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      09-29-2013, 08:24 AM   #133
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Quote:
Originally Posted by ixse View Post
too many "smart people" here lol.. go to actual track w some corners.. and do your shit talking with your lap times.. nobody gives a crap on if you shifted 500 rpm too early..
Perhaps at some levels, but the true track junkies and racers absolutely care if they shift 500 rpm too early, where and if engine speed is maximizing lap times. What makes you think shift points have nothing to do with lap times? Shit talking indeed.

Seat of the pants is fine for a DE but you'll find racers hunched over a laptop between sessions looking for tenths at any club race weekend, paying coaches for data analysis.

Posters like this are so disappointing to read on this board. A long time member goes out of his way with meaningful, thoughtful and factual input and we get this flippant childish reply and no respect. You contribute less than nothing.

Last edited by consolidated; 09-29-2013 at 10:07 AM..
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      09-29-2013, 03:33 PM   #134
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Quote:
Originally Posted by swamp2 View Post
Positively 100% incorrect.
You continue to proffer information is is incorrect in many ways. I was going to refute all of it but, this is the crux of it all.

You don't understand the physical definition of work. Work occurs when force or torque is applied over a distance or a rotation. Torque as measured by an engine dynamometer is not a measure of an engine's ability to perform work because it does not provide for the distance measurement, period. Did it not occur to you that torque is a vector quantity that is not conserved in a system where as work is a scalar quantity and is conserved? Really?

Neither force nor it's rotational analog can perform work, without being applied over either a distance or a rotation, respectively. Torque is not a measure of an engine's ability to proper a car forward. It's physical fact.


Also, I never said anything about Power versus Speed, I was talking about Power, exclusively. Reread what I said because you didn't read it correctly.
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      09-29-2013, 04:19 PM   #135
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Quote:
Originally Posted by Jonjt View Post
You continue to proffer information is is incorrect in many ways. I was going to refute all of it but, this is the crux of it all.
You can't because you are completely wrong. Keep up the A for effort part though.

Quote:
Originally Posted by Jonjt View Post
You don't understand the physical definition of work. Work occurs when force or torque is applied over a distance or a rotation. Torque as measured by an engine dynamometer is not a measure of an engine's ability to perform work because it does not provide for the distance measurement, period. Did it not occur to you that torque is a vector quantity that is not conserved in a system where as work is a scalar quantity and is conserved? Really?
I understand these basic concepts which can in fact be quite subtle in the most through way. Just so you know I have an advanced degree in physics and have worked professionally as a Mechanical Engineer. You can't really accomplish this without some solid understanding of these concepts. Also, my applicaiton of these concepts to real work vehicle performance issues has been pretty firmly established here on this forum.

No, talking about force or torque "conservation" is bs, but I never did. However, you are again showing your utter miscomprehension of the words and their physical concepts. Work is not conserved, 100% incorrect again. I think I am going to give up on you. Conservation concepts are not well applied to a car because it is filled with parasitic losses resulting in heat. However, the principle I think you meant to cite is the Work-Energy theorem which states the that the work done is equivalent the the change in enegry of an object.

Force and torque are physical and mathematical analogs in some fundamental ways they are identical they can both perform work. Dyno's provide a complete vs. rpm measurement of torque and knowing the entire torque curve and rpms is IDENTICAL to knowing the entire power curve vs. rpm.

Quote:
Originally Posted by Jonjt View Post
Neither force nor it's rotational analog can perform work, without being applied over either a distance or a rotation, respectively.
I never said otherwise, finally you get something correct.

Quote:
Originally Posted by Jonjt View Post
Torque is not a measure of an engine's ability to proper a car forward. It's physical fact.
Wrong again, a vehicles instantaneous acceleration can be calculated from torque and rpm or power, it is the same exact thing.

