Quote: Horsepower is simply torque in motion and how much work you can do with it.
Not so. Horsepower is simply how much work your torque and rpm are doing for you. Torque does the work, horsepower tells you how much.
Bye
OK, on edit. If your 'it' is torque you are correct.
* This post was
edited 01/09/05 06:06pm by JPhelps *
Quote: Remember, Torqe is more important that Horsepower
Nope. Horsepower at the rpms you actually run at is what gets you up the hill. Not published hp at peak rpms.
Ken
So when my Pete is turning 1100rpms going up a 7% grade pulling a total 39000lbs does that mean 425hp or 1650ft lbs of torque is at work since peak torque is at 1200rpms and peak hp starts at 1500.
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Yes, "it" is torque. Torque has to be in motion to do work. Torque in motion is expressed as horsepower. But can also be expressed as xxx ft/lbs of torque at x rpm if you prefer. It all comes out the same. If you do the math, more torque at a givin rpm always means more horsepower at that rpm. That's why diesels make more HP at low rpm. They make more torque.
'10 F250 XLT CC SB 5.4L 5spdTS 3.73 179miles
ex '95 Cummins,'98 12v Cummins,'01.5 Cummins,'03 Cummins; '05 Hemi
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"So when my Pete is turning 1100rpms going up a 7% grade pulling a total 39000lbs does that mean 425hp or 1650ft lbs of torque is at work since peak torque is at 1200rpms and peak hp starts at 1500."
Actually what it means is if you're to the floor you're pushing 1650 ft/lbs of torque at 1100rpm or "345 horsepower".
That doesn't mean for a minute I could tow that much weight up a 7% grade with my 345hp Hemi even at 5500rpm in 1st gear. Take away about 20% for driveline losses and then maybe more for "less than advertised power" if you can imagine a manufacturer stretching the numbers... Even if I could, it might not make it to the top. Although I'm theoretically capable of 345hp, I don't think WOT at peak hp for extended use is what it's intended for. But it is very comfortable turning 4200rpm towing our 10,040 lb 5th wheel up the grades. I need around 160hp on the flats and up to 260 uphill. The Hemi is plenty capable of that.
Quote: A horse pulling a plow can measure HP directly using a scale like a fish weight scale.
How much horsepower does a horse produce if it maxes out the fish scale but the plow doesn't move? Or does just trying to move the plow count as horsepower?
Two engines, one running 1500rpm @ 600ft lbs of torque with 1/1 gearing and another running at 4500rpm @ 200ft lbs of torque with a 3/1 gearing will do the exact same job. HP= Torque x RPM divided by 5252.
A 500 hp Garrett turbine spinning at 40,000rpm geared to 1800rpm will develope the same torque as a diesel or gas engine developing 500hp at 1800rpm geared 1/1. If one of those, whether turbine, gas or diesel is not producing the same torque at 1800rpm then it is not producing 500hp.
It is in the gearing. Modern pickups use the same gearing for gas or diesel altho the diesel has higher torque at lower rpm. With the proper gearing the Dodge hemi could pull as well as any diesel of same horsepower, just for not as long since it isn't made for that. The Cummins will run at 2700rpm 24/7 for weeks but how long will the hemi last at 5200rpm or whatever it is rated at?
* This post was
edited 01/10/05 06:26am by DSteiner51 *
DSteiner summed it up perfectly. Contrary to what some would have you believe, Horsepower is horsepower, and is what defines how fast you move a particular load. Torque is just a way of generating that horsepower.
Doesn't matter if you generate it (horsepower) with low torque at high-rpms like a gasser does, or low rpms and high torque like a diesel. If two engines are producing the same amount of HORSEPOWER (regardless of torque), they will move the SAME load, up the SAME incline, at the SAME speed.
Horsepower is what defines how quickly you move a given load. No doubt, generating that horsepower at lower RPMs with high torque like a diesel engine, is much more efficient, and a better way to go. But, you can generate the same amount of power (or more) with a gasser, as long as you don't mind turning a few more RPMs.
If you don't believe it, look at the power curve (horsepower vs. RPM) of a gasser, and a diesel engine. You'll see that even though the gasser is typically rated for a higher PEAK horsepower when turning 5,000 RPMs or so, when you look at the horsepower output in the RPM ranges that most of us run (2000-3000 rpm), the diesel IS indeed generating more horsepower than the gasser in those ranges. That, is why it has more pulling power, and typically has a higher tow rating.
(Now, lets see how long it is before I get an eye-rolling, cynical response from someone like PSDExcursion..LOL! )
Quote: So when my Pete is turning 1100rpms going up a 7% grade pulling a total 39000lbs does that mean 425hp or 1650ft lbs of torque is at work since peak torque is at 1200rpms and peak hp starts at 1500.
Look at a power curve for your engine, to answer that question. See how much horsepower your engine is putting out at 1100 RPMs. I would guess, at 1100 rpms, you're putting out around 375 hp (just a rough guess, impossible to know for certain without looking at a power curve for your engine).
Anyway, assuming thats true, the answer is, the 375 HP is what is at work moving that load, and in your case, that 375 hp is apparently enough to move 39,000 lbs up that 7% grade.
If somebody was crazy enough to pull 39,000 lbs with a gasser engine that puts out 375 hp at 5500 RPMs (just a hypothetical case), as long as he is geared such that he's turning the engine that fast on that incline, guess what? He'd move that same 39,000 lb load up that 7% incline at the same speed you're going.
Now, if you downshift at some point, and are turning more like 1500 rpms or higher, then, you are putting out closer to that max of 425 hp, and could go up that incline faster (depending on gearing, of course).
Its all simple mathematics, and the numbers don't lie.
Quote: Contrary to what some would have you believe, Horsepower is horsepower, and is what defines how fast you move a particular load. Torque is just a way of generating that horsepower.
Well said.
Quote: If you don't believe it, look at the power curve (horsepower vs. RPM) of a gasser, and a diesel engine. You'll see that even though the gasser is typically rated for a higher PEAK horsepower when turning 5,000 RPMs or so, when you look at the horsepower output in the RPM ranges that most of us run (2000-3000 rpm), the diesel IS indeed generating more horsepower than the gasser in those ranges. That, is why it has more pulling power, and typically has a higher tow rating.
Actually, it has more pulling power because it has more torque and as a consequence it has more horsepower. And that is exactly why people that buy OTR trucks look at the TORQUE curve of an engine. The horsepower curve of 99.99% of the vehicles built today has a rising line from maximum torque rpm to maximum horsepower rpm. IF you want to figure how much horsepower you will need at every rpm point along the curve it is fine to look at the horsepower curve, but if you want to do it the easy way, just look at the torque curve. If the maximum horsepower is sufficient to tow your load and the torque curve is fairly flat and broad you can count on that engine to be a good puller.
Quote: (Now, lets see how long it is before I get an eye-rolling, cynical response from someone like PSDExcursion..LOL! )
Well, you can count this as a cynical response if you want to, but in the real world, with the trucks that you an I can buy to haul our trailers with, he is exactly right. If everyone went with the 'horsepower is the only thing' mentality that some espouse we would all be driving hemi powered trucks. But we are not, are we? And in real life which one actually does a better job of towing?
* This post was
edited 01/10/05 10:23am by JPhelps *
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, even though we know you are right...
