[Polo08816]

Originally Posted by HighlandPete

BMW state that from a front wheel disturbance (say a pothole) "information is sent to the rear wheels so that sufficient cushioning is in place", makes sense, both technically and from experience. Take our typical BMW travelling 60mph, we travel 88 ft per sec, with our average wheelbase that means we have ~100ms to get the damper values changed to be prepared for the second wheel/axle impact. From what I read, a typical proportional valve (as used in VDC) can change from a soft to hard value in 20 - 30ms.

I find with my car that the second axle damping does change ahead of the second impact. I have one particular place where I cross a ridge in the road, been like it for years. Have travelled the road more than a thousand times in a wide range of vehicles with all kinds of suspension and damping settings, so know the way a rear axle thumps out the imperfection between 50 - 60mph. The adaptive suspension is different, you expect that regular rear 'thump', but it is softened as no passive suspension can do. A Jaguar with CATS suspension is the same, then we'd expect it to be, as that also is continuously adaptive.

I'm not convinced. In order to determine if it were truly adaptive (when the rear axle crosses over the bump), we'd need to review the software source code to see what it is actually doing instead of speculating simply by what we think we feel.

We'd also need to hold many more variables constant. Because if your contention is that adaptive suspension always makes the rear axle crossing less thumpy, we'd have to quantify it and prove that what you're feeling isn't attributable some of the following but not limited to:

1. Front axle impacts are felt more because there's additional feedback such as steering feedback that isn't part of the rear axle.
2. The exact same chassis isn't set up where the rear axle thump would be less to begin with

Also, what's your point of reference? Is it a F10 5 Series? With Adaptive Drive, you would have Active roll bars, no? Let's just say that you are completely right for a moment. The issue here is that the improvement you believed to have felt may not even be mirrored in the F3x's DHP for the fact that the F3x does not have Active Roll bars. A stiff roll bar may help in resisting roll in cornering, but it also makes the axle behave and feel more like a live axle in cases (over road imperfections).

If we're talking about ride quality over road imperfections, DHP may help. But the more effective solution is to not use low profile run flat tires.

Bottom line: The improvement in ride quality for road imperfections is going to be way more significant going from 19" RFT tires to 18" non-RFT tires than whatever adjustments could be made to DHP for the F3x platform.


http://f30.bimmerpost.com/forums/sho...d.php?t=942225

Originally Posted by Racer20

I'm a chassis engineer and I develop adaptive suspensions systems. This will be long.

Some limitations:

1. Road conditions
Very Small Bumps
Some events, like pavement cracks, roads with a coarse texture, or very small, light undulations, are too small or too fast to detect and/or react to. In these cases, no current command is sent, and the performance will depend on how the full soft mode was tuned. Also, instant response to every road input isn't really ideal either. If the damper reacts to every single tiny bump on the road, it can cause the ride to become busy and jerky. For example . . . Magneride has much faster response time potential, but they have to put an artificial threshold there anyway to prevent this issue.

Very Sharp Bumps
Larger events that are very sharp, like your pavement transition or a manhole cover, occur too quickly for the damper to react in the ideal manner. Its possible that the full soft mode isn't soft enough for these bumps, but it's more likely that the harshness you feel is actually a result of not enough damping at the instant that you first hit the impact. With lower damping, the tire kicks off the impact rather than enveloping it, and you get more/faster wheel motion than you would if you had more damping. This limitation will affect the body's reaction to the initial kick as well as how the wheel and body settle after the bump. If you bring in more damping faster at the initial impact, you can improve the impact quality on sharp bumps, but again, the ride can get jerky and busy on other types of roads. It's still all a compromise.

I believe the F30 Adaptive Dampers are made by Tenneco. I haven't driven one of their systems, but from what I know, this system is a bit behind the current state of the art. (Edit: this technology is advancing very quickly these days, so their system on the 4 series or 2 series will have a different tune and may use different valves or software, and may be better than the F30.) Sachs has some valve-based systems that are really good, and GM's latest Magneride cars are really good. Things are advancing pretty rapidly in my field right now, so within the next couple years these systems should be even better.

My Personal Thoughts . . .