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Originally Posted by Jonjt View Post
Also, I never said anything about Power versus Speed, I was talking about Power, exclusively. Reread what I said because you didn't read it correctly.
Sorry wrong. You stated I should scale the x and y axes of my plots and then I would be looking at power and your statement was and is 100% incorrect.
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      09-29-2013, 05:31 PM   #136
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Quote:
Originally Posted by Boss330 View Post
Your knowledge on these subjects are really impressive!!! Thanks for your input and sharing your knowledge with us!

Would this BMW 523i have a "optimum shiftpoint" at around 4250rpm for max acceleration?
If you believe I am saying or calculating that a car should shift at the point of peak torque (or highest rpm of torque plateau) you are very much misunderstanding (4250 rpm in this case). One must compute the vehicles thrust (accelerative force) AFTER losses and plot these vs. speed and gear. Since this car is not a performance car getting the actual torque or power curves was quite difficult (I could not find them). Thus I just used known peak values and let CarTest curve fit to construct the entire curves. It did not quite result in a totally flat torque curve between 1500-4250 rpm (which is the spec I could find) but was flat enough, maybe slowly and steadily declining from peak at 1500 rpm to 19X or so ft lb at 4250 rpm. Even finding the gear ratios wasn't fast but I did find those. Using all of this information I computed the ideal (rounded) shift points to be:

1-2: 7000 (redline)
2-3: 6900
3-4: 6700
4-5: 6600 (won't reach here, drag limited in 4th at ~135 mph)
5-6: 6300 "

Hope that helps.

Too much (boring) work to do the other car you mentioned. Build a spreadsheet, run the numbers yourself, if it very insightful and certainly non-trivial.

P.S. What are your calculations Jonjt?

And of course, last but not least, let's get back on topic.
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Last edited by swamp2; 09-30-2013 at 02:53 AM..
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      09-30-2013, 02:55 AM   #137
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Quote:
Originally Posted by swamp2 View Post
If you believe I am saying or calculating that a car should shift at the point of peak torque (or highest rpm of torque plateau) you are very much misunderstanding (4250 rpm in this case). One must compute the vehicles thrust (accelerative force) AFTER losses and plot these vs. speed and gear. Since this car is not a performance car getting the actual torque or power curves was quite difficult (I could not find them). Thus I just used known peak values and let CarTest curve fit to construct the entire curves. It did not quite result in a totally flat torque curve between 1500-4250 rpm (which is the spec I could find) but was flat enough, maybe slowly and steadily declining from peak at 1500 rpm to 19X or so ft lb at 4250 rpm. Even finding the gear ratios wasn't fast but I did find those. Using all of this information I computed the ideal (rounded) shift points to be:

1-2: 7000 (redline)
2-3: 6900
3-4: 6700
4-5: 6600 (won't reach here, drag limited in 4th at ~135 mph)
5-6: 6300 "

Hope that helps.

Too much (boring) work to do the other car you mentioned. Build a spreadsheet, run the numbers yourself, if it very insightful and certainly non-trivial.

P.S. What are your calculations Jonjt?

And of course, last but not least, let's get back on topic.
Wow!!! Thanks!

I suspected it wasn't as "easy" as I suggested in my previous post. Thanks for clarifying and elaborating.

Back to topic
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      09-30-2013, 12:33 PM   #138
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Problem:
Calculate appropriate shift points for an IC engine within a street car
Background:
Given:
F=ma
And
P=Fv

Where a is acceleration, v is forward velocity of the car, F is tractive effort at the wheels, P is power and m is the mass of the car. These equations are known to hold true at all instances in time, when applied to vehicle dynamics.

Substitute the first equation into the second:
P=mav
Realize that P, a and v are all functions of engine speed (assuming WOT) and enough traction to “hold” the tractive effort.
P(rpm)=ma(rpm)v(rpm)

Shift points should be designed to maximize a(rpm) at all times. Therefore, P(rpm) and v(rpm) are known (independent) values, where as a(rpm) is dependent (unknown).
(P(rpm))⁄(v(rpm))=ma(rpm)


A sanity check shows that via units analysis, the units of the left of the equation reduce to newtons. The units on the right side do as well.
So, what does this equation say? It relates the instantaneous tractive effort at the wheels of a car to the instantaneous acceleration experienced, at an instant in time.

