just out of curiousity, it may seem like a dumb question, but whats better - lots of horse power or lots of torque?

or is it the key to a strong running motor balance between both. looking to see ppls opinions on this.

 

I have always liked a little more torque -- especially for a street car -- than horsepower. On the street, light to light, traction being equal, torque rules!!

 

Torwue is mans best friend. That is what gets you moving and dictates acceleration. HP is what pulls you once your up and running.

Application dictates which would be better per application.
Drag racing a heavy car you need lots of torque, but too much and you have serious traction problems. Drag racers with light cars need little torque since they dont have much mass to put in motion and just needs lots of hp to pull it hard once it's going.

Street cars want torque. All most guys do is stoplight action, so by keeping all the power needed to get you up to speed, you dont have much need to let the hp kick in and pull you in top gear.

Just my opinion.

 

so then with more emphasis on torque being required to move the car, and hp for the top end and higher speeds, what kind of cam would I want in my TPI 350 sb?
the cam thats in the motor now has a 455 lift intake and exhaust, im thinking its a little weak.

 

Torque is the derivative of hp or essentially work. Hp is how much work you can perform per unit time, or the intergral of torque.

Hp is a calculation derived from torque. You can't have just torque and you can't just have hp, because you always have both at the same time.

What we are talking about here is peak hp and torque. The people that know what they are talking about don't care about peak numbers but average or area under the curve. Peak numbers are essentally meaningless, and only good for bragging rights.

The only ways peak numbers would be worth a damn at all is if ithe engine was connected to a CVT. But as of today all current production CVT's are pulley designs that can take very limited (small ) loads.

Its all about area under the curve. Choose a rpm range where you will normally want to make your power and build the engine for that range. This will give you the greatest area under the curve or average power.

 

Lift has little to do with power. Duration, and lobe angle are the key factors when specing a cam to a motor and it's intended purpose. There are so many factors that dictate what the grind should be to optimize performance I always suggest calling the manufacturer for their input since this is their bread and butter. Ask the specailists becasue you will get nothing but the old Comp 268 answer on this board, nothing wrong with it, but there are other grinds that will make just as much if not more power.

http://www.bulletcams.com/

I'm sold on these guys, I'm using alot smaller lift cam than 2 other set-ups almost identical to mine and both are running 13.5 compression, 670/720 lift, identical lsa, and almost almost dead nut duration. Theyre 300lbs, and 700lbs lighter and I'm running only .1-.2 slower with ALOT less compression and pump gas. Both other cams are Comp, mine is Bullet. Give them a call and see what they say, price is same as others, I got mine 1 week after I placed order and will buy from in the future!

 

I'm an Engineer by Trade. I'm not a mad scientist/physicist, nor does my car run in the 7s qtr mile, and not tying to get a post locked by starting an argument.........
However, I believe (from my experience) that there is some good information, but mostly bad information, in the post above.
That's all I have to say about that.

 

can you expand on this, whats your thoughts?

 

I mostly agree with you "me leigh". HP is a function of torque and technically speaking you can't have one without the other but that's really splitting hairs. True, peak hp #'s are pretty much for bragging rights (ie: a VTEC making 200hp at 7000rpm really serves no purpose because how often does that VTEC even drive around 7000rpm), but it is an indication of what a motor is capable of. Peak hp is strictly a "for reference only" number imo. The area under a curve (integral) is what you really want, and you really want most of that area in the rpm range of your application. So you pretty much summed it up.

(also an engineer by trade/degree)

 

Build an engine for tq. Hp will take care of it's self. A nice even tq. curve throughout the RPM range of the motor.

No I did not mean a desel before someone brings it up. Apples and oranges.

 

Consider for a moment that a given TQ at a given RPM is always a given HP...no matter what the engine.

HP = TQ x RPM/5252

People tend to think of HP and TQ as two different forces when one, TQ, is a force (force does NOT constitute work, action, or movement...three different words that say the same thing) and the other, HP, is a measure of work. HP is simply a measure of what happens when TQ does what it's trying to do...move a resistance. It describes how much resistance the force is able to overcome (move) in a given amount of time, or you could say it describes how much potential it has to accelerate a resistance (mass and weight.)

