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  #1  
Old 07-06-2011, 11:03 AM
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HP and the POWERBAND; WHAT'S REALLY IMPORTANT!

Ok, there are arguments all the time about HP vs. TQ, yada yada yada, this does that, and so on and so forth. Multiple times it has been hashed out. I won't pretend at one time I was not ignorant on this issue, but I feel that since it was hashed out for me, I should give back and throw this out in the open for everyone.

I will start with the best explaination by Tom (chvyrkr81) and continue on to post some of the discussions we have had over this, so hopefully most of the questions can be answered.

Quote:
Originally Posted by chvyrkr81 View Post
This should help explain powerband ratio...

A diesel that makes 500/1000 and a gasser that makes 700/500.

Gear 'em so the diesel is at it's TQ peak, and the gasser is at it's HP peak.

Put 'em head to head on the hill with the trailer that Jake mentioned, roll WOT and watch the gasser eat the diesel for lunch.

Now, if that's a very long hill the gasser will most likely kill itself before reaching the top, and even if it survives. Gasser's don't live long at that power level.

This is why diesel's are the kings of heavy hauling. In addition to their incredible ability to take abuse for mile after mile, they have excellent powerband ratio's that allow a driver to make use of his engines potential at a wide RPM range. I.E. powerband ratio.

Now, powerband ratio is quite literally that. Today, we'll talk about the 90% ratio of a couple engines making similar power. The 90% ratio is simply the ratio of RPM's that it makes at or above 90% of peak HP.

First, we have my old PMR motor's dyno sheet. 361/770. Not that impressive, right? But, lets take a look at the 90% powerband ratio. Max HP is 361, so 325 would be 90%. 325 HP begins at 2200 RPM's, and the pull ends at 3800+ with it still making 325 HP. So, the 90% powerband ratio we'll use for this motor is 3800 (rpm's) divided by 2200 (rpm's) = 1.72 ratio.



Now, we have a lightning motor. I pulled this off google, so I have no idea the history or application or mods. Just that it makes about the same max HP. We'll use the same 325 HP from my old motor, even though this gasser is making just a touch more. 325 HP begins at 4000 RPM's, and is still there at the end of the run at 5400 RPM's. So, once again, divide the upper end of the powerband by the lower end, and 5400 / 4000 = 1.35



Let's translate the difference there...

Put both motor's in the same truck, with a 3:73 rear end and a ZF6 trans. Run 'em down the road and go WOT at 50 MPH. Just so the gasser has a sporting chance, we'll put the diesel in direct drive, 5th @ 1900 RPM's, and the gasser in 4th @ 2500 RPM's.

Roll wide open.

At 57.9 MPH the diesel gets into it's 90% (2200 RPM's) and begins to pull away, it'll continue to pull in that powerband until it reaches 100 MPH. Incidentally, the upper MPH divided by the lower MPH is 1.72, ring any bells?

Lets get back to the gasser... In 4th at 50 MPH he goes WOT, but doesn't get to his 90% until 80.3 MPH, which lasts until he hits 5400 RPM's at 108.5 MPH. And, you guessed it, 108.5 / 80.3 = 1.35.

So, while he's luggin it up the hill hoping to get to 80 MPH so he can use his powerband to make a decent time of it in the gasser, you've been comfortably floating along right there in the powerband, lettin off the throttle for corners, and rollin right back into it on your way up that mountain.

Now, he could downshift to 3rd gear, and he'd be right at 4000 RPM's and the bottom of his powerband at 50 MPH. In which case he'd jump out on you while you got up to 57 and came into yours. But, at 67 MPH he'd be at his redline, and he'd have to shift to 4th, which would drop him back under his powerband to 3350 RPM's. And you'd come walking right on by him in fifth gear as he struggled to get his speed back.

Anybody remember Grandpa or Dad luggin his truck up a mountain? He'd lug out a gear, and downshift. The downshift would speed the truck up, and he'd shift again, only to repeat the process each time he fell out of his powerband.

Well, if Gramps had the powerband modern diesels do, he'd have never had to downshift.

So, hopefully I've done a fair job illustrating why diesels pull better.

It's not the torque, it's the powerband. Power = Horsepower.

Took a very long time to beat it into my head, and the above was the illustration that finally got it done.

