| newbie | 04-22-2002 11:39 PM |
Torque or Horses?..
Hi
simple question:
for better straight line acceleration, should one base changing gears on the torque curve, or power one?..
Thanks
simple question:
for better straight line acceleration, should one base changing gears on the torque curve, or power one?..
Thanks
| brainrally | 04-23-2002 01:16 AM |
Go with the Horsies (Horsepower).
| North Ursalia | 04-23-2002 02:09 AM |
Who only accelerates in a straight line anyway :)? "Horsepower sells car parts... torque wins races". A car with 400hp and 100 lb*ft of torque is still dog-ass slow ;).
Brian
[url]http://www.northursalia.com[/url]
[url]http://www.imprezamods.com[/url]
[url]http://www.scoobymods.com[/url]
[url]http://www.subaruwrxparts.com[/url]
Brian
[url]http://www.northursalia.com[/url]
[url]http://www.imprezamods.com[/url]
[url]http://www.scoobymods.com[/url]
[url]http://www.subaruwrxparts.com[/url]
| samowrx | 04-23-2002 02:21 AM |
hp matters for top speed, while torque is for acceleration.
| romanom | 04-23-2002 08:27 AM |
Horsepower = Torque applied over a distance in a certain period of time
Power is how much work you can do in a period of time.
Since torque is the only force and horsepower is just a figure calculated from torque, time and distance.......torque matters.
But time and distance are related to RPMs so you should use the power curve, if your gearing the car to use the ENTIRE RPM band.
An enginer that spins up quickly and can reach high RPMs can have very good power.
Power=Torque * distance * time
This why a car with low torque can still have great acceleration when you really let the engine lose, Honda S2000, Integra Type R.
For a street car I'll take high, low-end torque over high-reving though.
Power is how much work you can do in a period of time.
Since torque is the only force and horsepower is just a figure calculated from torque, time and distance.......torque matters.
But time and distance are related to RPMs so you should use the power curve, if your gearing the car to use the ENTIRE RPM band.
An enginer that spins up quickly and can reach high RPMs can have very good power.
Power=Torque * distance * time
This why a car with low torque can still have great acceleration when you really let the engine lose, Honda S2000, Integra Type R.
For a street car I'll take high, low-end torque over high-reving though.
| Travis R | 04-23-2002 08:40 AM |
First you take a graph of the vehicles acceleration (acceleration vs. speed). There will be 5 curves (one for each gear) on the graph, one after another, each overlapping the previous one by a small amount. The curves will resemble the torque curve. For maximum acceleration you want to minimize the area under these curves. That doesn't necessarily mean shifting at redline either, and it also means that you should probably shift at a different point for each gear.
basic answer: torque
basic answer: torque
| ColinL | 04-23-2002 10:27 AM |
with ideal gearing you generally want to keep the engine's RPM between the range where it makes max torque and max HP.
variable valve timing and/or turbocharging can muddle this though, since both can radically alter the shape of the torque curve. gearing can also alter it, if a given gear is very tall you could want to overrun the lower gear to keep the RPM up when you shift. most cars are like this for the 1-2 shift which generally should happen at the rev limit no matter what the torque curve looks like.
also, tractable power with a broad torque curve is useful for everything except drag racing. a narrow, explosive torque curve is hard to manage on a road course or autocrossing, and difficult to take advantage of on the street.
variable valve timing and/or turbocharging can muddle this though, since both can radically alter the shape of the torque curve. gearing can also alter it, if a given gear is very tall you could want to overrun the lower gear to keep the RPM up when you shift. most cars are like this for the 1-2 shift which generally should happen at the rev limit no matter what the torque curve looks like.
also, tractable power with a broad torque curve is useful for everything except drag racing. a narrow, explosive torque curve is hard to manage on a road course or autocrossing, and difficult to take advantage of on the street.
| brainrally | 04-23-2002 10:31 AM |
Shows what I know. :rolleyes:
| newbie | 04-23-2002 04:58 PM |
Thanks for the answers, Y'All
i've been "following" the torque carve, shifting at, roughly, 5 K, so that the engine hits the transmission at slightly below 4 K
pretty much tryin' to keep it at constant 4 K all the time
comes up to about a gallon a mile, but, it sure is one fun way to burn gasoline!
and, no, i have not considered joining GreenPeace ...
i've been "following" the torque carve, shifting at, roughly, 5 K, so that the engine hits the transmission at slightly below 4 K
pretty much tryin' to keep it at constant 4 K all the time
comes up to about a gallon a mile, but, it sure is one fun way to burn gasoline!
and, no, i have not considered joining GreenPeace ...
| TBreu007 | 04-23-2002 08:10 PM |
You buy HP and drive torque
| newbie | 04-23-2002 09:02 PM |
"You buy HP and drive torque", -
i do hope that You were trying to write "one buys HP and drives torque", since we have not met and You do not know me, and thus You would have no grounds to make a statement like that.
i do hope that You were trying to write "one buys HP and drives torque", since we have not met and You do not know me, and thus You would have no grounds to make a statement like that.
| Mako | 04-23-2002 09:41 PM |
:rolleyes:
| edekker | 04-23-2002 09:51 PM |
You can run the CarTest program and see for yourself.
I chose the Honda Prelude VTEC 1993:
I forced all gearshifts at the torque peak – 5700 RPM and ran the sim: -
0-60: 8.3s
1/4: 16.3s, 86.1 MPH
Then I forced all gearshifts at the horsepower peak – 6800 RPM and ran the sim again: -
0-60 7,5s
1/4: 15.6s, 91.9 MPH
Note: Before each run, don't forget to optimize the launch first.
Regards,
Ed.
I chose the Honda Prelude VTEC 1993:
I forced all gearshifts at the torque peak – 5700 RPM and ran the sim: -
0-60: 8.3s
1/4: 16.3s, 86.1 MPH
Then I forced all gearshifts at the horsepower peak – 6800 RPM and ran the sim again: -
0-60 7,5s
1/4: 15.6s, 91.9 MPH
Note: Before each run, don't forget to optimize the launch first.
