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      06-10-2013, 11:34 PM   #111
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Quote:
Originally Posted by flinchy View Post
yes, moment of force is what torque is, if you have a read of what i said, i clarify that torque is the force 'at a moment' and power is torque over time.
I guess you have not read what I wrote , moment here has nothing to do with the notion of time...

To be more precise, power is force applied on a distance over time; or in the polar referential: torque applied on rotations over time.


Quote:
Originally Posted by flinchy View Post
ED: at those 1m shift points... what's happening there?.. shift at 4250rpm? i can't read that graph haha

ahh is it some misc 'acceleration value'?

but yes, the 1M being a bit beefier in the midrange shifts a bit sooner than totally stock 135i's.... though it's still a case by case basis.. N54 to N54, you can have shift points varying up to 500rpm depending on the gear.
The graph I posted shows wheel torque (flywheel torque multiplied by the gear ratios) vs road speed for each gear (I should have included a legend, my bad). When the line of a gear crosses the line of the next gear, it is the optimal shift point. If the lines do not cross, it implies a shift at redline. Since some of the lines do cross, it means that those gears need to be shifted before redline. If you want the RPM shift points, you need to back calculate the RPM based on the road speed.

For the 1M, this means
1-2 68 km/h -> 7000 RPM
2-3 121 km/h -> 7000 RPM
3-4 173 km/h -> 6700 RPM
4-5 221 km/h -> 6525 RPM
5-6 259 km/h -> 6475 RPM

This is the power curve I used:
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Last edited by CanAutM3; 06-11-2013 at 12:11 AM.
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      06-11-2013, 12:14 AM   #112
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Quote:
Originally Posted by CanAutM3 View Post
I guess you have not read what I wrote , moment here has nothing to do with the notion of time...

To be more precise, power is force applied on a distance over time; or in the polar referential: torque applied [
it's an appropriate and fairly accurate analogy lol

because 'moment' is defined as

mo·ment
Noun
A very brief period of time.
An exact point in time.

so a moment of a force is a force is called such, as much as it's simply a specific name for a specific type of force... because it is without time

it's called these things for a reason.

"In mathematics, a moment is, loosely speaking, a quantitative measure of the shape of a set of points"

which basically sums up what i'm saying. a set of points without time.


torque in a car is indeed a rotating force... but it's a rotating force POTENTIAL (ie not moving), where power is converted to take into how much torque is applied per amount of time.

Quote:
Originally Posted by CanAutM3 View Post
The graph I posted shows wheel torque (flywheel torque multiplied by the gear ratios) vs road speed for each gear (I should have included a legend, my bad). When the line of a gear crosses the line of the next gear, it is the optimal shift point. If the lines do not cross, it implies a shift at redline. Since some of the lines do cross, it means that those gears need to be shifted before redline. If you want the RPM shift points, you need to back calculate the RPM based on the road speed.

For the 1M, this means
1-2 68 km/h -> 7000 RPM
2-3 121 km/h -> 7000 RPM
3-4 173 km/h -> 6700 RPM
4-5 221 km/h -> 6525 RPM
5-6 259 km/h -> 6475 RPM

This is the power curve I used:
yeah i figured that's the deal for shift points

and yeah that sounds about right haha

i worked it out a while ago for a 6MT 135/335i gear ratios that was fairly modified, and it was shifted a BIT higher than that list at the bottom (something like 6850 in 3-4 from memory), but yeah pretty much the same thing
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      06-11-2013, 12:27 AM   #113
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Quote:
Originally Posted by flinchy View Post
it's an appropriate and fairly accurate analogy lol

because 'moment' is defined as

mo·ment
Noun
A very brief period of time.
An exact point in time.

so a moment of a force is a force is called such, as much as it's simply a specific name for a specific type of force... because it is without time

it's called these things for a reason.

"In mathematics, a moment is, loosely speaking, a quantitative measure of the shape of a set of points"

which basically sums up what i'm saying. a set of points without time.


torque in a car is indeed a rotating force... but it's a rotating force POTENTIAL (ie not moving), where power is converted to take into how much torque is applied per amount of time.
You need to read a bit further down the definition of "moment"; again, it has nothing to do with time. It is a vector product.

