that video before. And in photos the three-pods of shift, HVAC, and infotainment look stuck on. In person they are harmonious and tightly fit. The infotainment system is GM’S latest, featuring both Android Auto and Apple Carplay along with available navigation and 4GLTE connection. Onstar is, of course standard. We didn’t play with the available apps, which will have to come later.
Terrain is available in three trim levels, SL/SLE starting at $25,970, SLT which is available with the diesel engine and starts at $32,295, and the high end Denali ($38,495) which is the more desirable trim level as it has an 8” infotainment system (versus 7” standard) LED headlamps and a heated steering wheel. We think it a poor decision that the premium diesel engine is not available on the premium Denali and hope that GMC will reconsider and offer the diesel engine in future Terrain Denali models as an option.
Back to the greasy side. Terrain offers two gas engines mated to 9-speed automatic transmissions, a 1.5L turbo (170HP/201 LB-FT) and a more powerful 2.0L turbo (252 HP/260 LB-FT). In the middle is a global engine, one we reported on in earlier this year, a 1.6L turbo-diesel. Its power output is 137 horsepower and 240 pound-feet of torque, which is slightly less than the 2.0L, but it delivers the best fuel economy at 28 City, and 39 mpg on the Highway. The diesel couples to a six-speed auto. All three powertrains are equipped with one of the smoothest Stop-start systems we’ve tested.
BEHIND THE SCENES
UDBG spoke extensively to Audley Brown, General Motors Director of North American Diesel Engine Calibration, about diesels. Basically, calibration engineering is more responsible for an engine's ability to meet emissions regulations than mechanical engineering, though they are interdependent. We spent several hours delving into the black arts of keeping a diesel (or gas motor) running clean and lean.
Hugely significant to the success of General Motors' success in diesel engines is a decision to bring all of the calibration engineering—essentially all the engine control software—in-house. We’ve reported on that several times. The first totally GM engineered engine was the 2.8-liter early in 2016, followed by the 6.6-liter L5P seen in the latest GM HD pickups. Though already a global engine, the 2.8-liter diesel was extensively re-engineered for the stricter emissions controls required in North America. It was the first small diesel in a sub-1500 pickup in many years and new in-market for GMC Canyon and Chevrolet Colorado when it arrived.
We asked Brown what it takes to make an all-new world-class engine. "Customers don’t see what algorithms were used to conquer Noise, Vibration, and Harshness. They experienced torque, clean emissions, and power," he told us.
The same Injection strategies that make the 6.6-liter Duramax quiet and powerful were used on the 1.6-liter, like up to ten injections per combustion cycle. If you recall, even five years ago 5-7 injections was a massive capability. Those extra injections are normally used pre-top Dead Center to assist in quietness and lowering emissions. Later injections, also possible, can help catalytic converters reduce emissions.
Because combustion and emissions are so vital to modern engines, GM added "lots of Phds" to their engine development programs, according to Brown. “Our ability to document combustion and exhaust improved and data collection expanded. The question was what to do with that data”.
Chemical engineers were hired "to manage the kinetics of not only fuel flow, but the entire exhaust stream. So it is fuel, air, DEF, all of that gets metered and adjusted because, ultimately we want emissions from the tail pipe to meet standards and standards over a broad range of conditions," Brown continued. When you think of fuel injection, many think only of generating torque. "We also inject fuel to generate heat; we need to heat aftertreatment systems to operate in well-defined bands of temperature control." Not too cold, not too hot, and some fuel helps create
exothermic (heat releasing) reactions to heat the exhaust system.
Brown told us, “During a single test trip we'll generate 30-40 gigabytes of data. We need to understand how to regress back to the effects on fuel consumption, emissions, or drivability.” The next criteria are noises. Some noise is good; some less favorable, it depends on the character of the noise. So once the data is developed they take into account what's happening with the turbocharger. "How do we size the turbo for the use-case of the vehicle? In the 2018 Terrain 1.6-liter diesel, it is sized to help with launch, to reduce turbo lag. It is a variable geometry turbo, but some people would think of applying a much larger turbocharger to get big power. The Terrain customer may not be looking for max velocity power. They want to know “What does it feel like?” A really strong hand pushing you forward from 1,300 RPM."
"We didn't talk about SCR. We use a single urea or DEF injector with multiple sensors in the stream for NOX and pressure. We're constantly looking at the performance of all components; the DPF, the SCR and measuring pressure, oxygen content and NOX content across all the devices." SCR is tricky. It is also highly temperature-sensitive. The system has to be warmed up, "but you cannot let it get too hot because efficiency drops off, the same with too cold. We want all of this to be transparent to the driver."
Brown told us "One of our slogans is, 'Diesels, It's Just Harder!’ Colleagues ask us why we're hiring all these engineers, Phds, researchers, and asking for so much. It's harder. If it were only about making power and torque, that's not hard. Any real engineer knows we have constraints, we're making tradeoffs, and we’re dealing with a system. And we want new, modern diesels to be not only quiet, we want them to be smooth in operation, we want them to look clean. The last thing we want is a Terrain (or Equinox, Cruze, Canyon, or Colorado) in white with a black soot spot on the bumper."