Regards,
Ed.
| TBreu007 | 04-24-2002 10:19 AM |
[QUOTE][i]Originally posted by newbie [/i]
[B]"You buy HP and drive torque", -
i do hope that You were trying to write "one buys HP and drives torque", since we have not met and You do not know me, and thus You would have no grounds to make a statement like that. [/B][/QUOTE]
My apologies for my gross abuse of the English language. Most of the time, my writing is much better. Since you are so quick to correct me, I would like to point out to you that you might want to analyze your own grammatical and punctuation skills as well; your reply was full of comma splices, letters that shouldn't be capitalized and just general ignorance.:monkey:
When did I-Club become grammar school:rolleyes:
[B]"You buy HP and drive torque", -
i do hope that You were trying to write "one buys HP and drives torque", since we have not met and You do not know me, and thus You would have no grounds to make a statement like that. [/B][/QUOTE]
My apologies for my gross abuse of the English language. Most of the time, my writing is much better. Since you are so quick to correct me, I would like to point out to you that you might want to analyze your own grammatical and punctuation skills as well; your reply was full of comma splices, letters that shouldn't be capitalized and just general ignorance.:monkey:
When did I-Club become grammar school:rolleyes:
| 97itr153 | 04-24-2002 12:10 PM |
If you dont know the answer...shut up.
Go to this website for more information!
[url]http://www.autospeed.com/A_1073/P_1/article.html[/url]
Anyone who thinks that the TORQUE curve should be used to determining the correct shift points...is an idiot...and should not be misguiding newbies on this forum...
Power (NOT TORQUE) is what determines BOTH acceleration as well as top speed.
In addition:
As a car goes from 0 to Top Speed, Weight becomes LESS important and Aerodynamics become MORE important.
:mad:
[url]http://www.autospeed.com/A_1073/P_1/article.html[/url]
Anyone who thinks that the TORQUE curve should be used to determining the correct shift points...is an idiot...and should not be misguiding newbies on this forum...
Power (NOT TORQUE) is what determines BOTH acceleration as well as top speed.
In addition:
As a car goes from 0 to Top Speed, Weight becomes LESS important and Aerodynamics become MORE important.
:mad:
| TheWRX | 04-24-2002 12:39 PM |
Great, I started getting confused by all these people with their scientific talk about torque. Just using high school physics, it's simple to explain why it's the power that counts, and unless somebody tells me what's wrong with my reasoning, I'll keep believing it:
Increasing the speed (v) of an object (accelerating it), means adding kinetic energy to it (E = 0.5 * m * v^2). Power (P) is the amount of energy produced per time (E = P * t). To accelerate the object to a certain speed as quickly as possible, you want to minimize the time t = E / P = 0.5 * m * v^2 / P. Looking at this, it's clear that making the power as large as possible will minimize the time.
This neglects additional energy that needs to be produced to overcome drag and rolling resistance. And the power will not be constant, so you'll have to look at the whole process in small time increments (use integration, to make it really clean). But I don't think it changes that you want to apply the maximum power you can get at any given time to get maximum acceleration.
Increasing the speed (v) of an object (accelerating it), means adding kinetic energy to it (E = 0.5 * m * v^2). Power (P) is the amount of energy produced per time (E = P * t). To accelerate the object to a certain speed as quickly as possible, you want to minimize the time t = E / P = 0.5 * m * v^2 / P. Looking at this, it's clear that making the power as large as possible will minimize the time.
This neglects additional energy that needs to be produced to overcome drag and rolling resistance. And the power will not be constant, so you'll have to look at the whole process in small time increments (use integration, to make it really clean). But I don't think it changes that you want to apply the maximum power you can get at any given time to get maximum acceleration.
| ColinL | 04-24-2002 03:29 PM |
97itr ... let me guess, you used to have a Honduh and now you've recently blessed us with your WRX-owning presence. I'm getting to be too old to flame you properly for your rant.
but first of all, I've read that autospeed article and I even understood it all which I'm not sure is the case for you.
in my post above about the torque curve, I didn't explain the role of gearing completely. wah. I still stand by the general concept that the engine should be in an RPM range between its peak torque and peak HP.
the question WASN'T asking the role of torque, horsepower, weight and aerodynamics in acceleration between different cars. the question is, how do you make a given car accelerate fastest.
:monkey:
but first of all, I've read that autospeed article and I even understood it all which I'm not sure is the case for you.
in my post above about the torque curve, I didn't explain the role of gearing completely. wah. I still stand by the general concept that the engine should be in an RPM range between its peak torque and peak HP.
the question WASN'T asking the role of torque, horsepower, weight and aerodynamics in acceleration between different cars. the question is, how do you make a given car accelerate fastest.
:monkey:
| SCRAPPYDO | 04-24-2002 03:36 PM |
If you really want to cut through the fog here, Its not just torque or horsepower. Its not that simply. First of all, horsepower as somebody else said is just a caluculated number. Its a derived figure. When you put your car on a dyno, all you measure is torque. The HP figure is just the torque value fed through a VERY simple equation.
So getting back to the question. What matters most. To put a really fine point on it. Torque matters most. But to sharpen the point even finer. Peak torque matters and where that peak torque occurs in the powerband. A flat torque plateau will yeild great acceleration, where a torque spike will leave a car feeling like its gasping for air and weak after an initial burst.
If you can get a very broad torque curve along a very large RPM band you will have a really well tuned engine that is a pleasure to drive. Since HP is directly related to RPM, An engine with lots of torque at high RPM will produce high HP.
Dont let all of this confuse you. Its really very simple. Their are patches involved of course and band aids and tweaks, but for the most part what is stated above is true.
Everything else aside (like gearing) and just focusing on just the car. Whats more important is Torque and where it occurs at.
Print it, copy it, and send it out, end of story.
SCRAPPYDO
stephen
So getting back to the question. What matters most. To put a really fine point on it. Torque matters most. But to sharpen the point even finer. Peak torque matters and where that peak torque occurs in the powerband. A flat torque plateau will yeild great acceleration, where a torque spike will leave a car feeling like its gasping for air and weak after an initial burst.