To expound a little more, which scenario has the potential for accelerating a given object faster…1000 ft lbs of TQ at 2000 RPM or 250 ft lbs at 8000? Answer? They have the same potential. Why? Because each scenario describes 380.8 HP. They have the same potential for accelerating a given object. It is the HP number you need to be concerned with. THAT is your measure of work performed and potential for work (acceleration.)

Looking at TQ would suggest that in a perfect world, we'd want the RPMs to come up to the peak TQ RPM and then stay there all the way down the track. Well, I can tell you, that would make for one dogass slow run.

TQ and HP are not an either/or thing. It's not a one or the other is a better thing. It's realizing that they are, in a sense, the same thing! Yes, TQ is completely and 100% important IF, and let me say again IF, we include the RPM that is associated with whatever figure we're talking about. If I say 500 ft/lbs of TQ and nothing else...what does that mean in terms of acceleration potential? It means NOTHING! Now, if I say 500 ft/lbs of TQ at 5000 RPM, what does that mean? It means 476 HP and THAT tells you of the potential for moving an object (which is to say, the potential for performing WORK...which is what HP is...an expression of work.)

You want the most HP laid to the ground over the course of the 1/4. That's the true but short answer. How to determine what shift points and converter this relates to is a lot more complicated. The peak HP and TQ figures have very little to do with this. The power curve (from well before and well after the HP peak), the gearing of the tranny, the converter characteristics, and the inertial properties of everything that rotates or reciprocates in the drivetrain and engine all play together to determine this.

 

Let's check your math & physics work here:

1000 lbs-ft of torque, multiplied by a 3.06 1st gear (TH700 style), multiplied by your run-of-the-mill 3.08 final gear ratio, with a 14" tire "lever" (28" diameter tire), would produce approximately 8000 pounds of "thrust" against the vehicle weight and rolling resistance. For the sake of simplicity, let's say that's 4000 lbs. That's a 2:1 thrust to mass ratio, or 2g.

Now, 250 lbs-ft of torque, multiplied by a 3.06 & 3.08 gear set, with a 14" radius tire, is approximately 2000 lbs of thrust - same 4000 lbs mass & rolling resistance, that's a 0.5:1 thrust to mass ratio, or 0.5g (I know, I know, "pounds" isn't "mass", but they ratio the same).

Still say 380 HP is 380 HP?

 

while I agree with you five7kid... I think that what he meant was that the 1000ft/lb torque machine would need to run the track through it's torque peak at a low RPM, then bang the gear, then go up to it's low RPM redline again, do it all over. Where the other one would run the track through less gears because of a higher redline, and more constant/flat torque curve. While his logic makes sense... it is flawed in some aspects...

We arent trying to re-create the wheel here... this is all already figured out.

 

Jeez, talk about some bickering in here.

I can tell you whats best. Whatever you want. Some guys build thier car to perform best for the street, with a lower RPM higher torque engine, others do it the other way, with a High RPM high HP engine.

Personally, I dont mind my car being more optimized for the track, and less for the street. I dont from stoplight to stoplight, I just like to bait 'em.

 

You can think whatever you want, torque is not a force, it has the same units as work, look it up.

I am a mechanical engineer so...

There is no such thing as a torque motor or hp motor, just different rpm ranges where power is made. People just simplify it like that because peak tq occurs before peak hp.

TQ simply mean how much work you can do, hp is how fast you can do that work. Look at semi's or diesel engine in general. They can performe lots of work because they produce lots of tq, but they can't perform that work very fast.

 

One small problem...the equation doesn't take into consideration RPM (afterall, we can't leave the line at zero RPM.)

"Torque is determined by multiplying the applied force by the distance from the pivot point to the point where the force is applied." This distance is not referencing movement. It's measuring the length of a lever and multiplying that by the force applied thereby giving you the rotational TQ at the center of rotation.

