POLL: Is Torque Important?

[Big_Daddy_T]

klenger is right. Low rpm hp is where its at. Its all hp. Once that crank is spinning. There is force and distance present. You wouldnt even explain it as torque. Youd call it hp. Without torque there is no hp. With torque its all hp.

So which would you prefer. Low rpm hp, driveability. Or high rpm hp, racing. I own a cummins because Im a pragmatist. I dont need high rpm hp. I dont race. I do drive and I do tow.

Klenger. Complicating the facts with explanations actually muddles it up more. The simple fact is. Its all hp. You get the hp by measuring the torque and thats what confounds us. Torque is what matters but when your talking about an engine you express it as hp.

 

[MMiller]

Hmm interesting discussion. Every dyno I have been around measures TORQUE, and HP is a number that comes from the amount of torque at a given rpm by a mathmatical EQUATION! I will admit that every dyno I have been around is some kind of brake dyno that loads the engine. None of the accelerate like mad for a little while measurement.



As far as *I* am concerned torque is everything. Without it all you have is a bunch of rpms. The more rpms, the less fuel ecomony. Torque is what is applied to the transmission that twists the shafts. Work around farm tractors, torque is what is doing everything.



Hp is the number used to sell cars, trucks, engines, tractors.



As far as the ford, chivvey, and dodge pulling loads, the factor is which truck is working at the right rpm. Hell a huge torque building engine won't pull for crap if it has way too much gear or is working against the governor all day. Pulling the hills is a package deal, get the whole package working together and you can pass everybody.



What everybody forgets when going down the road is aerodynamic losses. The amount of power that is needed to move the truck through the air. A peterbuilt with dual air cleaners, tall stacks, flat top sleeper, stretch frame pulling a tall reefer will take a BUNCH more power to pull through the air. That guy in the T2000 with full fairings, tight to the trailer can keep up with that pretty pete with alot less motor.



Michael-flame suit is on.

 

[JKlopp]

Well put BIG DADDY

An example claser to home would be the CTD vs the HEMI.

No one will debate who pulls harder and who goes faster.

Trivia..... The CTD has more torque at idle than the hemi does at full power.

 

[rbattelle]

Could it be,... . drum roll here... more HP as RPMs increase.

Could it also be because as RPM increases speed increases? Could it also be because torque rises along with Hp?



Here's the facts that cannot be disputed:



P = dW/dt



The differential equation for power. Discretize that equation and it's just change in work over change in time. Take the average and you get:



Pavg = W/(t2-t1)



Such that



W = Fd



Which is the equation for work (d is distance).



Torque is defined as:



T = r x F



Such that F is force and r is a radius. Note that's a vector cross product, not a simple multiplication. If you don't care about the radial component, then you can make it a simple product:



T = Fr



We conclude from this that power is a rate of work and torque is a moment.



There is no objective argument to say one is better than the other, there is only personal preference. If you want to do things fast, you need a lot of power. If you want simply to move massive objects without concern for how long it takes, you need torque. If you want to move large masses quickly, you need BOTH.



The choice of which is "better" is completely subjective, and everyone's entitled to their opinion. No one is wrong.



-Ryan

 

[Big_Daddy_T]

Reminds me of that song. "You cant have one without the other". When talking about an engine. Torque and hp are pretty much the same thing. If you say 600 lb ft at 1400 rpm. I can tell you what hp you are making. If the engine wasnt turning and it created force then yeah you could talk about torque. But it is turning. Because it is turning you have distance and time. A lb ft is whats present at the end of a 1 ft bar. So picture in your head a 1 ft bar moving in a circle. It moves just over 6 ft per revolution. So we have distance 6. 24 ft. We have time with per minute. Distance and time with force(torque) is called hp. Force distance time. HP. RPMs plus torque = hp. I understand 600 lb ft at 1400. Itll move one hell of a load. But because you have force distance and time its called hp. Now if the load didnt move. Then you didnt make any hp. Cause somethings gotta get done to call it hp.

