Cum­mins QSB6.7

Per­for­mance-Ori­ented Mar­itime Diesel

Diesel Power - - Torque -

SINCE THE com­pany’s in­cep­tion in 1919, Cum­mins has been in­volved with build­ing en­gines for mar­itime pur­poses. The power, econ­omy, and longevity of diesel en­gines make them ideally suited for powering seago­ing ves­sels.

To­day, Cum­mins offf­fers a broad se­lec­tion of marine en­gines that range in size from 104hp 5.9L en­gines to 4,200hp en­gines dis­plac­ing a mas­sive 95 liters. The ex­ten­sive lineup of oil-burn­ers serves in a mul­ti­tude of ves­sels, pro­vid­ing things like propul­sion and diese­l­elec­tric power gen­er­a­tion in every­thing from sport fi­fish­ers to freighters.

One such unit is the marine-spe­cific QSB6.7, which can be used for propul­sion or as an aux­il­iary pow­er­plant in recre­ational and com­mer­cial ves­sels. The en­gine was de­vel­oped along­side its au­to­mo­tive brothers: the B Series 6.7L and the offff-high­way QSB6.7. The vari­a­tions use the same ba­sic ar­chi­tec­ture, shar­ing many in­ter­nal com­po­nents, along with the block and cylin­der head. A key difff­fer­ence of QSB marine is the max­i­mum out­put of 550 hp and 1,250 lb-ftft of torque it pro­duces, which is a bit higher than its on-road sib­ling’s 385 hp and 930 lb-ftft of torque.

One of the key fac­tors al­low­ing Cum­mins to get that amount of power from the marine QSB is the sea­wa­ter cool­ing sys­tem’s abil­ity to keep tem­per­a­tures reg­u­lated. Sea­wa­ter is used in a sin­gle-loop, low-tem­per­a­ture aftfter­cooler that reg­u­lates coolant in the wa­ter jack­ets. The heat ex­changer has a tube-and-shell de­sign that pro­vides dura­bil­ity and ease of main­te­nance. The cool ocean wa­ter is also used to lower the tem­per­a­ture of the air go­ing through the chargedair cooler and cast-iron ex­haust man­i­fold. Safety and per­for­mance are im­proved by low­er­ing the man­i­fold’s sur­face tem­per­a­ture.

A Cum­mins Turbo Tech­nolo­gies rear-mounted, wa­ter-cooled,

marine-op­ti­mized tur­bocharger is matched to the 24-valve cylin­der head to pro­vide op­ti­mum power den­sity. An elec­tronic Bosch high-pres­sure com­mon-rail (HPCR) in­jec­tion sys­tem feeds fuel di­rectly into the cylin­ders from a cen­tral­ized in­jec­tor. Te­flon-coated alu­minum pis­tons with con­toured oil gal­leys help im­prove cool­ing, re­duce wear, and ex­tend en­gine life.

Fuel de­liv­ery is op­ti­mized for torque and fuel econ­omy. The HPCR sys­tem re­duces the en­gine’s deci­bel level at high rpm by in­ject­ing fuel at a fast rate. It also low­ers the rat­tle heard at idle by as much as 80 per­cent with the pi­lot in­jec­tion (a small amount of fuel that is in­jected be­fore the pri­mary shot). Com­po­nents used in the HPCR are hard­ened so the sys­tem will work with al­ter­na­tive fu­els like kerosene, JP8, and JP5. The sys­tem is also en­gi­neered with en­hanced com­pat­i­bil­ity to func­tion with var­i­ous emis­sions com­po­nents to vir­tu­ally elim­i­nate smoke.

A Cum­mins Quan­tum Sys­tem ECM mon­i­tors op­er­at­ing pa­ram­e­ters such as fuel con­sump­tion, duty cycle, en­gine load, and speed to en­sure peak per­for­mance while be­ing able to run di­ag­nos­tics and prog­nos­tics, as well as pro­vide com­plete en­gine pro­tec­tion. An elec­tri­cal in­ter­face box is used for all ves­sel con­nec­tions to re­duce in­stal­la­tion com­plex­ity.

The marine ver­sion of the QSB6.7 com­plies with U.S. EPA Tier 3, EU Stage IIIA, IMO Tier II, and Recre­ational Craft Di­rec­tive Stage 2 emis­sions reg­u­la­tions with­out an af­tertreat­ment sys­tem. It also meets In­ter­na­tional As­so­ci­a­tion of Clas­si­fi­ca­tion So­ci­eties stan­dards and the In­ter­na­tional Mar­itime Or­ga­ni­za­tion’s Safety of Life at Sea re­quire­ments.

A Cum­mins Turbo Tech­nolo­gies wa­ter-cooled waste­gate tur­bocharger is mounted on the rear of the QSB6.7 marine en­gine for ease of ac­cess. Walker Per­for­mance Fil­tra­tion’s air filter is used to re­duce noise.

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