Once movement takes place then work has taken place (a certain amount in a certain time) and this is measured by HP.

TQ at the wheels (more accurately, TQ at the contact patches) is not the same as TQ in ft/lbs at the crank.

To calculate the TQ at the ground at a given moment you would need to know the HP at the crank and the overall gearing...not the TQ at the engine. You would also need to account for drive-train losses.

Consider 100 ft/lbs at 1000 RPM v/s 100 ft/lbs at 10,000 RPM. In the first case we have only 19 HP. In the second case we have 190 HP. Think about it...if properly geared, in which case are we going to be accelerating quicker? That's right, 190 HP beats 19 HP if geared correctly and all else being equal.

Another example:

1. 1000 ft/lbs of TQ at 1000 RPM = 190 HP
2. 250 ft/lbs of TQ at 10,000 RPM = 476 HP

In case one we have a tremendous amount of TQ, or rotational force, with very low HP. In case two it's just the opposite. Which goes down the track quicker? To anyone who understands drag racing, case #2 blows away case #1 by a VERY wide margin to say the least.

I think there’s confusion with TQ at the contact patch with TQ in ft/lbs at the crank. Rethink that notion, considering gearing, and you'll understand why neither peak acceleration nor peak TQ to the ground is reached at the engine's peak TQ RPM.

In an ideal world, we'd all have infinitely variable ratio transmissions that would allow the engine to operate at its peak horsepower RPM 100% of the time, and convert the engine RPM to the changing wheel RPM."

Take a manual car (TQ converters change things up tremendously), and let off the gas at the HP peak in 1st gear and then slam it back to the floor just as the front suspension starts to rebound. Do the same at TQ peak. You'll be surprised.


But, to answer the original question more generally...


I'll quote David Vizard's book "How to Build Max Performance Chevy Small Blocks"
"Once you have grasped this you will realize achieving your target power is a matter of generating as much torque as possible within the RPM limits imposed by the parts available."

That is not my intent...and my apologies if my comments are taken as so. It's better to get off to a good start with good fundamentals and understanding than the alternative. A good, lively discussion where open-mindedness is used can only enhance the positives. Usually not the case, though, no matter how hard some try.



HP IS in fact a measure of work (it's very definition is "a unit of power"). The definition of "power" is "the ability or capacity to do something"...(that something is work) and TQ IS in fact a measure of force...rotaional force to be more exact.

We can all agree to disagree, then. We're all after the same thing anyway.

See you at the finish line!

 

I don't know where you went to school. If it will be easier for you 1hp is equal to 745.70103354 watts a unit of power, or 550.0007457 foot-pounds force per second.

 

Work- Abbr. w Physics. The transfer of energy from one physical system to another, especially the transfer of energy to a body by the application of a force that moves the body in the direction of the force. It is calculated as the product of the force and the distance through which the body moves and is expressed in joules, ergs, and foot-pounds.

Power- Physics. The rate at which work is done, expressed as the amount of work per unit time and commonly measured in units such as the watt and horsepower.

 

You blew it by saying that. A monkey on a 6 week power course can drive a train.

 

Why did you edit out the mechanical part? I am a mechanical engineer, and don't have to prove anything to you guys. Infact i could care less, think whatever you want. But by being wrong and spreading it, you make everyone else stupider.

 

Your'e a what? Editing engineer?

Anybody can run a word processor.

Sounds like you are getting a little hot under the collar. Relax, it's just a bunch of gear heads yacking.

 

No, i am just wondering why you edited out "mechanical" in what i originally posted.

I originally posted " I am a mechanical engineer so..."

An was just wondering why you took it out, thats all.

Oh yeah and i hate it when people are worng, because it makes everyone stupider. But hot under the collor, not even close.

 

I took it out cause I was wondering if you were one of those types that would blow your lid over it.

For future reference, please spell wrong "wrong" and not worng when using it in a sentence to describe stupid people. Would make you look smarter.