Development focused on three things; one, great fuel economy; two, very high power density; third, of utmost importance, was its noise and vibration characteristics. From the beginning, NVH was a focus.
“This is something you saw with the 6.6-liter last year and you see with the 1.6 this year,” Brown continued to explain. “We talked about some of the architectural decisions we made, like putting the accessory drive gearing on the
rear of the engine, which puts the bell housing around it as a buffer, the acoustic covers on top, and what gets into my detail as a combustion analyst, how we do our injections and how we build rate of pressure rise. That's key. It is a 29,000-psi system, but on each of those injections you have to think about the acoustic signature of the high-pressure pump and the actual fuel injection event itself because the rate of pressure rise is going to go up every time we make an injection. We're adjusting that (acoustic) signature every time. All this comes in to play.”
“When you look at that path, then you think of how should we design the block to reduce the radiated sound? Think of the head, the lowly oil pan, all the work that goes into that because all that sound can be amplified, damped, reduced, changed in frequency. The analysis team in Turin, Italy, and the US, and the (mathematical) tools that have been developed, are amazing. We're not saying we can reproduce with 100% accuracy the physical environment, but what we do through analysis we can make what we call splits, directional decisions. We make those decisions a lot faster through analysis.”
The 1.6-liter is a product of this modern computer aided, math model driven process. All the combustion modeling, the acoustic modeling, even the block was fundamentally done in software. “Earlier we were talking about the chemical kinetics and aftertreatment. That's not as focused on noise as it is on emissions, but much is from modeling. Our almost completely internally developed systems, from the main hardware to the controls and software, allow us to control the interactions between subsystems. So, from an air system I can feed an air model to a chemical model to see how it reacts in the system.”
Before we parted, Brown delivered a calibration engineer’s inside joke. “I don't make product decisions, I make them work.”
BEHIND THE WHEEL
We put several hundred miles on a variety of new Terrains, primarily the diesel. It is surely quiet and smooth, and it pulls strongly. That said we’d always like more power and cubic inches, but the small 1.6L diesel engine is more than enough for this lightweight CUV that tips the scales at about 3,600 lbs. for the FWD and about 3,800 lbs. for the AWD model. What impressed us, compared to the 2.0L gas engine, was its smoother application of torque, which was seamless over hilly terrain. We seldom wanted to downshift or stomp the pedal. We look forward to an extended review behind the wheel of the latest diesel CUV but for the brief time we spent in the new Terrain we were very happy and comfortable. The EPA estimated fuel economy ratings on the Terrain Diesel are 28 MPG City for both the FWD and AWD models and 39 MPG Highway for the FWD with a slight dip to 38 MPG on the Highway rating for the AWD models.
Not only is the interior design pleasant to look at it feels great too. Like most new GM vehicles the Terrain is a high-tech wonder loaded with convenience features both standard and optional that make us wonder how we got along without them in the past. Of course the Terrain is a car based CUV not a true truck, but it still has a roomy interior for its size and thanks to the folding seats allows you to store tons of cargo if needed.
If you are in the market for a family friendly CUV that gets excellent fuel mileage you owe it to yourself to check out the new Terrain diesel as soon as they are available on your local GMC dealer’s lots. Just be sure to tell them that your friends at Ultimatedieselbuilder’sguide sent you. UDBG
Fold down second row seating folds flat, and with the passenger seat folded you have a ladder’s worth of space, perfect for those “honey do” trips down to the local home improvement center.
The entire engine top is covered by molded foam. A hard topping makes for pretty graphics, dampening foam makes for a quiet engine, free(er) from injector noise.
Great view of a state-of-the-art, yet conventional appearing motor. Mechanical injectors are surrounded by sound absorbent material.
Atypically, timing is at the engine’s rear where it’s greatly covered by the transmission. This adds to quietness, one of this motor’s hallmarks.
When we said ready to roll we weren’t kidding. But where does the other bike rider sit?
Ready to ride and drive, our SLT diesel idles quietly, very quietly thanks to advance modeling and acoustic damping.
How can you tell the diesel from the 2.0L? By twin chrome or hidden exhausts, the gassers have the bling while the diesel features a low key approach with a hidden exhaust outlet, as seen on the right.
Theoretically, this is you. All adventure-ready and equipped to roll—all loaded up for the weekend. ( Note that a gasser Denali is shown here.—ed.)
The 2018 GMC Terrain is a great looking CUV and most importantly it is now available with a diesel power plant under the hood!!!
Here’s the Terrain Denali in all its elegance—but why no diesel for a premium luxury CUV? Come on GMC, give everyone the diesel option.
The rear lighting design is distinctive and large enough to be seen clearly at night. We like the unique shape and how well it matches the headlight design.
Headlamps, LED for Denali and HID for other model trims, are housed in an elegant shape similar to the tail lamp treatment.
The Terrain SLT for 2018 is far better than its predecessor in every way—looks, ride, handling and quietness. Looking at it from the side view shows how different the new Terrain is. Gone are the side pods of the 1st generation model, yet there’s...