HP vs Torque!?!

[chevyguy8413]

All about the torque.

What he said....steeper gears multiply torque (spin tires on pavement) but do not change h orsepower. Sometimes it is thought horsepower changes but the performance improvements ...."dig off the line" are all about torque multiplication and 1/4 mile improvements benefit from the engine's spending more time in its power band....are still derivative of the tractive effort which is a function of torque.

[BlackLT1Z28]

People drive torque but buy horsepower.

[Hot Black Trans-Am]

The simple way.

Low end = torque
high end = horsepower

If you want to feel the difference drive an S2000 that has no torque, but some good horse power then drive a diesel truck that has lots of torque and not much horse power compared to torque. You'll get the idea and know why it's good to have it balanced.

[BlackLT1Z28]

That's because of the formula:
hp=(torquexRPM)/5252
The higher the RPM's, the more power you'll generate, even if torque values stay constant or dwindle. Increase the RPM's, increase output.

[Krazy351w]

The simple way.

Low end = torque
high end = horsepower

If you want to feel the difference drive an S2000 that has no torque, but some good horse power then drive a diesel truck that has lots of torque and not much horse power compared to torque. You'll get the idea and know why it's good to have it balanced.

i know what u mean about that comparison. i had an 89 f150 with the inline 300 and someone had put one hell of a low rear end in it and put the fuckin tranny outa a diesel in it. i swear i could out pull a f350 or gmc 3500 but i could only go like 45mph tops cuz of the rear end. those inline 300's had like 150 hp but torque out the ass

[BlackLT1Z28]

Trucks have loads of low-end-torque, because truck, in general, are used for towing, not top end racing.

[Chris Arnold]

I'm an engineer and a physics major. I'm going to try to seperate what's wrong from what's right for those who are trying to learn. I suck at explanations and teaching. So, I'll leave that to others unless someone feels like arguing about it, but here are some notable posts:

This is about the best explanation that can be given in such a short post, excellent!:

Ok in physical terms , think of torque as the force produced (how intense the combustion cycle is) and horsepower is the accumulative effect of these cycles as RPM increases. Torque is frequently thought to be a function of displacement, when, in fact, other factors weigh heavily, as well....they all relate to air flow into the engine/cylinder filling. Horsepower is an indication of how high on the RPM curve the torque values are being maintained. Torque is measured; horsepowr is calculated from the torque and rpm by the following: BHP = (RPM x Torque)/5252

This explanation is really terrible and some of the things stated are almost completely backwards. Ignore pretty much everything in it except the first 3 lines:

HP=(torquexRPM)/5252

Torque is a measure of twist and is the amount of work an engine can do.
Horsepower is derived from torque (as from equation) and is a measure of how fast an engine can do that work.
If you look at a dyno sheet, you'll notice that at 5252 RPM's, horsepower and torque are equal to each other.
But having a high horsepower engine isn't neccesarily better than a high torque engine. And this is where gear ratios come in. Torque is multiplied by the gear ratios, but horsepower is not. Horsepower is a function of RPM, so when the gear ratio changes (shifting) the RPM's change also.
This is why high torque engines and high revving high horsepower engines can perform similarily on the streets.
Sure, making a crap-load of torque at a very high RPM would yield high horsepower output, but making huge amounts of torque at a high RPM as opposed to a low RPM are two different things. Making torque at a lower RPM is more useful than a higher one. But this is how cams increase engine performance. Cams can move the torque band of an engine by increasing the fill-rates of an engine to a higher RPM. Since torque is the amount of work that can be done, and the most power comes from large fill-rates of a cylinder, filling that cylinder more effieciently at a higher RPM can yield more power, but a loss of torque and power down low.
Sorry for the long post. Let's put it this way.
Torque is for burnouts and horsepower is for moving down the track.

The following post brings up an interesting point, but the author is wrong. HP is the determining factor. The most force that can be created at the rear wheels will always be at the engine's peak horsepower if geared correctly. So peak acceleration or towing ability of each engine would be exactly the same regardless if one were 600hp/1200 ft-lbs engine or a 600hp/300ft-lbs engine. The thing is, towing motors usually make more low-end torque, because towing at a low rpm is more engine friendly than towing at 10,000 rpm for example.

tourque is how much you can do HP is how fast you can do it.... if oyu have 1000ft/lbs of tourque and 10 hp you can haul a couple semis down the road but you won't do it very fast....