 

Blah blah, we all make type o's, who give s.h.i.t.? Seems when it comes right down to it, IMO, when a person starts nit picking the "little" stuff, that in itself is a sign of being flustered!

Anyways, I'll build my motor for torque

 

I never said i wasn't stupid.

 

 

As has been pointed out, the two concepts are related mathematically. Distinguishing between them is largely irrelevant. In the McDonald's parking lot where corporal punishment is inflicted upon simians, a car with "torque" pulls hardest at low RPMs, a car with "HP" pulls hardest at high RPMS. There isn't much more to it than that.

Rear-wheel torque accelerates the car. Peak acceleration occurs at peak rear-wheel torque. In a drag car, the engine is built with as high a powerband as possible, since this allows the use of lower gears for more torque multiplication, which results in more rear-wheel torque.

In a street car however, you don't necessarily want to be winding the engine out to 9000 RPM between stoplights, so most people prefer engines with low powerbands.

 

That's a good way to sum things up...

I'd like to also add, that by hp being the product of torque by RPM/5252... that if you build your engine for high revving (say, 9000 RPM) then your variable of RPM will make the horsepower number a hell of a lot higher, than if that same amount of torque was at a lower point...

for example.

Say you had two motors, both with peak torque number of 450, and you're wanting to make this car win drag races. Which motor do you put in it? One of the motors has a peak torque at 5000RPM, while the other has a peak torque at 9000RPM.

You'll probably want to put the motor in that has the most HP if you want to be winning drag races, right? Well, let's find out how much horsepower each should make at it's peak.

since tq x RPM/5252 = hp

5000 RPM motor
450 x 5000/5252 = 428.4 HP

9000 RPM motor
450 x 9000/5252 = 771.1 HP


Now, which one would I take the to drag strip with me? The 9000 RPM peak torque motor!

Which one would I put in my daily driver, or weekend warrior? The one that gets winded at 5000RPM. (actually, neither, that "5000 RPM motor" wouldnt be too streetable lol, but the "9000 RPM motor" would NOT be streetable).

This is all motor related though, the tranny gearing, the rear differential gearing, your suspension setup, etc, etc, etc, all has a play in what you can get from your car.

If you are asking what is better, HP or TQ... I'd have to tell you... RPM

I love my low-end, but if all you're looking for is some numbers (be it from a dyno, or a time card) then RPM is where you'll find it... Build your car to have maximum efficiency at the higher RPMs and you'll fly like a rocket..... you just wont be driving to the drag strip ;-)

 

Thinking you have to choose between torque or HP truly is "inflicting corporal punishment upon simians in the McDonald's parking lot". So is re-inventing the wheel http://www.carcraft.com/techarticles/868/index.html .

One of the nasty characteristics of physics is that, unlike the philosophy department, what we "think" doesn't change what "is".

 

WOW you guys are eather really smart or over thinking this HP stuff. You be the judge!

How do you guys sleep at night with all this on your mind?

 

With the help of my good friend 1,2,3,4,10,14b-hexahydro-2-methylpyrazino [2,1-a] pyrido [2,3-c] benzazepine

 

 

...which is cheaper if imported from Canada...

In a National Dragster magazine a couple of months ago, they had a column in the back by either Reher or Morrison (I forget which - don't have the copy in front of me - and probably don't have the spelling right). He said power is all about getting the most fuel & air burnt in the cylinders in a given amount of time - it doesn't matter whether you do it with big cubes at low RPMs or small cubes at high RPMs. He went on to say he was spanking Super Stock 440 Cudas back in the early 70's with his 1st gen 302 because he was winding it to the moon while they relied on their cubes - well, maybe so, but you can guess which would be easier to drive on the street. And, of course, that part of our sport is heavily influenced by the rules imposed upon it...

How do I sleep at night? My brain gets so worn out it just gives up.

No, wait, that's what happens at work...

 

To clear up definitions I'll quote my Physics Book for Engineers, and Marlan Davis (probably more intelligent than all of us clones combined)...I'll try to quote pertinent information instead of rewriting the whole book, of course.