All said and done, a GOOD adaptive system can be MUCH better than any passive system if properly tuned. I've heard mixed reviews of the F30 system, and I'm having a hard time finding one locally to test drive. Regardless, I've decided that my next car will have an adaptive system . . . I've just got to find one that meets my high standards. Unfortunately the stuff I'm working on now won't be on the market for a few more years, so I'm kind of stuck hoping the other guys have tuned something that I like.

[HighlandPete]

Originally Posted by Polo08816

I'm not convinced. In order to determine if it were truly adaptive (when the rear axle crosses over the bump), we'd need to review the software source code to see what it is actually doing instead of speculating simply by what we think we feel.

We'd also need to hold many more variables constant. Because if your contention is that adaptive suspension always makes the rear axle crossing less thumpy, we'd have to quantify it and prove that what you're feeling isn't attributable some of the following but not limited to:

1. Front axle impacts are felt more because there's additional feedback such as steering feedback that isn't part of the rear axle.
2. The exact same chassis isn't set up where the rear axle thump would be less to begin with

Also, what's your point of reference? Is it a F10 5 Series? With Adaptive Drive, you would have Active roll bars, no? Let's just say that you are completely right for a moment. The issue here is that the improvement you believed to have felt may not even be mirrored in the F3x's DHP for the fact that the F3x does not have Active Roll bars. A stiff roll bar may help in resisting roll in cornering, but it also makes the axle behave and feel more like a live axle in cases (over road imperfections).

If we're talking about ride quality over road imperfections, DHP may help. But the more effective solution is to not use low profile run flat tires.

Bottom line: The improvement in ride quality for road imperfections is going to be way more significant going from 19" RFT tires to 18" non-RFT tires than whatever adjustments could be made to DHP for the F3x platform.

I agree we'd like to see data with some baseline or point of reference, comparing a passive system with adaptive. I'm saying I can feel there is something different from the driving seat. I know how a passive system reacts over the particular ridge I've used as an example. The adaptive suspension is a different feel altogether, I've driven BMW wagons over the same road and even with rear air suspension the passive vs. adaptive is different. I've driven it with different wheels on my F11 including 17" with 55 aspect ratio tires. It is the same 'off beat' feel you just don't get with any passive suspension system, whatever the car or model.

ARS on the 5-series will make no difference on an axle rise and fall, any more than a fixed ARB. We are talking a straight road here, so an ARB is not part of the spring rate/damping equation in this situation.

I've another section of road with a wave of gentle undulations, again a piece of road which tests out any suspension system, both compression and rebound damping. I run onto this section and still wait for the adaptive to be caught out, because it feels too soft as I approach. But again the whole car stiffens as if I was running a much firmer suspension. The section of road is straight so once again ARS won't be the active element in controlling the vertical body movement, it is the damping which has firmed up.

I understand drivers like yourself may not be convinced on a system capable of adapting well enough on the fly to make it worthwhile, no problem with that from my perspective. Simply put, adaptive suits me better than a passive sport suspension in my driving conditions, with a whole range of poor quality roads to drive.

BTW, I've tested 5-series models 'back to back', and for me there is no comparison for the feeling of body control and composure on poor road surfaces.

[Polo08816]

Originally Posted by HighlandPete

I agree we'd like to see data with some baseline or point of reference, comparing a passive system with adaptive. I'm saying I can feel there is something different from the driving seat. I know how a passive system reacts over the particular ridge I've used as an example. The adaptive suspension is a different feel altogether, I've driven BMW wagons over the same road and even with rear air suspension the passive vs. adaptive is different. I've driven it with different wheels on my F11 including 17" with 55 aspect ratio tires. It is the same 'off beat' feel you just don't get with any passive suspension system, whatever the car or model.

ARS on the 5-series will make no difference on an axle rise and fall, any more than a fixed ARB. We are talking a straight road here, so an ARB is not part of the spring rate/damping equation in this situation.

I've another section of road with a wave of gentle undulations, again a piece of road which tests out any suspension system, both compression and rebound damping. I run onto this section and still wait for the adaptive to be caught out, because it feels too soft as I approach. But again the whole car stiffens as if I was running a much firmer suspension. The section of road is straight so once again ARS won't be the active element in controlling the vertical body movement, it is the damping which has firmed up.

I understand drivers like yourself may not be convinced on a system capable of adapting well enough on the fly to make it worthwhile, no problem with that from my perspective. Simply put, adaptive suits me better than a passive sport suspension in my driving conditions, with a whole range of poor quality roads to drive.