On EDIT: If we started up that hill at 50 MPH in 4th on the diesel, we'd have been around 2500 RPM's. In our powerband. When we got to redline at 76 MPH and shifted, guess what? Yup, still in the powerband in 5th, at about 2900 RPM's.

Just a little icing on the cake there.

Diesels get loads moving because the wide powerband ratio is available in every gear, at every shift. And from the stop, in first gear, it's available damn near off idle.
Now I'll start posting some of the discussions, no editting to leave anything out. After all, these were just some ol' boys talking, not a scientific community presentation

Hope yall enjoy
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  #2  
Old 07-06-2011, 11:20 AM
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Where we started the other day...

Quote:
Originally Posted by e99f2506sp View Post
All manuals have more torque from the factory too if I remember right. I don't remember anything in more hp, but I though the autos were 525ft lbs and the manuals are 550 or something like that.

Either way...manuals are clearly better
Quote:
Originally Posted by Jake View Post
...
I don't really wanna do this, but having more torque with no extra horsepower isn't really beneficial, except for maybe a slightly larger power band. My flame suit is on, because i know i'll need it, but i will say this, torque does not matter. I believe this smiley may now be appropriate.
....
Quote:
Originally Posted by Buffalo444 View Post
...

I agree having more torque without extra horsepower would not be benificial, but here's what I found out. The auto's were rated at 250/500, and the manual's were rated at 275/525. So they have more power But I completely agree torque does not matter, its all horsepower and powerband

...
Quote:
Originally Posted by Jake View Post
...

Thank you! You've seen my arguments with people that say torque matters and that more torque means pulling heavy weight is easier.

...
Quote:
Originally Posted by Buffalo444 View Post
...

Remember that argument on Facebook? I was on your side the whole time lol. Peak torque is only a number that can give you a general idea of what your powerband looks like.

...
Quote:
Originally Posted by Zytek_Fan View Post
Torque gets you moving off the line and from a slow speed, while HP keeps you moving and gets you going faster.
more to follow...
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  #3  
Old 07-06-2011, 11:31 AM
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and continued...

Quote:
Originally Posted by Buffalo444 View Post
Torque is a measure of force on an object, horsepower is a measure of work over time. So horsepower is what moves you. Having high torque allows you to produce horsepower at a lower rpm, thus giving you that "off the line" feel.
Quote:
Originally Posted by e99f2506sp View Post
Hmm. I disagree about the increase in hp and torque being a non issue, but whatever makes yall happy in your happy places. I'll just sit over here content in the knowledge I do indeed have 25 hp and 25 ft lb of torque more than the autos (plus the chip, they will program more power into a truck with a manual than they will a stock 4r100)

If it wasn't a big issue, the big 3 wouldn't spend millions to have a number that is 5 over the competition.

As far as loosing power during shifts, if you know where to shift and how to drive it, its also not an issue. Like was said, an auto is designed to slip, once you let the clutch out, a manual is set in that gear for the entire power band.

Anyway, carry on.
Quote:
Originally Posted by e99f2506sp View Post
Horsepower is how fast you hit a wall
Torque is how far you move it.
Quote:
Originally Posted by chvyrkr81 View Post
...

Horsepower is how fast your going, powerband is how far you move it.

Even though that analogy never made sense to me. I garuntee I can move the wall further hitting it at 50 in a 200 HP gasser dually than a 1000 fl lb regular cab at 50.
Quote:
Originally Posted by Buffalo444 View Post
dont you need the other half of the equation to make that statement true? i.e. you can move it farther with a 200 hp/ 300 ftlb gasser than a 100 hp/ 1000 ftlb diesel? i mean cuz the gasser dually could be a reg cab and the reg cab could be a gasser dually.... hell they could be the same truck.

...
Quote:
Originally Posted by Jake View Post
...

I remember the FB thing. (toward buffalo444)



No. (toward zyteckfan)



Yes. (toward buffalo444)



Increase in HP makes a difference, torque, not so much, like i said, only a possible larger power band. And they will not purposefully tune an auto less than a manual. (toward e99f2506spd)



No. (toward e99 f2506spd)

Get me at a time when i'm not half drunk still and not about to go to bed and i will educate all of you on horsepower and torque. Many of you will say i am full of chit, however, if you actually did some reasearch in physics, you would realize that i am right and all the other people that think that higher torque means its easier to pull a trailer and horsepower doesn't really matter are wrong. Horsepower is the essentially the ONLY thing that matters pulling a trailer.
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Old 07-06-2011, 11:39 AM
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and more........