If you can get a very broad torque curve along a very large RPM band you will have a really well tuned engine that is a pleasure to drive. Since HP is directly related to RPM, An engine with lots of torque at high RPM will produce high HP.
Dont let all of this confuse you. Its really very simple. Their are patches involved of course and band aids and tweaks, but for the most part what is stated above is true.
Everything else aside (like gearing) and just focusing on just the car. Whats more important is Torque and where it occurs at.
Print it, copy it, and send it out, end of story.
SCRAPPYDO
stephen
| romanom | 04-24-2002 03:43 PM |
[QUOTE][i]Originally posted by TheWRX [/i]
[B]Great, I started getting confused by all these people with their scientific talk about torque. Just using high school physics, it's simple to explain why it's the power that counts, and unless somebody tells me what's wrong with my reasoning, I'll keep believing it:
Increasing the speed (v) of an object (accelerating it), means adding kinetic energy to it (E = 0.5 * m * v^2). Power (P) is the amount of energy produced per time (E = P * t). To accelerate the object to a certain speed as quickly as possible, you want to minimize the time t = E / P = 0.5 * m * v^2 / P. Looking at this, it's clear that making the power as large as possible will minimize the time.
This neglects additional energy that needs to be produced to overcome drag and rolling resistance. And the power will not be constant, so you'll have to look at the whole process in small time increments (use integration, to make it really clean). But I don't think it changes that you want to apply the maximum power you can get at any given time to get maximum acceleration. [/B][/QUOTE]
To add energy you need POWER.....energy comes from power not the other way around. So the KE stuff doesn't work here.
It's even simpler than that (which I thought I explained in my first post, guess not).
Torque is just a force it doesn't make a car fast. Work is how much force you can apply over a distance.......Power is how much work you can do in a period of time.
Power=Force/Distance/Time=(Force*Time)/Distance
So, if you want to get the car moving to a certain distance in as little time as possible you need............POWER!
ALWAYS USE THE POWER CURVE.
Low end torque is nice for street driving because Power is a function of both RPMs (revs is a distance and minute is a time) and torque. So, low RPMs with a lot of torque means lots of power at the lower RPMs...........but it's always a matter of power.
The term low-end torque is a mis-nomer...it should be low end power.
To me this is a very simple concept. :p
[B]Great, I started getting confused by all these people with their scientific talk about torque. Just using high school physics, it's simple to explain why it's the power that counts, and unless somebody tells me what's wrong with my reasoning, I'll keep believing it:
Increasing the speed (v) of an object (accelerating it), means adding kinetic energy to it (E = 0.5 * m * v^2). Power (P) is the amount of energy produced per time (E = P * t). To accelerate the object to a certain speed as quickly as possible, you want to minimize the time t = E / P = 0.5 * m * v^2 / P. Looking at this, it's clear that making the power as large as possible will minimize the time.
This neglects additional energy that needs to be produced to overcome drag and rolling resistance. And the power will not be constant, so you'll have to look at the whole process in small time increments (use integration, to make it really clean). But I don't think it changes that you want to apply the maximum power you can get at any given time to get maximum acceleration. [/B][/QUOTE]
To add energy you need POWER.....energy comes from power not the other way around. So the KE stuff doesn't work here.
It's even simpler than that (which I thought I explained in my first post, guess not).
Torque is just a force it doesn't make a car fast. Work is how much force you can apply over a distance.......Power is how much work you can do in a period of time.
Power=Force/Distance/Time=(Force*Time)/Distance
So, if you want to get the car moving to a certain distance in as little time as possible you need............POWER!
ALWAYS USE THE POWER CURVE.
Low end torque is nice for street driving because Power is a function of both RPMs (revs is a distance and minute is a time) and torque. So, low RPMs with a lot of torque means lots of power at the lower RPMs...........but it's always a matter of power.
The term low-end torque is a mis-nomer...it should be low end power.
To me this is a very simple concept. :p
| TheWRX | 04-24-2002 04:52 PM |
[QUOTE][i]Originally posted by romanom [/i]
[B]To add energy you need POWER.....energy comes from power not the other way around.[/B][/QUOTE]
I'm not sure why you quoted my post and make it sound like you disagree with what I described. This was almost exactly my point, you need power to create (kinetic) energy.
[QUOTE][B]Power=Force/Distance/Time=(Force*Time)/Distance[/B][/QUOTE]
According to my formula collection:
Work=Force*Distance
Power=Work/Time=(Force*Distance)/Time
[B]To add energy you need POWER.....energy comes from power not the other way around.[/B][/QUOTE]
I'm not sure why you quoted my post and make it sound like you disagree with what I described. This was almost exactly my point, you need power to create (kinetic) energy.
[QUOTE][B]Power=Force/Distance/Time=(Force*Time)/Distance[/B][/QUOTE]
According to my formula collection:
Work=Force*Distance
Power=Work/Time=(Force*Distance)/Time
| romanom | 04-24-2002 05:19 PM |
[QUOTE][i]Originally posted by TheWRX [/i]
[B]
I'm not sure why you quoted my post and make it sound like you disagree with what I described. This was almost exactly my point, you need power to create (kinetic) energy.
According to my formula collection:
Work=Force*Distance
Power=Work/Time=(Force*Distance)/Time [/B][/QUOTE]
I don't know I'm just in pissed off mood today..so I'm gruppy!
:lol: :lol: :p :rolleyes:
Sorry...I just snapped...but I'm better now....I'll be fine once the voices in my head are gone! :(
(I am just kidding of course) Sorry, I read your post half a sleep and saw something else!
WILLIE SAYS: LET ME KICK ROMANOM'S ASS THEWRX!?
[IMG]http://www.thesimpsons.com/bios/images/bios_school_willie.gif[/IMG]
[B]
I'm not sure why you quoted my post and make it sound like you disagree with what I described. This was almost exactly my point, you need power to create (kinetic) energy.
According to my formula collection:
Work=Force*Distance
Power=Work/Time=(Force*Distance)/Time [/B][/QUOTE]
I don't know I'm just in pissed off mood today..so I'm gruppy!
