The point of my post is that the Caddy has quite a weight to hp advantage over our trucks so it seems unlikely they'd be slower at that moderate altitude.

 

Torque is the force an engine produces. Horsepower is a number which cannot be directly measured. It was developed by James Watt (I think) way back when he designed his steam engine, to produce a number which people could relate to. Everyone had horses. Horsepower numbers can be really deceiving. Formula One racer has 875 ponies at 13,500 rpm, but in reality, it's more like 450 ft/lbs of torque. It's just moving LOTS of air really quickly. Don't you think the PSD engine could move that little airplane (in reality) just as fast? But not accelerate that quickly.

 

You are correct that horsepower cannot be measured, it is calculated by multiplying the RPM and torque on an engine brake (dyno) and dividing by a constant (can't recall what it is and didn't check my engineering books, but it is 5000 something). That figure is then adjusted for standard day conditions so that comparisons are equal. The average normally aspirated engine will loose 3-5% of it's HP for every thousand feet of altitude (air density) and about 2-4% (I think) for every 5 degrees above standard day condition temp of 59 degrees. Turbocharged engines are not noticably affected by altitudes below 8,000 feet, or temp changes. This is why the turbo was applied to reciprocating aircraft engines in WWII.
Horsepower is the number that we like to relate to and is an important figure to consider for racing, but torque is what moves and accelerates a vehicle. Given two engines with the same horsepower rating, the engine with the highest and flattest torque curve will reach it's peak horsepower sooner, especially under load, such as a in a truck, or Excursion, or Cadillac.
In a lightweight vehicle (F-1 in your example, or in my case, superbike racing) horsepower is what gets the job done because the vehicles are geared to run at near their horsepower peak, which is always past the torque peak. Not so on the street. Torque accelerates a street vehicle with street gearing.
In the Cadillac vs. Excursion discussion, I have no doubt that the Cad would out-accelerate an Excursion from a standing start drag race, and would get it on top end too. However, the Cadillac's advantage fades rapidly (pun intended) when accelerating from a rolling start up a mountain grade. I believe (I know) that the Excursion is a better performer in real world conditions, much better if you live in the mountains (as in my example) and/or pull a trailer (which I often do). If you bought either just to win drag races, then I think that you've made a mistake.
I don't know what this has to do with this discussion, but random thoughts often creep in, so I'll mention that I have noticed that most of the Escalades in this area seem to be driven by females (maybe Shirley Muldowney?)

 

Bajarider, you are correct in your accounts. I believe the horsepower calculation is as follows. torquexrpm divided by 5,150. So in theory, and engine producing 1 ft/lb of torque spinning at 5,150,000 rpm would produce 1,000 horsepower. We all know that would not move a Ford Festiva. (although they barely have more power than that). I think the WWII planes had super turbochargers, with the speed of the plane forcing air through a blower wheel (like a squirrel cage) and that spinning the intake turbine. At least that's what it looked like when I was walking around looking at the engines of a B-17G.