[bosz]

Anyone here know if its possible for those tuner guys (JB4, Cobb, Dinan etc) to come out with some sort of tune for the electric steering?

Imagine if they offer different 'maps' like completely turning off or really reducing electric assist. Would make it feel like the E90 Hydraulic again.

According to wikipedia:

In the event of component failure that fails to provide assistance, a mechanical linkage such as a rack and pinion serves as a back-up in a manner similar to that of hydraulic systems.

So if the ECU can control the amount of assist through the different modes (ie comfort, sport), then tuners should be able to work something out!

Am I wrong in my thinking?

[HighlandPete]

Don't see anything wrong in the concept, as BMW have already chosen maps/programmes to have it the way it is, as you say. Plus the way EPS works, it is full of tuneable options, from a design perspective. A much more flexible design approach, than a hydraulic system.

Where it gets more complex, IMO, is what do we want from the steering? Like suspension tuning, the decision of how we want it, is a set of compromises. We may want more weighting, but we also want precision and sensitive road feel, so it is not just tightening up the steering, as that could be even worse to drive.

Personally I believe some of the negatives we sense, is BMW trying to mask some of the run-flat tire characteristics, as even a hydraulic system feels different (better IMO) once we change tires to non run-flat examples.

From my perspective it isn't hydraulic vs. an electric system that is the problem, as there are some pretty poor hydraulic systems out there and EPS can be a better steer. But how it is set up, both for the average driver and the enthusiast.

One thing bugging me, I've not yet defined myself what is missing from EPS, it feels as if the intervention may be too rapid, as if we don't get enough physical feedback before the steering is electronically corrected. Anyone else able to define the "missing bit" in EPS?

Maybe there would have to be some component changes, as well as a 'map' approach, to get what some feel is missing.

IMO, the F30 standard steering is really a pretty decent setup, a bit light, but still precise and a reasonable feel, despite the rubber on the rims. So not a bad place to start from for tuning.

HighlandPete

[grimlock]

Originally Posted by HighlandPete

One thing bugging me, I've not yet defined myself what is missing from EPS, it feels as if the intervention may be too rapid, as if we don't get enough physical feedback before the steering is electronically corrected. Anyone else able to define the "missing bit" in EPS?

In a mechanical system, you feel the road through the steering as a rotational force (or resistance to), and respond through the same wheel your command to the wheel. Like in a human arm, you feel its movement as such, and also move the same arm, so in real-time there is a flow of sensations (feedback from the arm) and commands from your brain, which in turn affect the oncoming sensations.. -hence, "feedback", or in the driving 'road feel'.

With EPS, its like having a motor attached to your arm, which responds by its own program, increasing the force of your arm when you only wanted to move it a little. In effect, its a direct multiplier (although the program can have different parameters, strong first, weak later etc.) which is why it feels 'unnatural', as it would if you suddenly had a hybrid motor implanted in your arm. But in theory, after you adjust to it, it should feel entirely natural (-perhaps showing the inabsoluteness of what is 'natural')
But there could a real effect on 'road feel' -if the force is too great, too small (a damping force), or comes at the wrong time, that force directly masks /interfeers with the sensations you receive through the wheel, unless your brain is able to 'figure out' the ESP program and adjust mathematically the altered input from the wheel, the the 'real road condition' and then give your command to that. Sounds nearly impossible. It would be like listening to music that has been mathematically altered, and not consistently either, -it would sound almost alien.

[Michael Schott]

Originally Posted by grimlock

In a mechanical system, you feel the road through the steering as a rotational force (or resistance to), and respond through the same wheel your command to the wheel. Like in a human arm, you feel its movement as such, and also move the same arm, so in real-time there is a flow of sensations (feedback from the arm) and commands from your brain, which in turn affect the oncoming sensations.. -hence, "feedback", or in the driving 'road feel'.

With EPS, its like having a motor attached to your arm, which responds by its own program, increasing the force of your arm when you only wanted to move it a little. In effect, its a direct multiplier (although the program can have different parameters, strong first, weak later etc.) which is why it feels 'unnatural', as it would if you suddenly had a hybrid motor implanted in your arm. But in theory, after you adjust to it, it should feel entirely natural (-perhaps showing the inabsoluteness of what is 'natural')
But there could a real effect on 'road feel' -if the force is too great, too small (a damping force), or comes at the wrong time, that force directly masks /interfeers with the sensations you receive through the wheel, unless your brain is able to 'figure out' the ESP program and adjust mathematically the altered input from the wheel, the the 'real road condition' and then give your command to that. Sounds nearly impossible. It would be like listening to music that has been mathematically altered, and not consistently either, -it would sound almost alien.

