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Discussion Starter · #1 ·
I would like to hear everyone's opinion about which is more important, torque or horsepower. It is my belief that horsepower does not exist because it cannot be measured. It can only be calculated. Therefore, horsepower is only a matter of theoretical interest. Torque, on the other hand, can be measured.
It is the force that propels our trucks forward. It is my belief that torque is the only thing that really matters.

If you think I'm crazy, go ahead and say so. But please provide a technical explanation to support your opinion. If you believe that horsepower is as important as torque, or even more important, please explain why. Perhaps we can all learn something from this.

Wolfhound
2001 2500 2wd auto, HTT 62/65/13 SS, FASS 95, DDP 75, Banks box, S&B, CFM, Flowmaster
 

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as John Force told me years ago...torque gets you off the line...the 8,000 h.p. wins the race....good thread start will be interesting!!
 

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Horsepower does exist. It is a measure of work (torque) done over time (RPM). I don't have a college degree so I'm not going to copy/paste all of the physics behind it but it's quite simple.

More horsepower at the wheels will accelerate you faster. There are two ways to increase horsepower. Increase torque at the same RPM or increase RPM while making the same torque. The second way is why Pro Stock engines rev so high. Once you get close to 100% volumetric efficiency the easiest way to make more power is to rev it higher and hold on to the torque.


The reason torque is so important in a diesel truck is towing/weight and lack of RPM.


If these engines made 350lb/ft max torque they would feel gutless because they only rev to 3200rpm. A gas engine making the same torque but revving to 6000rpm (assuming near peak torque runs most of the way to redline) will feel way more powerful and way faster overall.


The first way (increase torque at the same RPM) is beneficial to these things since they are built to tow and they are heavy. In order to pull heavy loads around without increasing RPM (in turn increasing horsepower to the ground) they need to have more torque down low where the truck runs at most of the time.

My gas truck runs ~2000rpm at 65mph

My Mega Cab runs ~2000rpm at 65mph

My gas truck makes more total power and accelerates much faster

But my Mega Cab makes way more torque (therefore more horsepower) at that lowly 2000rpm which means it can cruise with a heavy load behind it under less strain than the gas truck. The gas truck would need to be dropped down to third gear (increasing RPM, therefore increasing HP to the ground) to pull the same weight.



By definition one can not be better than the other. They are the same thing only one is measured over time.

What can be better is putting the torque where you NEED it. This means that gear ratios in the trans and rear end are equally as important as well as torque converters for you automatic guys.

In a drag race truck you want to make as much power as possible so you want the torque to really come on hard in the upper RPM. In a truck that tows 20k every day you want the torque between 1200 and 2500RPM specifically in that 1800-2000 range. That is where it spends most of it's time.



Engines are usually most efficient at peak torque RPM as well. That's just another side benefit.


Turbochargers kind of blur the lines a bit. It makes it a little more complicated than an N/A engine since you are artificially manipulating the atmosphere. The same principles apply though.
 

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^^^ Very well put.
 

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Discussion Starter · #5 ·
Torque Vs. Horsepower

FMX05, I agree that RPM is a very important factor in winning races. It is the ability of an engine to deliver a lot of torque at high RPM that will get you across the finish line first. However, I don't accept the ability to produce a lot of torque at high RPM as proof that horsepower exists. Horsepower is merely a concept that engineer James Watt thought of circa 1860 to help him sell his steam engine. It is an idea that exists only in the minds of men.

Wolfhound
2001 2500 2wd auto, HTT 62/65/13 SS, FASS 95, DDP 75, Banks box, S&B, CFM, Flowmaster
 

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FMX05, I agree that RPM is a very important factor in winning races. It is the ability of an engine to deliver a lot of torque at high RPM that will get you across the finish line first. However, I don't accept the ability to produce a lot of torque at high RPM as proof that horsepower exists. Horsepower is merely a concept that engineer James Watt thought of circa 1860 to help him sell his steam engine. It is an idea that exists only in the minds of men.

Wolfhound
2001 2500 2wd auto, HTT 62/65/13 SS, FASS 95, DDP 75, Banks box, S&B, CFM, Flowmaster


It is the easiest way to determine total power output.

300hp

That's easy to say.