:lol: :lol: :p :rolleyes:
Sorry...I just snapped...but I'm better now....I'll be fine once the voices in my head are gone! :(
(I am just kidding of course) Sorry, I read your post half a sleep and saw something else!
WILLIE SAYS: LET ME KICK ROMANOM'S ASS THEWRX!?
[IMG]http://www.thesimpsons.com/bios/images/bios_school_willie.gif[/IMG]
| newbie | 04-24-2002 07:39 PM |
[QUOTE][i]Originally posted by TBreu007 [/i]
[B]
When did I-Club become grammar school:rolleyes: [/B][/QUOTE]
You missed my point. I was merely implying that Your post had no info whatsoever. That's all.
Unfortunately, You decided to shout back.
Sorry about the confusion.
[B]
When did I-Club become grammar school:rolleyes: [/B][/QUOTE]
You missed my point. I was merely implying that Your post had no info whatsoever. That's all.
Unfortunately, You decided to shout back.
Sorry about the confusion.
| newbie | 04-24-2002 07:41 PM |
[QUOTE][i]Originally posted by edekker [/i]
[B]
Note: Before each run, donÂ't forget to optimize the launch first.
[/B][/QUOTE]
how?..
and, - for the sim app ... well, does not the fact that Subarus are AWD mean that it (the prognosis) will not be accurate?..
[B]
Note: Before each run, donÂ't forget to optimize the launch first.
[/B][/QUOTE]
how?..
and, - for the sim app ... well, does not the fact that Subarus are AWD mean that it (the prognosis) will not be accurate?..
| TBreu007 | 04-24-2002 09:04 PM |
My apologies...that is a VERY old saying I thought everyone knew.
You buy HP= When looking for performance parts, most people concentrate on how much HP it will get them without thinking about torque.
You drive torque= This the force that ACTUALLY driver "one's" car.
You buy HP= When looking for performance parts, most people concentrate on how much HP it will get them without thinking about torque.
You drive torque= This the force that ACTUALLY driver "one's" car.
| 97itr153 | 04-24-2002 11:10 PM |
For ColinL!
Actually i DO still own an Integra Type-R (killer car) as well as a WRX.
As far as max acceleration goes one should not look at the torque curve at all. Simple look at the power curve and shift at a point when the power in BOTH gears is the SAME. Obviously, this means that you will HAVE to go beyond the point of peak power. As for the point of peak torque...it means nothing...
As far as max acceleration goes one should not look at the torque curve at all. Simple look at the power curve and shift at a point when the power in BOTH gears is the SAME. Obviously, this means that you will HAVE to go beyond the point of peak power. As for the point of peak torque...it means nothing...
| edekker | 04-25-2002 12:01 AM |
Newbie,
The program (search the net) can optimize the launch – selected from one of several menu items. The program determines the optimal settings on parameters such as RPM and clutch slip (or drop).
AWD is taken into consideration – it's one of the many parameters.
It's not perfect, but I find the program trustworthy. It's fairly accurate for the most part, and it is at least accurate enough to determine whether one should shift gears based on the torque peak or the HP peak for all-out acceleration.
Moreover, shifting still higher than the HP peak insofar as to keep, or cross the HP peak between shift points in the attempt to achieve highest average power between shifts, can result in even better acceleration.
Regards,
Ed.
The program (search the net) can optimize the launch – selected from one of several menu items. The program determines the optimal settings on parameters such as RPM and clutch slip (or drop).
AWD is taken into consideration – it's one of the many parameters.
It's not perfect, but I find the program trustworthy. It's fairly accurate for the most part, and it is at least accurate enough to determine whether one should shift gears based on the torque peak or the HP peak for all-out acceleration.
Moreover, shifting still higher than the HP peak insofar as to keep, or cross the HP peak between shift points in the attempt to achieve highest average power between shifts, can result in even better acceleration.
Regards,
Ed.
| newbie | 04-25-2002 12:02 AM |
[QUOTE][i]Originally posted by TBreu007 [/i]
[B]...apologies...... torque= This the force that ACTUALLY driver "one's" car. [/B][/QUOTE]
a) np, - "...what we've got here ... is a failure ... to communicate"
b) so, the torque curve You say?..
[B]...apologies...... torque= This the force that ACTUALLY driver "one's" car. [/B][/QUOTE]
a) np, - "...what we've got here ... is a failure ... to communicate"
b) so, the torque curve You say?..
| newbie | 04-25-2002 12:05 AM |
[QUOTE][i]Originally posted by edekker [/i]
[B]...Moreover, shifting still higher than the HP peak insofar as to keep, or cross the HP peak between shift points in the attempt to achieve highest average power between shifts, can result in even better acceleration.... [/B][/QUOTE]
that is what i have been doing, just based shidting points on the torque curve ...
to all:
Thanks to all for the input. Still have no clear answer though ... it SEEMS that horses is where it's at ... not absolutely sure though ...
I am not shopping for a vehicle, I am more than pleased with my silver WRX wagon, - so, I am not questioning whether I should give preference to the ones with better torque or more horses, - I merely want to know at what rpm's to shift gears for better (faster) results.
Let me rephrase the question: if You were doing one eighth or a quarter mile on a strip, - at what rpm's would You shift the gears in WRX?.. Also, - for a proper fast launch, - one should let go off the clutch and engage gears at what rpm?..
C'mon, it can't be all that hard to figure out ...
I am not trying to be annoying, just trying to settle it once and for all.
[B]...Moreover, shifting still higher than the HP peak insofar as to keep, or cross the HP peak between shift points in the attempt to achieve highest average power between shifts, can result in even better acceleration.... [/B][/QUOTE]
that is what i have been doing, just based shidting points on the torque curve ...
to all:
Thanks to all for the input. Still have no clear answer though ... it SEEMS that horses is where it's at ... not absolutely sure though ...
I am not shopping for a vehicle, I am more than pleased with my silver WRX wagon, - so, I am not questioning whether I should give preference to the ones with better torque or more horses, - I merely want to know at what rpm's to shift gears for better (faster) results.
