We’re in the process of evaluating the all-new, all-aluminum F-250 Super Duty this week. We joked that this function was the “fart button,” based on its icon, but it’s really there to save your bacon when you’re hauling heavy loads.
The button is officially called the Engine-Exhaust Braking Function, and it’s only on the dash when you’ve selected the 6.7-liter Powerstroke Diesel engine.
The Power Stroke is a monster of an engine. In last year’s model of the Super Duty, it was capable of generating 860-lb.ft. of torque. For the 2017 model year, that figure skyrockets to an earth-turning 925-lb.ft., which is how the Super Duty can tow up to 21,000 pounds in the F-350 configuration. In the configuration we drove — the F-250 4×4 Regular Cab — the truck can tow 15,000 pounds with either the 3.31 or the 3.55 rear axle.
The torque curve is hardly a curve at all in these trucks. With your foot to the floor, the torque explodes almost straight up from idle to the point where it hits its peak at 1800 rpm. From there it simply flattens out at around 900 rpm and stays there until it begins to drop off at 2600 rpm.
If you’re looking for “fast,” there are other trucks. The engine generates 440hp, which is impressive, but unloaded, you simply don’t get the full effect of what all that torque is doing. You really need to be hauling a trailer near the maximum to comprehend just how much power this truck generates.
Trailering is also where the “fart button” comes into play. The Engine-Exhaust Braking Function is there to save both the brakes and the six-speed TorqShift transmission from overheating on long, steep descents when towing a heavy trailer. Pressing the Engine-Exhaust Braking Function button automatically activates tow/haul mode, which holds the proper gear to help maintain optimum power and reduce gear hunting when going uphill. On a downhill, tow/haul mode inhibits upshifting to help keep the vehicle from gaining speed.
Simultaneously, the Engine-Exhaust Braking Function restricts exhaust flow by opening the exhaust valves and releasing compressed air, so that energy isn’t transferred to the crankshaft. It creates back pressure, making it harder for the engine to turn, and thereby slowing the truck and trailer while keeping the brakes and transmission as cool as possible.
Ford provided a video showing how the system works:
We’ll have a complete review of the 2017 F-250 XLT 4×4 Regular Cab up later in the week.