I can also quote Wiki: "In physics, moment is defined as the perpendicular distance from a point to a line or a surface. It is frequently used in combination with other physical quantities as in moment of inertia, moment of force, moment of momentum, magnetic moment and so on."

Torque is a twisting force period, no "potential" here. Further, if you apply torque on an object and that object is not spinning you are not generating any power no matter how much time goes by. To evaluate power you need to consider torque, rotations and time.

Power = Torque x Rotations / Time

Quote:
Originally Posted by flinchy View Post
i studied mechanics of force at university, FWIW.. one of the few subjects in that degree i didn't fail HAH
Are you sure you didn't fail that course too

Last edited by CanAutM3; 06-11-2013 at 01:00 AM.
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      06-11-2013, 01:56 AM   #114
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Wow, where do I even start. As CanAutM3 mentioned, it does sound like you failed one or more of your "mechanics of force" classes. By the way I've never seen such a course title in any undergrad or graduate school engineering course catalogs...

Just for kicks though since you are degree dropping mine are in physics and mathematics and I've also worked as a Mechanical Engineer.

Quote:
Originally Posted by flinchy View Post
i did offer proof

if you hold power flat from 6000-8000RPM, you will ALWAY NO MATTER WHAT shift at redline for maximum acceleration, as ONLY there will the next gear provide better acceleration
100% positively false. As I and CanAutM3 have shown, gearing is required information to compute shift points. Period. You've not shown jack but reference some random web pages with non verifiable algorithms...


Quote:
Originally Posted by flinchy View Post
until YOU can show any evidence otherwise, that's the fact...
I've shown my evidence, what part of post #83 did you miss? This is pretty well equivalent to what CanAutM3 has shown. You agree with him and disagree with me? WTF?

Quote:
Originally Posted by flinchy View Post
heck.. i just plugged a stock F10 dyno into MULTIPLE calculators (Like the ones i posted) and STOCK it's redline shifting, it's not until tuned (like the graph i posted) that the midrange overtakes.


calculation being performed via any number of calculators (spreadsheets etc.) that use various points of torque curves + gear ratios+FD to work out at what point it's more effective to change

i even posted links to EXACTLY what i was using.
Do they plot and show potentially intersecting force at the wheels as a function of speed gear by gear? Until you can plot those and compare with mine we don't have any basis for comparison.

Quote:
Originally Posted by flinchy View Post
LOL it sounds like you're the one lacking understanding

you should google:

'Why-horsepower-torque-quot-changes-quot-dynos-quot-read-low-quot-peak-torque-is-not-when-you-accelerate-hardest-and-gearing-matters'

an article on 'the other site'



a crutch for truly understanding power? yeah no, more like how power actually works

power is torque over time (ie at an RPM), torque is power without time (hence torque is also called a 'moment of force')
anyone who disagrees with the above is simply wrong, as they can't prove anything otherwise (and conversely, proof in abundance for the CORRECT case)
You should google the plethora of good and lengthy debates here on this forum about power vs. torque. You clearly don't get it.

Let's review 100% independent of torque and gearing! Two cars A and B at the same speed and same weight. The car that can produce the most power (to the wheels of course) at that speed will always out accelerate the other. Period, no if's and's or but's

The problem is many peoples understanding is reconciling that statement with the additional fact that peak in gear acceleration (less some drivetrain inertial effects) occurs at the rpm where the peak torque is produced.

Hint: At a given speed a lower gear may be available which will often increase rpm, power and torque (to the wheels, the only place it matters, all the while REDUCING it at the crank)

Once you truly understand both of these statements (in bold above) and the fact that they are not contradictory, you may finally understand why power is both more important and more fundamental in vehicle performance.

Power is not torque over time. Power is fundamentally a product (literally multiplication or vector dot product) or a force and a velocity. In the case of rotating things the velocity is and angular velocity or rpm.

We are really digressing here into a debate I'm really quite tired of having...

Quote:
Originally Posted by flinchy View Post
but you seem to be lacking core understanding of torque+power+gearing+acceleration etc relationship.
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Last edited by swamp2; 06-15-2013 at 03:27 PM.
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      06-11-2013, 03:26 AM   #115
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Quote:
Originally Posted by swamp2 View Post
Wow, where do I even start. As CanAutM3 mentioned, it does sound like you failed one or more of your "mechanics of force" classes. By the way I've never seen such a course title in any undergrad or graduate school engineering course catalogs...