Let me rephrase the question: if You were doing one eighth or a quarter mile on a strip, - at what rpm's would You shift the gears in WRX?.. Also, - for a proper fast launch, - one should let go off the clutch and engage gears at what rpm?..
C'mon, it can't be all that hard to figure out ...
I am not trying to be annoying, just trying to settle it once and for all.
| edekker | 04-25-2002 12:29 AM |
Newbie,
It seems clear to me.
Accelerate beyond the HP peak to the point where HP drops to the same level on its rise for the next upshift. This method should make for the highest available average power between shifts – and the strongest overall acceleration.
What may confuse some people is that the strongest acceleration in any fixed gear does occur at the torque peak – that is true.
However by gear shifting, we have at our disposal is the ability to keep the torque multiplied at its highest possible rate, maintaining (to a certain degree, since gear ratios change in discrete steps) the highest output power possible. That's the key to rapid overall acceleration.
Regards,
Ed.
It seems clear to me.
Accelerate beyond the HP peak to the point where HP drops to the same level on its rise for the next upshift. This method should make for the highest available average power between shifts – and the strongest overall acceleration.
What may confuse some people is that the strongest acceleration in any fixed gear does occur at the torque peak – that is true.
However by gear shifting, we have at our disposal is the ability to keep the torque multiplied at its highest possible rate, maintaining (to a certain degree, since gear ratios change in discrete steps) the highest output power possible. That's the key to rapid overall acceleration.
Regards,
Ed.
| NebScoob | 04-25-2002 09:00 AM |
[QUOTE]As far as max acceleration goes one should not look at the torque curve at all. [/QUOTE]
Yes, and no... You should be looking at the cars acceleration
curve, which for any one gear has the same basic shape as
the torque curve.
Force=Mass*Acceleration
Acceleration=Force/Mass
I think thats right. Torque is a force. More Torque=More Acceleration. If you could plot a cars acceleration, in say Gs, and compare that curve to the torque curve, the two curves have the same shape.
[QUOTE]As for the point of peak torque...it means nothing...[/QUOTE]
Absolutely Correct...The torque peak is where you have the greatest acceleration, but it has nothing to do where you shift. Neither does HP peak, and here is why.
If you want to accerate as fast as possible, you want to keep the amount of torque going to the wheels as high as possible, and the amount of torque going to the wheels is higher in when your in first gear, then when you are in second.
So you should stay in the lower gear as long as possible and shift at redline right? Not quite. In most cars, as they approach redline, torque drops off very quickly, and in some cases, shifting to the next gear will give more torque to the wheels.
What you need to do to determine optimum shift points is look at the all the torque curves for each gear. I have done this in my RS...
[IMG]http://edadnotes.unl.edu/shiftpts.gif[/IMG]
Where the lines cross, you should shift. Most of the time I shift
near 6000 RPM, just short of redline, but I think one of the gears,
third or whatever, I can shift a little sooner. As you can see, I should be nowhere near my torque peak, which is around 4K.
....
So what about HP...It is a useful figure, and describes the potential of the car better. To maximize torque to the wheels, you will have to stay in each gear about as long as possible to take atvantage of the gearing. This means you are staying in the upper RPMS, where the HP peak ussually lives.
But, it still all boils down to torque...
A high reving engine does not make its torque in the engine, it makes it with the gearing...
Two, mythical cars...If the shift point is around 30MPH,
0-9000 RPM up to 30MPH (Less torque, same HP)
0-6000 RPM up to 30MPH (More torque, same HP)
But becuase of a gearing they can both make the same amount of torque to the wheels, same acceleration, similar preformace. THAT IS WHY HP is important. If you just look at torque, you can't compare the cars. If you look at HP, you can get a good idea of the preformace of the car.
Yes, and no... You should be looking at the cars acceleration
curve, which for any one gear has the same basic shape as
the torque curve.
Force=Mass*Acceleration
Acceleration=Force/Mass
I think thats right. Torque is a force. More Torque=More Acceleration. If you could plot a cars acceleration, in say Gs, and compare that curve to the torque curve, the two curves have the same shape.
[QUOTE]As for the point of peak torque...it means nothing...[/QUOTE]
Absolutely Correct...The torque peak is where you have the greatest acceleration, but it has nothing to do where you shift. Neither does HP peak, and here is why.
If you want to accerate as fast as possible, you want to keep the amount of torque going to the wheels as high as possible, and the amount of torque going to the wheels is higher in when your in first gear, then when you are in second.
So you should stay in the lower gear as long as possible and shift at redline right? Not quite. In most cars, as they approach redline, torque drops off very quickly, and in some cases, shifting to the next gear will give more torque to the wheels.
What you need to do to determine optimum shift points is look at the all the torque curves for each gear. I have done this in my RS...
[IMG]http://edadnotes.unl.edu/shiftpts.gif[/IMG]
Where the lines cross, you should shift. Most of the time I shift
near 6000 RPM, just short of redline, but I think one of the gears,
third or whatever, I can shift a little sooner. As you can see, I should be nowhere near my torque peak, which is around 4K.
....
So what about HP...It is a useful figure, and describes the potential of the car better. To maximize torque to the wheels, you will have to stay in each gear about as long as possible to take atvantage of the gearing. This means you are staying in the upper RPMS, where the HP peak ussually lives.
But, it still all boils down to torque...
A high reving engine does not make its torque in the engine, it makes it with the gearing...
Two, mythical cars...If the shift point is around 30MPH,
0-9000 RPM up to 30MPH (Less torque, same HP)
0-6000 RPM up to 30MPH (More torque, same HP)
But becuase of a gearing they can both make the same amount of torque to the wheels, same acceleration, similar preformace. THAT IS WHY HP is important. If you just look at torque, you can't compare the cars. If you look at HP, you can get a good idea of the preformace of the car.
| SCRAPPYDO | 04-25-2002 10:41 AM |
Ah, but if you understand the relationship between torque and horsepower, how you can derive HP from torque, the torque curve is a more useful tool. Couple that with the weight of the car, and the final drive ratios in all gears and you have all the tools you will need to figure out acceleration, shift points, etc. (Excluding aerodynamic drag and rolling friction of course).