Or if you have say a Honda S2000 with almost double the HP vers the tourque you can't pull as much but you can do a little very fast.

My .02 but They go hand in hand with each other in the grand scheme of things. and like building an engine you have to balance every thing out for your car as a whole.

This is another poorly researched post. I'm sorry to pick on you, but you're putting out a lot of bad info. I didn't even realize you were the same guy I wrote badly of before until I already replied to this post. The constant 1/5252 is not exclusive to any car or even to the internal combustion engine. It is just a constant used to get from TQ to HP. You could use the same formula on a steam boat wheel, or a windmill, or a vacuum cleaner, electric motor, etc... Revability of engines has nothing to do with the amount of torque produced. Pushrod engines are at an inherent disadvantage to overhead cam engines. If you go with a solid roller camshaft, that disadvantage is negated and there is no reason a big block (internally balanced) couldn't run the same rpm that any other car could. Why rev higher with your LS1? B/c your max hp would be proportionately higher, and your ability to accelerate would also be higher.

Yes, ALL engines (well car engines) are rated using the constant 5252. I don't remember exactly how that term came to be, but it has something to do with assumed travel, crank swing, and piston inertia that all engines inverably have. I won't get into that. But it's a constant based on the physics of a 4 stroke engine.

As for the second question, big block don't rev that high because of the amount of torque they can produce. Torquey pushrod engines are limited to their lower rev limit because of physics and their characteristics. That's why OHC engines have the ability to rev so much higher, but they don't make as much torque (power) down low.

And this will be a life-long debate, which is better, high-revving OHC motors or the lower revving monster torque engines? Both have trade-offs. But the thing that us GM pushrod guys enjoy is the fact that we DON'T have to rev so high to achieve max power. Why rev all the way to 9,000+ RPM's when we only have to get to 6,200 RPM's to reach maximum horsepower?

But torque and horsepower are essentially used to measure the same thing; go-juice.

This is a good point (whew, I agree with you):

That's because of the formula:
hp=(torquexRPM)/5252
The higher the RPM's, the more power you'll generate, even if torque values stay constant or dwindle. Increase the RPM's, increase output.

[djvaly]

I'm an engineer and a physics major. I'm going to try to seperate what's wrong from what's right for those who are trying to learn. I suck at explanations and teaching. So, I'll leave that to others unless someone feels like arguing about it, but here are some notable posts:

This is about the best explanation that can be given in such a short post, excellent!:



This explanation is really terrible and some of the things stated are almost completely backwards. Ignore pretty much everything in it except the first 3 lines:


The following post brings up an interesting point, but the author is wrong. HP is the determining factor. The most force that can be created at the rear wheels will always be at the engine's peak horsepower if geared correctly. So peak acceleration or towing ability of each engine would be exactly the same regardless if one were 600hp/1200 ft-lbs engine or a 600hp/300ft-lbs engine. The thing is, towing motors usually make more low-end torque, because towing at a low rpm is more engine friendly than towing at 10,000 rpm for example.


This is another poorly researched post. I'm sorry to pick on you, but you're putting out a lot of bad info. I didn't even realize you were the same guy I wrote badly of before until I already replied to this post. The constant 1/5252 is not exclusive to any car or even to the internal combustion engine. It is just a constant used to get from TQ to HP. You could use the same formula on a steam boat wheel, or a windmill, or a vacuum cleaner, electric motor, etc... Revability of engines has nothing to do with the amount of torque produced. Pushrod engines are at an inherent disadvantage to overhead cam engines. If you go with a solid roller camshaft, that disadvantage is negated and there is no reason a big block (internally balanced) couldn't run the same rpm that any other car could. Why rev higher with your LS1? B/c your max hp would be proportionately higher, and your ability to accelerate would also be higher.

This is a good point (whew, I agree with you):

I graduated engineering school 6 yrs ago.. I agree with most of the above explanations.. they seem very reasonable..

