[danielrm26]

Originally Posted by bavarian19

So you have now calculated the amount of work done. But if you do that amount of work in less time, its more POWER (P= W/t) and not acceleration. Acceleration is any change in velocity (Whether it be a change in magnitude or direction). If you pull at a constant rate, which you claim to do, there is no acceleration.

No offense, but you seem to be out of your league...

I'm well aware of the physics, and I even knew that statement wouldn't stand under appropriate pressure, but I hoped people like you would see the meaning and overlook it.

Here, if you have the same exact same car, and you're starting from rest and apply more power to the wheels -- what do you think happens? Answer me this: do you think it's possible NOT to accelerate faster given those conditions?

It's not. You MUST accelerate faster than if you applied less power. And since that's the question here -- which value matters for acceleration -- I thought it more than acceptable to just say it was acceleration.

I stand corrected. You're right that I should have been more precise. I ask you to reconsider, however, that I am out of my league. I most certainly am not, sir. Not at this level anyway.

[DLJJ3399]

Daniel, just so you know and you're not blindsided anymore, bavarian19 is a physics teacher.

You don't want to mess with the Bav!

By the way Bav, where’s the results of the string theory I requested.

If I'm at 4500 rpms in my 330 generating 300 lb-ft of torque and a 335 is at 1400 generating 300 lb-ft of torque, will we be neck n neck or equal?

At the top end the cars both equal out right?

[danielrm26]

Originally Posted by DLJJ3399

Daniel, just so you know and you're not blindsided anymore, bavarian19 is a physics teacher.

Indeed, and I appreciate his attention to detail and keeping me in line, but he didn't illustrate that I didn't know what I'm talking about. What he showed is that I need to be more careful with my language.

The beginning of my article actually touches on the physics portion of the issue, which I agree is very important.

[bavarian19]

Originally Posted by danielrm26

I'm well aware of the physics, and I even knew that statement wouldn't stand under appropriate pressure, but I hoped people like you would see the meaning and overlook it.

Here, if you have the same exact same car, and you're starting from rest and apply more power to the wheels -- what do you think happens? Answer me this: do you think it's possible NOT to accelerate faster given those conditions?

It's not. You MUST accelerate faster than if you applied less power. And since that's the question here -- which value matters for acceleration -- I thought it more than acceptable to just say it was acceleration.

I stand corrected. You're right that I should have been more precise. I ask you to reconsider, however, that I am out of my league. I most certainly am not, sir. Not at this level anyway.

That is just one of the flaws with your argument.


You also make calculations of HP based on a constant torque value over the range of rpm's. 99% of all cars, that is not the case. You will have peak rpm's for both torque and hp. Each car is drastically different, and so your performance numbers are drastically different as well...

... and I would love to hear your explanation for the constant value of 5252 you have in all of your calculations. From what is it derived?

[danielrm26]

Originally Posted by bavarian19

...and I would love to hear your explanation for the constant value of 5252 you have in all of your calculations. From what is it derived?

If you don't know that 5252 is an intrinsically meaningful number in the equation then you probably shouldn't be asking questions with such attitude in your voice. Not only did you not know the answer, but it was right in the article that you are attacking.

""Below 5252 RPMs any engine's torque will always be higher than its horsepower, and above 5252 RPMs any engine's horsepower will always be higher than its torque. At 5252 RPMs the horsepower and torque will be exactly the same." -- revsearch.com"

As for the torque constant issue, the constant torque is used to illustrate the numbers. The fact that this varies a bit over the band doesn't matter much.

[BK]

"Where does 5252 come from?"

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

[BMW0]

Simply; I heard from my father when I was kid was: Horsepower has influence w/ the topspeed of the motor. Torque is what propels you forward, serious torque is refered commonly to "necksnapping" force.

[Josh49]

Daniel,

First off, I wanted to sincerely apologize for what I said earlier. I misread your initial post and after skimming through the site was very frustrated for the innaccuracies that I read. I am going on holiday, but when I get back I (and bavarian as well) would love to help you fill in some of the blanks and help you with some of the things you are getting confused. We are all here to learn, I think it was awesome that you did the research and brought this to the table to help inform others and explain it to people. Have a happy and safe holiday season. Looking forward to the discussion when I get back..

