Login


12212006, 12:02 AM  #23  
New Member
4
Rep 19
Posts 
Quote:
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. 

Appreciate
0

12212006, 12:18 AM  #24 
Lack of charisma can be fatal...
30
Rep 365
Posts
Drives: 2006 330i
Join Date: Jan 2006
Location: Portland, Oregon USA

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 lbft of torque and a 335 is at 1400 generating 300 lbft of torque, will we be neck n neck or equal? At the top end the cars both equal out right?
__________________
Protect Me From What I Want...
_____________________________ 
Appreciate
0

12212006, 12:50 AM  #25  
New Member
4
Rep 19
Posts 
Quote:
The beginning of my article actually touches on the physics portion of the issue, which I agree is very important. 

Appreciate
0

12212006, 07:11 AM  #26  
General
287
Rep 18,856
Posts 
Quote:
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? 

Appreciate
0

12212006, 09:26 AM  #27  
New Member
4
Rep 19
Posts 
Quote:
""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. 

Appreciate
0

12212006, 10:43 AM  #28 
Smiling politely
111
Rep 7,934
Posts 
__________________
330i  Black Sapphire  Beige + Burl  Sport  Premium  Cold  Nav  CA  Sat prep 
Appreciate
0

12212006, 11:10 AM  #29 
Colonel
91
Rep 2,059
Posts 
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.
__________________
330i 6MT l 255 HP @ 5900 rpm 214 lbft Torque @ 3500 rpm l Alpine White l Beige l Aluminum l ZSP l 494 l PDC
"Freude am Fahren" = "Joy to Drive" 
Appreciate
0

12212006, 03:50 PM  #30 
Major General
118
Rep 6,664
Posts 
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
__________________
E90 325XI, MYSTIC BLUE ON BLACK/ALUM, STEP, NAV, PDC, CWP, XENON, SIRIUS, ALARM, MUD GUARDS, CLEARBRA, CHROME GRILLS AND TIPS, VALENTINE 1 (HARDWIRED), HO CERAMIC 40%, 161'S, REAR FOG MOD, LUX 4.0, BLACKLINES, OEM PEDALS, MTEC FOGS, GRUPPEM REP INTAKE. 156'S AND RUBBER MATS FOR THE WINTER. 
Appreciate
0

12212006, 03:55 PM  #31 
Private
0
Rep 79
Posts 
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 TorqueRPM 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 necktoneck 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. 
Appreciate
0

12212006, 07:42 PM  #35  
New Member
4
Rep 19
Posts 
Quote:
Cheers, Daniel 

Appreciate
0

12212006, 07:43 PM  #36 
Lack of charisma can be fatal...
30
Rep 365
Posts
Drives: 2006 330i
Join Date: Jan 2006
Location: Portland, Oregon USA

So no one answered my question.
If I'm at 4500 rpms in my 330 generating 300 lbft of torque and a 335 is at 1400 generating 300 lbft of torque, will we be neck n neck or equal? At the top end the cars both equal out right?
__________________
Protect Me From What I Want...
_____________________________ 
Appreciate
0

01012007, 07:11 PM  #37  
Your resident 4um troll
50
Rep 2,021
Posts 
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, Quote:
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 Last edited by teknochild; 01012007 at 08:14 PM. 

Appreciate
0

01012007, 07:18 PM  #38  
Your resident 4um troll
50
Rep 2,021
Posts 
Quote:
Quote:
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 Quote:
so your right in your conclusion that the second car is faster, but not in how you arrived at it Quote:
and so u guys dont think im only supporting daniel and totally one sided even though he made this comment off the wall Quote:
Quote:
Quote:
Quote:
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 Quote:
Quote:
Quote:
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. Quote:
Quote:
what you have really done is start another discussion about gearing Quote:
Quote:
torque is about HOW HARD the car pushes the crankshaft, while horsepower is about HOW OFTEN your car applies that force to the crankshaft Quote:
Last edited by teknochild; 01012007 at 08:43 PM. 

Appreciate
0

01012007, 08:38 PM  #39 
Your resident 4um troll
50
Rep 2,021
Posts 
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

Appreciate
0

01022007, 09:23 AM  #40 
Major General
118
Rep 6,664
Posts 
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 Profilewise: 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.
__________________
E90 325XI, MYSTIC BLUE ON BLACK/ALUM, STEP, NAV, PDC, CWP, XENON, SIRIUS, ALARM, MUD GUARDS, CLEARBRA, CHROME GRILLS AND TIPS, VALENTINE 1 (HARDWIRED), HO CERAMIC 40%, 161'S, REAR FOG MOD, LUX 4.0, BLACKLINES, OEM PEDALS, MTEC FOGS, GRUPPEM REP INTAKE. 156'S AND RUBBER MATS FOR THE WINTER. 
Appreciate
0

01022007, 12:47 PM  #41 
Major
24
Rep 1,160
Posts 
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? 
Appreciate
0

01022007, 02:34 PM  #42 
Major General
118
Rep 6,664
Posts 
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.
__________________
E90 325XI, MYSTIC BLUE ON BLACK/ALUM, STEP, NAV, PDC, CWP, XENON, SIRIUS, ALARM, MUD GUARDS, CLEARBRA, CHROME GRILLS AND TIPS, VALENTINE 1 (HARDWIRED), HO CERAMIC 40%, 161'S, REAR FOG MOD, LUX 4.0, BLACKLINES, OEM PEDALS, MTEC FOGS, GRUPPEM REP INTAKE. 156'S AND RUBBER MATS FOR THE WINTER. 
Appreciate
0

01022007, 02:54 PM  #43  
Your resident 4um troll
50
Rep 2,021
Posts 
Quote:
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 

Appreciate
0

01022007, 02:56 PM  #44  
Your resident 4um troll
50
Rep 2,021
Posts 
Quote:


Appreciate
0

Post Reply 
Bookmarks 
Thread Tools  Search this Thread 

