Diesel World - - Contents -

With the clean diesel era now in full swing, en­thu­si­asts are be­gin­ning to em­brace emis­sions-com­pli­ant per­for­mance. Af­ter all, most of us don’t want to bla­tantly void the war­ranty on our $80,000 trucks, or go tear­ing into a brand-new ve­hi­cle. Thank­fully, fears of trash­ing the diesel par­tic­u­late fil­ter and blow­ing through gal­lon af­ter gal­lon of DEF have be­gun to sub­side—and in the case of this ar­ti­cle, it’s been proven that the 6.7L Power Stroke can sup­port 580 rwhp with the fac­tory emis­sions sys­tems in place. The hid­den ben­e­fit of mak­ing DPF-ON mod­i­fi­ca­tions is that no one else will ex­pect your truck to run so strong. The mod­ern diesel sleeper is a smoke­less truck. They’ll never see it com­ing. Dur­ing in-house test­ing of their own ’18 F-350, the folks at Fleece Per­for­mance En­gi­neer­ing dis­cov­ered that cus­tom tun­ing could push the new Fords into the 540hp range—but they also knew more power could be gleaned from added air­flow. And since Fleece is in the busi­ness of build­ing high-flow, di­rect-re­place­ment vari­able-ge­om­e­try tur­bocharg­ers—namely the renowned VNT Chee­tah line—the crew set about de­sign­ing a drop-in unit for the 6.7L Power Stroke. To see the fin­ished prod­uct in­stalled and tested we trekked over to Fleece’s Browns­burg, In­di­ana, fa­cil­ity. By the end of the day the com­pany’s tuned, emis­sions-friendly du­ally would pick up another 40 rwhp with the 63mm Chee­tah in the mix.

If you’re look­ing to give your tuned 6.7L Ford a com­pet­i­tive edge, this stealthy turbo up­grade is just right for you.


 On the drive side of the Chee­tah, a 10-blade tur­bine wheel with a 66mm ex­ducer is uti­lized. The larger-than-stock tur­bine pro­vides vastly im­proved flow at higher rpm, but thanks to the vari­able ge­om­e­try de­sign of the fac­tory-based Gar­rett GT37, lowrpm re­sponse isn’t sac­ri­ficed in the least. In fact, when com­bined with pre­cise cus­tom tun­ing (with op­ti­mized vane func­tion­al­ity), the torque curve is broader than what the fac­tory turbo of­fers.  The job of tear­ing into the 6.7L Ford and re­plac­ing the stock turbo was left in the hands of Fleece’s lead tech­ni­cian, Jake Richards. First things first, Richards drained both cool­ing sys­tems (the pri­mary sys­tem is ded­i­cated for the en­gine, while the sec­ondary sys­tem is used for the wa­ter-to-air in­ter­cooler, EGR sys­tem, and trans­mis­sion and fuel cool­ers). The low-mile coolant would be reused later.

 Be­gin­ning with ’17 model year en­gines, Ford be­gan us­ing a small oil fil­ter that pro­trudes into both the tur­bocharger’s cen­ter car­tridge and the pedestal. Equipped with a tiny in­ter­nal screen, it serves as an added in­sur­ance mea­sure against de­bris from the block mak­ing its way into the turbo’s oil sup­ply cir­cuit.

 Af­ter drain­ing both cool­ing sys­tems, Richards moved on to the re­moval of the fac­tory air in­take, in­ter­cooler pipes, throt­tle valve, and the up­per and lower in­take man­i­fold. From there, the driver-side up-pipe was loos­ened, while the pas­sen­ger-side up-pipe and the down­pipe were re­moved.

 With its coolant lines, oil lines and all four pedestal bolts re­moved, the fac­tory turbo was ready to be pulled off the en­gine. Af­ter man­han­dling the turbo for­ward in the lifter val­ley in or­der to clear the cowl, Richards was able to hoist the fac­tory Gar­rett up and out of the way.

 Once the stock turbo had been pulled, Richards made quick work of sep­a­rat­ing it from the pedestal. Af­ter be­ing cleaned up and hit with a coat of black paint, the fac­tory pedestal would be swapped over to the Chee­tah charger.

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