Very good thought provoking post. There are a lot of factors that make up steering feel. Much if it is in the suspension settings and not the steering. I don't know the technical aspects of how BMW specs camber and caster settings but their specs are one reason the e90 steering is relatively heavy. Also, as you allude to, road feel is subjective.

The future of EPS should be interesting. In many ways, at least in regard to sportier cars, the tuning and execution of such a system is in its infancy. We can see that BMW has tuned the system in the 3 series differently than in the 5 series. Porsche is now using it in the latest 911 and Boxster and the reviews are lukewarm. I just read a review of the EPS in the new Subaru brz and this system was given high marks.

[sr5959]

Originally Posted by bosz

Anyone here know if its possible for those tuner guys (JB4, Cobb, Dinan etc) to come out with some sort of tune for the electric steering?

Imagine if they offer different 'maps' like completely turning off or really reducing electric assist. Would make it feel like the E90 Hydraulic again.

According to wikipedia:

In the event of component failure that fails to provide assistance, a mechanical linkage such as a rack and pinion serves as a back-up in a manner similar to that of hydraulic systems.

So if the ECU can control the amount of assist through the different modes (ie comfort, sport), then tuners should be able to work something out!

Am I wrong in my thinking?

I would give it some time. I like the steering much better now after 3k miles than I did when I first got the car.

[HighlandPete]

Originally Posted by grimlock

In a mechanical system, you feel the road through the steering as a rotational force (or resistance to), and respond through the same wheel your command to the wheel. Like in a human arm, you feel its movement as such, and also move the same arm, so in real-time there is a flow of sensations (feedback from the arm) and commands from your brain, which in turn affect the oncoming sensations.. -hence, "feedback", or in the driving 'road feel'.

With EPS, its like having a motor attached to your arm, which responds by its own program, increasing the force of your arm when you only wanted to move it a little. In effect, its a direct multiplier (although the program can have different parameters, strong first, weak later etc.) which is why it feels 'unnatural', as it would if you suddenly had a hybrid motor implanted in your arm.

I'm not sure this is the whole story, as a hydraulic assisted steering system still has a 'sensing' link, a torsion bar, which allows for valving variation. The EPS has a torque transducer doing the same thing.

We have two torque sources, the steering wheel torque and the steered wheels torque, it is these forces that are the basis of road feel and road feedback.

Both systems offer design variation for sensitivity of steering inputs and damping of road shocks.

I cannot see where the difference is, to tuning either system to get what is required. I've studied the ZF design data for standard hydraulic assisted rack and pinion, servotronic, all levels of EPS including Dual Pinion and Paraxial Servo, and see no reason why an EPS system is less tuneable than the hydraulic based systems. As a design engineer I'd say EPS ought to be far more tuneable and able to give exactly what the manufacturer wants.

Problem could be as you suggest... "what is natural?"

BTW, I've driven hydraulic systems that are definitely inferior to the F30 EPS system. How hydraulic systems are tuned and set up, can still be found wanting.

HighlandPete

[bosz]

Originally Posted by HighlandPete

I'm not sure this is the whole story, as a hydraulic assisted steering system still has a 'sensing' link, a torsion bar, which allows for valving variation. The EPS has a torque transducer doing the same thing.

We have two torque sources, the steering wheel torque and the steered wheels torque, it is these forces that are the basis of road feel and road feedback.

Both systems offer design variation for sensitivity of steering inputs and damping of road shocks.

I cannot see where the difference is, to tuning either system to get what is required. I've studied the ZF design data for standard hydraulic assisted rack and pinion, servotronic, all levels of EPS including Dual Pinion and Paraxial Servo, and see no reason why an EPS system is less tuneable than the hydraulic based systems. As a design engineer I'd say EPS ought to be far more tuneable and able to give exactly what the manufacturer wants.

Problem could be as you suggest... "what is natural?"

BTW, I've driven hydraulic systems that are definitely inferior to the F30 EPS system. How hydraulic systems are tuned and set up, can still be found wanting.

HighlandPete

I was waiting for an engineering post!

So in summary, you are saying that EPS is tuneable and to high degree?