Cheers,
Josh49

[Top_Gear]

Guys,

Here is the easiest way to think about it.

(1) The ACCELERATION of your car is proportional to the force applied by the tires on the road. This is known in physics as Newton's law of motion (or F = M x A).

(2) The force applied by the tires on the road is proportional to the TORQUE generated by your engine/drivetrain.

So based on the above two statements your car's ACCELERATION is proportional to your engine's TORQUE (minus drivetrain friction losses). So the larger the torque your engine makes, the faster your acceleration will be.

The catch is that your engine does not make the same amount of torque at all RPMs. As you accelerate from a lower speed/RPM to a higher one, the torque generated by your engine changes which in turn changes the acceleration of your vehicle.

Now to drive the point home think of an ideal situation of two identical cars whose engines have same Torque-RPM curves but with one key difference. Car #1 has a 6000 RPM redline while car #2 has 8000 RPM redline. The two cars begin to race and they are neck-to-neck when they both hit the 6K RPM mark. At that point car #1 shifts to a higher gear while car #2 stays on the same gear until 8K RPM. At that moment car #2 will be winning the race because it has managed to stay on the lower gear longer thereby delivering the lower gear Torque to the pavement which produces a higher acceleration than car #1. Remember when car #1 hit its readline at 6K RPM and shifted to a higher gear it immediately REDUCED its torque output to the wheels and this made it fall behind car #1. It just could not sustain the high torque that car #2 was able to by staying in the lower gear LONGER!!!

So, in summary, acceleration is all about torque but the car that wins the race is the one that is able to put out that torque for a LONGER period of time. The concept of LONGER is captured by the HORSEPOWER rating of the engine. So one last time, torque is about HOW HARD the car accelerates while horsepower is about HOW LONG your car can keep that torque coming out of its engine.

I hope this helps.

[GuillaumeSoete]

Now this is torque :

[BK]

[NaViT]

Originally Posted by GuillaumeSoete

Now this is torque :

HAHA THATS GREAT!

[danielrm26]

Originally Posted by Josh49

Daniel,

First off, I wanted to sincerely apologize for what I said earlier. I misread your initial post and after skimming through the site was very frustrated for the innaccuracies that I read. I am going on holiday, but when I get back I (and bavarian as well) would love to help you fill in some of the blanks and help you with some of the things you are getting confused. We are all here to learn, I think it was awesome that you did the research and brought this to the table to help inform others and explain it to people. Have a happy and safe holiday season. Looking forward to the discussion when I get back..

Cheers,
Josh49

Totally understood, man, I've jumped before looking a few times in my day as well -- no hard feelings. I look forward to when you return so we can go through this very interesting issue together. I'd really enjoy filling in any gaps in the explanation and/or in my understanding of the subject.

Cheers,

-Daniel

[DLJJ3399]

So no one answered my question.

If I'm at 4500 rpms in my 330 generating 300 lb-ft of torque and a 335 is at 1400 generating 300 lb-ft of torque, will we be neck n neck or equal?

At the top end the cars both equal out right?

[teknochild]

NOOOOOOOO i saw this post on the other forums and finally got so pissed i registered on one and posted, then i was like i bet its here too so i searched and here it is <_<

how many of you disagree with this statement: the longer you stay around your peak horsepower the faster you will be

ive read people saying things ranging from telling people to shift right after peak torque for a faster 1/4 to when your in a higher gear you have lower torque but your horsepower is the same (seriously people cant be that retarded can they?)

edit:[and this is basically the same stuff the OP is saying in his article, im trying to add a diffrent way of explaining/example and more importantly and answer for the butt dyno, and i think the example i put down with punching a ball is better than the RPG example of attacking because it follows the same idea while allowing people to visualize motion aswell]



now ill admit i probably dont know much compared one or two others in the thread, but this is how i visualize it for easy understanding

if you punch a ball with 50 pounds of force in a second its going to start rolling pretty fast, now if you hit it with 25 pounds of force twice in a second its not going to experience the same burst of acceleration but its going to go just as far just as fast as the first ball

now what happens if you hit it with 25 pounds of force 3 times in a second? same amount of force, still lower than the 50 pounds, but at the end of that second it is definatly going to be going faster than the first ball, and while technically at the moments of impact the acceleration will be lower than the 50 pound hit the acceleration over that second is going to be higher for sure

