Diesel vs gas......................

Rvndave wrote:
Torque can be measured, horsepower is a calculation using torque and RPM. Torque is what turns my wheels. If someone wants to use a higher HP number and think they are going to be at the top of a mountain first, you will see them at the top, but only if the diesel waits for them!!!!! Another factor not being considered is the fact that the air is thinner as we go up the mountain, a turbo or supercharger reduces this power loss. I don't see how a naturally aspirated gas engine with lower torque numbers is going to beat a turbo diesel with comparable loads, and wind resistance to the top of a mountain. I suspect Hannibal is going by the seat of the pants feeling, or his past diesel had problems with his engine that reduced power output.

If you're going to spec an engine for a motorhome or OTR truck, how do you calculate how much torque will be needed to run 60mph up a 6% grade? You first have to know how much horsepower is needed. It's horsepower. Torque is a static measurement. It implies no movement at all. Horsepower is a measurement of work over time. If you break it down further, you'll see that the NA gas engine loses a lot of horsepower at high altitudes and it's peak horsepower is at high rpm so unless the driver is willing to run at 5k rpm, reduce that hp to it's 4k rpm value and it makes better sense why the diesel tows better with two equal hp trucks. There's more to it than just peak hp and more torque means you make more hp at lower rpm but it's still horsepower that determines the speed you're able to tow.