[grimlock]

Originally Posted by HighlandPete

I'm not sure this is the whole story, as a hydraulic assisted steering system still has a 'sensing' link, a torsion bar, which allows for valving variation. The EPS has a torque transducer doing the same thing.

We have two torque sources, the steering wheel torque and the steered wheels torque, it is these forces that are the basis of road feel and road feedback.

Both systems offer design variation for sensitivity of steering inputs and damping of road shocks.

I cannot see where the difference is, to tuning either system to get what is required. I've studied the ZF design data for standard hydraulic assisted rack and pinion, servotronic, all levels of EPS including Dual Pinion and Paraxial Servo, and see no reason why an EPS system is less tuneable than the hydraulic based systems. As a design engineer I'd say EPS ought to be far more tuneable and able to give exactly what the manufacturer wants.

Problem could be as you suggest... "what is natural?"

BTW, I've driven hydraulic systems that are definitely inferior to the F30 EPS system. How hydraulic systems are tuned and set up, can still be found wanting.

HighlandPete

Hi Pete

The difference between the torsion bar and servo assist is the addition of an additional outside force, a simple multiplier of the mechanical force you have given the steering wheel, right?
With a purely mechanical system all the force that is required to turn the wheel is provided by you physically turning the steering, outside of help from the road gradient etc.
But with the servo/electronic, you suddenly become He-man and it only requires a small fraction of the force to get the car steering where you want.
The un-naturalness is perhaps the result of the excess of this steering force (you are too strong) in relation to the road steering force -camber/road undulations that move or are felt through the steering - 'road feel'.
Can you feel it when you have run a forklift through a cardboard barrier/box? Probably not. But if you walk into one, you would notice, because you are carrying alot less force than when you are operating a vehicle. Probably a super-sensitive device could measure the minute change in momentum in the forklift, but we could not sense it as humans, because the change is too small.
A simple experiment, does road-feel in smaller vehicles, or ones with different steering set-up which require different physical steering force, change the amount of road-feel that is obtainable with servo steering even after fine tuning?

[grimlock]

On "what is natural",
One in which the road force on the steering wheel is matched (in terms of magnitude of force) with the required drivers input/steering force.
But this presents problems already, if you could mechanically steer a massive car (hypothetically) the force required would be too large. You may not even be able to overcome the road crown and end up like a bowling ball in the ditch. But at least you will be able to 'feel' the road! It's tugging massively at you as you try in vain to keep the car out of the ditch. No lack of road feel here.
Ok, add the required servo, so you can steer the damn thing.
Now you can control it at will. And here is when the complaints about 'road feel' start. "It feels like a game." "I ran over a cart of bricks and didn't notice until I heard workmen shouting.."
How to get back road feel?
Going back to the definition of road feel (steering wise) as the force imparted on the steering wheel by the road.. so we need sensors to measure this force.
Here is the problem, if lets say the road imparts a steering force of 100 ('whatevers', let's not get too technical) on our massive car, and a human can only reasonable steer with 10, how do you receive input from your road force sensor when you servo is acting in the opposite way? I don't think you can.
So basically if you want help steering a car, you're directly talking over the 'road feel' imparted mechianically by the road on the car. I don't see how it can be otherwise, the steering wheel can only do two things right? Turn one way or the other.
Is this correct? No idea.
Anyone drive a Tonka truck, you know like those used in mining? Or an airplane? Any 'steering feel' in those?

[Elk]

Originally Posted by grimlock

Or an airplane? Any 'steering feel' in those?

Smaller, non-hydraulic planes impart a great deal of feel to both stick and rudder. Once hydraulics are used, there is relatively little. This is not a good analogy however as there is little concern for "steering feel" in large planes.

My guess is that EPS can be readily tuned. I bet BMW will provide less boosted steering the more its buyers complain about the current feel.

(Great posts, especially HighlandPete. Very thoughtful.)

[HighlandPete]

Originally Posted by grimlock

Hi Pete

The difference between the torsion bar and servo assist is the addition of an additional outside force, a simple multiplier of the mechanical force you have given the steering wheel, right?
With a purely mechanical system all the force that is required to turn the wheel is provided by you physically turning the steering, outside of help from the road gradient etc.
But with the servo/electronic, you suddenly become He-man and it only requires a small fraction of the force to get the car steering where you want.
The un-naturalness is perhaps the result of the excess of this steering force (you are too strong) in relation to the road steering force....