I guess when I see a torque curve I automaticaly see a HP curve as well. I have done the conversion so many times, its beginning to be second nature.
I dont put much weight in derived numbers, which is what HP is. I would rather analyze the raw data.
If you know how many FT-LBs are at the flywheel at all given RPM, and you know the gear ratios in the transmission and the differentials, and you know the rolling diameter of the tires, you could very easily calculate how much torque actually gets to the ground and moves you.
Whoever said you want to stay in the sweet spot of the torque curve is absolutely correct, it just so happens that its usually the same range as the HP curve. And the reason why is because HP is calculated from Torque.
When I see HP I think torque, when I see Torque, I can then calculate HP.
But its torque that actually moves the car.
SCRAPPYDO
stephen
I guess when I see a torque curve I automaticaly see a HP curve as well. I have done the conversion so many times, its beginning to be second nature.
I dont put much weight in derived numbers, which is what HP is. I would rather analyze the raw data.
If you know how many FT-LBs are at the flywheel at all given RPM, and you know the gear ratios in the transmission and the differentials, and you know the rolling diameter of the tires, you could very easily calculate how much torque actually gets to the ground and moves you.
Whoever said you want to stay in the sweet spot of the torque curve is absolutely correct, it just so happens that its usually the same range as the HP curve. And the reason why is because HP is calculated from Torque.
When I see HP I think torque, when I see Torque, I can then calculate HP.
But its torque that actually moves the car.
SCRAPPYDO
stephen
| edekker | 04-25-2002 11:34 AM |
SCRAPPYDO,
That is not entirely correct.
Torque cannot move a car anymore than torque applied to a frozen bolt can move the bolt. The bolt must move first – the torque is then applied at a certain [I]rate[/I] - before any work is actually done.
The same goes true for the car; it is the [I]rate[/I] at which the torque is applied which determines the amount of work the engine puts out.
[Gotta get back to work]
Regards,
Ed.
That is not entirely correct.
Torque cannot move a car anymore than torque applied to a frozen bolt can move the bolt. The bolt must move first – the torque is then applied at a certain [I]rate[/I] - before any work is actually done.
The same goes true for the car; it is the [I]rate[/I] at which the torque is applied which determines the amount of work the engine puts out.
[Gotta get back to work]
Regards,
Ed.
| edekker | 04-25-2002 12:00 PM |
It is true that we need to know about the torque curve ... [I]first[/I].
But only in order to calculate the HP curve; that is truly the extent in which we need to know about the torque curve. The HP curve, and only the HP curve, is what we need to see in order to determine optimal shift points.
We should [I]not[/I] be concerned about the strongest acceleration in any particular fixed gear.
What we should be concerned with is the point where can we achieve the strongest acceleration at any given [I]speed[/I].
For any given speed there will be an optimal gear ratio, which will multiply the torque to the highest level the engine can put out; that point occurs at the HP peak.
Ed.
But only in order to calculate the HP curve; that is truly the extent in which we need to know about the torque curve. The HP curve, and only the HP curve, is what we need to see in order to determine optimal shift points.
We should [I]not[/I] be concerned about the strongest acceleration in any particular fixed gear.
What we should be concerned with is the point where can we achieve the strongest acceleration at any given [I]speed[/I].
For any given speed there will be an optimal gear ratio, which will multiply the torque to the highest level the engine can put out; that point occurs at the HP peak.
Ed.
| NebScoob | 04-25-2002 04:30 PM |
[QUOTE]Torque cannot move a car anymore than torque applied to a frozen bolt can move the bolt. The bolt must move first – the torque is then applied at a certain rate - before any work is actually done.[/QUOTE]
Wrong...Torque is a force, and according to Newtons Second Law, a force acting on object, not only moves it, it accelerates it.
F=MA
A=F/M
Your stuck bolt, is a bad example...The mass would be artificialy high, and there are resistance forces greater that what you are applying. Apply enought torque and the bolt would turn, along with everything it was frozen to.
Besides, a car has a finite mass, so the torque force will accelerate it. The whole the bolt must move before work is done, is like arguing past and presence tense.
Work is done.
vs...
work is being done.
[QUOTE]The same goes true for the car; it is the rate at which the torque is applied which determines the amount of work the engine puts out. [/QUOTE]
Exactly Right...However...
The amount of the work the engine puts out has nothing to do with the acceleration of the car.
The amount of work the engine puts out is HP... A car does more work over time at 5000rpm than at 2000rpm..., but how fast it can go from 2000rpm to 6000rpm has nothing to do with the amount of work begin done by the engine at a set rpm..during a given time period.
[QUOTE]We should not be concerned about the strongest acceleration in any particular fixed gear.[/QUOTE]
I thought that was what we were concerned about? We want to maximize acceleration from some mph A to mph B, and want to know when to switch gears. So for every MPH between A a B, we have to look at which particular fixed gear we should be in to have the best acceleration.
If you meant the strongest acceleration point...meaning troque peak, I agree. It means nothing.
[QUOTE]What we should be concerned with is the point where can we achieve the strongest acceleration at any given speed.
For any given speed there will be an optimal gear ratio, which will multiply the torque to the highest level the engine can put out; that point occurs at the HP peak. [/QUOTE]
What point? RPM point? Whould that be the shift point? I kind of get what you are saying, but we can't pick and choose our gear ratios like that...Unless you want an continuously variable transmission, where the engine runs at a constant speed and the trans varies the ratio to get the acceleration....If you had one of those then the HP peak would be the ideal hold RPM....
Wrong...Torque is a force, and according to Newtons Second Law, a force acting on object, not only moves it, it accelerates it.
F=MA
A=F/M
Your stuck bolt, is a bad example...The mass would be artificialy high, and there are resistance forces greater that what you are applying. Apply enought torque and the bolt would turn, along with everything it was frozen to.
Besides, a car has a finite mass, so the torque force will accelerate it. The whole the bolt must move before work is done, is like arguing past and presence tense.
Work is done.
vs...
work is being done.
[QUOTE]The same goes true for the car; it is the rate at which the torque is applied which determines the amount of work the engine puts out. [/QUOTE]
Exactly Right...However...