So, how does this relate to engine performance?

Analysis:
Given:
v1=velocity in lower gear
v2=velocity in higher,adjacient gear
(P(rpm))⁄(v1(rpm))=ma(rpm) and (P(rpm))⁄(v2(rpm))=ma(rpm)


Let us say that we are driving an S55 equipped vehicle and at an instant in time, we are accelerating, the throttle is wide open and the engine is spinning at exactly 7000rpm. We have a choice, we can either wind this motor out to redline or, we can shift up, to the next gear and continue accelerating. We need to know what choice will net the greatest a(rpm) value.

Note that the last, say ~600rpms of the lower gear produces overlapping v(rpm) values with say, the first ~400rpms of the higher gear, due to the fact that the ratio of the higher gear is higher.

During this overlap “phase” we can switch gears or we can stay in the lower gear and still have the same forward vehicle speed. The difference will be that the engine speed will be higher in the lower gear and lower in the higher gear.

So, what do we want? Let’s revisit the equations.

Since we already stated that there will be a velocity overlap, we know that v1(rpm)=v2(rpm). Also, recall that tractive effort at the wheels is equal to (P(rpm))⁄(v(rpm)). Since the velocity will be the same at the end of the lower gear and in the beginning of the higher gear, this means that determining the appropriate shift point to maximize a(rpm) is a function of maximizing power available at the wheels to accelerate the car.

If torque values begin to roll off at high rpms, the acceleration the car experiences will begin to decrease as the rpms continue to climb, in comparison to the acceleration the car experienced when the torque was higher, in the same gear. You can characterize this by saying that in gear, tractive effort is a multiple of engine torque or, you can say that dKE⁄dt≈v(rpm)(dv(rpm))⁄dt. Either way is technically correct.

That seems undesirable. And, certainly it is. But, that doesn’t mean that you will see higher tractive effort by up shifting, even if more engine torque is available at lower engine rpm. Why? Because though higher engine torque might be available (depending on the exact ratio of the higher gear), there is less torque multiplication because of the higher ratio. In order for there to be more tractive effort, the available torque at the lower engine speed has to be high enough to compensate for the lower torque multiplication.

In other words, because power (unlike torque) is conserved in a drive train (Pwheel=Pengine-(Pwindage+Pfriction+Ppumping+Pinertial+Pmiscellane ous in all gears), you shift when the power available to move the car forward is higher in the higher gear than it is in the lower gear.

Given the fact that the torque curve of the S55 starts to decrease before redline and that power starts to taper a bit before fuel cutoff, it is possible that an early shift may be necessary in order to maximize a(rpm). HOWEVER, given the fact that the dropoff is slight and begins late, I am not yet convinced that short shifting is going to be necessary, particularly because we don’t have a proper engine dyno graph, because we don’t have gear ratios and because that fall off isn’t that great.

To illustrate, pretend that two identical F80 M3s appear at an instant in time T and are a given displacement from an ordinate, ∆x. Assume that both cars are driven by identical drivers and that traction is not an issue. Assume that the only difference between the two cars is that one car is at say, 7000rpms in second gear and the other car is at, say 5500rpms (just a guess) in third gear. At this instant in time, the car that can provide the greatest power for acceleration will accelerate the fastest. This is regardless of the amount of torque the engine is producing at these respective rpms. Though tractive effort is a multiple of engine torque, decreasing maximum a(rpm) does not mean that an upshift to a higher peak engine torque value will net higher tractive effort.

This was my main point. It is certainly possible to characterize tractive effort and shift points as a function of engine torque. But why? It requires extra computation and, is largely beyond the purview of the average M3/M4 owner. The easiest method to determine shift points would be to say to the owner, “when power available to more the car forward in the lower gear is less than that available in the higher gear, shift.” That is why I said one should concern themselves with power, in this case.

CVT transmissions do exactly this. They are designed to maximize power available at the wheels, even if peak engine torque is lower at this point that it is at a lower point in the RPM range.