But what is the difference? Hydraulic or servoelectric assistance, both are torque multipliers. That is my point, they both have the same potential for variable assistance, according to the design parameters. Neither is more powerful than the other.

You can have over assisted hydraulic systems, devoid of road feel and feedback, so it is not an EPS problem in itself.

Both systems boast the ability to adjust to steering torque input, (servotronic hydraulic systems having more complexity and electronic sensing for the hydraulic valving) so getting nearer to the wider variables available from EPS.

Both systems have the ability to vary the damping of road shocks, so no advantage to a hydraulic system.

To my mind we are dealing with what the car makers feel we need. Typically they set the car up with a comfort steering programme, cars like our BMW have the option of a sport setting which basically means more steering torque is needed to get assistance, plus we can be given more road feel and feedback by changing the steering damping forces.

It is all so variable in the design parameters, so we should be able to get exactly what we want, BMW have chosen to set it up as it is, so they have decided what they feel is the best setting, both for comfort and sport. Perhaps we simply don't like what they have decided as the 'optimum' BMW settings.

The reference to aviation control is one definitely examined by automotive engineers, the same issues of control feel and feedback apply.

As to the view that EPS is tuneable, certainly ZF see it as a very flexible system, to quote:

The use of ZF Servolectric allows one to adjust the steering characteristics (e.g. steering effort, selfcentering and damping) by programming the control unit, thus adapting them perfectly to different vehicle philosophies. By using identical hardware components, this electronic programming enables universal adaptation of the steering system to very different types of vehicles and applications (for example sedan, SUV, sports coupé or van).

I see it that way as well. Now whether the aftermarket tuners can 'map' EPS as a simple stand alone upgrade, that could be a different issue.

HighlandPete

[grimlock]

Originally Posted by HighlandPete

But what is the difference? Hydraulic or servoelectric assistance, both are torque multipliers. That is my point, they both have the same potential for variable assistance, according to the design parameters. Neither is more powerful than the other.

You can have over assisted hydraulic systems, devoid of road feel and feedback, so it is not an EPS problem in itself.

Both systems boast the ability to adjust to steering torque input, (servotronic hydraulic systems having more complexity and electronic sensing for the hydraulic valving) so getting nearer to the wider variables available from EPS.

Both systems have the ability to vary the damping of road shocks, so no advantage to a hydraulic system.

To my mind we are dealing with what the car makers feel we need. Typically they set the car up with a comfort steering programme, cars like our BMW have the option of a sport setting which basically means more steering torque is needed to get assistance, plus we can be given more road feel and feedback by changing the steering damping forces.

It is all so variable in the design parameters, so we should be able to get exactly what we want, BMW have chosen to set it up as it is, so they have decided what they feel is the best setting, both for comfort and sport. Perhaps we simply don't like what they have decided as the 'optimum' BMW settings.

The reference to aviation control is one definitely examined by automotive engineers, the same issues of control feel and feedback apply.

As to the view that EPS is tuneable, certainly ZF see it as a very flexible system, to quote:



I see it that way as well. Now whether the aftermarket tuners can 'map' EPS as a simple stand alone upgrade, that could be a different issue.

HighlandPete

In the mechanical system, torque multiplication is used, where extra steering turning travel is converted into higher torque values to move the larger steering components -no external energy is used-, whereas with a servo the input calls upon extra force (energy) that is no supplied by the driver.
In the non-servo system, the maximum steering force is that which the driver can provide. In the servo system, only a small input is required to trigger any size steering assist required to move any size load.
How this effects 'feel' is like this; imaging you are steering a large car into a gradient while parking. With a hyrdraulic system that uses torque multiplication with no servo, the multiplication factor must be sufficiently large so that by the driver's own force/energy the wheel can be turned working against gravity. Let's say the factor is just large enough so that the wheel can be turned using a large amount of effort.. when he relaxes to say half the effort required, the wheel starts to turn back off its own accord under gravity, -he feels the wheel turning against his still applied 50% force.. can we call this 'road feel'?
With the servo, the driver only needs to use 10% of his force to turn into the gradient, the motor supplies the rest of the energy.
So if he wants to relax the wheel to replicate the 50% force of the non-servo, what must he do? He inputs only 5% of the force.. the servo supplies the rest of the 45%.. the car behaves in exactly the same way.
But what does the driver feel? He feels he is now using 5% force as opposed to the previous 10%.. whereas without the servo, he goes from 100% to 50% .. although the % drop in force is the same, what is 'felt' is maximal effort to half-effort, and low effort to half-of low effort. The difference felt is much more noticeable because the magnitudes of force supplied by the driver is much greater with the non-servo.

