2015 Light-Duty V-8 Challenge: Davis Dam

Ford 8

Knowing how pickup trucks run at the track or how well they can tow weight through congested cities or over mountain highways is just one way of determining their capabilities. We believe another important test that is a top priority for any V-8 half-ton pickup is how well it can tow and control a trailer up a steep grade.

With those priorities in mind, we took our crew of half-tons and horse trailers to one of the most rugged hill climbs in Arizona. Arizona Route 68 just outside of Kingman is home to the infamous Davis Dam grade, a hill climb so challenging the Society of Automotive Engineers uses this same route to define the J2807 towing criteria that all truckmakers must adhere to.

2015LD_Davis_F2

As you can see, the fastest trucks were the 6.2-liter V-8 GM pickups, with the Chevrolet Silverado 1500 getting to 60 mph in 19.92 seconds and the GMC Sierra 1500 in 20.05. The Ram ran 26.15, with the Ford a nose behind at 26.28 seconds. Trailing the pack was the Tundra, which we could see was struggling with the extra weight, at 28.39.

2015LD_DavisDamSpeeds_F2

Interestingly, no truck was faster than the Ram Hemi and ZF eight-speed to 10, 20 or 30 mph, but then it fell considerably behind through 40, 50 and 60 mph. The Ford, on the other hand, did not start well at up to 30 and 40 mph, but it really opened up with pushing to 50, 60 and beyond. Several of our drivers thought the Ford sounded the best when pulling the load as well.

How We Conducted the Testing

In the name of full disclosure, SAE typically does its testing in the middle of the summer when normal temperatures hover at or above 100 degrees. We did our tests in December, when temperatures were in the 70-degree range after a rainstorm had come through the valley a few days earlier. Still, testing on this slope challenged all the half-ton competitors equally.

Rather than risk breaking any speed laws on our test runs and doing a bottom-to-top (almost 12 miles long) wide-open-throttle run, we instead chose one of the steepest parts of the climb to conduct some zero-to-60-mph runs. Our test section was a little more than halfway up the climb on a 6.8 percent grade. We found a safe pull-off along the highway with plenty of visibility behind us, making sure there was no traffic; likewise, we made sure we could see far enough in front of us as well.

Each run was performed with the air conditioning off, windows rolled up, our 6,700-pound trailer safely attached and each transmission in Tow/Haul mode.

Cars.com photos by Evan Sears

GMC 8

Tundra 21

 

 

 

Overview | Acceleration | Quarter-Mile | Braking | Fuel Economy | Davis Dam | Results

Comments

Time should always be on the X axis.

I can't see the Chevy line at all on the chart. I guess that's how close it was to the GMC. Seems the axle ratio doesn't make all that much difference with the 8-speed.

Interesting how close the Ram and Ford were overall. The Ram seems to have a torque advantage at lower RPM. I am surprised that the Ram ran out of wind above 30 mph.

The Tundra is showing its age and the suspension choice for a "road" test was dumb.

Not a fan of GM trucks but overall very impressed with the Chevy and GMC!

@MPG Man,

Usually I would agree, but I think a case can be made for the graph with speed as your X. We don't technically care how fast we're going at X time, we care how long it took us to get to X speed. X being our input (how fast we are) and Y being our output (how long did it take). Just a thought.

It doesn't really make sense that the Ram would get caught by the F150. It has a gearing advantage and makes more power across the entire RPM range. Unloaded the Ram may have struggled to keep accelerating its extra weight but that shouldn't be a factor while pulling a trailer. I would think that either:

1.) Ram's Tow/Haul mode takes things conservatively once a certain speed is reached in an attempt to increase the longevity of the engine.
2.) Ram's power numbers they release for the hemi in the 1500 are "generous".
3.) The 5.0 in the F150 is underrated.
4.) Ford is really aggressive with their fuelling and shift maps, which could negatively affect the longevity of the engine.

The Ford is 660 lbs. lighter then the Ram.

@Mileage Man - A DOHC engine will live at higher revs longer than a OHV engine. You may be correct in your assumption or it may be a case of ECM programming aimed at MPG.

The "over rated versus under rated" theory is an interesting one.

@Todd - lighter weight should make a bigger difference at lower speeds. You have less weight to accelerate.

I think I speak for everyone that now we want to see the new 2015 3.5 ecoboost f150 take on the GM 6.2 eight speed combo! Please make it happen soon! Thanks pickuptrucks.com for the info. It sure helps us prospective truck buyers. All these new trucks are just plain sweet! These trucks would destroy the half-ton pickups from just ten years ago. Competition and technology are great.

To really see how good their designs are they should run the 2015 F150 "Ecoboost V-6,turbo,3:55 and the Silverado 1500 6,2L,with the 3:55 axle and load the 2 trucks to their 12,000lb tow limit.This would give us a good idea of how their design hold up.They both advertise best in class in tow,bed payload.

@Mileage Man
It does make sense. Ford's updated 5.0 V8 prefers to live in the 3250-6500rpm region instead of 0-3250rpm. The gearing of their ZF 6hp based transmission runs 2nd gear 35-70mph.
The Ram's gearing is much more 'aggressive' 1st- 0-25. 2nd- 25-40mph. 3rd- 40-65mph.
The extra mass of the Ram, and the inferior aerodynamics explain why the F150 catches up.
But there is also a possibility that the Ram does not switch its dual length intake manifold runner system correctly. If the intake manifold switched to the short runners for top end power in 2nd gear, upon upshifting into 3rd gear the manifold should switch back to the long runners for enhanced cylinder filling. If this is the case, that would explain the oddly slow 40-50mph acceleration of the Ram. [worse than the Toyota? Which also has a dual length intake manifold which should switch from long to short ~45mph]

George C, your transmission argument doesn't hold water. At full throttle acceleration both transmission should strive to maximize power production by the engine (or torque to the wheels). The 8HP in the Ram has a gearing advantage at all speeds and in all ratios. Then, the rear end ratio will provide more amplification in the Ram.

I don't have CD numbers for the F150, but I would be *shocked* if the F150 had a lower CD than the Ram. Its mostly irrelevant since the trailer will cause the lion's share of the drag anyway.

Your intake runner theory may however be correct, it wouldn't surprise me if Chrysler's engineers had some shoddy program with them. They certainly have used lousy programming in the past with their torque management programming.



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