Last edited by Jonjt; 09-30-2013 at 01:01 PM..
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      09-30-2013, 01:13 PM   #139
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Quote:
Originally Posted by Jonjt View Post
...
In other words, because power (unlike torque) is conserved in a drive train (Pwheel=Pengine-(Pwindage+Pfriction+Ppumping+Pinertial+Pmiscellane ous in all gears), you shift when the power available to move the car forward is higher in the higher gear than it is in the lower gear.
...
This was my main point. It is certainly possible to characterize tractive effort and shift points as a function of engine torque. But why? It requires extra computation and, is largely beyond the purview of the average M3/M4 owner. The easiest method to determine shift points would be to say to the owner, “when power available to more the car forward in the lower gear is less than that available in the higher gear, shift.” That is why I said one should concern themselves with power, in this case.
Nice glaring contradiction...

You claim power is conserved then provide an equation showing how power is not conserved (we all know it is not based on dynos).

And you still think you can calculate shift points without knowledge of RPM DEPENDENT parasitic losses using crank power only?

Sorry bud, I am not going to wade through the rest of your analysis to find any other major errors or contradictions. Calculating shift points exactly just isn't trivial for the average enthusiast. Luckily many of us can still do a reasonably good job by feel alone.

Use your "method" to show me exactly how to calculate shift points for any car where the exact shape of the power or torque curves are known. Until then STFU, really, your foot keeps going deeper and deeper.
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      09-30-2013, 01:40 PM   #140
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Quote:
Originally Posted by swamp2 View Post
Nice glaring contradiction...
You're going to have to expound on that one. There is no contradiction. From engine power, you subtract all the parasitic losses, as you called them (Pwindage, Ppumping, Pinertia, Pfriction, Pmiscelleanous, etc) and you get wheel power. Even after all the losses, the goal is still to maximize power available at the wheels, for a given vehicle speed. And, since the wheel speed is the same at the end of the low gear as it is in the beginning of the high gear, the drive train losses will be equal. The engine losses will be higher but thankfully, the engine dyno graphs we have measure power after all the engine losses have been accounted for. It does not measure combustion power.

Quote:
Originally Posted by swamp2 View Post
You claim power is conserved then provide an equation showing how power is not conserved (we all know it is not based on dynos).
I think you mean is conserved.

I any case, I did already. You quoted it. Power is neither created no destroyed in the drive train. That is what I mean by conserved. It all goes somewhere and, you can keep track of it. Pin=Pout (though heat, friction, moving fluids, accelerating masses, etc) whereas torque can and is multiplied by gears; ie Tin≠Tout. There is no physical law that mandates this.

Quote:
Originally Posted by swamp2 View Post
And you still think you can calculate shift points without knowledge of RPM DEPENDENT parasitic losses using crank power only?
Never said you could. What assumptions are you making about parasitic losses? Where are they being generated, how are they being generated, at what rpm, what shaft, etc?

Edit: When you say rpm dependent parasitic losses, I hope you aren't talking about engine induction, exhausting, pumping, windage, friction and inertial, etc losses. Right?

Quote:
Originally Posted by swamp2 View Post
Use your "method" to show me exactly how to calculate shift points for any car where the exact shape of the power or torque curves are known.
I only posted in this thread about shift points to point out that giving members a general mandate that focuses upon power instead of engine torque would be more beneficial but, I can expand the scope of my work here in this case.

So, the only vehicles I have are ones I've built. If you provide values for engine power and torque (from a proper engine dyno graph) and assumptions about parasitic losses (including correlations with shaft speeds, and what components they come from) we can do the same vehicle and compare notes. If you REALLY want, I can even run some external flow analyses on those vehicles and include speed dependent drag information in the force balances. However, I can't include anymore than a few operating points. I don't have the time to do a proper sweep across the operational speed range these cars see. Interpolation error will be nontrivial at higher speeds but, that's all I can manage right now.