since this is basically what your engine is doing, applying a certain amount of force to the wheels, in intervals, to make them roll, and since horsepower is basically how often torque is applied to the wheels, while HP raises your rate of acceleration (over time not instant) is going to raise with it





i think the problem everyone is dealing with (again i THINK im not an expert) is that you dont get pushed back in your seat by just acceleration, but by the acceleration of your acceleration (jerk it can be called) and when u slam on the gas even more so

and of course as torque stays constant or is raising, your jerk is going to be higher than if torque was going down, so once you get past your peak torque your not increasing your acceleration[jerk] as fast as before, but your acceleration is STILL increasing from peak torque to peak horsepower, and the higher your acceleration the faster your going to go

i think this is why the "butt dyno" pushes so many people into thinking torque = acceleration and if it[torque] is going down so is their acceleration, when in reality its their jerk [acceleration of acceleration] that is starting to decrease (but is still positive which is important) you want the highest acceleration possible, even if the jerk is lower at that point




just to pull a few things out of this thread,

So based on the above two statements your car's ACCELERATION is proportional to your engine's TORQUE (minus drivetrain friction losses). So the larger the torque your engine makes, the faster your acceleration will be.

no, this would be true if torque was contant but we all know its not, if hp is > torque your going to accelerate faster, by your reasoning there are some engines out there that should be shifting around 4k even though though they have peak hp around 8k, which is just not true

what you should have said is

"your car's ACCELERATION is proportional to your engine's TORQUE and RPMs (which IS what HP is). So the larger this is, the faster your acceleration will be."




also that 5252 number, it doesnt really meen anything, we could make a new measurement called l337 and have it be "l337 = tq x rpms" and it would meen the same thing as hp, the numbers would just be a lot bigger and harder to compare, the number comes from the same reasoning as the width of a train track (being the width of carriage wheels or some crap), there is no REAL reason for it except for the way things worked in days past (some stupid horse that set the standard proabably), but it works wonderfully to reduce the size hp to comparable values

i was very surprised when bavarian said "and I would love to hear your explanation for the constant value of 5252 you have in all of your calculations. From what is it derived?" to the OP as if its something HE pulled out of the air, especially after someone said bavarian was very knowledgable on the subject


short version:

*more horsepower is going to = higher acceleration

*people who spoon feed us peak HP and TQ numbers are jerks (would be much better to have a sort of average that gives emphasis depending on the gearing of the car)




before i start a flame war like the lsd one i seem to have created before, i want to put a disclaimer here, i am by no meens an expert, these are my opinions/conclusions, since i feel they are correct i will defend them fiercly unless someone comes at me with a logical response backed up by facts

using something like "but those diesel racers with barely any hp but tons of torque are just as fast as high hp racers, so more torque is more important than more HP" will get you immediatly flamed , those diesel racers have a ton of average hp compared to those high peak hp racers, which is why they were banned

[teknochild]

Originally Posted by DLJJ3399

So no one answered my question.

If I'm at 4500 rpms in my 330 generating 300 lb-ft of torque and a 335 is at 1400 generating 300 lb-ft of torque, will we be neck n neck or equal?

At the top end the cars both equal out right?

if your saying your neck and neck on a road, both going the same speed, using the same gear/gearing (well i guess you couldnt be if ones at 1400 and the others at 4500 but it makes it simpler), and lets say you both keep the 300 torque during the example, and then you both punch the throttle, the 330 is definatly going to pull away, rather quickly, infact thats a wonderfull example of how just torque does not = acceleration, you have to consider torque AND rpms, and this is of course what horsepower is

Originally Posted by Insider

So if a car, like the 335i, makes 300 ft/tq at 2,000 rpm and 5,000 rpm, does the car accelerate just as fast at 2,000rpm as 5,000 rpm?