 

[Big_Daddy_T]

I didnt answer the original question. What makes the cummis awesome is the gobs of torque it makes at low rpms. I dont really care if I have over 225hp. Hp never really meant that much to me. The rpm that you make the hp at is whats really important. Thats why I love diesels. No gas engine makes this much torque so low in the rpm band. The more low rpm hp you have the better you move a load. Thats why low rpm torque rocks. There is no discussion about hp or torque. They are the same thing. Just at different ends of an equation. Ill take a torque monster any day over a high revver. So 600lb ft and 200 hp over 300 hp and 300 lb ft. Even though the 300hp engine is faster. We didnt buy a diesel to race. LOL. Well, things are different nowadays.

 

[C Schomer]

The more tq. you have, the faster you get to the peak HP. High tq. #s come from low end fuel. High HP #s come from top end fuel. If you have both, you accelerate faster and hold the top end better. I voted the top answer because of our low end tq. From what I've read, the v8s don't have much below 2k rpm. Mine dynoed 292/812, in Castle Rock, and I could pull the Co. passes faster in 4th at higher rpm than I could in 5th, near the peak tq. rpm - and 5th gear thanked me! Craig

 

[NIsaacs]

I am not inteligent enough to understand the scientific explanation of HP vs torque. However I do know that an 855 Cummins Big Cam III w/400hp and 1400 ft. lbs. of torque in a class 8 truck, will blow the doors off an identical class 8 w/400hp and 900 ft. lbs. of torque, 5. 9 Cummins.



I also think that a high torque, low hp, motor with lots of gears, with out pull a high hp, low torque motor with just a few gears. So maybe the torque multiplication of any givin vehicle has something to do with how it pulls or accelerates. Like Craig said, he could pull the Colo. hills faster in 4th at high rpm, than he could in 5th at low rpm. With the torque multiplier of 4th vs 5th, he was actually sending more torque to the rear axle. Does this make sense?





"NICK"

 

[J&LRam]

there is a good articale in TDR mag issue number 45 , page 24, from Joe Donnelly and Doug Leno about torque/horse power.

For my use ,torque in towing is the biggest factor in the engine being able to tow 12000 lb down the road at a RPM that doesn't eat up more fuel. BUT, when the 6-8% grades are to be tackled then RPMs need to come up for the engines horse power to help the torque get my load to the top. With high RPMs [more HP] I'm using more fuel and as soon as I can I lower RPMs and stay in peak torque to go on down the road. You need both to tow but torque is used more in towing .

Boggers, sledders, drag racers use the higher RPMs [HP] to accelerate but then the 600 ft/lb moves the load until HP can come to play... ... .

 

[Kennywould]

http://www.revsearch.com/dynamometer/torque_vs_horsepower.html

 

[RustyJC]

I can say my truck (which is BOMBed for towing a heavy 5ver - see signature) has a high torque rise configuration. I can say it makes good torque down low. I can also say that it makes more horsepower at 2350 RPM (my 70 MPH cruise) than my previous V-10 Ram gasser. All of these are true, but the engine doesn't give a hoot. It just yanks that 16,000 lb GVWR 5ver up a 6% grade at 70 MPH in 6th gear without downshifting - the previous V-10 (which made peak BHP at 4000 RPM and peak torque at 2800 RPM) was at 3500 RPM at 55 MPH in 2nd gear (47RE with 3. 54 axle) to pull the same grade with our previous 13,500 lb GVWR 5ver!



Rusty

 

[Sled Puller]

Well Rusty, you just needed 83 more gears, to make the gaser run properly.



I'm sure it will be an option on newer trucks!!!LOl



So- did the gasser fail in the torque department, or the HP department?

 

[RustyJC]

Well Rusty, you just needed 83 more gears, to make the gasser run properly.

Actually, Sled, that's more true than you think. Part of the problem was the wide gear split between 2nd and 3rd on the 47RE - you had to wind the heck out of the V-10 in 2nd to hold 55 MPH because 3rd was geared too high and the engine couldn't hold speed in 3rd.

So- did the gasser fail in the torque department, or the HP department?

Yes.