So perhaps to tune in more 'feel' the assist needs to be much less, in otherwords let the driver do more work, otherwise there is no difference to using a joy stick.
But if less assistance is provided, the steering becomes heavier, it becomes tiring, like driving a truck or bus.
Is there no way to get steering feel back with large cars?

Could it be the lack of feel with the new models is due to other suspension/steering changes rather than servo-assist? The increased damping for comfort rather than sport?
The fault may lie elswhere..
Steering assist appears to be a simple issue, where the limitation is more assist=less feel ?

[HighlandPete]

Originally Posted by grimlock

With a hyrdraulic system that uses torque multiplication with no servo, the multiplication factor must be sufficiently large so that by the driver's own force/energy the wheel can be turned working against gravity. ?

I don't see where you are coming from, hydraulic assistance is also using an external power source, it is power assisted steering, can be as light as any EPS system, in some cases even lighter, much lighter than the BMW EPS system.

What I'm saying, the torque sensing (which controls the rate of power assistance), can be to identical values for both hydraulic and EPS, same effort from the driver to change direction. Makes no difference whether it is an electrical servo motor, or an oil pump and hydraulic ram generating the force.

What I'm seeking, is why EPS is not giving the same 'feel' as hydraulic assistance, when the design and working parameters are claimed to be virtually identical. With EPS having more scope for linking added features such as park assist, lane departure control, etc.

HighlandPete

[Elk]

Originally Posted by HighlandPete

What I'm seeking, is why EPS is not giving the same 'feel' as hydraulic assistance, when the design and working parameters are claimed to be virtually identical.

This is the correct question. I only wish I could answer it. Your analysis is dead-on as to the mechanics.

My guess is it is a marketing decision. BMW has become a mainstream car and, thus, caters to its market. It is the same unfortunate reason the F30 now has massive cupholders.

[HighlandPete]

Originally Posted by Elk

This is the correct question. I only wish I could answer it. Your analysis is dead-on as to the mechanics.

My guess is it is a marketing decision. BMW has become a mainstream car and, thus, caters to its market. It is the same unfortunate reason the F30 now has massive cupholders.

I tend to agree with the marketing decision answer, as EPS can be whatever they want, clearly many of the customers want a lighter steering, without too much feedback.

As I've said before, BMW are choosing the settings, same as they choose suspension settings. We as customers may like (or not like) the way the cars ride.

HighlandPete

[grimlock]

Originally Posted by HighlandPete

I don't see where you are coming from, hydraulic assistance is also using an external power source, it is power assisted steering, can be as light as any EPS system, in some cases even lighter, much lighter than the BMW EPS system.

What I'm saying, the torque sensing (which controls the rate of power assistance), can be to identical values for both hydraulic and EPS, same effort from the driver to change direction. Makes no difference whether it is an electrical servo motor, or an oil pump and hydraulic ram generating the force.

What I'm seeking, is why EPS is not giving the same 'feel' as hydraulic assistance, when the design and working parameters are claimed to be virtually identical. With EPS having more scope for linking added features such as park assist, lane departure control, etc.

HighlandPete

Sorry I was working on a lot of assumptions, I looked up the wiki on power steering to get a better idea..

Perhaps the reason is that its 'just not good enough yet'.. with the savings in cost, efficiency, and more applications, the refined old hydraulic pump was abandoned for the newer EPS that is not yet perfected.
Call to action, engineers?

[grimlock]

Originally Posted by HighlandPete

I tend to agree with the marketing decision answer, as EPS can be whatever they want, clearly many of the customers want a lighter steering, without too much feedback.

As I've said before, BMW are choosing the settings, same as they choose suspension settings. We as customers may like (or not like) the way the cars ride.

HighlandPete

Perhaps the EPS is design limited wrt steering feel due to inherent differences in using hydraulics vs. direct motor control.. the software may already be optimized for what is achievable with the current physical setup
note: which is why i avoided the steering update on my my2010 f10 after some people said it was heavier, and didn't seem to rave that it was any better

[RPM90]

Originally Posted by bosz

Anyone here know if its possible for those tuner guys (JB4, Cobb, Dinan etc) to come out with some sort of tune for the electric steering?