Last edited by Jonjt; 09-30-2013 at 02:20 PM..
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      09-30-2013, 01:43 PM   #141
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Jonjt, I applaud you for dealing with his agenda.
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      09-30-2013, 01:47 PM   #142
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Quote:
Originally Posted by Jonjt View Post
You're going to have to expound on that one. There is no contradiction. From engine power, you subtract all the parasitic losses, as you called them (Pwindage, Ppumping, Pinertia, Pfriction, Pmiscelleanous, etc) and you get wheel power. Even after all the losses, the goal is still to maximize power available at the wheels, for a given vehicle speed.


I think you mean is conserved.

I any case, I did already. You quoted it. Power is neither created no destroyed in the drive train. That is what I mean by conserved. It all goes somewhere and, you can keep track of it. Pin=Pout (though heat, friction, moving fluids, accelerating masses, etc) whereas torque can and is multiplied by gears.


Never said you could. What assumptions are you making about parasitic losses? Where are they being generated, how are they being generated, at what rpm, what shaft, etf?


I only posted in this thread about shift points to point out that giving members a general mandate that focuses upon power instead of engine torque would be more beneficial but, I can expand the scope of my work here in this case.

So, the only vehicles I have are ones I've built. If you provide values for engine power and torque (from a proper engine dyno graph) and assumptions about parasitic losses (including correlations with shaft speeds, and what components they come from) we can do the same vehicle and compare notes. If you REALLY want, I can even run some external flow analyses on those vehicles and include speed dependent drag information in the force balances. However, I can't include anymore than a few operating points. I don't have the time to do a proper sweep across the operational speed range these cars see. Interpolation error will be nontrivial at higher speeds but, that's all I can manage right now.
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      09-30-2013, 03:15 PM   #143
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Jonjt:

Any system that converts power into heat (classic drivetrain losses) is NON-CONSERVATIVE. Just because you can account for the power losses does not mean it is conserved. The power at the crank is not available at the wheel and hence power IS NOT conserved. It appears you understand this but are using imprecise language. Perhaps what you mean is that energy, counting heat energy is conserved. However, conservation of energy starting with fuel energy is not really a useful way to approach vehicle performance...

How is power easier to be used to calculate shift points if you still need parasitic power losses. You claimed a power approach is simpler and say it is not.

Using a dyno with wheel power would be superior but dynos vary RADICALLY in the real world and are totally unreliable except for extremely careful A to B comparisons before and after a modification under identical conditions. Even then very important things like intake system performance are not captured.

Regular Cd and Area numbers are plenty accurate. CFD is needed for an OEM to improve Cd not or enthusiasts to calculate drag nor top speed nor any other basic performance metric. I too have CFD at my disposal but certainly do not have the very extensive training required with it to prevent "garbage in, garbage out". I suspect neither do you.

Take your method and apply it the BMW 523i. I think it is time to simply put up or shut up... Really.
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      09-30-2013, 03:18 PM   #144
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Quote:
Originally Posted by bplewis24 View Post
Jonjt, I applaud you for dealing with his agenda.
Which is? I'd say butt out when you have no idea.

Just for clarity sake I can give you a clue. I enjoy the application of basic science/math/engineering to vehicles, both performance and manufacturing. I enjoy sharing some insights on these topics with the generally well informed and often times the more technically leaning members here. I also try very hard to dispel common myths about vehicle performance. Unfortuntely that often leads to debates.
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      09-30-2013, 03:39 PM   #145
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Quote:
Originally Posted by swamp2 View Post
Jonjt:

Any system that converts power into heat (classic drivetrain losses) is NON-CONSERVATIVE. Just because you can account for the power losses does not mean it is conserved. The power at the crank is not available at the wheel and hence power IS NOT conserved. It appears you understand this but are using imprecise language. Perhaps what you mean is that energy, counting heat energy is conserved. However, conservation of energy starting with fuel energy is not really a useful way to approach vehicle performance...
Perhaps my language was imprecise. Let me expound a bit.
My basis is that power cannot be created or destroyed, you can account for it in any closed system. And since the difference between an open system and a closed system is a matter of scope/reference frame, analyzing this particular system with Pin=Pout is only a matter of picking the right components to include in the energy balance. If I had said that flywheel power is not equal to wheel power and I had not cared to deal with the losses in everything in between then sure, mathematically it isn't conserved. But, out of habit perhaps, I just like to say Pin=Pout since it's universally and macroscopically true.

