30,000 lbs behind the Ram

Why is it odd?

From your own figures the Nissan made more HP up to about 9,000 ft. By then the Nissan was so far ahead that they beat the oil burner up the hill.

I think Mr. Truck didn't know what he was talking about. We need Cummins to comment, but the only reason I can imagine for why the transmission would downshift by letting up on the accelerator on the uphill run is because the truck would have lost some of its speed... then it might downshift when he mashed it again.

The driver and passenger tester always discuss how thin the air density is at 11,000 feet but with a turbo that is almost irrelevant. On a gasser that is normally aspired it does make a difference of about 2.5 percent per 1000 feet.

What is really odd is when they tested the new Cummins 5.0 Nissan against the gasser, the 5.6 gasser went up the Ike a few seconds faster than the turbocharged 5.0 Cummins. They have different transmissions, perhaps different axle ratios and the gasser has a 1000 pound less towing rating. Maybe if the Cummins was tested towing 1000 pounds less to equal the test towing numbers of the gasser, the whole test might have been more equitable. I certainly don't put much stock in the test results.

jmtandem wrote:

I thought the whole point of the Ike tests was to mash the pedal to the floor and let the trucks do their thing.

That is what the testers say about some of the tests. This Ram test the driver said he would not manually shift it going up hill but would let off the throttle to let it shift. It is an impressive truck!!

I think Mr. Truck didn't know what he was talking about. We need Cummins to comment, but the only reason I can imagine for why the transmission would downshift by letting up on the accelerator on the uphill run is because the truck would have lost some of its speed... then it might downshift when he mashed it again.

blofgren wrote:

4x4ord wrote:
I watched the F450 run up the Ike video again. Mr Truck left the Ford to shift on its own at about 6:30 in the video. The transmission waited till the engine rpm dropped to nearly 2000 rpm and 39 mph before shifting. That is a significant mistake ......at 2000 rpm the engine only makes 350 hp.Mr Truck should have made a manual downshift at 2300 rpm and 45 mph. The engine would have revved to 3000 rpm where it makes 420 hp. The Powerstroke has very significant torque rise from 3000 to 2600 rpm that he could have made use of. It depends how long he ran the engine below 2300 rpm but I suppose that blunder could have cost him 15 seconds.

I thought these super duper smart new automatic transmissions knew exactly what gear to be in at all times, even more than the driver. :B. LOL.

If the goal is to race up a mountain with your foot to the floor you can reach the top a little quicker by manually selecting the optimum gear at just the right time but when you're casually enjoying your drive it might feel a little more relaxing having your engine loaf along at 2000 - 2300 rpm instead of spinning in the 2600 - 3000 rpm range. I find the Allison behind the Duramaxs I've owned are tuned to be more aggressive with their shift points than the Fords and I don't mind having to manually wake up the lazy Ford on the occasions that I want a little more performance.

I thought the whole point of the Ike tests was to mash the pedal to the floor and let the trucks do their thing.

That is what the testers say about some of the tests. This Ram test the driver said he would not manually shift it but would let off the throttle to let it shift. It is an impressive truck!!

I thought the whole point of the Ike tests was to mash the pedal to the floor and let the trucks do their thing.

4x4ord wrote:
I watched the F450 run up the Ike video again. Mr Truck left the Ford to shift on its own at about 6:30 in the video. The transmission waited till the engine rpm dropped to nearly 2000 rpm and 39 mph before shifting. That is a significant mistake ......at 2000 rpm the engine only makes 350 hp.Mr Truck should have made a manual downshift at 2300 rpm and 45 mph. The engine would have revved to 3000 rpm where it makes 420 hp. The Powerstroke has very significant torque rise from 3000 to 2600 rpm that he could have made use of. It depends how long he ran the engine below 2300 rpm but I suppose that blunder could have cost him 15 seconds.

I thought these super duper smart new automatic transmissions knew exactly what gear to be in at all times, even more than the driver. :B. LOL.

"I wouldn't necessarily make the shift but if I knew the hill was going to cause it to happen anyway I would shift sooner rather than wait."

I always downshift if I see a grade in front of me that I will downshift on. It takes less fuel and you don't loose speed if on cruise control like I usually tow in.

All these little things a person can do are actually fun to figure what works well.

Cummins12V98 wrote:
Downshifting with the Aisin trans is a waste of time when climbing a grade. I have tried it thinking a higher RPM would net a higher MPH. Downshifting while descending does work well by keeping the RPM in the high 2,000's.

Combined 33K in 2nd would hold around 33 MPH as seen in video on this 14 percent grade.

Wow. Impressive.

I haven't seen a torque curve for the new 900 lbft Cummins but you can be certain that at 1900 rpm the engine is making no more than 325 hp. If you downshift at 2100 from 4th to third you will jump to 2800 rpm where your making 385 hp. I'm not sure what the torque value of the cummins is at 2100 rpm but I do know that by downshifting from 4th to third at 2121 rpm brings your engine rpm up to 2800. At 2800rpm the engine makes 722 lb ft of torque. When that torwue is multiplied by the 1.32 third gear ratio your definitely going to gain making the downshift. You're equivalent to 953 lbft of torque in 4th gear which is more torque than the engine can deliver at 1800 rpm and you don't have to slow down to get it. I wouldn't necessarily make the shift but if I knew the hill was going to cause it to happen anyway I would shift sooner rather than wait.

burningman wrote:
I'm glad I'm not in the market for a new truck, I don't know which one I'd buy!
I've been a Ford and Chevy guy most of my life but that was the old-school stuff that really hasn't got anything to do with the new trucks today. The only reason I have a Dodge is I wanted a Cummins, and that's only because I do my own work and the straight six is so much easier, and I don't like that on the Fords you have to lift the cab off just to change a fuse or empty the ash tray.

Pickup diesels are getting to a pretty high stress level. The biggest truck I drive has a Caterpillar C15. It's rated at 550hp, not a whole lot more than the new pickups or my hot-rodded old 5.9 Cummins, but it's a 15.2 liter monster. The one I drive the most has a 10.7 liter Cummins M11 that dynoed 370hp at the wheels.
Makes me wonder how these pickups are going to stay together! I'm sure the pickup horsepower numbers are inflated because they are measured at higher RPM but they are awfully strong.

When it was new, my GMC 3500 dually with a gas 454 was the strongest pickup available!
What's next, hybrid electrics that make 2000 ft/lbs right from a dead stop?

Probably!!

The big Cat or Cummins engines deliver high hp hour after hour in many applications. A pickup truck pulls hard on the odd hill every once in awhile.
Regardless, these little pick up truck engines making 350 HP at 2000 rpm is nothing to sneeze at. In order to move one of these trucks up the hill in 11.5 minutes with a 30,000 lb trailer in tow, the truck needs to put an average of 300 hp to the pavement over the entire run. A test like this demonstrates that the trucks have transmissions and cooling systems in place to utilize the power they are making. It's interesting to note that it takes just as much power to pull a 16000 lb RV up a hill like this at 60 mph as it took for the Ram to pull the 30,000 lb trailer up in the 12.5 minutes.