Where would the car accelerate most quickly? Peak torque or peak HP?

no it would not accelerate at the same rate, it would accelerate much faster at 5k rpms, to re word your other question, "where would the car be accelerating most quickly"? peak hp

Originally Posted by Josh49

Say there's a car that produces 200 hp (peak at max hp rpm) and 170 ft-lbs of torque (peak at max torque rpm). Now there's another car whose engine has a turbo on it and produces 200 hp and 230 ftlbs at the respective max rpm. The second car will accelerate much faster and put you into the seat much harder than the first car. At lower rpms, where torque is at it's peak, the amount of torque to crank your wheels off the line and accelerate you is much higher. You will accelerate faster. Morever, most turbo cars have high, flat torque curves, so you will have a large values of torque over the lower to mid rpm range. This equals acceleration, as well as put you into the back of your seat, driving bliss..

I would choose the second car..

yea that second car is faster, no doubt about that, but what if the first car had the ability to reach a peak HP of 210, that second car is STILL probably going to be faster, but that first car is going to be able to reach a higher maximum acceleration, and lets say it was possible for both cars to just stay at their peak HPs (at full throttle through some amazing unthinkable gearbox) eventually that first car would overtake the second, because at 210 HP the car will be accelerating faster than the car at 200horsepower

so your right in your conclusion that the second car is faster, but not in how you arrived at it

Originally Posted by Josh49

I did not mean to be rude or arrogant. I am the exact opposite. Most of this information gathered is not accurate, and was trying to inform other members of the innacurarcy of this information. I do not want a lot of other members reading this and being mislead.

he might misuse some terms, a lot of us do, but his conclusions ARE accurate




and so u guys dont think im only supporting daniel and totally one sided

even though he made this comment off the wall

Originally Posted by danielrm26

Generating lots of force (torque) means nothing when discussing acceleration. 18-wheel trucks and tractors have a TON of torque, but you wouldn't want to race one.

not really, there are many diesel cars out there that are very fast even though they have low HP, becasue they have that "TON" of torque right away so they have a lot more hp right away comapred to a gas engine that relies on high revs, the diesels may have a lower maximum acceleration cabability, but many have a higher average acceleration than their counterparts, although im sure you already knew this, just the way you said it was asking for it

Originally Posted by bavarian19

I teach that exact physics to my 8th graders. Nothing complicated about it.

Your conclusion is somewhat far fetched though...


Just one example from your conclusion:

"So that means we've moved the same distance, but in less time. That's acceleration, folks."


No. Its not. You did work (W=Fd), but in less time. You take the Force of the object your lifting (your weight, which is = the mass of the object x 9.8 m/s/s) and you multiply that by the distance lifted.

Use the metric system (as any true Scientist would tell you), so you multiply the Force you calculated, by the converted distance in meters (1,915.058 4 meters)

So you have now calculated the amount of work done. But if you do that amount of work in less time, its more POWER (P= W/t) and not acceleration. Acceleration is any change in velocity (Whether it be a change in magnitude or direction). If you pull at a constant rate, which you claim to do, there is no acceleration.

No offense, but you seem to be out of your league...

at first when i skimmed this i thought you knew what your talking about, which you clearly do, but unfortunatly your not talking about the subject of horsepower, torque and their relation, all your doing is arguing semantics with daniel and not the actuall point, his misuses some terms and arrives at some conclusions inproperly, but his conclusions are correct

Originally Posted by bavarian19

That is just one of the flaws with your argument.


You also make calculations of HP based on a constant torque value over the range of rpm's. 99% of all cars, that is not the case. You will have peak rpm's for both torque and hp. Each car is drastically different, and so your performance numbers are drastically different as well...

... and I would love to hear your explanation for the constant value of 5252 you have in all of your calculations. From what is it derived?

he uses torque that way in order to simplify things, there is no issue with this because he is not comparing engines, he is simply trying to show that more hp = more acceleration, even if torque is lower at those RPMS, and i already commented on the fact that your confusion at the use of 5252 shows that your just arguing semantics with him, and that possibly dont know much about the actually subject of horsepower and torque

Originally Posted by BMW0

Simply; I heard from my father when I was kid was: Horsepower has influence w/ the topspeed of the motor. Torque is what propels you forward, serious torque is refered commonly to "necksnapping" force.

your father also told you that shutting your car off for 5 minutes and restarting it takes more gas than just idling for 5 minutes, but he was wrong (least in this age he is)







and as for top gear, your so incredibly wrong its not even funny, some conclusions were sort of right, but how you arrived at them was just gleh

edit: actually bothered

Originally Posted by Top_Gear

(1) The ACCELERATION of your car is proportional to the force applied by the tires on the road.

