But you make a perfect point: torque without motion is useless. Motion, without any force behind it (if such a state could exist), is equally as useless. They're both components of power. So back to my original statement - you want to sustain a given weight at a given speed - you need a certain amount of power to do so. How you arrive at that power output doesn't matter.
Let's arbitrarily say you want to move 10,000lbs at 30MPH. After factoring in drag, inertia, etc. etc., you conclude you need 175HP to do that. You may produce that power with an engine putting out 600ft.lbs. of torque, turning at ~1500RPM, or an engine putting out 200ft.lbs. of torque, turning at ~4600RPM.
Ever caclulate, or seen mention of, a drag car's horsepower based on trap speed and weight? Same principle. You can't calculate torque that way, because you don't know the RPM.
Actually, these are very different statements, because force (torque in this case) can exist without producing movement, as in our lug wrench scenario, when it is insufficient to produce work. But work can never exist without force, because there has to be something creating the motion over time/distance to be measured.
That's because torque isn't calculated, it's measured. Point being that HP is a function of torque... it isn't a force, it isn't doing anything, it is just an expression of how much is being done by the forces in play... almost like a comentator to a ball game, they're not involved in the playing of the game, but they are necessary in helping know what is going on...sort of...
I agree with Matthew. It is all about torque. Torque is NOT limited to static measurements. Torque can be applied in motion. Being a mechanic I sure hope you know what a running torque is. Horsepower cannot be measured without motion but torque can. Horsepower cannot be measured at all without torque.
How do you figure out horsepower numbers? It's torque x rpm / 5252. Horsepower is nothing more than an expression of torque mathematically diluted by rpm. No matter what engine you measure, the torque rating is the basis of the hp measurement. Horsepower will *always* be lower than torque below 5252 rpm and *always* be higher than torque above 5252 rpm. Horsepower is just a marketing gimmick dreamed up in the 1800s by James Watt to sell steam engines. And you are still buying it.
Torque is the key to acceleration. Acceleration is expressed as g force. The g force potential can be figured for any vehicle by knowing the thrust and weight of the vehicle. You can figure out what the thrust is by knowing the torque output of the engine, the transmission and rear gearing, and tire diameter. I can explain this in more detail if you'd like me to.
Torque can measured as both static and dynamic forces.
That power to weight ratio you speak of is actually a thrust to weight ratio. Weight and driveline efficiency is the key to this race.
Peak ratings aren't much of a factor here. F1 engines must be strong throughout the entire rpm range, up to 18,000 rpm. If the 4.7L V8 can produce more than 270 lbs/ft of torque through 18,000 rpm, then yes, it would be faster.
Comments from the last F1 race winner's engine team on torque and acceleration:
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Alonso's engine engineer Remi Taffin explains how to get the best out of the RS25 V10 in Australia."Melbourne is a tough circuit for engines: its succession of straights broken up by slow corners mean good torque is more important than peak power in order to accelerate out of the slow and medium-speed corners."
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Taffin, Engine Race Engineer."A torquey engine is always a plus-point in Canada, as it allows the car to launch out of the slow corners when accompanied by good traction. Gear ratios must also be studied carefully in order to be able to optimise the torque curve of the V10 around the lap."
The original statement was that to move a load of x lbs. at y MPH, requires z HP. However that HP is created, be it lotsa torque with low RPMs, or little torque and lotsa RPM, matters not.
Somehow, people are missing the fact that HP is the force with motion, which indicates work done, or capable of being done.. I'll readily agree that its an arbitrary unit, but that unit comes from a finite formula that can have the same result despite different numbers being plugged in.
I think the quotes from the F1 guys are comical. Both refer to specific tracks... wonder what they say about other tracks where wide open running dictates that HP is the key?
Also comical is the statement that no matter what engine you are looking at, torque is the basis of the hp rating. No quite true. Many dynos measure kW, which can be converted directly to HP. Most industrial engines have a kW rating, and most overseas diesel manufacturers, especially the Europeans, use kW ratings without hp being mentioned until it hits the US market.
That is the point that I disagree with. A horsepower number does not describe an engine's ability the same at different rpms. 100 horsepower at
1,000 rpm is 10 times stronger than 100 horsepower at 10,000 rpm. 100 lbs/ft of torque has the same ability no matter what rpm it occurs at.
100 hp @ 1,000 rpm = 525.2 lbs/ft torque
100 hp @ 10,000 rpm = 52.52 lbs/ft torque
Yes, and most people don't know that rpm has just as much to do with horsepower ratings as anything else. They throw around horsepower numbers like they mean something without the rpm. How many times have you heard someone brag about the horsepower their engine makes? Want to shut them up? Ask them what rpm that horsepower occurs at. Most often, they don't even know. So what good is that number? Horsepower tells you nothing of the engine's performance without knowing the rpm.
I'm glad you got a chuckle from the F1 guys. I do think they are better engineers than comics though. I don't know what they say about the other tracks. If you find out, let us know. Pick anyone to quote if you like, but please use credible sources. Don't quote Joe Bling saying that the 22's that he put on his Civic make 500 horsepower so it now goes 300 mph in the straights. I will consider any comments from any credible source that says a high horsepower number is more important than torque.
Those dynos still measure the engine's torque and then convert it to kW. Also, I said "no matter what engine" and I should not have. I didn't intend that to include jet engines, nuclear power plants, or other exotics.
Sorta works the same for Torque, thats why they usually pair each one with an RPM.
No one claimed one was more important than the other except you. Fact is, the two cannot be separated, nor can they happen without RPM and get anything done.