BTW, I've tested 5-series models 'back to back', and for me there is no comparison for the feeling of body control and composure on poor road surfaces.

Roll bar stiffness will absolutely affect ride quality. Ask any mechanical or chassis engineer and they will tell you the same.

Think about a roll bar this way. Why do you think a lot of off-road vehicles have roll bar disconnects? Because on technical off-road courses such as rock climbing, there is a need for greater axle articulation - which is the "rise and fall" - difference in ride height at each end of the axle. For on-road applications, the goal is the opposite...

Now let's back up a bit. What's the purpose/definition of a roll bar? "To reduce sway or body roll by minimizing the suspension compression/extension on opposite sides".

In order to make that work, the left and right control arms are mechanically linked. An "independent" rear suspension is not as "independent" as it would appear to be now. That means that bumps, vibrations, etc. from one control arm are transferred/propagated to the other control arm to some degree.

Why do we use roll bars? Well, it's a pretty damn cost effective way of altering effective spring rate when we need to. But there's a downside, the stiff the roll/sway bar, impacts ride quality.

Now if the Adaptive Suspension system works the way you allege it to, it would alter the stiffness of the Active Roll bar depending on the input of other sensors. If the priority was comfort and there were a lot of potholes and you're driving in a straight line, then it should reduce the stiffness to preserve ride quality.

The point is that the system you are describing in the F10 5 Series is not applicable to the F3x platform.



Now if you were to ask me if I'd get an F30 with DHP in 2016, the answer is most likely "Yes." But not the same reasons you would. I'd get it because it would be non-removable from the Track Handling Package which includes the M Sport Brake. The cost of retrofitting the M Performance Brakes exceeds the cost of replacing DHP dampers one time. Also, the main problem with the 2012-2015 Sport suspension is it's softness - for which the lack of spring is the problem. That problem was addressed in 2016 with the LCI and I'd be more comfortable with leaving the car in stock configuration (Track Handling Package) for it's entire life.

[HighlandPete]

Originally Posted by Polo08816

Roll bar stiffness will absolutely affect ride quality. Ask any mechanical or chassis engineer and they will tell you the same.

You are missing the point I'm illustrating, I'm using a driving situation which is as close as we can get to 3-series adaptive damping. I'm driving a straight piece of road where an ARB (active or not) does not change the spring rate/damping of axle movements, that is why I'm using that driving condition.

ARS is virtually de-coupled in the straight ahead state, it is why single wheel bumps are also softer in the 5-series with ARS. There is no cross axle interference as with a fixed ARB in straight line driving. We are not talking about single wheel movements, or in bends, where the variables of ARB function come into play.

Same for the undulating 'straight' road, ARS is not working for or against the adaptive damper rates. The ARB ends/links rise and fall without any cross axle torque, only the friction within the mounting bushes are of note and will cancel out side to side.

If we move to driving bends and cross car undulations then we are into different territory, where the 5-series with ARS fitted is not comparable to the 3-series adaptive suspension. Hence not illustrating those situations where ARS really does assist driving dynamics. The ability to tune understeer/oversteer characteristics on the fly, according to how hard you drive is a design function which a driver can sense quite easily.

[Polo08816]

Originally Posted by HighlandPete

You are missing the point I'm illustrating, I'm using a driving situation which is as close as we can get to 3-series adaptive damping. I'm driving a straight piece of road where an ARB (active or not) does not change the spring rate/damping of axle movements, that is why I'm using that driving condition.

You are also missing the point. It's not comparable.


You're talking about the 5 Series's system which can:
1. Alter effective spring rate
2. Alter dampening characteristics (how quickly is up for debate)

Compared to the 3 Series's system:
1. Alter dampening characteristics (again, how quickly is up for debate).


They're not the same. They shouldn't be compared.

[HighlandPete]

Originally Posted by Polo08816

You are also missing the point. It's not comparable.


You're talking about the 5 Series's system which can:
1. Alter effective spring rate
2. Alter dampening characteristics (how quickly is up for debate)

Compared to the 3 Series's system:
1. Alter dampening characteristics (again, how quickly is up for debate).


They're not the same. They shouldn't be compared.

I agree we are not able to truly compare, as the 3-series only has a basic version of VDC, a single proportional valve controlling both compression and rebound valving, plus only two base settings. The 5-series has VDC II, (CDC 2e in ZF speak). Individual proportional valves for compression and rebound, working independently, plus 3 base modes.