The amount of the work the engine puts out has nothing to do with the acceleration of the car.
The amount of work the engine puts out is HP... A car does more work over time at 5000rpm than at 2000rpm..., but how fast it can go from 2000rpm to 6000rpm has nothing to do with the amount of work begin done by the engine at a set rpm..during a given time period.
[QUOTE]We should not be concerned about the strongest acceleration in any particular fixed gear.[/QUOTE]
I thought that was what we were concerned about? We want to maximize acceleration from some mph A to mph B, and want to know when to switch gears. So for every MPH between A a B, we have to look at which particular fixed gear we should be in to have the best acceleration.
If you meant the strongest acceleration point...meaning troque peak, I agree. It means nothing.
[QUOTE]What we should be concerned with is the point where can we achieve the strongest acceleration at any given speed.
For any given speed there will be an optimal gear ratio, which will multiply the torque to the highest level the engine can put out; that point occurs at the HP peak. [/QUOTE]
What point? RPM point? Whould that be the shift point? I kind of get what you are saying, but we can't pick and choose our gear ratios like that...Unless you want an continuously variable transmission, where the engine runs at a constant speed and the trans varies the ratio to get the acceleration....If you had one of those then the HP peak would be the ideal hold RPM....
| romanom | 04-25-2002 05:08 PM |
F=MA is a statement that says any object with mass that is accelerating must apply a force. Acceleration is not the same as velocity or even movement.
you can have a force with out MOVEMENT.
Please refrain from just pulling stuff out with out understanding the true meaning.
Go outside and push on your wall...you are applying force..is your house now doing burnouts down the street...NO!
power is all that counts! Power is very simply the rate at which you do work. Work is how much force you apply over a distance.
Now since cars move a distance and the idea is to make the time required to move that distance as short as possible you require POWER!!!!!!!
Power is what makes things move a certain distance in a certain period of time.
Now if you can apply more torque that's great because that means more power at any specific RPM...but it's always about the POWER!
you can have a force with out MOVEMENT.
Please refrain from just pulling stuff out with out understanding the true meaning.
Go outside and push on your wall...you are applying force..is your house now doing burnouts down the street...NO!
power is all that counts! Power is very simply the rate at which you do work. Work is how much force you apply over a distance.
Now since cars move a distance and the idea is to make the time required to move that distance as short as possible you require POWER!!!!!!!
Power is what makes things move a certain distance in a certain period of time.
Now if you can apply more torque that's great because that means more power at any specific RPM...but it's always about the POWER!
| edekker | 04-25-2002 07:42 PM |
Newbie,
You're right, we can't pick our ratios out of the blue like that, but if we [I]could[/I], then the engine RPM where the HP peaks is the point to choose – your 'ideal hold RPM' as we go for all-out acceleration.
But we do have the next best thing, our transmission gear ratios.
As I had mentioned in one of my previous posts, our available gear ratios can still afford us a means to achieve near strongest acceleration as we run the course, i.e. keep accelerating just beyond the HP peak to the point where HP drops to the same level on its rise for the next upshift. This would somewhat center the HP peak in each band; and make for the highest available average power between shifts – and the strongest overall acceleration, from start to finish.
Regards,
Ed.
You're right, we can't pick our ratios out of the blue like that, but if we [I]could[/I], then the engine RPM where the HP peaks is the point to choose – your 'ideal hold RPM' as we go for all-out acceleration.
But we do have the next best thing, our transmission gear ratios.
As I had mentioned in one of my previous posts, our available gear ratios can still afford us a means to achieve near strongest acceleration as we run the course, i.e. keep accelerating just beyond the HP peak to the point where HP drops to the same level on its rise for the next upshift. This would somewhat center the HP peak in each band; and make for the highest available average power between shifts – and the strongest overall acceleration, from start to finish.
Regards,
Ed.
| Ryouga | 04-25-2002 09:22 PM |
You guys all have it wrong. The best shift point is determined by the g plot (curves showing how many g's are produced at a particular rpm in each gear). You need to take differential slices of the area under the curves and shift at the point at which the area is shrinking in the lower gear while it is growing in the higher gear, and the g's in the higher gear are greater than or equal to the g's produced in the lower gear. ;) :p :D :lol:
| NebScoob | 04-26-2002 02:33 AM |
Accerlation is the key word ...We are not talking about the amount of movement over time. We are talking about changing the speed of the movement.
[QUOTE]you can have a force with out MOVEMENT[/QUOTE]
Of course, but that's not what I'm saying...Resistance forces, high masses, ect, can all lead to a situation where you can apply torque to something and it won't move. THAT JUST DOES NOT HAPPEN in the example a car..Force applied, mass is fixed so object accelerates...
[QUOTE]Now since cars move a distance and the idea is to make the time required to move that distance as short as possible you require POWER!!!!!!![/QUOTE]
Again, correct. But every time you talk about time over a distance, your loosing site of acceleration.
If I want to decrease the time it takes to go from point A to point B, I can just move faster over that distance by adding power. (I go 50mph instead of 30 mph, by driving at a higher RPM)
If I want to increase the distance I can go in a certian amount of time I can just go faster over that distance by adding power. (
Adding power can change the speed of the car, but it has nothing to do with how fast the change in speed occurs.
[QUOTE]Power is what makes things move a certain distance in a certain period of time.[/QUOTE]
If I'm interested in how fast I can accelerate the car from 0-100 where does distance come in? HP is a measure of force over a distance... the distance could be 10 feet, it could be a mile... There is no certain time, there is no certain distance....
If I go 0-100 mph in 6 seconds, how much ground did I cover?
If I go 0-100 mph in 500 ft, how long did it take me?
Do you see why how much work an engine can do, (how fast it can go over a certain distance), is different than how fast it can accelerate?
We are talking about acceleration.
Ryouga,
If you plot the g's for a car, I can guarentee the curve will match the torque curve...and you will get the same shift points.. G's are just a measure of acceleration, and torque is pretty much proportaional to acceleration. Since torque is more easily measured by all dynos, it's a bit more convenient.
Oh....getting tired...