Those dynos measure output, be it torque or kW. Hydrualic dynos measure torque, electric dynos measure kW output.
Inertial dynos (Dynojet, for example) don't... they measure power (be it HP or KW), and interpret torque based on engine RPM. This is why a lot of times, diesel guys only get HP ratings from their dyno runs - becuase they don't feel like setting up the cumbersome little optical sensor to read RPM from the engine.
I'm almost sorry to have started this, if in fact I did. My only point is that Torque is the force that turns the shaft. it doesn't matter how fast you turn the shaft, it is still torque that is turning it. At no point does the force or even the name of the force change into something else, it is always torque. HP never turns the shaft it is an expression of the resulting motion. You must have torque to produce HP but you do not need HP (or kW, etc.) to produce torque. Torque is the force at play and HP is an expression of the work performed.
Everything you say about torque is true - I'm not arguing that. The initial statement was in reference to someone's claim that (and I'm paraphrasing here) "the ability to pull [move] a load is all about gearing". I countered that, "no - when it comes to moving a load, it's all about HP". Weights being equal, the vehicle with the ability to generate more HP will go faster.
What I WASN'T discussing was the ability to ACCELERATE a load to a certain speed. That makes it a much more complicated equation, because then you're usually talking about starting from a stand-still, which because of the limitations of modern drivetrains, requires that the engine be able to produce enough HP to overcome static friction/inertia/etc. (everything that resists motion and acceleration), at a relatively low RPM. Since one component of the HP equation is being limited, torque (the other component) becomes the deciding factor in being able to overcome those static forces. This is where gearing, torque curves, etc. etc. come into play. If we could eliminate those artificial limitations (let's say we have an infinitely variable transmission that would let an engine operate at it's peak HP output all the time), then that little 800HP 3.0L V10 engine would out-pull a big Cummins 600HP 14L I6 in every conceivable measurement: 60 ft. times,
1/4 mile times, top speed, you name it. The fact that the V10 would implode itself before the Cummins reached full operating temperature isn't germane to this discussion :^)
Back to my original statement... the vehicle that produces more horsepower will be able to move a given load at a faster overall rate than the vehicle with less HP.
And oh yeah.... my Dodge is better than Larry's Chevy - which is where this whole thing started in the first place
Stop thinking that HP is _ONLY_ "torque times RPM divided by 5252". HP is a measure of work done over time. Work is the moving of a load over a distance. The dynojet knows the load (weight of the drum). It knows the distance the load is moved (turned). It knows the time between samples. Work done over time is power. It's a simple calculation. 1 HP equals
33,000 ft.lbs. of work per minute, or 550 ft.lbs. of work per second A foot pound is the energy required to move 1 pound 1 foot.
I dunno... maybe some wheelspin/slippage? Those are also old dyno sheets, before I put on twin turbos. I have to take the outer rear tires off to fit the truck on the dyno, so my contact patch goes down by 50% :)
What's this for? It's to show that a horsepower number alone does not accurately describe the ability an engine has to do work.
You said "If it takes 100ftlbs to turn a shaft, one shaft will turn 6 times as fast, meaning more work is done." We'll use that same shaft again comparing the two 100 horsepower engines.
The engine that makes 100 hp @ 1,000 rpm has 525 lbs/ft of torque. That's plenty of torque to do the job. In fact it can run 5 shafts each requiring
100 lbs/ft of torque all at the same time. The engine that produces 100 hp @
10,000 rpm makes less than 53 lbs/ft of torque. If it takes 100 lbs/ft of torque to turn the shaft, it will not be able to turn the shaft at all. No work is being done.
I'll give you another example. Say I'm out shopping for a new push mower. I get frequent rain and one corner of my back lawn doesn't drain very well. The lawn is always wet there and the grass grows very fast. My old mower cut fine everywhere in my lawn, including the high wet grass. It had a good 5 horsepower engine when new but now it's old and uses too much oil. I leave a trail of smoke behind every pass. I assume any 5 horsepower push mower with the same size blade will work the exact same way, so that's what I go shopping for. I want a brand new mower just like my old one, but the old model is discontinued. I find the same brand mower with the same 21" blade, a 5hp engine, and rear mounted collection bag. Same thing as the old one right? Well, no. It looked the same and had all the same advertised specifications, but it wasn't the same thing. I didn't realize that my old mower was rated 5 horsepower @ 500 rpm and the new one is 5 horsepower @
1,000 rpm. The grass doesn't really care if it gets whacked by a blade spinning around at 500 rpm or 1,000 rpm, so the end result should be the same. It should make tall grass short. I try out my new mower. I get the front lawn done and it looks very nice. That 1,000 rpm mower cuts the lawn very cleanly and deposits much more of the clippings into the bag than my old mower ever did. I'm very happy with my new mower even though I still don't know about the higher blade speed. I assume the old engine was getting weak and this new one is more powerful. Now I go around back. I get three feet into the wet high grass and the mower stalls. I have to drag it back out of the wet area to get it started again. I push it another three feet into the wet grass and it stalls again. It takes me hours longer with this new mower to cut the wet area than it did with my old mower. 5 horsepower isn't always exactly the same as 5 horsepower. The old mower had twice the torque that my new mower has. The new mower has twice the blade speed that the old mower had. Which one gets more work done? If you ask the guy that has to push the mower through the tall wet grass, it's the old one.
I'm not saying that horsepower ratings are meaningless. I'm only saying that horsepower ratings are less meaningful without an rpm to go along with them.
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