You are still misunderstanding the way the ARB is not influencing the spring or damping rates on a straight drive. There are therefore very similar characteristics in how the damping can change in that situation for both 3 & 5 series cars.

[Polo08816]

Originally Posted by HighlandPete

I agree we are not able to truly compare, as the 3-series only has a basic version of VDC, a single proportional valve controlling both compression and rebound valving, plus only two base settings. The 5-series has VDC II, (CDC 2e in ZF speak). Individual proportional valves for compression and rebound, working independently, plus 3 base modes.

You are still misunderstanding the way the ARB is not influencing the spring or damping rates on a straight drive. There are therefore very similar characteristics in how the damping can change in that situation for both 3 & 5 series cars.

I'm not misunderstanding the way ARB is not influencing spring or dampening rates. Yes, in a perfect scenario where both rear wheels roll over the same obstacle at the same exact time, the ARB would have little to no effect. But unless you can prove through instrumentation that this is the exact scenario, then it's based on a lot of assumptions. But the other part is that if the system works as you say it does, and you don't actually roll over the same obstacle at the same moment, with ARB de-coupled you'd have "more independent" system and thus, your ride quality would be better. But this isn't comparable to the F3x is it?

[HighlandPete]

Originally Posted by Polo08816

I'm not misunderstanding the way ARB is not influencing spring or dampening rates. Yes, in a perfect scenario where both rear wheels roll over the same obstacle at the same exact time, the ARB would have little to no effect. But unless you can prove through instrumentation that this is the exact scenario, then it's based on a lot of assumptions. But the other part is that if the system works as you say it does, and you don't actually roll over the same obstacle at the same moment, with ARB de-coupled you'd have "more independent" system and thus, your ride quality would be better. But this isn't comparable to the F3x is it?

But we are not simply talking about improved ride quality, but how the rear axle damping adjusts for impact after a front axle interference.

For a moment forget the 5-series with ARS, I mentioned the Jaguar with CATS suspension. That too does exactly the same and gives that 'adjusted' rear axle feel over the ridge type obstruction. That like the 3-series has only got adaptive damping, no active ARBs. Both the Jaguar and the 5-series act the same way over the same ridge with VDC function. Any passive suspensions I've driven over it don't react that way, simply variations on typical passive suspension 'thump outs' of the ridge at the rear.

[Polo08816]

Originally Posted by HighlandPete

But we are not simply talking about improved ride quality, but how the rear axle damping adjusts for impact after a front axle interference.

For a moment forget the 5-series with ARS, I mentioned the Jaguar with CATS suspension. That too does exactly the same and gives that 'adjusted' rear axle feel over the ridge type obstruction. That like the 3-series has only got adaptive damping, no active ARBs. Both the Jaguar and the 5-series act the same way over the same ridge with VDC function. Any passive suspensions I've driven over it don't react that way, simply variations on typical passive suspension 'thump outs' of the ridge at the rear.

This chassis engineer would disagree with you. Based on his experience, the Adaptive Suspension simply isn't quick enough to react to road imperfections the way you believe the system is - for the F3x platform.

http://f30.bimmerpost.com/forums/sho...d.php?t=942225

Originally Posted by Racer20

I'm a chassis engineer and I develop adaptive suspensions systems. This will be long.

Some limitations:

1. Road conditions
Very Small Bumps
Some events, like pavement cracks, roads with a coarse texture, or very small, light undulations, are too small or too fast to detect and/or react to. In these cases, no current command is sent, and the performance will depend on how the full soft mode was tuned. Also, instant response to every road input isn't really ideal either. If the damper reacts to every single tiny bump on the road, it can cause the ride to become busy and jerky. For example . . . Magneride has much faster response time potential, but they have to put an artificial threshold there anyway to prevent this issue.

Very Sharp Bumps
Larger events that are very sharp, like your pavement transition or a manhole cover, occur too quickly for the damper to react in the ideal manner. Its possible that the full soft mode isn't soft enough for these bumps, but it's more likely that the harshness you feel is actually a result of not enough damping at the instant that you first hit the impact. With lower damping, the tire kicks off the impact rather than enveloping it, and you get more/faster wheel motion than you would if you had more damping. This limitation will affect the body's reaction to the initial kick as well as how the wheel and body settle after the bump. If you bring in more damping faster at the initial impact, you can improve the impact quality on sharp bumps, but again, the ride can get jerky and busy on other types of roads. It's still all a compromise.

