FIRST DRIVE

WESLIDEBEHIND THEWHEELOFTHE

Ultimate Diesel Builder's Guide - - Contents - Text: Thom Can­nell Photography: Thom Can­nell and courtesy of GMC

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...

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