Just for kicks though since you are degree dropping mine and in physics and mathematics and I've also worked as a Mechanical Engineer.
Australia.. can't remember the exact title of the course but i have a bigass 'statics of materials and mechanics' book to use as a sweet paperweight.

quite surprising at your job though lol. i mean.. ok not really, you got all the other stuff spot-on and in great detail. you clearly know most of your stuff!

Quote:
Originally Posted by swamp2 View Post
100% positively false. As I and CanAutM3 have shown, gearing is required information to compute shift points. Period. You've not shown jack but reference some random web pages with non verifiable algorithms...
verifiable via hand

(i worked it out on paper with a calculator first)

Quote:
Originally Posted by swamp2 View Post
Do they plot and show potentially intersecting force at the wheels as a function of speed gear by gear? Until you can plot those and compare with mine we don't have any basis for comparison.
yeah the page i posted with the REALLY GOOD calculator seems to still be down

really saddening, GREAT online tool.

Quote:
Originally Posted by swamp2 View Post



You should google the plethora of good and lengthy debates here on this forum about power vs. torque. You clearly don't get it.

i have, they're nearly literally word for word what i'm saying, you should take your own advice and have a google

power is torque over an RPM. fact... verified by the conversion formula.

Quote:
Originally Posted by swamp2 View Post
Let's review 100% independent of torque and gearing! Two cars A and B at the same speed and same weight. The car that can produce the most power (to the wheels of course) at that speed will always out accelerate the other. Period, no if's and's or but's

The problem is many peoples understanding is reconciling that statement with the additional fact that peak in gear acceleration (less some drivetrain inertial effects) occurs at the rpm where the peak torque is produced.
well, close... the car with the higher AVERAGE of power over the accelerating rev-range will out accelerate... you can have a car that momentarily has WAY (or more realistically, slightly) more power, but throughout the revs has slightly less... if you're talking at specifically 6547 RPM car vs car identical gearing... for that RPM, yeah, of course.

your second paragraph is inaccurate... if you have peak torque at say... 6000RPM.. redline at 10k... and torque drops by 5% of the peak value linearly to redline.... well, peak acceleration will continue to redline, as the value of torque is applied more times per second than it was at peak... it's like.. hm... say 500ft-lb 6000/min is 3,000,000... where at 10,000RPM it's 4,000,000... your car is making more power but less torque. ... 571whp vs 761whp... at less torque.

so ... i guess previous discussions weren't taking into account how many times the force is applied per timeframe AS WELL as gearing. if you haven't thought about this... well.. think about it.

which of the above RPM's are you going to make peak acceleration gearing taken into account now?

Quote:
Originally Posted by swamp2 View Post
Hint: At a given speed a lower gear may be available which will often increase rpm, power and torque (to the wheels, the only place it matters, all the while REDUCING it at the crank)

Once you truly understand both of these statements (in bold above) and the fact that they are not contradictory, you may finally understand why power is both more important and more fundamental in vehicle performance.
yeah... that's not even up for debate haha

second paragraph.. well yeah, it's all related.. power being more important is kinda my point (though i didn't know how to fully voice it until now, my bad),

Quote:
Originally Posted by swamp2 View Post
Power is not torque over time. Power is fundamentally a product (literally multiplication or vector dot product) or a force and a velocity. In the case of rotating things the velocity is and angular velocity or rpm.
HP = Torque (lb/ft) * rpm / 5252

RPM = time in this case... maybe i should say 'over a frequency'.. bu

yes, it's what you're saying (in arbitrarily more complex terms than they need to be).. however, the multiple in the real world is time... or frequency, if you want to be more accurate.

for 99% of the population, my explanation is a LOT easier to understand and give them that 'oh' moment haha


Quote:
Originally Posted by swamp2 View Post

We are really digressing here into a debate I'm really quite tired of having...

