F350 Super Duty vs 3500 Denali vs The Ike Pulling 30k lbs

RoyJ wrote:

4x4ord wrote:
I've been screwing around with the numbers and I think the Duramax time was not really that far off what should have been expected based on a 39000 lb truck and trailer and 2220 ft of elevation gain climbing the hill. Based on those same numbers the Ram should climb the hill in about 12 minutes. The thing that doesn't add up is that the Ford should not have been able to climb the hill in 6 minutes and 20 seconds running at the rpm it ran at unless it is putting out more power than Ford claims.

4x4ord, I'm curious what your calculation shows, if we pretend the L5P has a bigger turbo that does not lose hp at elevation. According to GM's graph, the engine is suppose to climb from 380 to 445hp from 2300 to 2800 rpm:



We know the high elevation dyno flattens out at 320 rwhp from 2300 - 2800 rpm. Assuming it climbs 55hp (account for drivetrain loss), so that it dynos 375 rwhp @ 2600 - 2800 rpm. What time would that turn out?

I'll let you play with the numbers:

Here's the way I come up with numbers to make the Ford run reasonable and predict a run time of 10 minutes 50 seconds for the Ram:
The distance from the freeway entrance at Dillon to just before the Eisenhower tunnel is 7.6 miles according to Google maps.
The elevation change from the ramp at Silverthorne/Dillon (9038 ft) to the Eisenhower tunnel (11158 ft) is 2120 ft.

The power required to raise 39000 lbs 2120 ft in 620 seconds is exactly 242.4 HP
Additionally there is drag and rolling resistance which can be approximated as follows:
For the Ford to travel 7.6 miles in 10 minutes 20 seconds it averaged 44 mph.
Weight of truck and trailer is 39000 lbs
HP based on frontal area and drag calculator at bottom of page
If I plug in a frontal area of 90, a coefficient of drag of .7, a speed of 44 mph and a weight of 39000 lbs the calculator spits out a HP requirement of 97 hp

242 plus 97 equals a rear wheel HP requirement of 339 HP. If the driveline is 85% efficient the Ford would have to be making 399 HP at the crankshaft to accomplish what it did.

the Ford is rated at 475 HP at 2800 rpm and 340 HP at 1700 .... looking at power curves of the Powerstroke it seems reasonable to assume it looses about 12.5 HP per 100 rpm. This would mean the Ford could make 400 HP at 2200 rpm.

Using the same logic and calculations for the Ram:

The Cummins makes 400 HP @ 2800 rpm and 343 HP at 1800 rpm
It seems reasonable to assume it will run up the hill in 3rd gear between 2100 and 2900 rpm. It should be able to average about 376 HP while running in that rpm range. Using the same 85% efficiency number 376 crank HP is 320 rear wheel HP.

If it can average 42 mph it would reach the top of the hill in 10 minutes 50 seconds.
According to the drag formula it would require 89 HP tp overcome drag and rolling resistance at 42 mph.

320 minus 89 leaves 231 HP which is the required HP to raise the 39000 lbs 2120 feet in 10 minutes and 50 seconds.

Edit: I guess I should have quoted the definition of HP:
1 horsepower is the power required to raise 550 lbs 1 ft in 1 second

So 39000 lbs x 2120 ft / (620 seconds x 550) is 242.46 HP

Edit: Fixed the error of calling 650 seconds 6 minutes 50 seconds changed it to to read 10 min 50 sec.