Ford’s new Su­perDuty diesel pumps up power

Winnipeg Free Press - Section F - - AUTOS - JIM KERR

THERE is a power race go­ing on in the truck world, and Ford has upped the stakes again with the 2015 Su­perDuty 6.7 diesel en­gine.

There are sev­eral changes to the en­gine to give it more power and torque, which in the work world where these trucks are used for tow­ing or haul­ing loads means they are even more ca­pa­ble.

In the last decade, Ford’s Su­perDuty diesel has gone from 325 horse­power and 570 foot-pounds of torque to the cur­rent 440 horse­power and 860 foot­pounds of torque. Along with other changes to frame, trans­mis­sion, axles and sus­pen­sion over the years, the 2015 model has in­creased tow­ing ca­pac­ity to an in­cred­i­ble 31,200 pounds for fifth-wheel trail­ers. This is close to what semi trucks were haul­ing only a few years ago on the road, and the Su­perDuty does it with style and com­fort you could never find in a semi.

So what gives the 2015 en­gine so much power? It is a com­bi­na­tion of many things, but let’s start with the turbo. The turbo is now larger for more air­flow, but it also has been changed to a vari­able-vane de­sign and elim­i­nated the waste-gate. Vari­able vane tur­bocharg­ers use small vanes, that can have the an­gle change that they sit at. As the an­gle changes, the ex­haust gases are di­rected more or less at the tur­bocharger wheel to con­trol en­gine boost. The re­sults are more pow­er­ful boost at low rpm.

The Su­perDuty takes ad­van­tage of the vari­able-vane turbo in another way, by us­ing the vanes to pro­vide en­gine brak­ing on down­hill grades. A but­ton on the dash turns on the en­gine brak­ing, and the com­puter will op­er­ate the vanes so the ex­haust gas flow is re­stricted. On long, down­hill grades, es­pe­cially when tow­ing, this can take a lot of load off the ve­hi­cle brakes and makes for safer tow­ing.

The cylin­der heads and ex­haust man­i­folds have also been changed to al­low for more air­flow. In­creas­ing air­flow is what al­lows for the big­gest in­crease in power, but to get more power, you also need to be able to pro­vide more fuel. New fuel in­jec­tors and high-vol­ume fuel sys­tems de­liver that fuel when you need the power, but Ford claims the en­gine is also more fuel-ef­fi­cient than last year’s model.

One of the keys to main­tain­ing peak power on any en­gine is cool­ing. If the cool­ing sys­tem is lim­ited, so is the amount of power that can be con­tin­u­ally pro­duced. The Su­perDuty uses two com­pletely sep­a­rate cool­ing sys­tems. Both sys­tems are com­pletely sep­a­rate, with their own ra­di­a­tors and en­gine-driven wa­ter pumps. The main cool­ing sys­tem has a 27.8-U.S.-quart ca­pac­ity and cools the en­gine block, cylin­der head, en­gine oil and ex­haust gas re­cir­cu­la­tion sys­tem.

The se­condary cool­ing sys­tem has an 11-U.S.-quart ca­pac­ity and is used to cool the fuel, trans­mis­sion oil and the air to a liq­uid in­ter­cooler that cools the in­take air. In this sys­tem, the fuel cooler uses about one per cent of the cool­ing, the trans­mis­sion oil uses about 10 per cent of the cool­ing and the in­ter­cooler uses nearly 90 per cent of the cool­ing. The ra­di­a­tor for this sys­tem is a two-pass de­sign, which means the coolant flows through the top half and then flows back through the bot­tom half. This de­sign pro­vides a longer time for the coolant to be cooled by the pass­ing air and is more ef­fi­cient. The trans­mis­sion-oil cooler draws coolant from the mid­point of the ra­di­a­tor (af­ter the first pass) and the tem­per­a­ture of the coolant in­creases from about 30 de­grees C to about 45 de­grees C be­fore re­turn­ing to the ra­di­a­tor. The in­ter­cooler takes coolant af­ter the sec­ond pass and the 30 C coolant heats to about 60 C as it passes through the in­ter­cooler. Ther­mostats on both these sys­tems re­duce the coolant flow when coolant tem­per­a­tures are low.

The cool­ing sys­tem is in­te­gral to long-term re­li­a­bil­ity and power, so although it may seem a bit com­pli­cated, sep­a­rat­ing the en­gine cool­ing from the in­ter­cooler and trans­mis­sion cool­ing makes a lot of sense.

When­ever an en­gine is de­signed for more power, other parts should also be up­graded. The six-speed au­to­matic trans­mis­sion may look sim­i­lar, but in­ter­nally, it has a new torque con­verter and in­ter­nal me­chan­i­cal parts to han­dle the in­creased power. This is the same trans­mis­sion Ford will use in the new F550 and F650 se­ries trucks, so the Su­perDuty re­ally is built for heavy-duty ca­pa­bil­ity.

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