yeah every post it gets more and more off topic and i have no idea why we're arguing, or really what we're arguing about... it's not even in the 100% real world where temperature variations, fuel quality, the direction of the wind, how you hold your pants up... effects how well a car accelerates, and shift points lol.
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      06-11-2013, 12:37 PM   #116
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Originally Posted by solstice View Post
Theory aside, in daily driving I will see little to no incentive to take this type of engine to the redline. Keeping it at full boil in the midrange will be more rewarding than extending it to a flat rpm peak. That you save both some fuel and engine component life doesn't hurt either. The S65 is such a savage towards the peak in both symphony and power that you run it up there all day long, or as often as you can. I think no matter how we dice it, there will be a difference in how we enjoy these cars unless BMW pull another rabbit out of the hat. I will not bet against them even if I chalk it down as unlikely.
I agree. Will we like the next M3/M4? Ask yourself this question: Is the current M5/M6 better than the past V10 high revver? Is the current F30 better than the last e90/e92? Based on my experience with the current and past M5's, I'd say no. Based on the Car magazines that went from ranking the 3 series and M's 1st place, while being accused of taking money from BMW to calling the M5 and M6 essentially fat soulless money makers from a once great M divison.

Hell, they say a ATS and Lexus are better drivers now.

BUT GREAT NEWS: RECORD PROFITS FOR BMW!

I think I've crossed the dark side to Porsche. Off topic, but the new GT3 with it's NA 3.8L 9,000RPM redline proves high revving engines are not dead just because BMW chooses to abandon it's principles.
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      06-11-2013, 01:17 PM   #117
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Quote:
Originally Posted by Hoosiers View Post
I agree. Will we like the next M3/M4? Ask yourself this question: Is the current M5/M6 better than the past V10 high revver? Is the current F30 better than the last e90/e92? Based on my experience with the current and past M5's, I'd say no. Based on the Car magazines that went from ranking the 3 series and M's 1st place, while being accused of taking money from BMW to calling the M5 and M6 essentially fat soulless money makers from a once great M divison.

Hell, they say a ATS and Lexus are better drivers now.

BUT GREAT NEWS: RECORD PROFITS FOR BMW!

I think I've crossed the dark side to Porsche. Off topic, but the new GT3 with it's NA 3.8L 9,000RPM redline proves high revving engines are not dead just because BMW chooses to abandon it's principles.
While I do not particularly like the new M5 and M6, they drive way to big and feel heavy when maneuvered and the engine lack the soul of earlier iterations. However I have not given up on the F80, from the footage it looks very agile and taut and when it comes to the engine it will likely not be anywhere close to the emotional experience of the S65 but the fat midrange can be enjoyed in a different way. As a package you have to assume that the M-division want to build something to quite critics and show what they are still capable of. I think it's going to be great, IF they get the steering right. That is my biggest concern by a mile. If it's anything like the steering in the F10 I'm done with BMW.
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      06-11-2013, 10:13 PM   #118
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Wow, this barely deserves an (ongoing) response but here we go...

Quote:
Originally Posted by flinchy View Post
verifiable via hand

(i worked it out on paper with a calculator first)
Great post it all up, shift point calculations for the F10 M5. With the required curves I keep mentioning and posting.

Quote:
Originally Posted by flinchy View Post
yeah the page i posted with the REALLY GOOD calculator seems to still be down

really saddening, GREAT online tool.
Sounds great,

Quote:
Originally Posted by flinchy View Post
power is torque over an RPM. fact... verified by the conversion formula.
Again no, incorrect. Power is by DEFINITION the product of a force multiplied by a velocity, which is generalized into rotating devices to power = torque x angular velocity (all in SI units of course). You can't escape these, they are the definitions...

Quote:
Originally Posted by flinchy View Post
well, close... the car with the higher AVERAGE of power over the accelerating rev-range will out accelerate... you can have a car that momentarily has WAY (or more realistically, slightly) more power, but throughout the revs has slightly less... if you're talking at specifically 6547 RPM car vs car identical gearing... for that RPM, yeah, of course.
You keep missing the most basic point, INSTANTANEOUS was the point of my first "rule".