I believe the F30 Adaptive Dampers are made by Tenneco. I haven't driven one of their systems, but from what I know, this system is a bit behind the current state of the art. (Edit: this technology is advancing very quickly these days, so their system on the 4 series or 2 series will have a different tune and may use different valves or software, and may be better than the F30.) Sachs has some valve-based systems that are really good, and GM's latest Magneride cars are really good. Things are advancing pretty rapidly in my field right now, so within the next couple years these systems should be even better.

My Personal Thoughts . . .

All said and done, a GOOD adaptive system can be MUCH better than any passive system if properly tuned. I've heard mixed reviews of the F30 system, and I'm having a hard time finding one locally to test drive. Regardless, I've decided that my next car will have an adaptive system . . . I've just got to find one that meets my high standards. Unfortunately the stuff I'm working on now won't be on the market for a few more years, so I'm kind of stuck hoping the other guys have tuned something that I like.

[x986]

Originally Posted by Polo08816

For uneven roads with many potholes, the solution is 18" non-RFT tires with more sidewall.

OMG, somebody gets it. And don't forget another little 'technical term', unsprung weight. I didn't get a third Bimmer because I think it is a thing of beauty, I got it because I think it makes the best compromises available for my style driving. It's a, what would you call it? 'Driving Machine'.

[HighlandPete]

Originally Posted by Polo08816

This chassis engineer would disagree with you. Based on his experience, the Adaptive Suspension simply isn't quick enough to react to road imperfections the way you believe the system is - for the F3x platform.

I've read the comments of the chassis engineer (read it when first posted as well) he isn't saying it doesn't react as BMW claim, his words are carefully written and show the possible limitations of a semi active suspension.

Getting back to the key issue, are you saying you don't believe BMW when they say the rear damping can be modified in less than the time it takes for the front to rear axle, to pass over the same pothole? Also that companies like ZF can't achieve that function with suspension systems we have fitted to our BMWs?

[snowghost]

The two guys with identical cars except for DHP strikes home for me in the fact I have owned 2 F30 335i M-Sports, one with Passive and my current with DHP.

DHP noticeably flatter in hard cornering, and more damping in Sport Mode than Passive.

On bumpy roads, and freeway expansion cracks there is a noticeable difference even at speed between Comfort and Sport. The most obvious difference to me between Passive and DHP occurred when driving over speed bumps. Much more damping of the front end with the DHP.

I opted to go a step further and got Dinan Springs and ECU Shockware. But that's a whole other story.

[Polo08816]

Originally Posted by HighlandPete

I've read the comments of the chassis engineer (read it when first posted as well) he isn't saying it doesn't react as BMW claim, his words are carefully written and show the possible limitations of a semi active suspension.

Getting back to the key issue, are you saying you don't believe BMW when they say the rear damping can be modified in less than the time it takes for the front to rear axle, to pass over the same pothole? Also that companies like ZF can't achieve that function with suspension systems we have fitted to our BMWs?

I tend to believe what BMW says when it's not something generated by their marketing department.

The problem with what is in bold above is that is NOT what BMW says.

http://www.bmw.com/com/en/insights/t...ive_drive.html

What they specifically say is this...

Each axle has its own independent motor that can adjust the dampers on each individual wheel. When the road surface under one side of the vehicle differs in character from that on the other side - such as when driving on roads with gravel shoulders - Adaptive Drive instantly adjusts the suspension settings of the wheels on one side to practically eliminate any perceptible unevenness in the road.

That IS different from what you're asserting.

The scenario BMW provides is when the left and right side of the car are traveling over slightly different terrain such as one side being on a gravel surface and the other on pavement, NOT when the front axle has ran over a pothole and the car subsequently adjusts the rear axle's dampening.

In fact, BMW's scenario is in line with what Racer20 has stated as the limitations of adaptive suspension. It simply can't adjust fast enough to anomalies (ie. potholes) that are random, nor should it.