yes but the amount of force applied over time is more important, who cares if you fire a cylinder with 500torque once if someone else is firing a cylinder with 100 torque 50 times

Originally Posted by Top_Gear

(2) The force applied by the tires on the road is proportional to the TORQUE generated by your engine/drivetrain.

again not taking into account how many times that force is applied over time

Originally Posted by Top_Gear

So based on the above two statements your car's ACCELERATION is proportional to your engine's TORQUE (minus drivetrain friction losses). So the larger the torque your engine makes, the faster your acceleration will be.

already fixed this statement in the above post:

your car's ACCELERATION is proportional to your engine's TORQUE and RPMs (which IS what HP is). So the larger this is, the faster your acceleration will be.

Originally Posted by Top_Gear

The catch is that your engine does not make the same amount of torque at all RPMs. As you accelerate from a lower speed/RPM to a higher one, the torque generated by your engine changes which in turn changes the acceleration of your vehicle.

your right torque does change as rpms change in most engines, and as torque changes so does acceleration (assuming the same rpm value) but you are undoubtedly trying to imply that as torque lowers acceleration will lower no matter the roms, and thats not true

Originally Posted by Top_Gear

Now to drive the point home think of an ideal situation of two identical cars whose engines have same Torque-RPM curves but with one key difference. Car #1 has a 6000 RPM redline while car #2 has 8000 RPM redline. The two cars begin to race and they are neck-to-neck when they both hit the 6K RPM mark. At that point car #1 shifts to a higher gear while car #2 stays on the same gear until 8K RPM. At that moment car #2 will be winning the race because it has managed to stay on the lower gear longer thereby delivering the lower gear Torque to the pavement which produces a higher acceleration than car #1. Remember when car #1 hit its readline at 6K RPM and shifted to a higher gear it immediately REDUCED its torque output to the wheels and this made it fall behind car #1. It just could not sustain the high torque that car #2 was able to by staying in the lower gear LONGER!!!

this doesnt drive your point home at all, infact if anything all it does is drive home the point that horsepower is crucial, since the engine that revs to 8k produces the same torque as the 6k engine but produces more HP, but thanks for backing up this side of the argument, really A+

what you have really done is start another discussion about gearing

Originally Posted by Top_Gear

So, in summary, acceleration is all about torque but the car that wins the race is the one that is able to put out that torque for a LONGER period of time.

let me fix this for you, so in summary acceleration is all about horsepower, which is all about torque and engine speed combined, the car that wins the race is the car that can put out the most torque over time

Originally Posted by Top_Gear

The concept of LONGER is captured by the HORSEPOWER rating of the engine. So one last time, torque is about HOW HARD the car accelerates while horsepower is about HOW LONG your car can keep that torque coming out of its engine.

your totally confused here , you seem to think the horspower is gearing.... and your very wrong, ill try and correct it for you though

torque is about HOW HARD the car pushes the crankshaft, while horsepower is about HOW OFTEN your car applies that force to the crankshaft

Originally Posted by Top_Gear

I hope this helps make you completly ignorant to what torque and horsepower actually meen because im actually a bafoon who knows nothing and should be shot for spreading such ridiculouse information

[teknochild]

i got a little rough with topgear there but it just so infuriating and i wish i could just delete his post before people read it and actually believe it, either that or bludgening him to death with a blunt object would make me just as happy

[Josh49]

First off, read the situation I gave again. I don't know where the number 210 hp came from. You can read where you quoted me again. I don't see 210 anywhere.

Here is a better explanation of the rest of it.

Car A: 200 hp at Peak HP RPM, 170 ftlb of torque at Peak Torque RPM, NA
Car B: 200 hp at Peak HP RPM, 230 ftlb of torque at Peak Torque RPM, Turbo
Profile-wise: At all RPM, the amount of torque applied from the turbo engine is greater than that of the naturally aspirated motor.
Everything else: Both cars have same hp, same gearing, same differentials, same wheels and tires, etc.

Linearly, Sum of all Forces = mass x acceleartion
Likewise, Rotational, Sum of all moments (torques) = moment of inertia x angular acceleration.