Quote:
Originally Posted by flinchy View Post
your second paragraph is inaccurate... if you have peak torque at say... 6000RPM.. redline at 10k... and torque drops by 5% of the peak value linearly to redline.... well, peak acceleration will continue to redline
100% positively, FALSE. The acceleration curve "mirrors" the torque curve and this comes fundamentally from F = ma. You can also grab the more detailed formula 2-9b from the Gillespie text book, Fundamentals of Vehicle Dynamics. Again ignoring the (typically) minor corrections in the second term, the peaks corresponding become obvious. Please stop while you are ahead. You can also spreadsheet up this type of solution as many forum members have done themselves to see this point. Each ongoing post here makes you look all the more incorrect and quite frankly ignorant.

Quote:
Originally Posted by flinchy View Post
so ... i guess previous discussions weren't taking into account how many times the force is applied per timeframe AS WELL as gearing. if you haven't thought about this... well.. think about it.

which of the above RPM's are you going to make peak acceleration gearing taken into account now?
Really, WTF, I can't even understand this gobbeldy-gook


Quote:
Originally Posted by flinchy View Post
HP = Torque (lb/ft) * rpm / 5252
Yes, finally something correct. This is the exact same formula as power = torque x angular velocity (as I keep saying) just using terrible English units instead of the preferred SI units which help keep the concepts simple as the fundamental unit system for physics... Now that being said, yes when working in hp and ft lb the above formula is quite useful.


Quote:
Originally Posted by flinchy View Post
RPM = time in this case... maybe i should say 'over a frequency'
Again no. RPM is in no way equal to or equivalent to time. Yes time must march along in the background, in the same way it does for most simple Newtonian mechanics problems, for something to spin in the first place but that's about it.

Force, torque and power are all both instantaneous and potentially time varying quantities.

Quote:
Originally Posted by flinchy View Post
yes, it's what you're saying (in arbitrarily more complex terms than they need to be)..

for 99% of the population, my explanation is a LOT easier to understand and give them that 'oh' moment haha
No, no, no. I insist on keeping it simple and focusing on concepts, pot meet kettle... Big fat chance on the second point. You language is so imprecise and has been riddled with errors. If you think that begets clarity you've got even more problems.

I'm far from perfect but here on this forum I do have a thrust and a bit of role as one who brings clarity and transparency to aspects of vehicle performance through correct science and math (often statistics or lack thereof). You've got a long way to go to offer any help or clarity here on these particular topics. Please, please for you own education.

Here are some pointers, thank me later for all of the solid materials here. PLEASE, PLEASE, save yourself, do some reading:

Does final drive really matter
Power to weight is the most critical metric in performance (late in the thread an agreement is finally reached)
Another like the above (particularly my post #134)
Peak in gear acceleration is (not quite) at peak torque
Bruce's good old write up on power vs. torque
The lack of low end torque in the E9X M3. #1 and #2
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      06-11-2013, 10:51 PM   #119
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Quote:
Originally Posted by swamp2 View Post



100% positively, FALSE. The acceleration curve "mirrors" the torque curve and this comes fundamentally from F = ma. You can also grab the more detailed formula 2-9b from the Gillespie text book, Fundamentals of Vehicle Dynamics. Again ignoring the (typically) minor corrections in the second term, the peaks corresponding become obvious. Please stop while you are ahead. You can also spreadsheet up this type of solution as many forum members have done themselves to see this point. Each ongoing post here makes you look all the more incorrect and quite frankly ignorant.
ahahahahah ok, until you sit down and learn the fundamentals, this discussion is over. it's hilarious you've managed to so deeply convince yourself that what i'm saying isn't correct... peak power at redline increasing steadily with a torque taper, yet you'll accelerate faster while producing less power at peak torque in the midrange? hahah

i think i just realized we were having two simultanous separate arguments.

every evo owner ever disagrees with you
http://amsperformance.com/amsperform...Q16-782STD.jpg

same for GT-R's, RB's and 2j's...

even formula 1 cars disagree with you (peak torque some 2000rpm before redline)

Quote:
Originally Posted by swamp2 View Post
Really, WTF, I can't even understand this gobbeldy-gook
yeah it makes sense how you're not understanding when you lack such basic reading and comprehension skills.

Quote:
Originally Posted by swamp2 View Post
Again no. RPM is in no way equal to or equivalent to time. Yes time must march along in the background, in the same way it does for most simple Newtonian mechanics problems, for something to spin in the first place but that's about it.
got it, 'minute' isn't a measurement of time.