Think about it! In the scenario BMW actually provides, how would the car know that the left side of the car is driving over pavement and the right side of the car is driving over gravel? It can't make that determination based on just the inputs of the right front corner of the car. To a computer that would just appear to be a bump in the road. It only knows that the right side of the car is driving over a gravel surface if BOTH the right front and right rear suspension were experiencing similar measurements. Only then would it adjust for the right side of the car driving over gravel.

[RM7]

Adaptive increases chassis stability. Diving, squatting, weight shift, etc. It's ok, but in general no where near the suspension of my c5 camaro. Shocks were way better there, with the same or less travel. The harder I push the 4 series with the adaptive, the better it feels, to a point at least. Of course, these are passenger BMWs, so I wouldn't expect them to be as good, at least unless we are talking m3/4, but then it's not good enough to justify the price for handling alone, especially with kits like 1LE becoming available at lower price points. If BMW wanted to stay on top of the premium market, they'd offer (as an option) premium/performance suspension in all of their 2, 3 and 4 series, but they really don't, not at any serious level.

[Polo08816]

Originally Posted by JamesNoBrakes

Adaptive increases chassis stability. Diving, squatting, weight shift, etc. It's ok, but in general no where near the suspension of my c5 camaro. Shocks were way better there, with the same or less travel. The harder I push the 4 series with the adaptive, the better it feels, to a point at least. Of course, these are passenger BMWs, so I wouldn't expect them to be as good, at least unless we are talking m3/4, but then it's not good enough to justify the price for handling alone, especially with kits like 1LE becoming available at lower price points. If BMW wanted to stay on top of the premium market, they'd offer (as an option) premium/performance suspension in all of their 2, 3 and 4 series, but they really don't, not at any serious level.

Interesting that you bring that up GM. Let's do a bit of theoretical stuff for as second.

Let's work with this assumption: GM's MagneRide system is better then BMW's Electronic Damper Control

Here's what Chevy states for their MagneRide system in the Corvette configurator:

Magnetic Selective Ride Control™
Generation 3 of this suspension-damping system delivers precise, real-time body-motion control. The system:

"Reads" the road every millisecond
Changes damping in just 10–15 milliseconds
Includes Performance Traction Management

Situation

F30 sedan traveling at 75mph with a wheelbase of ~110 inches covers approximately 1.3 inches per millisecond or approximately its own wheelbase in about 100ms.


MRC total system delay from input in front axle to output in rear axle:

1 ms Sampling rate
? ms Software processing for all inputs
15 ms Changes to dampening*


*this assume GM means it only takes 10-15 ms to change dampening after software issuing the command to change dampening.
*it also assumes that it means target level is reach at the end of 15ms, not just started/initated

>16ms best case scenario.

It appears to be theoretically possible for GM's MagneRide system to be able to change rear axle dampening based on front axle input.


But BMW never really provides us with quantifiable properties for it's Adaptive Drive/Dynamic Drive/Electronic Damper Control system.

It never even explicitly mentions the front axle vs. rear axle scenario in its literature either... If the system was so advanced/great/fast, why wouldn't it be advertised as such just like GM's MagneRide system.


Another way to separate out which events an adaptive system can respond to quickly and which it can't is to look at all the inputs it can process:

1. Cornering - A system can predict body roll from direct driver inputs such as steering angle, speed, etc. to know that the car will roll and make quick adjustments to the EDC to reduce *initial* body roll.
2. Braking - A system can predict dive from direct driver inputs such as brake pedal pressure/travel to know that the car will dive and thus reduce *initial* dive

But potholes are another story. The system can't predict that a pothole is coming up because it can't use direct driver inputs to deduce that. Therefore, responses to potholes must be slower because it relies on what the chassis sensors are telling the system first.


Also, EDC can only resist body roll and dive. Given enough time, theoretically, it will still reach the same steady state as a passive suspension with similar spring rates. If you want to reduce or eliminate a level of body roll or dive, it will probably need to come from increasing spring rates.

[HighlandPete]

Originally Posted by Polo08816

Situation

F30 sedan traveling at 75mph with a wheelbase of ~110 inches covers approximately 1.3 inches per millisecond or approximately its own wheelbase in about 100ms.


MRC total system delay from input in front axle to output in rear axle:

1 ms Sampling rate
? ms Software processing for all inputs
15 ms Changes to dampening*


*this assume GM means it only takes 10-15 ms to change dampening after software issuing the command to change dampening.
*it also assumes that it means target level is reach at the end of 15ms, not just started/initated

>16ms best case scenario.