Quote:
Originally Posted by Buffalo444 View Post
I'm pretty sure you, Tom, and I had this discussion a while back. Idr what thread (I know I said I wanted a 3000 ft/lb dt 360 or 466) but anyway we went through the whole schpeal, I didnt get it at first, but once the 90% powerband and peak torque example was used, it clicked, and I got it.

I'm going to look for it.

I'll be back.
Quote:
Originally Posted by Buffalo444 View Post
Yup, cant find it.

Key points are:

-It was a lightning versus a modded 7.3 (366 peak rwhp vs 360 rwhp)
-peak horsepower and the 90% powerband
-shifting and staying in the powerband
-the 90% powerband rpm ratio's
-operational efficiency at peak hp of each truck
-how a 700 hp/ 500 ft lb truck can out pull (in every way, but thats it) a 500 hp/ 1000 ft lb truck

That should definately ring some bells to some of yall. Heck one of ya even posted a graph (dyno chart) of each truck.

but off to bed for me...
Quote:
Originally Posted by chvyrkr81 View Post
Think I did the homework to break it down.

And it was in this thread.
Quote:
Originally Posted by e99f2506sp View Post
Nevermind, I just remembered I don't care....

No need to start anything about it. You've got your views and I got mine. We've already talked way too much about it and obviously disagree. If we get the chance to talk about it over a beer someday, great, that will be a lot more fun and not get anyone butthurt. If not, we'll just agree to disagree
Quote:
Originally Posted by Jake View Post
Its not about "views." It's about physics, and what is actually true. Any engine makes torque. Torque is rotational force. Horsepower is a measurement of torque over time. Without the time part of the equation, it means nothing. You can take a 10 foot bar and a socket and put 100 pounds of force on it, equaling 1000 foot pounds. However if whatever you are applying that torque to doesn't move, you have done nothing. Now if you apply that torque at say 100 RPMs, you have now made 19.04 horsepower.

And i'm not butthurt. Just trying to stop the spread of false information.
Quote:
Originally Posted by e99f2506sp View Post
Ok, I get what you are saying, and it certainly sounds good, but by your logic you are still making torque by adding 100 rpms to the equation. I'd like to see the torque numbers you are producing when you are making 19.04 hp or whatever, clearly it will be more than the 1000 ft lbs you would be making by putting 100 lbs on a 10 foot bar...

You also said that torque is nothing in pulling trailers...I just don't see how that is true when big trucks have say 1500ft lbs of torque and only 480 hp. Clearly torque plays a roll. Horsepower moves any set amount of mass in a straight line with no other variables other than wind.

If that mass comes across a hill, or is taking off from a stop light and needs to accelerate for any reason, torque is way more important that hp.

I am just trying to play this out and get information out there, lets not play the "trying to stop the spread of false information" card just yet, nothing bugs the hell out of me more than someone who isn't open to opposing views whether they be right, wrong, or otherwise hilarious. (coughliberalscough)
Quote:
Originally Posted by Jake View Post
in red was posted in a quote of e99f2506spd's previous comment

The torque in my example stays at 1000 ft lb. At 100 RPM, in order to make 19.04 HP, you must apply 1000 ft lbs. In order to make 19.04 horse at 1000 RPM, it only requires 100 ft lbs. Now if you took that same 1000 ft lbs and bumped it up to 1000 rpm, you are now making 190.4 horsepower.

It really isn't anything. An engine that has higher torque will have more horsepower at a lower RPM than an engine that creates less torque, so it will feel as though its more powerful, but it is still horsepower that determines how well it gets it moving. A 480 horse honda will pull the same weight at the same speed and accelerate the same, given that the honda could hold that much weight, and that the honda was in its power band. The difference is that the semi makes 480 horse at a lower rpm, whereas the honda makes it at higher rpm, so you'd just have to slip the living hell out of the clutch to have the honda start that load moving while still in its power band. However if they were both already moving up a hill at 50 MPH and both were already in their power band, they would pull the same.

Explained above.



I'm not playing any card. This is solid scientific stuff i'm telling you. There is no correct opposing view, this is how it is. Many will not believe it. I didn't at first either. I used to think torque is what really mattered too. Then i started listening to people saying the same things i am now and researching. Its just hard to wrap your mind around this concept when your whole life you have been told by people that were ignorant to what is really fact.

