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

Cummins12V98 wrote:
I have posted the picture of the sign several times in the past. Is says “14% NEXT 4 MI”. I’m having trouble posting pics. It was several miles and it was STEEP.

It was second for sure. I can’t lock first and can’t go 30-35 in first.

I believe you..... I'm just having a hard time time understanding it..... Here's my thought process:
If it takes 430 reverse HP to hold your unit from accelerating on a 14% grade, and if 40HP comes from drag and rolling resistance the driveline needs to account for the other 390. If 60 HP is lost through the driveline the engine would need to generate 330 reverse HP. Spinning the engine around at 3000 rpm, without an exhaust brake, might take about 75 HP. So, the exhaust brake would have to generate another 255 negative HP. If the engine is thought of as an air pump it would be pumping 6.7 x 3000 rpm = 20100 liters per minute of air = 710 cfm.

Pumping 710 cfm @ 100 psi above atmospheric pressure requires about 180 HP so I am left wondering where the additional negative 75 HP could be coming from. (and that would be with 100 psi back pressure which I believe is more than your exhaust brake would generate)