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06-10-2013, 11:34 PM | #111 | ||
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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:
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: 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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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:
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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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 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:
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:
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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...
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06-11-2013, 03:26 AM | #115 | |||||||
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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:
(i worked it out on paper with a calculator first) Quote:
really saddening, GREAT online tool. Quote:
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:
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:
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:
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 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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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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06-11-2013, 10:13 PM | #118 | ||||||||
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Wow, this barely deserves an (ongoing) response but here we go...
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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:
Force, torque and power are all both instantaneous and potentially time varying quantities. Quote:
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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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) yeah it makes sense how you're not understanding when you lack such basic reading and comprehension skills. Quote:
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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 Last edited by CanAutM3; 06-12-2013 at 10:43 AM.. |
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06-12-2013, 10:48 PM | #121 |
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Yep, I'm done. I tried, as have you.
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06-13-2013, 07:08 PM | #122 | ||||
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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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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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06-15-2013, 03:35 PM | #126 | ||
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You said, Quote:
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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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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05-31-2015, 06:47 PM | #131 |
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