Quote:
Originally Posted by swamp2 View Post
No, no, no. I insist on keeping it simple and focusing on concepts, pot meet kettle... Big fat chance on the second point. You language is so imprecise and has been riddled with errors. If you think that begets clarity you've got even more problems.

I'm far from perfect but here on this forum I do have a thrust and a bit of role as one who brings clarity and transparency to aspects of vehicle performance through correct science and math (often statistics or lack thereof). You've got a long way to go to offer any help or clarity here on these particular topics. Please, please for you own education.

Here are some pointers, thank me later for all of the solid materials here. PLEASE, PLEASE, save yourself, do some reading:

Does final drive really matter
Power to weight is the most critical metric in performance (late in the thread an agreement is finally reached)
Another like the above (particularly my post #134)
Peak in gear acceleration is (not quite) at peak torque
Bruce's good old write up on power vs. torque
The lack of low end torque in the E9X M3. #1 and #2
simple. right.

my language has been for the lowest common denominator who could be reading... inaccuracies? please.

most of those links are simply not part of this discussion.. re:diffs... shorter final drive will net better acceleration (minus shift times if MT) if you make peak power at redline.. longer final drive will net better acceleration if you have a 'peaky' power/torque curve (a la stock frame turbo N54... you'll find 60-130 type acceleration will be far superior in longer gearing like 2.56 compared to shorter like 3.46)

as for the "Peak in gear acceleration is not quite at peak torque..." thread..

you seem to simultaneously disagree with other points you've made in this thread... and agree with others of mine (re: peak power acceleration)


ED: yeah that post seems to flip back and forth with very unclear information.

i think we have been talking about two different things:... you peak acceleration at a specific RPM

me: still talking about when you should shift in a gear.

all i've been saying is it's impossible to have any change in gear ratio (longer) that will accelerate you faster assuming you produce peak power at redline.

Last edited by flinchy; 06-11-2013 at 11:07 PM.
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      06-11-2013, 11:15 PM   #120
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You are more patient than I am . I have given up on flinchy...

...or maybe the laws of physics are inverted on the other side of the equator

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      06-12-2013, 10:48 PM   #121
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Originally Posted by CanAutM3 View Post
You are more patient than I am . I have given up on flinchy...

...or maybe the laws of physics are inverted on the other side of the equator
Yep, I'm done. I tried, as have you.
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      06-13-2013, 07:08 PM   #122
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Quote:
Originally Posted by flinchy
Quote:
Originally Posted by swamp2 View Post



100% positively, FALSE. The acceleration curve "mirrors" the torque curve and this comes fundamentally from F = ma. You can also grab the more detailed formula 2-9b from the Gillespie text book, Fundamentals of Vehicle Dynamics. Again ignoring the (typically) minor corrections in the second term, the peaks corresponding become obvious. Please stop while you are ahead. You can also spreadsheet up this type of solution as many forum members have done themselves to see this point. Each ongoing post here makes you look all the more incorrect and quite frankly ignorant.
ahahahahah ok, until you sit down and learn the fundamentals, this discussion is over. it's hilarious you've managed to so deeply convince yourself that what i'm saying isn't correct... peak power at redline increasing steadily with a torque taper, yet you'll accelerate faster while producing less power at peak torque in the midrange? hahah

i think i just realized we were having two simultanous separate arguments.

every evo owner ever disagrees with you
http://amsperformance.com/amsperform...Q16-782STD.jpg

same for GT-R's, RB's and 2j's...

even formula 1 cars disagree with you (peak torque some 2000rpm before redline)

Quote:
Originally Posted by swamp2 View Post
Really, WTF, I can't even understand this gobbeldy-gook
yeah it makes sense how you're not understanding when you lack such basic reading and comprehension skills.

Quote:
Originally Posted by swamp2 View Post
Again no. RPM is in no way equal to or equivalent to time. Yes time must march along in the background, in the same way it does for most simple Newtonian mechanics problems, for something to spin in the first place but that's about it.
got it, 'minute' isn't a measurement of time.

Quote:
Originally Posted by swamp2 View Post
No, no, no. I insist on keeping it simple and focusing on concepts, pot meet kettle... Big fat chance on the second point. You language is so imprecise and has been riddled with errors. If you think that begets clarity you've got even more problems.

