Lighter, smaller In­ter en­gine

New Zealand Truck & Driver - - Contents -

NORTH AMER­I­CAN TRUCK­MAKER NAV­IS­TAR HAS launched a new 12.4-litre en­gine – em­pha­sis­ing its small size and light weight.

e In­ter­na­tional A26 is based on Nav­is­tar’s pre­vi­ous N13 (and orig­i­nally the MaxxForce 13) en­gines, which also dis­placed 12.4-litres – giv­ing a clue to the source of many of the new en­gine’s hard parts. Most of the ro­tat­ing parts are car­ry­over and also fea­ture in the Ger­man MAN D26, from which the A26 en­gine is de­rived.

e use of the 12.4-litre num­ber is de­lib­er­ate, to un­der­score that this is smaller and lighter – by 600 to 700 pounds (272-317-kilo­grams) – than a 15-litre. It weighs-in at 2299 lbs (1042kg) thanks to lightweight­ing fea­tures in­clud­ing an alu­minium clutch hous­ing and built-up mod­u­lar camshaft, both of which fea­tured on the N13 en­gine and on the D26.

Devel­op­ment of the A26 took a fresh ap­proach, says Nav­is­tar – one “that em­pha­sised sim­plic­ity over com­plex­ity and us­ing only proven com­po­nents to de­liver in­dus­try-lead­ing up­time.”

e suc­cess of the pro­ject, says Bill Kozek, Nav­is­tar pres­i­dent of truck and parts, has “fun­da­men­tally changed how we de­sign diesel en­gines.”

Ev­ery com­po­nent is en­gi­neered to max­imise up­time. From the cylin­der head gas­ket up, the A26 is an all-new de­sign, far sim­pler than the N13, Nav­is­tar says. De­signed to be as sim­ple as pos­si­ble to guar­an­tee re­li­a­bil­ity, dura­bil­ity and max­i­mum up­time, the head ows more air than pre­vi­ously with re­duced fric­tion and pump­ing loses.

Fea­tured is a Bosch com­mon-rail fuel in­jec­tion run­ning at 2500 bar (36,300 psi) which gives the A26 a range of 370 to 475-horse­power (275-354kW ), and torque rat­ings be­tween 1350 and 1750 pounds-feet (1830-2372Nm). A sin­gle vari­able ge­om­e­try tur­bocharger re­places the se­ries tur­bos and fea­tures a ti­ta­nium wheel for dura­bil­ity.

ere’s also a sim­ple plug-in con­trol mod­ule for easy ser­vice with­out re­mov­ing the turbo. With a far sim­pler cool­ing sys­tem, with­out the in­ter-stage charge-air cooler, the A26 is 55 lb (25kg) lighter than the en­gine it will even­tu­ally re­place.

“e A26 was de­signed from the ground up to de­liver in­dus­try-lead­ing up­time, dura­bil­ity and re­li­a­bil­ity,” says Nav­is­tar’s

e 12.4-litre A26 has its roots in ear­lier Nav­is­tar and MAN en­gines – Nav­is­tar opt­ing for proven com­po­nents in the in­ter­ests of op­ti­mis­ing up­time. e cylin­der head (be­low) is en­tirely new – and, like the rest of the en­gine, was de­signed with sim­plic­ity to the fore VP of ad­vanced en­gi­neer­ing, Dar­ren Gos­bee.

“e A26 is as sim­ple as a mod­ern en­gine can be, and we’ve built up­time into ev­ery part of the devel­op­ment process, from de­sign to cal­i­bra­tion to test­ing.”

Nav­is­tar says SAE test­ing shows the A26 has 5% bet­ter econ­omy than the N13 from three years ago. When in­stalled in the ProStar re­place­ment, the In­ter­na­tional LT, there’s a 9% im­prove­ment in fuel econ­omy.

Com­bus­tion con­trol makes the A26 the qui­etest en­gine in the In­ter­na­tional lineup, says the com­pany. e A26’s sculpted crank­case, which is iso­lated from the oil pan through a spe­cially-de­signed rub­ber gas­ket, ab­sorbs vi­bra­tion and re­duces harsh­ness. With a far lower ther­mal load on the cool­ing sys­tem, the A26 goes from an 11-bladed fan to a qui­eter six-blade fan. Along with spe­cially de­signed cam/ac­ces­sory gear teeth and so­phis­ti­cated cal­i­bra­tion, the en­gine is de­signed for re­duced noise.

e cylin­der block is cast and ma­chined in Nav­is­tar’s fa­cil­ity in Brazil and the A26 en­gine is to be built up at the Alabama In­ter­na­tional en­gine plant.

e A26 went into pro­duc­tion last month and will be avail­able in the US in In­ter­na­tional’s new line­haul LT (ProStar re­place­ment) and the re­gional haul RH from this month. e N13 re­mains in pro­duc­tion till the end of the year for In­ter’s vo­ca­tional HX and all Class 8 mod­els still with Star still in their names (ie WorkS­tar, PayS­tar etc).


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