It appears to be theoretically possible for GM's MagneRide system to be able to change rear axle dampening based on front axle input.


But BMW never really provides us with quantifiable properties for it's Adaptive Drive/Dynamic Drive/Electronic Damper Control system.

It never even explicitly mentions the front axle vs. rear axle scenario in its literature either... If the system was so advanced/great/fast, why wouldn't it be advertised as such just like GM's MagneRide system.

I also wish BMW were more open with their data, but using data which can be found, what does the BMW system offer?

Let's use BMW data (readily available) that there is communication every 2.5ms to/from the EDC satellite control units. That technical data aligns with the BMW 'marketing' blurb for VDC.

A control unit on each wheel evaluates movements four hundred times a second and adjusts the shock absorbers accordingly. The electronics system works so fast that when the front wheels encounter a pothole, information is sent to the rear wheels so that sufficient cushioning is in place. The rebound and compression damping are continually and independently set to end the need for compromise which means that the dampers adapt to the state of the road irrespective of which Driving Dynamic Control mode is selected, for exceptional ride comfort even when driving hard on bumpy surfaces.

BMW state that 'event' data transmission is a total of 5ms, (time+event controlled cycle). The dampers BMW use (ZF Sachs) have a variable valve opening/closing timing according to voltage required. From current change to reaction in the damper during the adaptation phase can be approximately 5ms. Time to completely change the open/close state of the proportional valve is up to 35ms (approx. 35ms closing, approx. 15ms opening).

So take a worst case, assuming the proportional valve is open and needs to close under full damping loadings. We have an event time of 5ms plus 35ms to close the valve, a total of 40ms. (Plus 2.5ms if we have just missed a communication). That is worst case, opening the valve is approximately half the time.

OK, so we may be twice as slow in reaction times as the GM MagneRide system, but using your own time frame of 100ms, we still have over 50ms "to spare" in the worst case scenario for changing front to rear axle damping rates.

[Polo08816]

Originally Posted by HighlandPete

I also wish BMW were more open with their data, but using data which can be found, what does the BMW system offer?

Let's use BMW data (readily available) that there is communication every 2.5ms to/from the EDC satellite control units. That technical data aligns with the BMW 'marketing' blurb for VDC.



BMW state that 'event' data transmission is a total of 5ms, (time+event controlled cycle). The dampers BMW use (ZF Sachs) have a variable valve opening/closing timing according to voltage required. From current change to reaction in the damper during the adaptation phase can be approximately 5ms. Time to completely change the open/close state of the proportional valve is up to 35ms (approx. 35ms closing, approx. 15ms opening).

So take a worst case, assuming the proportional valve is open and needs to close under full damping loadings. We have an event time of 5ms plus 35ms to close the valve, a total of 40ms. (Plus 2.5ms if we have just missed a communication). That is worst case, opening the valve is approximately half the time.

OK, so we may be twice as slow in reaction times as the GM MagneRide system, but using your own time frame of 100ms, we still have over 50ms "to spare" in the worst case scenario for changing front to rear axle damping rates.

It seems like you're using a quote from this site:
http://www.bmw.com/com/en/newvehicle...trol.html#more

It's dated from 2010 and almost never appears elsewhere even on the BMW USA site.

As for the F3x platform, this is more applicable:
http://www.bmw.com/com/en/newvehicle...nsion.html#t=l

Whichever setting is chosen, the Adaptive M suspension's electrically controlled dampers calibrate to suit the road conditions within fractions of a second. The system also uses numerous sensors that measure wheel vibrations, as well as vehicle speed, in order to achieve optimal damping and vehicle safety.

It seems to say that it can change the dampening within milliseconds of whatever selection is made in the cabin, but doesn't claim to have the same capabilities of the "Dynamic Damper Control" in the 5 Series as the page from 2010.

[Racer20]

Originally Posted by Polo08816

Interesting that you bring that up GM. Let's do a bit of theoretical stuff for as second.

Let's work with this assumption: GM's MagneRide system is better then BMW's Electronic Damper Control

Here's what Chevy states for their MagneRide system in the Corvette configurator:

Situation

F30 sedan traveling at 75mph with a wheelbase of ~110 inches covers approximately 1.3 inches per millisecond or approximately its own wheelbase in about 100ms.