I'm far from perfect but here on this forum I do have a thrust and a bit of role as one who brings clarity and transparency to aspects of vehicle performance through correct science and math (often statistics or lack thereof). You've got a long way to go to offer any help or clarity here on these particular topics. Please, please for you own education.

Here are some pointers, thank me later for all of the solid materials here. PLEASE, PLEASE, save yourself, do some reading:

Does final drive really matter
Power to weight is the most critical metric in performance (late in the thread an agreement is finally reached)
Another like the above (particularly my post #134)
Peak in gear acceleration is (not quite) at peak torque
Bruce's good old write up on power vs. torque
The lack of low end torque in the E9X M3. #1 and #2
simple. right.

my language has been for the lowest common denominator who could be reading... inaccuracies? please.

most of those links are simply not part of this discussion.. re:diffs... shorter final drive will net better acceleration (minus shift times if MT) if you make peak power at redline.. longer final drive will net better acceleration if you have a 'peaky' power/torque curve (a la stock frame turbo N54... you'll find 60-130 type acceleration will be far superior in longer gearing like 2.56 compared to shorter like 3.46)

as for the "Peak in gear acceleration is not quite at peak torque..." thread..

you seem to simultaneously disagree with other points you've made in this thread... and agree with others of mine (re: peak power acceleration)


ED: yeah that post seems to flip back and forth with very unclear information.

i think we have been talking about two different things:... you peak acceleration at a specific RPM

me: still talking about when you should shift in a gear.

all i've been saying is it's impossible to have any change in gear ratio (longer) that will accelerate you faster assuming you produce peak power at redline.
Tech engineer here so physics are not the strong suit.

Don't you want to change gears so that the gear you go into can accelerate faster than the gear you shifted from? For instance shift so that the rpms fall to max torque of the next gear? I guess this means are you shifting manual or dct? Will change this due to lag of gear engagement.

T
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      06-14-2013, 12:33 AM   #123
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Quote:
Originally Posted by Mangler View Post
Tech engineer here so physics are not the strong suit.

Don't you want to change gears so that the gear you go into can accelerate faster than the gear you shifted from? For instance shift so that the rpms fall to max torque of the next gear? I guess this means are you shifting manual or dct? Will change this due to lag of gear engagement.

T
Give the entire thread a re-read and look at the graphs, "Drive Power in Gears" and Torque Curve in my OP. I'll discuss with a bit more detail below.

With any normal gear box you always accelerate significantly worse with each successive shift (see Time to Acceleration graph or perhaps better titles Acceleration vs. Time...). There is simply no way around that. But as is obvious, you can't stay in any gear indefinitely. When concerned with maximum performance, the ideal shift point is one simply that maximizes the acceleration across the gear change (at each point in time individually). Shift too early and you lose out on more time at a much higher acceleration in your current gear. Shift too late and the next gear chosen earlier would have provided more thrust. Again the simplest way to explain how to calculate this is to shift either at redline or at the rpm/speed at which curves of vehicle thrust vs. speed, gear by gear, intersect. If they do not intersect the shift will be at redline. Some cars like the E92 M3 should be shifted at redline in all gears. Some vehicles should always be shifted before redline and others are a mix. The key components to the calculation and that affect ideal shift points are the drive force vs. speed curves. You get the drive force from the crank torque (rated engine torque vs. rpm - converted to vs. speed) minus parasitic and gearbox inertial "losses" as well as the gear ratios, final drive ratio and drive wheel radius. However, generally speaking, the shape of these drive force curves will mirror the engines crank torque curve. Drastically falling torque curves at higher rpm generally will lead to ideal shifts before redline since the curves will be more likely to cross.

There will some corrections to this "algorithm" based on shift times. Strictly speaking this algorithm assumes "DCT like" instantaneous shifts. Actual rpms/speeds for ideal shifts would become slightly higher when accounting for speed losses due to drag loss when no power is being applied when the clutch is disengaged during a shift.

This is really more engineering than physics, perhaps one would say applied physics...
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      06-15-2013, 12:00 PM   #124
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Looking quicker than I was expecting.
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      06-15-2013, 12:57 PM   #125
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Quote:
Originally Posted by swamp2
Quote:
Originally Posted by Mangler View Post
Tech engineer here so physics are not the strong suit.

