Black Mountain whooped my butt !!

Ron Gratz wrote:

rhagfo wrote:
I am wondering about your math?:h If it only takes 156 hp to go 40 mph, then why was the OP struggling to maintain 40 mph, his 2005 6.0 should have more than 160 hp.
Well yes it does rated at 360 hp, so why then the issue, maybe not 60, but should have been and easy 50 mph.

The math was okay, but I inadvertently calculated aerodynamic drag using speed in ft/sec instead of speed in mph as required by the formula I was using.
My previous post has been edited to show the corrected numbers, and new numbers for the effect of rolling resistance.

The OP's engine, when new, might have been rated at 300 hp.
But, there is no way of knowing how much power was being delivered to the rear tires on the trip up Black Mountain.

As Marty has stated, the actual power being transmitted to the pavement might have been significantly less than the engine's rated power.

Ron

A combination weight of 15000# and frontal area of 85 sq ft moving up a 6% grade at 60 mph will require about

90

hp to overcome aerodynamic drag, about 150 hp due to rate of climb,

and about 25 hp to overcome rolling resistance

.

The same weight and frontal area moving up the 6% grade at 40 mph will require about

40

hp to overcome aerodynamic drag, about 100 hp due to rate of climb,

and about 15 hp to overcome rolling resistance

.

If going up the hill at 60 mph requires

265

hp, and going up the hill at 40 mph requires

155

hp, the higher speed will require an addition of about

110

hp.

If the non-boosted airflow through the radiator at 40 mph is not sufficient for proper cooling, the fans will provide necessary increased airflow -- and the fans will not be consuming

110

hp.

The OP stated he was going about 40 mph at the top of the grade and "the trans never really got hot, just a tad over 200."
Doesn't sound to me as though he had a cooling problem.

Edited,

in red

, to correct for using speed in ft/sec instead of mph for calculating aerodynamic drag, and to include power required to overcome rolling resistance.

Ron

:h :hWell the OP's engine should have been rated at 345 hp, so here we go again! if the OP had a 345 hp rated and only takes 265 to move up the hill at 60 mph, why then was he going 40, and loosing speed??