Other scientific facts that are undeniable; the planet is round, and it orbits the sun. Those can not be argued, though at a time they were. Just the same as the HP/torque thing. It can not be argued, it is what it is.
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Old 07-06-2011, 11:44 AM
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Quote:
Originally Posted by Buffalo444 View Post
bravo Jake. i was afraid i was going to have to correct him and use my entire lunch doin it on the phone. lol.

if you look at it, the reason the torque on the dyno changes is only because more fuel and air are consumed. if you take an electric motor (instant torque because its all in the current) the horsepower is purely limited by rpms. because it is an equation. a 1000 ft lb electric motor spinning at 500 rpms is only going to pull half as hard as a 1000 ft lb electric motor spinning at 1000 rpms. right? so its simple. torque is only as useful as the amount of work it can do over time. which hey, guess what, thats horsepower!
Quote:
Originally Posted by e99f2506sp View Post
the "talk in bold" refered to was Jake's comment : "people that were ignorant" or something, see previous post

Please keep the type of talk in bold to a minimum, nothing good can come of it and it certainly is not helping anyone look good. I'm not the smartest kindergardener on the playground, but I still have yet to grasp your views even after some light researching and chatting with you.

What your saying works if you keep the torque static at 1000 lb ft. It will not however work in a range, like a dyno. Clearly torque plays a bigger roll in your example that hp though because your still operating at 1000 lb ft with only 19.04 hp. If you add 1000 rpm, you only have 190 hp but you still have 1000ft lb.

What you are also saying about the honda vs the big truck plays into my views perfectly. The reason the truck makes its power at a lower rpm is because it makes its torque at a lower rpm. Why do you think they have so many gears...to keep it in its torque curve while accelerating. If it was to keep it in its hp curve, they would shift at higher rpms than 12-1400 out of 3000. Once it hits its cruising speed, it makes no difference anymore other than good mpg and to keep itself moving against wind speed so thats when its relatively low hp numbers kick in. If they hit a hill, they drop a gear and get back into the torque curve and take off. It wont cruise down the highway at 150mph like the honda will though because thats where the hondas hp curve is, up high in the rpms. Bore and stroke come into play here to change the hp vs torque curve. Big trucks...big bore and long stroke...lots of torque and low rmp. hondas...smaller bore and short stroke....lots of hp and higher rpm. People bore out engines and add heads to increase bore and stroke to increase torque numbers, its really the only way to do it. Horsepower can be added by adding fuel (injectors, etc)

The reason you have to slip the clutch in the honda really depends on where the torque curve is...i gotta find a 480hp honda to figure that one out.

My dads track car with only 280hp will blow the doors off of a mustang with 300 hp because my dads car has 340 lb ft of torque and the mustang only has 320. Sure the mustang will probably get it in a top speed race, but its not geared for that its geared to get him down the quarter or around the road course faster than everyone else. Granted power to weight ratio comes into play with this example as with any, but keeping all other variables the same other than hp an torque numbers, it would operate as Ive stated.
Quote:
Originally Posted by e99f2506sp View Post
quoting buffalo444

Please, no one feel the need to "correct me" we all have better things to do. I still think yalls point works when you keep a certain number static, but it makes no since when it comes to a range....which all engines endure.

Electric motors have huge torque numbers, and very low hp numbers.

look at a motor from tesla for example. the peak torque is at 400 rpm, right down low while your accelerating, and its peak hp is at 6000rpm up there where its needed to keep itself speeding along at 125mph
more to come.... stilll
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  #6  
Old 07-06-2011, 11:50 AM
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whew, this one took some work...

Quote:
Originally Posted by Jake View Post
That is dead on. quoting buffalo444

comments in red were used through out e99f2506sp's post

Ignorance was not meant as an insult. Ignorance is not stupidity. Ignorance is defined as a lack of knowledge, or simply, unknowing. So the word fits perfectly with what i was saying. I'm not calling you stupid at all, just ignorant. Huge difference.