Rusty

 

[C Schomer]

HP is still more important for speed but you've got to have the right gear to utilize the peak hp. With my 3. 54 diff and 245 tires, 4th gear is perfect for the majority of hard pulls. 4th gear tops out about 68 mph and is perfect for my load. By using 4th on the passes, I'm in my peak hp area and is faster than 5th and being in my peak tq. area. HP is the ability to do work and the more hp, the more work. As long as the peak tq is at lower rpm than the peak hp, you won't be able to do as much work at the peak tq rpm - given you have the right gear for each. Craig

 

[Big_Daddy_T]

Peak torque is always at a lower rpm than peak hp.



You cant do as much work at peak torque. But not always is peak hp required to do the work at hand. If you only need 150hp to do the work at hand. Then you can do the work at peak torque. I dont tow at peak hp very often. So peak hp isnt needed very often. Most of the time its somewhere between peak torque and peak hp where you will do most of your work. Sled pulling and racing being different from every day driving. Most of the time we will only use 50-100 hp to maintain speed. The heavier the load and the more the wind resistance. The higher the number.



Peak hp is only present under load at full throttle at the peak hp rpm. Just because you are at 2700 or 2900 rpm. Doesnt mean you are making peak hp.

 

[EMD Diesel Power]

That is absolutely true: torque is not a force. Torque is a force applied across an arm, also known as a moment.

Theres a contradiction in terms..... Torque isnt a force.....



yet the definition said here is: Torque is a force... ...



One of the reasons I dont argue about it... . I know whats right and everybody else can figure it out on thier own. I've got an degree in engineering. :-laf :-laf Doesn't mean much though!



PS... yeah I edited it... . original post didnt come out right! Oo. Oo. Oo.



And yes... . its all fun and games!!! I'll post my opinion later... . too busy to think about it right now! :{

 

[rbattelle]

One of the reasons I dont argue about it... . I know whats right and everybody else can figure it out on thier own. I've got an degree in engineering.

Ouch! Be cool, EMD... this thread is meant to be educational! An engineering degree is not a license to dismiss others' ability to grasp abstract concepts nor their capacity to learn and understand new things. Everyone deserves respect for their individual mental capacity whether they have a fancy-pants engineering degree or not. Since you're obviously an extraordinary engineer, share some of that knowledge with the rest of us common folk!



Perhaps I should correct myself: torque is not a force, torque is a couple.



All in good fun. .



-Ryan

 

[AKAMAC]

A quote from Kennywoulds' link;



Here's an interesting bit of trivia; below 5252 rpm any engine's torque number will always be higher than its horsepower number, and above 5252 rpm any engine's horsepower number will always be higher than its torque number. At 5252 rpm the horsepower and torque numbers will be exactly the same.



I must have missed something... ..... Do diesels behave differently than the laws of physics dictate? Torque is a measureable "force". HP is a timed application of force. I can calulate the required HP for a motor with a given head pressure and GPM, I can't factor the required torque of said motor without taking into account the GPM required for the flow application: This would be reverse calcs for acquiring HP for TQ.



Just look at the average electrical motor. It is rated in HP. Also note that it has a given RPM. The motor has torque rating that is the constant for rated RPM... ...



Guess what that torque # is... ... .....



Torque is king.

 

[Animal]

The easiest way I’ve found to explain HP verses TORQUE is to use this analogy.



You have two guys that can lift their weight (TQ), one weights 300lbs. the other weights 150lbs. They have to move two weights weighing 150lbs each. They both can do the work in the same amount of time (HP).



So to do the above work both can do the job, but lets change it around a little.



Now the weight they have to move is one 300lb. Item, which one can do the job?



Enough said!

 

[Big_Daddy_T]

You cannot express work as torque. Work is horsepower. If you are moving a load. You would express it in hp. You can actually figure out exactly how much hp each task will require. Right down to climbing a 6% grade at 65mph. Or just maintaing speed without a load. When talking about moving objects. Its hp. The sooner you make the hp you need to do the work. The easier it is. A cummins can do the work at 2000 rpm that would take a gasser 4000-4500 rpm. Same amount of work. Twice as much force. Force is just force until something moves. Once it moves you call it hp.



I know Ive repeated myself a bunch. Just remember if somethings moving call it horsepower.