And, while I have done an analysis including combustion power, it is indeed arduous. The energy input, in the case, is the power the engine produces at the flywheel. Forget all the combustion processes and mechanical engine losses. Since we have an engine dyno graph, who the hell cares about combustion power?

Quote:
Originally Posted by swamp2 View Post
How is power easier to be used to calculate shift points if you still need parasitic power losses. You claimed a power approach is simpler and say it is not.
I say it's simpler because you don't need to include the forces and torque multipliers that these parasitic losses impose on various drive train components. For example, let's say that you loose 20hp at an instantaneous transmission input shaft speed of 5500rpms, in the transmission. You can either just subtract that losses from the engine power or, you can calculate torque loads on each internal shaft and calculate the resulting drop in available torque at the transmission output shaft.

That sucks. Characterizing losses at a function of shaft speeds anywhere in the drive train is easier, IMO if you just use a power based loss calculation instead of trying to find the reduction in shaft torque. The conversion to torque is IMO easier to do at the wheels because you dont need to worry about the mechanics of friction, pumping, windage, etc losses in each drivetrain component. Furthermore, most drivers can more easily (IMO) comprehend the idea of power and it's dependence on engine speed than the complexities of torque, torque multiplication and how lossess effect net torque in the moment balances throughout the drive train.

Quote:
Originally Posted by swamp2 View Post
Using a dyno with wheel power would be superior
Damn straight.

Quote:
Originally Posted by swamp2 View Post
But we don't have that, unfortunately. but dynos vary RADICALLY in the real world and are totally unreliable except for extremely careful A to B comparisons before and after a modification under identical conditions. Even then very important things like intake system performance are not captured.
Indeed, an absolute measurement isn't possible but, then again, measuring energy output from a system is in essence a relative measurement. If you wanted to calculate a shift point by comparing available power at the wheels in different gears and looking at curve intersect points, you could do it on one dyno and get the same results as you would on another (theoretically), so long as you setup each correctly and are consistent with your analysis.

I would say that induction performance can be characterized on a dyno, just not in absolute terms.

Quote:
Originally Posted by swamp2 View Post
Regular Cd and Area numbers are plenty accurate. CFD is needed for an OEM to improve Cd not or enthusiasts to calculate drag nor top speed nor any other basic performance metric. I too have CFD at my disposal but certainly do not have the very extensive training required with it to prevent "garbage in, garbage out". I suspect neither do you.
Eh, Cd numbers are not great for characterizing actual drag forces on bodies across a wide range of speeds, particularly since the F value in the numerator varies non-linearly with the V value. If you were to run a simulation at a range of forward speeds and look at the correlation between free stream velocity and drag force, the correlation would indeed be non-linear.

Although, for our purposes a Cd value and area would at least provide consistent values for drag in the force balance, between us. Since we speculating about shift points, the 100% accuracy isn't needed.

I actually do (perform? haha) CFD on a daily basis. External non compressible flow is not my specialty but, I have some experience with it. In any case, this is why I said I wouldnt have time to do a thorough analysis. External aero cases take millions of cells and lots of time to solve. Don't have time for that......

Quote:
Originally Posted by swamp2 View Post
Take your method and apply it the BMW 523i. I think it is time to simply put up or shut up... Really.
Data? If you have an analysis finished already, send me exactly the data you have used to perform the analysis and I will run it the way I've proposed. Be sure to specify if you have included drag values in the calculation and how (Cd times area, or actual drag simulations).

If not, I'll just pick something and go with it.

