Cat vs Powerstroke torque curves

Wes Tausend wrote:
I couldn't get the portion of post below this paragraph, to take yesterday, but it is still a real-time situation to why HP is more important in a race. Offhand, one could theoretically get to the top of a hill first with 1 footpound, if rpms were high enough (millions!) to generate more HP than a 1000 footpound diesel limited to only 6000 rpm. The amount of torque is not important in such a race as long as there is any at all. So you are right, it takes some torque along with HP... but not a lot.

ShinerBock wrote:

I don't think he is spot on in the article. To say that it is only horsepower that helps you up hills is false. It is a combination of both. You need torque to overcome the force pulling you back and that force working against you is constantly changing. If you don't have enough torque to do the work, then all the horsepower in the world is not going to help you.

Take a Ram 2500 6.4L Hemi and 6.7L Cummins. They both have the exact same transmission gearing with the rear end gear advantage going to the Hemi(3.73 or 4.10) versus the 3.42 of the Cummins. The Hemi has 40 hp more while the Cummins has 371 lb-ft more torque. Send both up a grade 7 hill with 14k lbs strapped to them and I guarantee the 6.7L Cummins will get to the top quicker even though the Hemi has more horsepower.

ShinerBock, I had to look for your statement, "To say that it is only horsepower that helps you up hills is false." I found something similar, perhaps what you meant, in bold type below.

Quote
"Debunking Horsepower and Torque Myths



....Myth 1 - An engine with more torque 'pulls' better.

What's the difference in the previous example? Doesn't torque make you go up the hill? The difference is in the gearing of the rigs. The diesel-rig probably has overall gearing like 2.28:1 (with a redline below 3000 RPM you need high gearing), and the gas-engined rig has overall gearing more like 4.56:1. Even though the torque of the engines are vastly different, after compensating for the gear ratios of the differential and transmission, the torque at the rear axle is the same. After correcting the gearing to operate within the operating RPMs of each engine, the lesser torque of the higher-speed engine is multiplied to be the same. So it isn’t engine torque that decides how fast you go up the hill, it is horsepower...."
UNQUOTE


I don't agree with everything the Laine Family page says either, but taken in context I think he is correct about HP on hills. He doesn't say it's better, but just that it ultimately determines maximum speed up the hill. As an example I have the two trucks described in post #7. Wide open, the 310 hp 3/4 ton Excursion V-10 gasser should beat the 235 HP F-250 diesel up a hill with the same camper in tow. But the F-250 has 500 footpounds of torque, and the Excursion only has 450. However the reason is the Excursion will shift down, then wind out to find it's HP peak and more than make up the actual increased geared-down torque to the rear tires at a faster rate up the hill.

By the same token, the Hemi will theoretically beat the Cummins up the hill during a race providing it can run at it's full HP peak RPM's. Since there is a good chance the Hemi gearing will not perfectly match it's powerband HP peak, I too would probably more enjoy the lower RPM purr of that fine 6 cylinder wideband diesel than the scream of the peaky Hemi, and the diesel might even beat the Hemi if:
1) either the gearing matches better,
2) or more likely, the diesel powerband is so wide that gearing match is a lesser concern.

Wes
...

An engine that is making HP is producing both rpm and torque...that is what engine HP is. Similarly an engine that is producing torque is running at some rpm and is therefore also producing HP. Both peak HP and peak torque say a limited amount about a truck's towing abilities. When equipped with the necessary gears to allow a higher HP engine to conduct its work at the rpm where it makes higher HP will always result in the higher HP engine out pulling or out accelerating or reaching a higher top speed than the lower HP engine. The diesel powered trucks are designed and purchased for pulling heavier loads than similar gasoline powered trucks. Engineers equip the gasoline trucks with gears for pulling lighter loads so to talk about a towing competition between two trucks; one equipped with a diesel and the other equipped with a Hemi and expect the competition to be fair might be quite a bit to expect. If the torque was measured at the end of a gear reduction behind the Hemi and the end of the crank on the Cummins it is quite possible that the torque curves of the two engines would look fairly similar. (I haven't actually seen the Hemi's torque curve)