[QUOTE]you can have a force with out MOVEMENT[/QUOTE]
Of course, but that's not what I'm saying...Resistance forces, high masses, ect, can all lead to a situation where you can apply torque to something and it won't move. THAT JUST DOES NOT HAPPEN in the example a car..Force applied, mass is fixed so object accelerates...
[QUOTE]Now since cars move a distance and the idea is to make the time required to move that distance as short as possible you require POWER!!!!!!![/QUOTE]
Again, correct. But every time you talk about time over a distance, your loosing site of acceleration.
If I want to decrease the time it takes to go from point A to point B, I can just move faster over that distance by adding power. (I go 50mph instead of 30 mph, by driving at a higher RPM)
If I want to increase the distance I can go in a certian amount of time I can just go faster over that distance by adding power. (
Adding power can change the speed of the car, but it has nothing to do with how fast the change in speed occurs.
[QUOTE]Power is what makes things move a certain distance in a certain period of time.[/QUOTE]
If I'm interested in how fast I can accelerate the car from 0-100 where does distance come in? HP is a measure of force over a distance... the distance could be 10 feet, it could be a mile... There is no certain time, there is no certain distance....
If I go 0-100 mph in 6 seconds, how much ground did I cover?
If I go 0-100 mph in 500 ft, how long did it take me?
Do you see why how much work an engine can do, (how fast it can go over a certain distance), is different than how fast it can accelerate?
We are talking about acceleration.
Ryouga,
If you plot the g's for a car, I can guarentee the curve will match the torque curve...and you will get the same shift points.. G's are just a measure of acceleration, and torque is pretty much proportaional to acceleration. Since torque is more easily measured by all dynos, it's a bit more convenient.
Oh....getting tired...
| NebScoob | 04-26-2002 09:35 AM |
Well after thinking things over a bit more...I'd like to clarify things
a bit...
I suggested a method of determining shift points based on the torque curve, becuase it most resembles what you feel, and what you can measure in terms of acceleration.
You shift the car, when the lines representing torque to the wheels cross. You can do no better, it's that simple.
However, I do recognize that you can base your shifts off of the HP curve. [B]A car working near it's power peak will accelerate the fastest, too, since your maximizing the amount of work the car is able to do.[/B] That's about all you are able to say, since HP is not any kind of measure of acceleration.
A car with a CV Trans would accelerate best at the power peak. If you maximize the area under the HP curve for each shift, you should be able to determine where to shift, too...but since both the RPM before you shift, and the RPM after you shift will change, trying to maximize that area is a little more difficult. And then one gear depends on the next...If you graphed each HP curve for each gear vs. Velocity, I think you could do it.
So the answer to the original question is, I guess you could look at the HP Curve, and try to stay close to the power peak. Graphing Power in each gear vs Velocity may help, but I'm not sure just how to use a graph like that. I'd have to see one...
Or you could do like I suggest, and and take the torque curve, and graph it as torque to the wheels in each gear, then shift where the lines cross....
Either way should work and come up with the ideal shift points.
a bit...
I suggested a method of determining shift points based on the torque curve, becuase it most resembles what you feel, and what you can measure in terms of acceleration.
You shift the car, when the lines representing torque to the wheels cross. You can do no better, it's that simple.
However, I do recognize that you can base your shifts off of the HP curve. [B]A car working near it's power peak will accelerate the fastest, too, since your maximizing the amount of work the car is able to do.[/B] That's about all you are able to say, since HP is not any kind of measure of acceleration.
A car with a CV Trans would accelerate best at the power peak. If you maximize the area under the HP curve for each shift, you should be able to determine where to shift, too...but since both the RPM before you shift, and the RPM after you shift will change, trying to maximize that area is a little more difficult. And then one gear depends on the next...If you graphed each HP curve for each gear vs. Velocity, I think you could do it.
So the answer to the original question is, I guess you could look at the HP Curve, and try to stay close to the power peak. Graphing Power in each gear vs Velocity may help, but I'm not sure just how to use a graph like that. I'd have to see one...
Or you could do like I suggest, and and take the torque curve, and graph it as torque to the wheels in each gear, then shift where the lines cross....
Either way should work and come up with the ideal shift points.
| Ryouga | 04-27-2002 09:22 AM |
Hmm. I guess I didn't make my post silly enough. :lol:
| gypsymoth | 05-03-2002 11:51 PM |
After reading this thread, I realized the debate going on here is the same conflict that I mentioned in the following thread:
[url]http://www.i-club.com/forums/showthread.php?s=&threadid=181678[/url]
In that thread, I calculated the ideal shift points using two well known algorithms. However, they gave two different sets of results. Although both are based on the torque curve, one maximizes the area under the HP curve, while the other one maximizes the area under the torque curve. Same as the debate here.
The question is, which one is correct? It is obvious that there can be only one correct answer in this case. One set of shift points has to be faster than the other one. Which one is it? Would some of you knowledgeable folks please go to the other thread and put in your input? Thanks.
Chieh
--
Chieh's Web - [url]http://Chieh.CameraHacker.com/[/url]
[url]http://www.i-club.com/forums/showthread.php?s=&threadid=181678[/url]
In that thread, I calculated the ideal shift points using two well known algorithms. However, they gave two different sets of results. Although both are based on the torque curve, one maximizes the area under the HP curve, while the other one maximizes the area under the torque curve. Same as the debate here.
The question is, which one is correct? It is obvious that there can be only one correct answer in this case. One set of shift points has to be faster than the other one. Which one is it? Would some of you knowledgeable folks please go to the other thread and put in your input? Thanks.
Chieh
--
Chieh's Web - [url]http://Chieh.CameraHacker.com/[/url]
| trinidriver | 05-04-2002 12:38 AM |
I'm glad someone else asked because I have been confused about this forever. No, physics did not help me understand the practical implicaitons. Thanks guys.
| thng | 05-04-2002 03:15 PM |
My rule?
Torque gets you there. Power keeps you there.
Now if I can only meet the engineer that mapped the stock ECU...
Torque gets you there. Power keeps you there.
Now if I can only meet the engineer that mapped the stock ECU...
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