Last edited by Jonjt; 09-30-2013 at 04:37 PM..
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      09-30-2013, 04:58 PM   #146
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Quote:
Originally Posted by Jonjt View Post
I say it's simpler because you don't need to include the forces and torque multipliers that these parasitic losses impose on various drive train components.
Only perhaps simpler in theory absolutely not in practice since dyno's just don't work... They don't offer enough repeatability nor absolute accuracy to do these calculations. If they do it is now on you to prove it.

Quote:
Originally Posted by Jonjt View Post
Characterizing losses at a function of shaft speeds anywhere in the drive train is easier, IMO if you just use a power based loss calculation instead of trying to find the reduction in shaft torque. The conversion to torque is IMO easier to do at the wheels because you dont need to worry about the mechanics of friction, pumping, windage, etc losses in each drivetrain component. Furthermore, most drivers can more easily (IMO) comprehend the idea of power and it's dependence on engine speed than the complexities of torque, torque multiplication and how lossess effect net torque in the moment balances throughout the drive train.
I believe this is my 3rd request. All of the data needed is available. Go calculate the shift points. Seems obvious now that you can't because you need dyno results. Let's not even get into how much random and sysematic error are in dynos. They are not reliable for this.

Quote:
Originally Posted by Jonjt View Post
Damn straight.
Award for quote out of context of the year. Really...


Quote:
Originally Posted by Jonjt View Post
Eh, Cd numbers are not great for characterizing actual drag forces on bodies across a wide range of speeds, particularly since the F value in the numerator varies non-linearly with the V value. If you were to run a simulation at a range of forward speeds and look at the correlation between free stream velocity and drag force, the correlation would indeed be non-linear.
But not non-linear enough to introduce significant errors in standard road car vehicle performance calculations or simulations... Which you also admitted. Ugh.

Quote:
Originally Posted by Jonjt View Post
Data? If you have an analysis finished already, send me exactly the data you have used to perform the analysis and I will run it the way I've proposed. Be sure to specify if you have included drag values in the calculation and how (Cd times area, or actual drag simulations).

If not, I'll just pick something and go with it.
Take the latter approach. Again how are you going to do this without either losses and my approach or a wheel dyno. A wheel dyno is not avaialable in this case. A factory crank dyno is not even avaiable.

Drag isn't required for this calculation as it does not affect the force applied, it is the resisting force.

Really, how many times, hate to be so blunt but put up or shut up...
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      09-30-2013, 05:22 PM   #147
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Quote:
Originally Posted by swamp2 View Post
Only perhaps simpler in theory absolutely not in practice since dyno's just don't work... They don't offer enough repeatability nor absolute accuracy to do these calculations. If they do it is now on you to prove it.



I believe this is my 3rd request. All of the data needed is available. Go calculate the shift points. Seems obvious now that you can't because you need dyno results. Let's not even get into how much random and sysematic error are in dynos. They are not reliable for this.



Award for quote out of context of the year. Really...




But not non-linear enough to introduce significant errors in standard road car vehicle performance calculations or simulations... Which you also admitted. Ugh.



Take the latter approach. Again how are you going to do this without either losses and my approach or a wheel dyno. A wheel dyno is not avaialable in this case. A factory crank dyno is not even avaiable.

Drag isn't required for this calculation as it does not affect the force applied, it is the resisting force.

Really, how many times, hate to be so blunt but put up or shut up...
Ugh you dont seem to understand a good portion of my post but whatever.............

If you recall, this discussion is centered around an estimated power curve and an estimated torque curve. None of this is accurate, this is not practice, not yet. You even pointed out that we don't have a proper factory crank dyno and that we are all just guessing. I brought up this power method to SIMPLIFY this estimation, since we can't actually produce an accurate result regardless of how comprehensive the methods are.

I've responded twice asking for you to provide the same losses you are guessing at so I can do my calculation but, you have yet to produce anything. Comparative analyses are useless without data sharing. You can't validate anyone's technique without knowing what went into it. You even pointed this out by referencing the "garbage in, garbage out" nature of CAE.

I can go pull some data from some source, make some loss estimations and just produce some numbers. It won't happen until I get home, though.