Imagine if they offer different 'maps' like completely turning off or really reducing electric assist. Would make it feel like the E90 Hydraulic again.

According to wikipedia:

In the event of component failure that fails to provide assistance, a mechanical linkage such as a rack and pinion serves as a back-up in a manner similar to that of hydraulic systems.

So if the ECU can control the amount of assist through the different modes (ie comfort, sport), then tuners should be able to work something out!

Am I wrong in my thinking?

I had a 2006 A4 with servotronic. It's function, as it is today, is to decrease steering effort below, say, 15mph, to make it easier to manuver the car in parking lots. Once the vehicle speed went past the prescribed mph servotronic would increase the effort, or decrease it's effect.
I pulled the servotronic fuse to see what would happen.
The steering became firmer/heavier/harder at all speeds.
Some who did the same thing said that the steering feel was better.
I don't agree. People confuse steering effort with steering feel, and they are not the same.

Steering feel comes from various factors like suspension tuning, tires, steering rack, steering ratio, steering arms, bushings, etc...
Pulling the fuse simply removed the power assist of that system, but the other items stayed the same, nothing changed. Yet, some felt there was "better" steering feel.

Electric assist still uses a BMW rack and pinion steering rack, along with all the BMW steering component know how.
So why are some reporting that steering "feel" is not the same?
I think it's mainly due to how electric assist works compared to how hydraulic assist works. Hydraulic is pretty much a continuous assist system as it's always there. If the system is designed to give more or less depending on vehicle speed, as some do/did, that variation was more linear in it's effort. That then gives the driver a sense of smoothness and continuity, a feeling of directness.
Electric assist comes in only when it's needed. IOW, it's not always assisting like a hydraulic system. With electric, sometimes there is no assist and at other times, mainly when steering away from center, the system activates. When it does activate it's more active as to how much assist it's giving, thus it's not a linear feel, as it might be nicely weighted on center and as soon as you start a turn it comes on and may change in the middle of the steering arch. I think that non-continuous assist is giving an impression of "lacking" good steering feel.
And it's very real. We expect a smooth application of steering assist as if it's not even there even when it is. In BMW's hydraulic system that feel was heavier and continuous. With electric assist that variable assistance is throwing off how the driver feels the steering working. Plus, it feels a bit lighter.
All that is just my speculation.

In the limited time I had in driving a 328i, I liked the steering.
But, I didn't get a chance to drive on any twisty roads with continuous back to back turns by which to judge how well the system works.
Overall, the steering effort felt a bit lighter than my 135i and how I remember my E46. My former E46 had nicely heavy steering effort with a very smooth linear assist feel. It was great. Also, I only drove it in "sport" mode, so I can't compare how the steering feels in the other settings.
The F30 328i steering felt quite accurate though, and the overall heft and feel were superior to the A4 and S4 I had driven that day as well.

I think BMW will continue to tweak their systems and get the assist to transition smoother. Plus, they could make the steering effort heavier quite easily, and they did that back in the early days of the E46. The first couple of years the steering effort was light, too much assist, and many complained about the steering "feel". In following couple of years BMW increased the steering effort by reducing the power assist, and all of sudden people were much happier and said that BMW steering feel came back. However, nothing changed in the steering system other than the effort was increased to make the steering effort harder/heavier.
So, maybe that's all BMW needs to do for now, increase the steering effort.

BTW, those of you who have your new 3's, you can find and remove the servotronic fuse and see how it feels then. You can always put it back in.
Just remember to shut your car off to remove it, and shut if off when you put it back in. I don't know if it will be as easy as it was in my A4, but it's something to consider, and it's your choice. Remember, I'm not telling you to do it.

[HighlandPete]

Originally Posted by RPM90

Steering feel comes from various factors like suspension tuning, tires, steering rack, steering ratio, steering arms, bushings, etc...
Pulling the fuse simply removed the power assist of that system, but the other items stayed the same, nothing changed. Yet, some felt there was "better" steering feel.

