150705-1309 EDT
kwired, and others:
The government is driving design. To meet fuel economy requirements the vehicles must become lighter. This means using more expensive higher strength materials, and structural design changes.
The stiffness and load capability of a mechanical structural member is a function of the modules of elasticity, yield strength, and the moment of inertia of the structure's cross section. In the past some mechanical courses were required of all engineering students.
Just looking at a mechanical object does not tell you durability and capability. To a trained eye some information is visible. Do you know the alloy of a material by just looking at it? Probably not.
When I designed my home I specified a breezeway 20 feet wide by 35 feet. There is a front and rear cross member to support the roof structure (beams). The architect was going to use a 1" x 12" steel plate with attached wood for these beams. I told him that made no sense, and he changed the specification to a channel iron. Less weight for greater strength and stiffness.
In the past Ford did tests at their Arizona test track in a sand trap with the truck under test greatly overloaded, much beyond the load rating. The competition did not compare in ruggedness.
Here are the engine specifications I could find.
Available Engines | 3.7L Ti-VCT V6 FFV 275 hp @ 6000 rpm 260 lb.-ft. @ 4000 rpm |
| 3.5L EcoBoost® V6 310 hp @ 5000 rpm 400 lb.-ft. @ 2250 rpm |
| 3.2L I5 Diesel 185 hp @ 3000 rpm 350 lb.-ft. @ 1500 - 2750 rpm |
Under normal driving conditions with an automatic transmission Ford will keep engine RPM around 2000 RPM. This general region is where you want to look at HP and/or torque. The speed-torque curves for the different engines are not provided, but a conventional gasoline engine has torque drop substantially as RPM is lowered from peak HP. The EcoBoost has a more flat torque curve, and the diesel probably flatter.
Note: 400 #-ft at 2250 RPM = 400*2250/5500 = 164 HP, and 350 #-ft at 2750 RPM = 350*2750/5500 = 175 HP.
I believe you need to look at the different engine options relative to the kind of load you expect to carry.
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