Evolv­ing the 16.4L DC16 V-8 to meet strin­gent emis­sions stan­dards

Diesel Power - - Contents -

AS EMIS­SIONS stan­dards be­come more strin­gent ev­ery year, en­gine man­u­fac­tur­ers con­tinue re­fin­ing their prod­ucts in an ef­fort to keep them vi­able.

In the mod­ern-diesel space, sim­ply adding more emis­sions equip­ment to an en­gine to com­ply with stan­dards is a tem­po­rary fix at best. In or­der to truly meet emis­sions re­quire­ments head on, a new pow­er­plant or an up­dated ver­sion of an ex­ist­ing en­gine must be de­signed from the in­side out. Sca­nia un­der­stands this, and the com­pany has taken its es­tab­lished work­horse, the DC16 diesel V-8, and made it lighter, more ef­fi­cient, and cleaner.

For years, Sca­nia’s DC16 has been a go-to en­gine for ev­ery­thing from over-the-road trucks to ore haulers. The fam­ily of DC16 engines cur­rently has four mem­bers, mak­ing 520 hp (1,991 lb-ft of torque), 580 hp (2,212 lb-ft of torque), 650 hp (2,433 lb-ft of torque), and 730 hp (2,581 lb-ft of torque). Three of the engines (520, 580, and 650) have an all-new, 176-pound-lighter lay­out that only bor­rows the

block and con­fig­u­ra­tion from the previous gen­er­a­tion, while the 730 (due to its higher out­put) re­tains the last-gen­er­a­tion plat­form, up­dated to im­prove ef­fi­ciency and emis­sions.

One of the more dra­matic changes oc­curs in the tur­bocharg­ing sys­tem on three of the engines (730 car­ries over a vari­able-ge­om­e­try tur­bocharger). Gone is the sin­gle-scroll VGT that is fed by a sin­gle col­lec­tor for both cylin­der banks. In its place is new tech­nol­ogy Sca­nia calls a ro­tated twin-scroll fixed-ge­om­e­try turbo. The twin scroll’s tur­bine is fed by two ex­haust-gas col­lec­tors, one per cylin­der bank. The ex­haust gases are uti­lized more ef­fi­ciently by the FGT, which is lighter and more ro­bust than the ’charger it re­places. It is also mounted di­rectly to the block in the val­ley to make it more stable, with a vi­bra­tion-proof oper­at­ing en­vi­ron­ment.

The DC16’s in­duc­tion and in­jec­tion pro­cesses are cal­i­brated to work with the se­lec­tive cat­alytic re­duc­tion af­tertreat­ment. The in­take is now straighter and pro­vides more di­rect air­flow into the en­gine. Fu­el­ing is man­aged by Sca­nia’s XPI high-pres­sure pump that feeds diesel through a cen­tral pipe and long dis­tri­bu­tion lines to the in­jec­tors. For in­creased ef­fi­ciency and re­duced fuel con­sump­tion, the pump is com­prised of only two pis­tons and has max­i­mum cylin­der pres­sure of 210 bar. The in­jec­tion sys­tem uses a max­i­mum pres­sure of 1,800 bar (down from 2,400 bar) to bet­ter com­ple­ment the SCR tech­nol­ogy.

Bet­ter ef­fi­ciency also comes through re­duc­ing fric­tion.

Sca­nia re­worked the DC16’s cylin­der heads, pis­tons, pis­ton bolts, crank­case, crank­shaft, and bear­ings to pro­vide bet­ter seal­ing and a re­duc­tion of fric­tion. The mod­u­lar heads (each cylin­der has an in­di­vid­ual head) are ac­cu­rately ma­chined and de­signed to with­stand the ther­mal and me­chan­i­cal stresses that oc­cur dur­ing mil­lions of com­bus­tion cy­cles.

Dif­fer­ent tech­nolo­gies are used to fur­ther re­duce the par­a­sitic loss that in­creases fuel con­sump­tion on all four engines. The air com­pres­sor and coolant pump only en­gage when needed, help­ing re­duce drag on the oil-burner. A pi­lot-con­trolled oil pump al­lows the pres­sure to be adapted to the en­gine’s needs, while a ther­mo­stat reg­u­lates and op­ti­mizes oil tem­per­a­ture and pres­sure. The fuel pump and com­pres­sor are also moved to the rear of the en­gine to sim­plify the belt-drive sys­tem.

Low-out­put, large-dis­place­ment engines pro­duce too much air for the amount of heat de­vel­oped, which can af­fect the SCR sys­tem. So a spe­cial camshaft that holds the in­take valves open longer dur­ing the com­pres­sion phase is used in the 520. By do­ing

this, the en­gine ac­tu­ally gets less air in the cylin­der, which helps main­tain a higher work­ing tem­per­a­ture for a more ef­fi­cient burn. The com­pres­sion ra­tio on the 520 is also raised to 22.2:1. Amer­i­can en­gi­neer Ralph Miller de­vel­oped this tech­nol­ogy dur­ing the ’50s.

The emis­sions sys­tem (ex­clud­ing the 730) con­sists of only SCR tech­nol­ogy—there is no EGR. The SCR has an in­te­grated ex­haust si­lencer that is used to man­age the af­tertreat­ment. In­ter­nally, it con­sists of an ox­i­diza­tion cat­a­lyst, AdBlue mixer, two par­ti­cle fil­ters (short fil­ters with asym­met­ri­cal walls for re­duced back pres­sure), three par­al­lel SCR cat­a­lysts, and three am­mo­nia slip cat­a­lysts that scrub the ex­haust. The whole unit is only 24 inches wide, which saves valu­able space. The 730 uses the same

SCR, but it re­tains an EGR. All four engines meet EPA Tier 4 fi­nal and Euro

Stage VI emis­sions stan­dards.

The new­est gen­er­a­tion of Sca­nia’s DC16 uses a twin-scroll fixed-ge­om­e­try tur­bocharger that is fed di­rectly from the two ex­haust col­lec­tors, one from each cylin­der bank. The FGT is lighter and more ro­bust than the sin­gle-scroll vari­able-ge­om­e­try turbo it re­places. The in­take is re­designed for more di­rect air­flow into the cylin­ders. The high-pres­sure fuel pump and air com­pres­sor are moved to the rear of the en­gine.

Par­a­sitic drag in the en­gine is re­duced by a wa­ter pump and air com­pres­sor that dis­en­gage when not needed. The en­gine’s weight was cut 176 pounds by sim­pli­fy­ing the lay­out with fewer parts.

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