To know how much power my engine is putting out at the crank without using horsepower I would have to say "It makes 262lb/ft of torque at 6000rpm"


They both mean the exact same thing, and are the exact same amount of power.

One is easier to use.

Peak horsepower, peak torque, and the RPM that each is at are the only things that matter. Peak torque will tell you where the engine is most efficient, peak horsepower will tell you how much power it is capable of producing, and the RPM at each one is important for determining how the engine is best used.

Torque*RPM/5252 is the equation for HP in case anyone is wondering. That is why the horsepower and torque lines on a dyno graph always cross at 5252rpm, and why it is impossible to make more torque than HP above 5252rpm.
 

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Discussion Starter · #7 · (Edited)
It sounds like we are in total agreement. And I am learning something of value from this exchange. I did not know that the lines on a dyno always cross at 5252 RPM.

You are right, 300 horsepower is easier to say than 262 ft/lb of torque at 6000 RPM. The important point here is that horsepower can only be arrived at by mathematical calculation. It cannot be measured directly because it doesn't really exist. Horsepower is a concept that is used for convenience and for selling engines.

Thank you FMX05. You are one of the experts on this site. I'm sure a lot of guys will be watching for more of your posts as a way to expand our education.

Wolfhound
2001 2500 2wd auto, HTT 62/65/13 SS, FASS 95, DDP 75, Banks box, S&B, CFM, Flowmaster
2007 Magnum 5.7, stock with K&N air filter.
 

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I believe Enzo Ferrari once said "Torque wins races, horsepower sells cars."

And fmx that is cool about the dyno lines! I had never noticed that before!

Sent from my DROID RAZR MAXX
 
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Torque and HP are mathematically related at every single rpm.

As noted on every single engine torque=hp at 5252 rpms, and likewise hp is 50% of the torque at 2626 rpms, and hp is double torque at 10,504 rpms.

I realize that many people say that hp cannot be measured, only calculated.. But that's not really true. Dyno's measure hp, and need to calculate torque (which is why you have to monitor rpms on the dyno to get a torque graph).

Torque = (HP x 5252) / RPMs's
HP = (RPM x Torque) / 5252
RPMS = (HP/Torque) / 5252

Another way to look at it, if you have a motor rated at 325 hp at 30000 rpms it makes 569 ft/lbs of torque. A motor rated at 325 hp at 6000 rpms makes 284 ft/lbs. If you gear them both to be at their respective rpms at 60 mph they are both putting the same amount of power to the rear wheels. Which means they could both pull the same weight up the same hill at the same speed.

Which one do you think would be faster off the line? The one that peaks at 3000 rpms, as it makes more hp sooner.

If you know torque and operating rpms you know how quickly a motor builds power, the quicker it builds power the faster it can accelerate. Maintaining that speed is dependent on horsepower, not torque. A 200/600 motor will be slower up a grade than a 300/300 motor, if the gearing is correct, even thou it makes 2x the torque.
 

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Torque and HP are mathematically related at every single rpm.

As noted on every single engine torque=hp at 5252 rpms, and likewise hp is 50% of the torque at 2626 rpms, and hp is double torque at 10,504 rpms.

I realize that many people say that hp cannot be measured, only calculated.. But that's not really true. Dyno's measure hp, and need to calculate torque (which is why you have to monitor rpms on the dyno to get a torque graph).

Torque = (HP x 5252) / RPMs's
HP = (RPM x Torque) / 5252
RPMS = (HP/Torque) / 5252

Another way to look at it, if you have a motor rated at 325 hp at 30000 rpms it makes 569 ft/lbs of torque. A motor rated at 325 hp at 6000 rpms makes 284 ft/lbs. If you gear them both to be at their respective rpms at 60 mph they are both putting the same amount of power to the rear wheels. Which means they could both pull the same weight up the same hill at the same speed.

Which one do you think would be faster off the line? The one that peaks at 3000 rpms, as it makes more hp sooner.

If you know torque and operating rpms you know how quickly a motor builds power, the quicker it builds power the faster it can accelerate. Maintaining that speed is dependent on horsepower, not torque. A 200/600 motor will be slower up a grade than a 300/300 motor, if the gearing is correct, even thou it makes 2x the torque.
I'm lost, so how do you go about measuring are motors they don't spin to 5252RPM's, on the dyno TQ and HP meet way before 5252RPM?:confused013:
 

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Discussion Starter · #13 ·
It looks like the discussion is over . . . and just when we had an expert arrive on the scene with information about a dynamometer that measures horsepower and calculates torque!! Sad to let that kind of knowledge go to waste.
 