Electric assist still uses a BMW rack and pinion steering rack, along with all the BMW steering component know how.
So why are some reporting that steering "feel" is not the same?
I think it's mainly due to how electric assist works compared to how hydraulic assist works. Hydraulic is pretty much a continuous assist system as it's always there. If the system is designed to give more or less depending on vehicle speed, as some do/did, that variation was more linear in it's effort. That then gives the driver a sense of smoothness and continuity, a feeling of directness.
Electric assist comes in only when it's needed. IOW, it's not always assisting like a hydraulic system. With electric, sometimes there is no assist and at other times, mainly when steering away from center, the system activates. When it does activate it's more active as to how much assist it's giving, thus it's not a linear feel, as it might be nicely weighted on center and as soon as you start a turn it comes on and may change in the middle of the steering arch. I think that non-continuous assist is giving an impression of "lacking" good steering feel.
And it's very real. We expect a smooth application of steering assist as if it's not even there even when it is. In BMW's hydraulic system that feel was heavier and continuous. With electric assist that variable assistance is throwing off how the driver feels the steering working. Plus, it feels a bit lighter.
All that is just my speculation.

I don't think you are just speculating, I'm on the same line of thought as well. It is in situations like this that I, as a design engineer, try (mentally) to get inside the mechanisms and walk through what is happening.

I've not got the complete answer, but am also coming to the conclusion it is the nature of hydraulics that suit the human touch, whereas the EPS approach is a more precise mechanism, we lose something in how we as humans connect to that feeling.

I've a bit of experience with hydraulics myself, (my father was a hydraulics engineer) and I've seen him adjusting spool valves to get an initial oil 'bleed' which allowed operators to get more precision and feel from machines like the JCB. It would allow the operator to be more at one with the machine when needing higher accuracy of control. It got away from the undesired on/off actuation, which some drivers hated, they wanted feel and feedback. Sound familiar?

We know the hydraulic steering system is running pressurised, but there is still the mid point at no rotatonal torque, where the valving is neutral, no oil is powering the rack movement. But as we turn the wheel oil will flow. EPS can replicate this function, but I do wonder how the damping side of the steering rack parallels the way hydraulic cylinders work. We have rising and falling pressure and variable flow, damped in itself with friction, such as from the seals, even the oil flow itself. That function is, in my mind, the possible area where we have a more natural feel, rather than the more pure mechanical movements from a stepper motor, however well the torque is controlled. So it may be more of an on/off switching feel, without the cushioning effect of the hydraulic system. We may sense an unnatural feel, however fast in millseconds the electronic proccessing occurs and translates to movement which we detect, either from our steering input, or from the wheels, or from a blend of both.

I mentioned tires in a previous post, many of us have changed tires on a hydraulic system and completely changed the steering feel and road feedback, so we could still need to think outside the EPS mechanism for what is really giving the 'feel' factor.

Driving F10/11 models, the wheels and tires make a difference to the steering feel of EPS. This also teaches me, both hydraulic and EPS are influenced by other disturbing factors, some beneficial, others negative, particularly to the enthusiast driver.

HighlandPete

[bosz]

Whoa this thread got hijacked by engineering mumbo jumbo !

So in short, the steering wheel is tuneable ?

[HighlandPete]

Originally Posted by bosz

Whoa this thread got hijacked by engineering mumbo jumbo !

So in short, the steering wheel is tuneable ?

Sorry about the hijack... but the tuning idea does beg what is wrong, and why hasn't BMW 'just' made EPS identical to the feel of older models?

I suggest unless any tuners know what is really lacking, they could just make it different, not necessarily better.

I can see they could stiiffen up the steering, if that is really what the market wants, but that is not going to mean it is better. Same as suspension tuning isn't a guarantee the car will handle better, different maybe, but not always an improvement.

Let's see what the aftermarket offers. BTW, we may have to wait sometime, as it could be a complex bit of software to develop.

HighlandPete

[Howardsk]

This is my first time posting so forgive me for any mistakes in etiquette.
Yesterday I picked up a 2014 435xi Sport. It replaces a 2012 528xi which replaced a 2010 335xi coupe. As I need AWD ...I could not wait to see if and when the 235M came out with AWD. But the handling and steering is too assisted even in sport mode. Even more so than my 5.. Forget comparing it to the 3.

I also want to know if there is anyway to tune it to get tighter steering and reduce body sway. The car is just not tight and precise as, at least, a 4 coupe should be.

Dinan is coming out with tuner kits for the 4 but not for 6 months.

I love the car and it is still better than anything in its class.... But it seems BMW is losing its soul in its desire to water down its cars to appeal to a mass market...and take market share from Mercedes Benz.

Any advice would be appreciated.

H