[Chris Arnold]

I'm confused... are you agreeing or disagreeing with me?

[djvaly]

I'm confused... are you agreeing or disagreeing with me?

agreeing, that's why most of them comments are good some get ambiguous but for the most part they are ok.

[Phlash_riot]

So what are the losses for a higher RPM car? Do you get anything lost in the fact that the piston has to go one way(combustion phase) then stop then go in the opposite direction?

I would THINK that you would lose more HP the higher yo go because the amount of up and downs is a loss in power.. it takes power to start and stop those pistons hence why a rotary engine has so much HP for such a smaller displacement......

[BlackLT1Z28]

Ok,
I understand why you disagreed with some of the things I said, because I didn't explain myself fully or just didn't type what I meant.
But some of my other things are fact and shouldn't be included with some of my other neglected statements.
Torque is multiplied by the gear ratios.
At 5252 RPM's, torque and horsepower values are equal.
An increase in VE (volumetric efficiency), hence, an increase in fill rates, will produce more torque, because more work can be done by the engine.
I never said that the constant 1/5252 was JUST for internal combustion engines, I just didn't know if it could be applied to other engines, therefore I just put in parenthesis (well, car engines) to define the fact that I was relating to car engines.
And I never said that big blocks couldn't rev higher. They just don't need to. If they did, they would run out of cam real quick and output numbers would drop off. By design, cams only have one RPM value that will yield maximum power. That's why high-end cams don't produce lots of low-end torque and why low-end torque cams run flat in the upper RPM ranges.

[djvaly]

Ok,
I understand why you disagreed with some of the things I said, because I didn't explain myself fully or just didn't type what I meant.
But some of my other things are fact and shouldn't be included with some of my other neglected statements.
Torque is multiplied by the gear ratios.
At 5252 RPM's, torque and horsepower values are equal.
An increase in VE (volumetric efficiency), hence, an increase in fill rates, will produce more torque, because more work can be done by the engine.
I never said that the constant 1/5252 was JUST for internal combustion engines, I just didn't know if it could be applied to other engines, therefore I just put in parenthesis (well, car engines) to define the fact that I was relating to car engines.
And I never said that big blocks couldn't rev higher. They just don't need to. If they did, they would run out of cam real quick and output numbers would drop off. By design, cams only have one RPM value that will yield maximum power. That's why high-end cams don't produce lots of low-end torque and why low-end torque cams run flat in the upper RPM ranges.

I understand what u mean, I agree

[BlackLT1Z28]

I just didn't want all of my posts to be considered crap because there is good information in there.
But I do understand how some of that other stuff can be construed as being misinformation. I'm not the best of putting all my thoughts organized on paper to be understood by all. I'm not saying everything I said was correct or right, but it just didn't come out right.

[djvaly]

no problem here chief. we're here to learn from one another, shoot there's some days when I hit a bottle and come in here buzzed. and I forget what a "piston" is .. neah. j/k hey no worries, we learn from each other.

[Chris Arnold]

I just didn't want all of my posts to be considered crap because there is good information in there.
But I do understand how some of that other stuff can be construed as being misinformation. I'm not the best of putting all my thoughts organized on paper to be understood by all. I'm not saying everything I said was correct or right, but it just didn't come out right.

All of it and you are a total waste of... j/k... No worries man. I didn't mean to attack you personally. I'm just trying to keep the information straight.

Chris

[mahoney1]

check these out!

http://auto.howstuffworks.com/question622.htm

http://auto.howstuffworks.com/horsepower.htm

[Hot Black Trans-Am]

I just didn't want all of my posts to be considered crap because there is good information in there.
But I do understand how some of that other stuff can be construed as being misinformation. I'm not the best of putting all my thoughts organized on paper to be understood by all. I'm not saying everything I said was correct or right, but it just didn't come out right.

I have this problem often...

[Krazy351w]

SO what are we talking about again

[BlackLT1Z28]

All of it and you are a total waste of... j/k... No worries man. I didn't mean to attack you personally. I'm just trying to keep the information straight.

Chris

Oh no, its cool. I'm not offended or anything, just wanted to clarify that some of it wasn't total crap, but the 'filler' was.