It works when the torque is not static as well. If you can apply more torque at a higher RPM, you make more horsepower. Torque is work, or the rotational force an engine makes in this example. Engines don't truly make horsepower. Horsepower is a measurement of the amount of work (torque) done over time (RPM). Therefore if an engine can do more work in a shorter amount of time, it will accelerate faster/pull more weight. Take the semi engine that makes 1500 ft lb at 1500 rpm. At that point it is making 428.4 horsepower. Now if you could spin that engine to 3000 rpm and 1000 ft lbs of torque, it is now making 571.2 horse. Less torque, but more work is being done.

This is correct.

Also correct, there are other reasons for this though, such as a narrower usable RPM range and it will accelerate faster (assuming shifts are done quick enough) if there is a smaller gap between gear ratios

It is to keep it in its HP curve, they make their HP at low RPMs.

They drop a gear to get it to where it makes more HP.

Not true, that is all in the gearing. There are semis that run over 120 mph across the desert.

Yes, big bore and big stroke will equal more low end torque, which means it makes more horsepower in the low RPM range. Horsepower is also increased when you bore and stroke an engine, and both are added by more fuel.

This is correct. The powerband in a honda motor may not come in til over 4000 RPM, whereas the semi has it dang near off idle.




It works whether a number stays static or varies. The formula is the same.



Give both cars the same gross weight and same gearing and i promise you the mustang will beat the track car. Which you actually just admitted yourself, you just don't know it. Look at what you said. The track car has lower gearing, and is lighter. Of course it will beat the mustang. Same reason a 200 horse honda would put a whoopin on my truck that puts down around 300-325.



Why do you think it need the HP at 125 to keep it moving? I'll answer that for you. Wind drag. When your speed doubles, the wind resistance quadruples. According to the "torque is what is more important" theory, you would want torque up there to help push it through that wind resistance, which in a sense is just simulated weight.

Just for S&G's... Tesla dyno chart.

ok, still more coming.
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Old 07-06-2011, 11:52 AM
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Quote:
Originally Posted by e99f2506sp View Post
Sorry, but it sounds like you just said that an engine creates hp due to torque....so is torque necessary then, or should we just get rid of it? Your arguing against yourself with every post...You yourself said it takes a certian amount of torque to create hp.

"Take the semi engine that makes 1500 ft lb at 1500 rpm. At that point it is making 428.4 horsepower. Now if you could spin that engine to 3000 rpm and 1000 ft lbs of torque, it is now making 571.2 horse. Less torque, but more work is being done."

Your driving my point home exactly with every post! It takes torque to get a mass moving, and hp to keep it moving, your quote from above makes perfect since!

If narrower rpm range is an issue...why not go ahead and make a semi engine that revs to 8, 10, 16k? even if it would hold together in that long stroke, big bore engine, thats not where torque happens in that kind of an engine.

And actually what i said was... "keeping all other variables the same other than hp an torque numbers, it would operate as Ive stated." There are thousands of variables that would give each car an advantage...suspension, brakes, tires, etc, but as far as the track car beating the mustang around a track if both cars weighed, say 2400lbs, my dads car would beat the mustang all day long...it has more torque.
Quote:
Originally Posted by e99f2506sp View Post
Ohh, and I just read your part about the tesla...

I never said "torque is most important" overall. It is most important down low in the rmps, to get a mass moving. Hp is most important once the mass is moving to keep it moving...hence the high torque numbers low in the rmp range and high hp numbers high in the rpm range. I've said all along that it takes hp to keep it moving in wind drag.

Your arguing my point as much as your own... its you and me against yourself it seems...

I'm making a case for hp just as much as torque really, just fighting more for torque cause that seems to be the part you don't want to believe exists.
then another one of jake's difficult posts...
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Old 07-06-2011, 11:54 AM
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Interesting conversation piece, pretty funny read.
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Old 07-06-2011, 12:11 PM
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Quote:
Originally Posted by Jake View Post
words in red were in another quote of e99f250sp

An engine makes torque, so yes it is important, but what i'm getting at is more torque alone will not get a trailer moving easier. I never said we didn't need torque. I am not arguing with myself at all. My wording may not be perfect because I'm tired, but the point is definitely there, you just don't want to see it because you think I'm full of chit.

The sentence in blue is totally false. Horsepower gets it moving and keeps it moving. Torque alone does not determine an engine's power or it's ability to move heavy objects. You need a measurement of time to go along with that. And that, ladies and gentlemen, is what horsepower is. Work done over time. Take a 500 horse semi and a 500 horse gasser. Make all variables equal, weight, final drive ratio, wind resistance, etc. Get them both in their power band and run them both side by side up a 10% grade. I promise, they will pull side by side.

