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

I think someone mentioned that GM doesn't display actual temps. My 2017 Ford came without displaying temperature vales .... the numbers are an add on. Notice how the bar graph reads identical at 181F as it does at 205F.

The bargraph starts into the normal at 120, by 180 it is in the center of the normal. 205 still the center. Maybe it's still in the center at 220? I'll have to pay attention when I'm towing.

rhagfo wrote:
Looking at that dyno sheet best towing RPM is between 2,270 and 2,300 rpm, near max HP and max torque. After 2,270 the torque rating starts dropping off.

When you have a power curve to look at you can totally ignore the torque curve The power curve tells the whole story. According to that graph the Duramax makes peak HP at about 2500 rpm. If a gear change makes a 17% difference in rpm then up shifting at 2750 would drop the rpm down to about 2280. The power changes little over that rom range so the engine would always be putting maximum power to the rear wheels.

Looking at that dyno sheet best towing RPM is between 2,270 and 2,300 rpm, near max HP and max torque. After 2,270 the torque rating starts dropping off.

I would like to see a dyno sheet on the new Powerstroke. Maybe my assumption that the engine builds power evenly throughout the power band is way off base. It could be that the torque builds rapidly, then levels off before dropping sharply. If so the power would build much quicker earlier in the power band which would explain why the Ford ran such low rpms and why the Duramax couldn't keep up.

RoyJ wrote:

4x4ord wrote:
^^^ I think if the fan on the GM was cutting in and out we would have heard it. I kind of think it was either always on or always off. The thing that is hard for me to understand is this: The Ford is supposed to make 1050 lbft of torque at 1600 rpm which is 320 hp. It is rated at 475 hp at 2800 rpm. The power very likely builds quite uniformly over the power band which means it likely gains about 13 hp per 100 rpm. This means the Ford should be capable of making around 398 hp at the 2200 rpm it ran at.

The GM is supposed to make 445 hp at 2800 and 279 hp at 1600. Therefore the Duramax builds about 14 HP per 100 engine rpm. If we say the Duramax ran at about 2600 rpm it should have been able to generate about 420 hp at that rpm. The time difference up the mountain between the two trucks indicates the Ford was putting out about 63 more hp than was the Duramax. If the Ford was making 398 HP the Duramax was only making 335 ..... yet it should have been capable of making 420.

Not sure if an elevation glitch, but TFLT's Duramax dyno is very poor:



As per this dyno, above 2300 rpm or so it makes a constant 320 rwhp.

If we believe their 2020 PS's dyno of 469, which is nearly identical to the crank rating, at 2200 rpm the PS is making ~390 rwhp, or 70 more than the L5P.

Pretty close to your 63 hp calculation!

Is that dyno sheet from the actual truck that they used in the towing test? It seems as though it's not just an isolated truck. I thought the reason the Duramax they put up against the Ram failed to perform better might have been on account of the shift points programmed into the Alison transmission, but,after seeing the high rpms used in this run up the mountain I recognize that the Alison is tuned to aggressively use the high end of the power curve. It seems strange to tune the transmission to run high engine rpm if there is no additional power to be has there.

^^^ Roy is pointing out that a 4.30 final drive along with the low gears of the 10 speed allow the 7.3 to provide enough torque. The problem with the 7.3 is the loss of power that a nonturboed engine experiences at 10,000 feet of elevation.

RoyJ wrote:

rhagfo wrote:

4x4ord wrote:
I'd like to see a video of the 7.3 pulling that trailer up the Ike. I'd be willing to bet it would out do at least 1 of these diesels.

It will not have enough torque,and not pulling 30,000#. Listed at 430 hp and 475 lb ft torque, it would need some serious deep gears to even make the climb.

With the 4.7:1 1st gear on 10R140, and 4.30s, torque won't be a problem even at 37,000 GCW (way above the 7.3's rating).

Taking TFLT's 407 lb-ft rwtq dyno result, and 32" tires, the max tractive effort is: 407*4.7*4.3*12/16 = 6169 lbs

6169 / 37000 = 16.7% gradability in 1st gear, which is far steeper than the IKE, even when you factor in rolling and aero resistance.

What it won't have is horsepower to pull the load at the speeds the diesels can, at elevation.

It isn’t short on HP it is way short on Torque.

ShinerBock wrote:
From what I have read and what I have scene in past reviews, the L5P Duramax normally runs at 210F coolant temps even unloaded which is where it was at in the video the whole way up.

My 18 L5P has never run any where near that hot unless it was at or near full load. Yes the gauge shows 210F, shows 210 all the way from 170F till the fan came on at 218F. GM stiffed the gauge with the LLY's and it still the same. If you want a true read you need to read the ECM through the OBDII
Part stores still list 180f & 185f T-stats for a 2018 and that's what the ScanGauge shows unloaded
GM (at least thru 2018) uses a 4 stage fan clutch, it's not real obnoxious till stage 3

4x4ord wrote:
^^^ I think if the fan on the GM was cutting in and out we would have heard it. I kind of think it was either always on or always off. The thing that is hard for me to understand is this: The Ford is supposed to make 1050 lbft of torque at 1600 rpm which is 320 hp. It is rated at 475 hp at 2800 rpm. The power very likely builds quite uniformly over the power band which means it likely gains about 13 hp per 100 rpm. This means the Ford should be capable of making around 398 hp at the 2200 rpm it ran at.

The GM is supposed to make 445 hp at 2800 and 279 hp at 1600. Therefore the Duramax builds about 14 HP per 100 engine rpm. If we say the Duramax ran at about 2600 rpm it should have been able to generate about 420 hp at that rpm. The time difference up the mountain between the two trucks indicates the Ford was putting out about 63 more hp than was the Duramax. If the Ford was making 398 HP the Duramax was only making 335 ..... yet it should have been capable of making 420.

Not sure if an elevation glitch, but TFLT's Duramax dyno is very poor:



As per this dyno, above 2300 rpm or so it makes a constant 320 rwhp.

If we believe their 2020 PS's dyno of 469, which is nearly identical to the crank rating, at 2200 rpm the PS is making ~390 rwhp, or 70 more than the L5P.

Pretty close to your 63 hp calculation!

rhagfo wrote:

4x4ord wrote:
I'd like to see a video of the 7.3 pulling that trailer up the Ike. I'd be willing to bet it would out do at least 1 of these diesels.

It will not have enough torque,and not pulling 30,000#. Listed at 430 hp and 475 lb ft torque, it would need some serious deep gears to even make the climb.

With the 4.7:1 1st gear on 10R140, and 4.30s, torque won't be a problem even at 37,000 GCW (way above the 7.3's rating).

Taking TFLT's 407 lb-ft rwtq dyno result, and 32" tires, the max tractive effort is: 407*4.7*4.3*12/16 = 6169 lbs

6169 / 37000 = 16.7% gradability in 1st gear, which is far steeper than the IKE, even when you factor in rolling and aero resistance.

What it won't have is horsepower to pull the load at the speeds the diesels can, at elevation.