WORK
Consider an object that undergoes a displacement s along a straight line under the action of a constant F...
The work done by the constant force is defined as the product of the component of the force in the direction of the displacement and the magnitude of the displacement.
Work is done by F on an object under the following conditions:
1) the object must undergo a displacement
2) F must have a nonzero component in the direction of s.

From the first condition, we see that a force does no work on an object if the object does not move. (s=0). For example, if a person pushes against a brick wall, a force is exerted on the wall but the person does no work since the wall is fixed.

TORQUE
When a force is exerted on a rigid body pivoted about some axis, the body will tend to rotate about that axis. The tendency of a force to rotate a body about some axis is measured by a quantity called torque. It is very important that you recognize that torque is defined only when a reference axis is specified. The moment arm (or lever arm) of the force F, represents the perpendicular distance from the rotation axis to the line of action of F.

POWER
Power is defined as the time rate of energy transfer. If an external force is applied to an object, and if the work done by this force is "delta"(change)work in the time interval "delta"time, then the average power during this interval is defined as the ratio of work done to the time interval.


Marlan Davis's words for Simplification

WORK EXPLAINED
Force is a pulling or pulling action of one body against another. Depending on the resistance to the application of the force, it may or may not result in movement. If force is applied and movement does occur, you've performed work, or the movement of an object from one position to another.
Work = D (distance moved) x F (force applied)

TORQUE EXPLAINED
By definition, work is calculated as a vector force, exerted in a straight line. But engines (as well as nuts and bolts wehen tightened or loosened) rotate around an axis. The expression of this rotational or twisting force is called "torque", which is measured in units of force times distance from the axis of rotation. When an engine is said to make "200 lb-ft of torque", it means that 200 pounds of force on a 1-foot lever is needed to stop its motion.
To avoid confusion, the unit of measure for torque is the pound-foot (lb-ft), while for work it is the foot-pound (ft-lb). Remenber, work and torque aren't exactly the same. Movement must occur for work to be done, but that is not true for torque. Exerting 10 lb-ft of torque that has been tightened to 50 lb-ft won't produce any movement.
If torque does produce movement---as is the case with your engine---any "distance" traveled as the crank rotates is equal to the circumference of a circle, not a straight line ... so 1 lb-ft of torque produced during one revolution actually is about equal to 6.28 ft-lb of work or mechanical energy:
2(pi)r x 1 lb-ft of torque = 2 x 3.1416 x 1-foot lever x 1 lb-ft = 6.28321 ft-lb of work.

POWER
An expression of the rate or speed at which work is performed.
------------------------------------------------------------------
We've been through it already....TQ X RPM = Power.
Yes, if you build for torque power will result...just re-read my previous posts.

...what I posted previously holds true:


All of the above is also recognized by the NCEES (National Council of Examiners for Engineering and Surveying)

"Click" yet?

 

=============================

" " I don't know where you went to school. If it will be easier for you 1hp is equal to 745.70103354 watts a unit of power, or 550.0007457 foot-pounds force per second. " "

================================


Ah, the key here is this: "foot-pounds force per second". That is a rate, "per second".

Same as power is a rate (watts), joules per second, in this case, if I remember correctly. So if you have foot pounds per time, that is power.


But the torque of an engine in foot pounds is not a unit of power.


<<------------ mechanical engineer in training who is killing time in the computer lab before class

 

I say build the motor that has its torque band where you need it. If the powerband doesnt match the setup then not much else matters...

<------- Mechanical engineer thats too lazy and time strapped to build the motor he really wants Some day...

 

Im working... Im just resting my eyelids for a minute.

 

good call deep. (im not gonna quote your whole post)

torque
noun
a force which causes something to rotate

thats all i was gonna post.....

thats right outta the dictionary...

 

We dont race calculators.

Call Bullet cams and answer the questions that they ask. You will get the right cam.

You will be happy and your car will perform well without knowing how much power it has.

 

NUFF SAID!!!! More with Less in the cam department.