Ram Eco-Diesel vs F150 2.7 TT - Davis Dam

Turtle n Peeps wrote:

RoyJ wrote:

mt1729 wrote:
HP is great for a car but for towing, torque gets it done. I had a old Mack with a 350 hp diesel. It had about 1420 ft lbs torque. It was a little slow pulling 70,000 lbs up a 7% grade but it always made it. How fast do you think a high hp lower torque engine would do? Even a 850 hp Nascar engine? They would power out & stop.

Neglecting wind resistance, the Nascar engine would pull the rig exactly 2.43 times faster.

Here's a way to think about it, if the Nascar V8 makes 850 hp at 9000 rpm (496 lb-ft torque), and I bolted a 5:1 planetary gearset onto the bellhousing, then I would magically turn it into an 850 hp @ 1800 rpm, 2480 lb-ft @ 1800 engine.

If I bolted that onto the Mack's transmission, you wouldn't be able to tell that apart from a highly modified Cat C15, aside from the sound...

See, torque can be manipulated by gearing, while hp ALWAYS stays constant.

The only reason a Big Rig uses low revving diesel instead of high revving gasoline V8s is due to fuel economy and longevity. That Nascar engine would last 500 miles and get 1 mpg pulling a semi trailer.

^^^^^^^^^^^ should be a sticky.

HP does not remain constant when you run it through the friction and losses of a gear box. Normally 15 to 18% loss. You end up with 82 to 85% of your HP left once run through a gear box. Anyone that's ridden a mountain bike with a Rohloff gearbox up hill, racing, can tell you all about the losses, they are huge.

We are talking tow vehicles here, not racing motors, so racing motors and racing HP and racing torque numbers are unwarranted in this thread. Towing a trailer is doing work. When you want work done, you buy a diesel motor to get the heavy work done efficiently.