MRC total system delay from input in front axle to output in rear axle:

1 ms Sampling rate
? ms Software processing for all inputs
15 ms Changes to dampening*


*this assume GM means it only takes 10-15 ms to change dampening after software issuing the command to change dampening.
*it also assumes that it means target level is reach at the end of 15ms, not just started/initated

>16ms best case scenario.

It appears to be theoretically possible for GM's MagneRide system to be able to change rear axle dampening based on front axle input.


But BMW never really provides us with quantifiable properties for it's Adaptive Drive/Dynamic Drive/Electronic Damper Control system.

It never even explicitly mentions the front axle vs. rear axle scenario in its literature either... If the system was so advanced/great/fast, why wouldn't it be advertised as such just like GM's MagneRide system.


Another way to separate out which events an adaptive system can respond to quickly and which it can't is to look at all the inputs it can process:

1. Cornering - A system can predict body roll from direct driver inputs such as steering angle, speed, etc. to know that the car will roll and make quick adjustments to the EDC to reduce *initial* body roll.
2. Braking - A system can predict dive from direct driver inputs such as brake pedal pressure/travel to know that the car will dive and thus reduce *initial* dive

But potholes are another story. The system can't predict that a pothole is coming up because it can't use direct driver inputs to deduce that. Therefore, responses to potholes must be slower because it relies on what the chassis sensors are telling the system first.


Also, EDC can only resist body roll and dive. Given enough time, theoretically, it will still reach the same steady state as a passive suspension with similar spring rates. If you want to reduce or eliminate a level of body roll or dive, it will probably need to come from increasing spring rates.

What he said.

[AGONXF30]

I have a 2012 Sport and I have Adaptive M and in Sport+ I can feel the suspension get stiffer. I have driven in many crappy roads across the US and I can feel the difference. It is subtle, but it is there. In comfort mode the roads around here are a lot more bearable. Also the car had a weird sideways shift with RFT over certain potholes, it is not longer as pronounced with regular UHPAS tires, it is like the sidewalls cause the weird shift.

[HighlandPete]

Originally Posted by Polo08816

It seems to say that it can change the dampening within milliseconds of whatever selection is made in the cabin, but doesn't claim to have the same capabilities of the "Dynamic Damper Control" in the 5 Series as the page from 2010.

VDC I is clearly not as advanced as VDC II in the 5-series, it's a shame BMW don't state the actual figures for VDC I. Their statement "more or less instantly", in the F30 training material is not what we'd expect from BMW in technical material.

What we do know, VDC I, like the more advanced systems is designed around the Skyhook principle, vertical movement is part of the continuous monitoring under the VDM controller. Front to rear axle/body movements are part of the skyhook regulation. VDC I uses the FleyRay bus, so similar data transmission speeds are in operation for VDC I & II. BMW do state VDC I requires damper adjustment with very rapid cycling, compared with VDC II, which doesn't have such high demands, due to the independent compression/rebound proportional valves. That rapid cycling for compression and rebound control from the same valve is likely its limitation.

I can see situations where VDM control would calculate the requirement for low compression and high rebound rates, (or vice versa). VDC II can provide that, VDC I may have to be a compromise.

[AudiA4]

Originally Posted by AGONXF30

I have a 2012 Sport and I have Adaptive M and in Sport+ I can feel the suspension get stiffer. I have driven in many crappy roads across the US and I can feel the difference. It is subtle, but it is there. In comfort mode the roads around here are a lot more bearable. Also the car had a weird sideways shift with RFT over certain potholes, it is not longer as pronounced with regular UHPAS tires, it is like the sidewalls cause the weird shift.

It is my understanding that you've psyched yourself out...Sport+ only modifies the stability control system. Everything else remains the same, even wth DHP (which I also have).

[AGONXF30]

Originally Posted by AudiA4

It is my understanding that you've psyched yourself out...Sport+ only modifies the stability control system. Everything else remains the same, even wth DHP (which I also have).

Oh you mean between sport and sport+. For me sport+ is the got to and I do not use Sport, but for me sport+ does a bit more than plain sport. It holds the gears in place, mimicking more of a manual than in sport, which will shift. I also have VSS, which feels a bit tighter in sport+. I might have to use sport more often to see if it is placebo or not. In reality, I am usually in Comfort, or Sport+ most of the time. I can feel a difference in handling and road feel between the two.