They don't rev that high because they would scatter. They have rev limiters for a reason. There are 2 approaches to making horsepower. One way is like a semi engine. High torque, or high RPM.


If you made all variables the same other than the engines, the mustang with a few more horse but less torque WILL beat the track car. I guaran-fing-tee it. I would even go as far as betting the title's of our trucks on it. Run the mustang in a quarter mile, then pull the track car motor out and put it in the mustang, and run the quarter again. Your mind will be blown.
Quote:
Originally Posted by Jake View Post
I'm gonna bow out for the night. Perhaps by the time i get back someone that is a little better at wording things than myself will have chimed in and explain exactly what i have already said only using different words that might explain it better. I'm hoping Tom comes in on this. I can tell you right now he will say that what i have said is dead accurate and true, and possibly elaborate on it a bit more than my currently tired brain can do right now.
Quote:
Originally Posted by e99f2506sp View Post
It will win in the quarter mile yes, it has more horsepower, but my dad will beat him in the 1/8th cause hes got torque to get him off the line

Its another reason it will win on a road course over a mustang with all other variables the same...because it has torque to pull itself through a corner and accelerate out the other side. otherwise a ford edge would beat my dads car assuming all other variables were the same, it has 285 hp. However, it only has 250 lb ft of torque...so there is no way it would keep up.

And as far as thinkin your full of ****, I don't I wouldn't have spent the last few hours away trying to research your point of view and talking to you about it if I thought you were.
Quote:
Originally Posted by e99f2506sp View Post
I gotta hit the hay too bud, Good chattin with ya. There aren't any winners or loosers here, just more educated people.

If Tom chimes in, I'm out for good. Theres no fightin that brick wall with the crayons and safety scissors I got just kidding Tom.

I'll continue to do research on it, clearly you think your on to something so I am more than open to reading opposing views, and have. I just have found reasons not to believe them in every case so far...
Quote:
Originally Posted by e99f2506sp View Post
Sorry, was laying in bed thinking about this, and came up with the simplest solution I could...

Say you have a bolt that you need to loosen. You put the breaker bar on there and pull, that is torque against the bolt just as an engine put torque against the ground starting from a stop. The bolt breaks loose and you spin the breaker bar, that spinning at a steady speed is horsepower just as driving your vehicle at a steady speed is. You spin the bar faster, feeling the torque against your hand, just like pressing on the accelerator, putting more torque against the ground to speed up a vehicle.

If speed is constant at any speed, no accelerating is happening, then horsepower is working...maintaining the vehicle at a speed with no other forces against it but wind...

If speed is changing up or down, torque is working, whether it be from the engine through the tires to the ground to speed you up, or friction agains the brakes to slow you down.

By what you are saying, I could just as easily run down and get a ford edge (sorry, grandparents just bought one so I know all its specs) because it does have 10 more horsepower than my truck (without tunes) and just as easily tow the focus in my sig, or my trailers around daily for work assuming I could get the frame to handle the weight? The fact that my truck has 275 more lb ft of torque is irrelevant and unnecessary?

I know for a fact we could both haul the same load at 50mph across flat terrain perfectly fine, hell with 10 more horsepower the edge may do it more efficiently, but put 10k behind both of them and take off from a stop and which one would win?
Quote:
Originally Posted by Buffalo444 View Post
Ok, first off use a torque wrench to break that bolt loose. What happens to the ft lbs once its un-seized? They drop off. So there is not torque and no horsepower, because it isnt doing work.


Here is the GLARING HOLE I find in Jake's arguement, which is probably why you are not seeing why its horsepower doing the work. First off, remember we are talking PEAK HP numbers, which do not show a powerband. We need a dyno sheet for that.

Lets take your 285 hp ford edge vs your 275 hp truck. This is why you would be faster, Because your 90% hp powerband is MASSIVE compared to the edge. For the most part, gassers tend to peak horsepower right around redline, due to the fact most of them are indirect injected and require air flow and engine speed to build power and inject fuel, two things powerstrokes do directly via forced induction (turbo charging) and direct injection (our heui system). So lets say you are just cruising along, around 2k rpms in each vehicle. The powerstroke is well within its powerband (90% peak horsepower), and the edge is probably about 1k under its powerband. You are probably geting 2 times the horsepower to the ground just cruising around.