At any RPM, and while accelerating, the torque produced by the engine of Car B is higher. (I defined above moment of intertia for both cars was identical.) Therefore, the angular acceleration of the wheels on Car B will be greater.

Not including vector notation, linear velocity at a point on the edge of the wheel = the radius of the wheel x the angular velocity of the tire.

Taking a derivative, the linear acceleration at the perimeter of the wheel (and car assuming no slippage) is still directly proportional to the angular acceleration of the wheel. (first derivative: tangental acceleration = radius x angular acceleration)

So. The larger torque of Car B directly relates to the faster rotational acceleration of the wheels, which directly relates to the faster tangental acceleration at the tip of the wheel. All factors remaining the same (sprung weight, moment of inertias, etc) Car B will accelerate faster.

As I said before, I would choose Car B.

The purpose of this exercise was to disprove the "Horsepower is what matters" statement. It is wrong. Both Car A and B have the same horsepower, yet car B is faster. Horsepower and Torque need to be looked at. Moreover, if I were choosing between two engines, I would not only want to see Peak Torque and Peak HP, I would want to see both complete engine maps before making a decision.

[obLu]

Errr ... sorry, I need some cliffsnotes. But one thing I don't think was addressed in any of this:

How does this account for diesel motors? If HP is a strict function of torque, then how come diesel engines always have much more torque than HP?

[Josh49]

I think many people are missing the fact that an engine develops peak Torque and peak HP at different RPM's. Peak Torque is usually generated in the lower RPM band while Peak HP is usually generated in the high RPM band. An engine does not constantly put out 215 hp or 185 ftlbs of torque for instance. These are numbers specific to an exact RPM* for that engine.

[teknochild]

Originally Posted by obLu

Errr ... sorry, I need some cliffsnotes. But one thing I don't think was addressed in any of this:

How does this account for diesel motors? If HP is a strict function of torque, then how come diesel engines always have much more torque than HP?

i understand its a long read i answered exactly that, infact i warned against asking it but i wont flame, hp is a function of torque and rpms, diesel motors do not rev high at all, most stop at 4k where a gas motor goes to 7k or even 20k, and for your next question after reading that, "if horsepower is what points to acceleration why are these diesel motors with such low hp figures as fast as gas motors with high figures", because they have their torqure right away, so at 2k while a gas motor still only has 50hp the diesels motor already has like 200

the problem comes that we only get peak #s when we should have something almost like an average










josh YOU are the one over your head, you understand the calculations, terminology, and general principles, but you are TOTALLY missing what horsepower is, car b does NOT have the same horsepower as car A, the OPs article does not arrive at the conclusion "peak horsepower is what points to acceleration" or at least i did not in anything i wrote down, infact i adressed the issue of peak numbers several times i thought

if a car has more horsepower at any point vs a car with lower horsepower and more torque, at that point the car with more horsepower will have higher acceleration, this is whats meant by "horsepower is acceleration"


furthermore "Rotational, Sum of all moments (torques) = moment of inertia x angular acceleration." out of curiosity how would you calculate the "sum of all moments"? yea thats what i thought, do u get it yet?

also the 210hp is what i changed to show you that HP is equivalant to acceleration


your statement "horsepower and torque need to be looked at" thats wrong, torque and rpms is what needs to be looked at, and this is what HP is, when you look at the hp (not just peak) of a car thats what your doing looking at torque and rpms together, infact you can show me the dyno of two cars with only horsepower showing on the dyno and i can tell you which car is faster (provided everything but the engine is the same) this simple statement should be able to totally put this discussion to rest, you can do the same thing whith a dyno only showing torque, but it is going to take a longer time, because wether you know it or not your going to be calculating the horsepower in your head


you really need to get this in your head, horsepower IS TORQUE APPLIED OVER TIME

[teknochild]

Originally Posted by Josh49

I think many people are missing the fact that an engine develops peak Torque and peak HP at different RPM's. Peak Torque is usually generated in the lower RPM band while Peak HP is usually generated in the high RPM band. An engine does not constantly put out 215 hp or 185 ftlbs of torque for instance. These are numbers specific to an exact RPM* for that engine.

fine ill kill you using your own statment, where is a car accelerating the fastest, while torque is increasing up to peak torque or between peak torque and peak horsepower where torque is decreasing and horsepower is increasing?