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No one said it was over.. just no one saying anything else...

There are tools to measure torque and tools to measure horsepower. Dyno's measure horsepower because horsepower is a measure of work over time. A dyno knows the amount of energy it takes to accelerate it's drum. The faster you accelerate it the more hp, i.e. more work in less time. Torque wrenches measure torque because you want to know the total force applied.

Same reason that a truck can pull a hill at 2500 rpms making 600 ft/lbs but has a hard time at 1600 rpms making 600 ft/lbs, 2500 rpms is more hp, so less time required to do the work (thou the same work is done).

Clear as mud?
 

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Think about it like this. Torque is the force behind the rotation of the crank. The more torque, the harder it is turning.

Horsepower is the total amount of power the crank is turning out.


300lb/ft of torque at 150rpm is way, way less power 150lb/ft of torque at 5000rpm because that 150lb/ft is being applied to the crank 33x more often than the 300lb/ft is at 150rpm.

Even though the hits are smaller, there are way more of them, which is actually more power.
 

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I'm lost, so how do you go about measuring are motors they don't spin to 5252RPM's, on the dyno TQ and HP meet way before 5252RPM?:confused013:
When you look at a dyno sheet, one side will have hp and the other side will have tq. The high for hp on the graph is say 500, the high for tq we will say is 1000, since both are on the same graph its going to look like they meet on the graph, but really they are not even close. What they are saying is at 5252 rpms you will have 350 hp and 350tq for example.
 

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Discussion Starter · #17 ·
It looks like everyone in the discussion actually believes that horsepower is a real entity that can be measured directly. So, I have done some reading online about dynamometers. Everything I have read indicates that dynamometers measure torque and RPM. With that, they calculate horsepower. Here is something that I copied and pasted directly from wikipedia on the topic of dynamometers:

"A dynamometer or "dyno" for short, is a device for measuring force, moment of force (torque), or power. The power produced by an engine, motor or other rotating prime mover can be calculated by simultaneously measuring torque and rotational speed (RPM)."

For those of you that actually believe that horsepower can be measured directly, and not calculated, please provide a source where I can go to read about such a device.

Wolfhound
2001 2500 2wd auto, HTT 62/65/13 SS, FASS 95, DDP 75, Banks box, S&B, CFM, Flowmaster
 
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If I could be this interested in learning my college homework I'd have a masters by now lol
 

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It looks like everyone in the discussion actually believes that horsepower is a real entity that can be measured directly. So, I have done some reading online about dynamometers. Everything I have read indicates that dynamometers measure torque and RPM. With that, they calculate horsepower. Here is something that I copied and pasted directly from wikipedia on the topic of dynamometers:

"A dynamometer or "dyno" for short, is a device for measuring force, moment of force (torque), or power. The power produced by an engine, motor or other rotating prime mover can be calculated by simultaneously measuring torque and rotational speed (RPM)."

For those of you that actually believe that horsepower can be measured directly, and not calculated, please provide a source where I can go to read about such a device.

Wolfhound
2001 2500 2wd auto, HTT 62/65/13 SS, FASS 95, DDP 75, Banks box, S&B, CFM, Flowmaster

Torque - Wikipedia, the free encyclopedia


Everything is calculated... It's just a different unit of measure to relay a different set of information.

To say it doesn't exist is like saying Miles Per Gallon is fictional. It has to be calculated, but it is real.
 

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It really doesn't matter, as horsepower without rpms is a useless number, just as torque without rpms is a useless number. If you know any two of the three you can calculate the third.

Horesepower is work over time, a dyno is based on time to accelerate.. Torque doesn't really have a time specification, just total work. So if a dyno just measured torque it wouldn't matter if you took 4 seconds or 80 seconds to get from 0 to 100, it would take "x" torque. HP is the rate at which it got there.

Diesels are great because they do 2x the work (3K rpm vs 6K rpm) of a gas engine for the same hp, they would do it slower than a gas motor with the same torque, but when a gasser and a diesel have the same hp you get more work quicker from the diesel.
 
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