Now here is where I have to say something else, every time you say something will be quicker at doing something you are AUTOMATICALLY TALKING HORSEPOWER. Torque is load on an object, it can be statically defined. Horsepower is work done over time. The reason the higher torque vehicles have that "off the line" feel is because of one thing, they produce more HORSEPOWER, earlier. That's it.

And the reason those massive semi engines dont run at those high of rpm's is one thing, supply. What happens when you have a 4x4x4' empty hole and go to fill it with water. Using as big of hose as you need, you can only fill it so fast. That's physics. Now take a 16x16x16' hole and try doing the same thing. Again it can only fill so fast, and it CAN NOT be filled as fast as the smaller hole, due to physics. SO fueling is the limiting factor, as well as delays in the mechanics of it all (take our heui system for example, we are really limited where we can effectively use our fuel as far as rpms go)

Now here is why two trucks, with the same curb weight, same horsepower, and same gearing can race and have a clear winner every time. Say we take some stock big block gasser that produces around 300 rwhp at 5k rpms, and makes about 450 ft lbs of torque. Then we take a mildly modded 7.3, that makes about 300 rwhp and 600 fl lbs of torque. Set em up in two 4x4 trucks, autos, same rear ends, torque converters with the same stall speed (say 2.3k rpms). Make em weight exactly the same. now here they go:

Both trucks are lined up, both get to brake boost to load up the trans and be ready to start the race. The gasser is maxed at 2300 rpms, its barely making 50% of its max horsepower. So its about to launch with 150 hp. The 7.3 is sitting at about 275 hp, a little over 90% of it peak hp. Its going to launch in its power band.

Both trucks launch; the 7.3 making way more horsepower and doing way more work than the big block, so its pulling ahead. The gasser is winding up trying to get to its peak hp, which is near redline. It can't keep up.

The trucks both go to shift. The 7.3 shifts and drops down to 2300 rpm, and stays well within its powerband. The big block shifts and drops to 2300 rpms, and falls right out of its powerband. The 7.3 keeps pulling ahead and the gasser keeps falling behind.

The trucks reach their speed limiters. The 7.3 long before the big block. Because the 7.3 stayed in its powerband the whole time, it did more work in a shorter period of time, got out ahead, and now in o/d will maintain the lead. The big block fell in and out of its powerband, fell behind, and now even when in o/d its out of its powerband.

So now you see ( I hope ) HORSEPOWER is what moves you, and POWERBAND is what determines how efficiently you move.
Quote:
Originally Posted by chvyrkr81 View Post
Powerband ratio...

That's what isn't being explained that should turn the light on.

I can make 2300 ft lbs of TQ with a ten foot bar, but if I can't do that quickly (RPM) then I won't get any loads moving.

Now, add some RPM to that and we can start moving some weight with it. But, TQ at RPM is called power, or horsepower.

Back to powerband, the ability of those OTR tractors to produce 480 HP at 1200 - redline is what gets the load moving. When you're making max power right off idle, and have the gearing to multiply that power, you end up with a machine that can move anything you hook to it. Or destroy the drivetrain trying.

But you can't do any of that without RPM, and TQ at RPM is HP.
INSERT TOM'S ORIGINAL EXPLAINATION

Quote:
Originally Posted by e99f2506sp View Post
I read through your posts Tom, and if I understand what you are saying correctly, Torque times rpms equals horsepower?

Example...

T = Torque
R = RPM
H = HP

So, T x R = H correct?

I think the confusion happened back when Jake said something about more torque is unnecessary to move a load, when according to the math equation that I understand from your explination, the more torque you have, gives you more horsepower at lower rpms?

So according to the T x R = H math equation, there can be any amount of infinite numbers for T and R and that will always give you a different number after the equal sign. However, that can't and won't work in any other way... ex H x R ≠ T and H x T ≠ R.

That being said, it sounds like we are discussing the same point, torque is indeed important? Whether it is Horsepower that gets a load moving off the line or not, torque is definitely needed because without T the equation is R = H and that can't work...

Please explain, I am very interested in this now. Again, no hard feelings to you Jake, I'm glad you brought this up.
I think there is still more after this...
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  #10  
Old 07-06-2011, 12:15 PM
Viking Heavy Diesel

 

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You guys are really pulling out all the stops.
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