Don't you want to change gears so that the gear you go into can accelerate faster than the gear you shifted from? For instance shift so that the rpms fall to max torque of the next gear? I guess this means are you shifting manual or dct? Will change this due to lag of gear engagement.

T
Give the entire thread a re-read and look at the graphs, "Drive Power in Gears" and Torque Curve in my OP. I'll discuss with a bit more detail below.

With any normal gear box you always accelerate significantly worse with each successive shift (see Time to Acceleration graph or perhaps better titles Acceleration vs. Time...). There is simply no way around that. But as is obvious, you can't stay in any gear indefinitely. When concerned with maximum performance, the ideal shift point is one simply that maximizes the acceleration across the gear change (at each point in time individually). Shift too early and you lose out on more time at a much higher acceleration in your current gear. Shift too late and the next gear chosen earlier would have provided more thrust. Again the simplest way to explain how to calculate this is to shift either at redline or at the rpm/speed at which curves of vehicle thrust vs. speed, gear by gear, intersect. If they do not intersect the shift will be at redline. Some cars like the E92 M3 should be shifted at redline in all gears. Some vehicles should always be shifted before redline and others are a mix. The key components to the calculation and that affect ideal shift points are the drive force vs. speed curves. You get the drive force from the crank torque (rated engine torque vs. rpm - converted to vs. speed) minus parasitic and gearbox inertial "losses" as well as the gear ratios, final drive ratio and drive wheel radius. However, generally speaking, the shape of these drive force curves will mirror the engines crank torque curve. Drastically falling torque curves at higher rpm generally will lead to ideal shifts before redline since the curves will be more likely to cross.

There will some corrections to this "algorithm" based on shift times. Strictly speaking this algorithm assumes "DCT like" instantaneous shifts. Actual rpms/speeds for ideal shifts would become slightly higher when accounting for speed losses due to drag loss when no power is being applied when the clutch is disengaged during a shift.

This is really more engineering than physics, perhaps one would say applied physics...
Pretty much what I said. Shift when the next gears acceleration area under the curve is more than staying the the gear you are in. All of this is dependent on shift times.

T
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      06-15-2013, 03:35 PM   #126
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Quote:
Originally Posted by Mangler View Post
Pretty much what I said. Shift when the next gears acceleration area under the curve is more than staying the the gear you are in. All of this is dependent on shift times.
Not quite.

You said,

Quote:
Originally Posted by Mangler View Post
Don't you want to change gears so that the gear you go into can accelerate faster than the gear you shifted from?
Although I think I know what you meant this is not correct, when shifting for maximum performance the acceleration after said shift is either equal to that just before the shift or less.

Also, you don't have to worry about area under the curve (which formally is integration, of course) or averaging an area under the curve. Just maximize propulsive force at every single instantaneous point in time. This is a simpler concept.

The language describing science must be very precise to be correct!
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      06-29-2013, 07:52 AM   #127
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Intreating, but I've always wondered if the new M3/M4 will be equipped with the hydraulic steering or the newer electric steering?? Also if the new M3/M4 is equipped with the electric steering, i would want to see a lap comparison between the new M3 and the E92 in the rain. why? to see which would have more road feel.
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      07-05-2013, 02:21 PM   #128
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Originally Posted by MTrezzz View Post
Intreating, but I've always wondered if the new M3/M4 will be equipped with the hydraulic steering or the newer electric steering?? Also if the new M3/M4 is equipped with the electric steering, i would want to see a lap comparison between the new M3 and the E92 in the rain. why? to see which would have more road feel.

it's already confirmed to have EPS akin to the units in the 991
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      07-06-2013, 09:39 AM   #129
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it's already confirmed to have EPS akin to the units in the 991
So electric steering, carried from the 991? or something very similar?
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      05-31-2015, 06:00 PM   #130
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Wow these wete impressive predictions years ago! Nice job swamp. Trap is a bit lower at 118 to 119 but mostly otherwise spot on
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      05-31-2015, 06:47 PM   #131
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Wow these wete impressive predictions years ago! Nice job swamp. Trap is a bit lower at 118 to 119 but mostly otherwise spot on
Pretty much very impressive
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