Last edited by Jonjt; 09-30-2013 at 05:58 PM..
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      09-30-2013, 05:34 PM   #148
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Quote:
Originally Posted by Jonjt View Post
I'm about to get on a call, I cannot start doing the math until I get home.

Just answer this one simple question, did you or did you not use the posted engine power and torque curves, without numbers, to calculate the estimated shift points?

I can just pull the data from anywhere but, without the same data between the two of us, this comparison is meaningless. You should know this.
I believe that he wrote previously that there was no power and torque curves (dyno chart) available, and that he just used the factory stated hp and torque numbers as per my link in a previous post.

Not sure if that was what you were asking though...
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      09-30-2013, 05:38 PM   #149
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Quote:
Originally Posted by bplewis24 View Post
Jonjt, I applaud you for dealing with his agenda.
And what agenda is that?

He has provided very informative and interesting performance calculations for the F8x cars in other threads.

I don't see any agenda here. Please enlighten me.
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      09-30-2013, 05:51 PM   #150
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Quote:
Originally Posted by Boss330 View Post
I believe that he wrote previously that there was no power and torque curves (dyno chart) available, and that he just used the factory stated hp and torque numbers as per my link in a previous post.

Not sure if that was what you were asking though...
Just to save time looking through the thread, link?
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      09-30-2013, 06:35 PM   #151
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Quote:
Originally Posted by Boss330 View Post
And what agenda is that?

He has provided very informative and interesting performance calculations for the F8x cars in other threads.

I don't see any agenda here. Please enlighten me.
His post was edited by someone.
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      09-30-2013, 06:42 PM   #152
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this is hands down the biggest nerd fest of a thread i have ever seen
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      09-30-2013, 07:27 PM   #153
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Originally Posted by ScarecrowBoat View Post
this is hands down the biggest nerd fest of a thread i have ever seen
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      09-30-2013, 07:36 PM   #154
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Quote:
Originally Posted by Jonjt View Post
Ugh you dont seem to understand a good portion of my post but whatever.............
You are welcome to your opinion.

Quote:
Originally Posted by Jonjt View Post
If you recall, this discussion is centered around an estimated power curve and an estimated torque curve. None of this is accurate, this is not practice, not yet. You even pointed out that we don't have a proper factory crank dyno and that we are all just guessing. I brought up this power method to SIMPLIFY this estimation, since we can't actually produce an accurate result regardless of how comprehensive the methods are.
I am willing to bet that the interpolated power and torque curves I have used are more than accurate enough to capture the trends (multiple pre-redline shifts required) and absolute values of the shift points within a couple hundred rpm. Unfortunately, there is no validation case I can find for this car. Not really a big deal since for the life of you, you can't seem to calculate much of anything...

Quote:
Originally Posted by Jonjt View Post
I've responded twice asking for you to provide the same losses you are guessing at so I can do my calculation but, you have yet to produce anything. Comparative analyses are useless without data sharing. You can't validate anyone's technique without knowing what went into it. You even pointed this out by referencing the "garbage in, garbage out" nature of CAE.

I can go pull some data from some source, make some loss estimations and just produce some numbers. It won't happen until I get home, though.
Losses are a key part of estimates and simulations which use a crank value of course. They are completely relevant both for performance results and shift points (obviosuly related). If:

1. You have no idea what reasonably accurate losses are, and,
2. Your "simplified" power based calculation method (that is so simple and insightful) requires these values.

Then I am at a total loss here (no pun intended) as to the superiority of your method, either in theory but especially in practice.

I'll be happy to tell you all of the details that went into my calculation once you provide a post with a detailed account of your calculation of these F10 523i shift points. You could also run the E92 M3 M-DCT and show redline shift points across the board.

A better test case might be the F10 M5. There has been discussion here and at m5board.com (me included) about it's shift points. I'm pretty sure there was empirical evidence posted over there that the M5 needs to be shifted pre redline in many gears and my simulation matched that.

Wow, I am getting bored with this...
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