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      09-25-2013, 06:53 PM   #1
solstice
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F8X EPS improvement, how and when?

Anyone who want to take a stab at analyzing how this unboosted return to center system works? Is it always in effect or only when the wheel is not turned etc. Here's a piece from car and driver comparing the E90 and F30 that highlights just how important and how much potential this feature has for steering feel.

10] The slip angles producing cornering forces at the tire patches create what’s known as aligning torque—essentially, the tire trying to return to straight-ahead running. This aligning torque is fed back through the rack-and-pinion steering gear to the steering wheel. It’s part of the information the driver uses to learn what’s going on where the rubber meets the road. The K&C machine reported that aligning torque is 64 percent lower in the 328i than in the 335i. While the switch to electric power steering may improve mileage, it’s a bummer for Bimmer driving satisfaction.

Source: http://blog.caranddriver.com/a-tale-...-so-different/
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      09-25-2013, 07:00 PM   #2
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i just posted this in another thread. Electronic steering has been improving as the enginners figure out proper algorhithms for the servos.


X3 < F30 < X1 .... go test drive an X1 and see what you think of the steering. Then realize that it will be better in the 1M.
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      09-25-2013, 10:29 PM   #3
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Which X1 did you drive? The X1 was based on the E90.. which had hydraulic steering.
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      09-25-2013, 10:36 PM   #4
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Quote:
Originally Posted by M3 Adjuster View Post
i just posted this in another thread. Electronic steering has been improving as the enginners figure out proper algorhithms for the servos.


X3 < F30 < X1 .... go test drive an X1 and see what you think of the steering. Then realize that it will be better in the 1M.
Unless you drove a RWD X1, it has the same hydraulic steering as the E90 on which it is based.
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      09-26-2013, 12:43 AM   #5
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Originally Posted by Needsdecaf View Post
Unless you drove a RWD X1, it has the same hydraulic steering as the E90 on which it is based.

the X1 is built on the same car line as the 1 series and is produced in Leipzing Germany. , it is not based on the E90. I have seen the car line in that plant... and there were X1s... 3 door and 5 door 1 series, as well as the 1M and 1 series coupes, all on the same car line.



As far as the steering... apparently it varies by model..


I did indeed drive a RWD sdrive28 which has electric steering. The car also had stop/start technology.
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Last edited by M3 Adjuster; 09-26-2013 at 12:56 AM..
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      09-26-2013, 01:00 AM   #6
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Excerpt of http://www.motortrend.com/features/p...m4_first_ride/
"Speaking of cornering, you'll be ordering that up via electric power steering. But fear not, we're assured, the team has sweated the road-feel details like never before. Exhaustive testing of zillions of combinations of racks, ratios, electric motors and rack "transmissions." The end result is a unique rack using the 5 Series' transmission with a smaller electric motor that's quicker to rev. And to keep the steering feel pure, the EPS motor does one thing and one thing only: Helps you dial in exactly as much steering as you wish. It never assists with quotidian tasks like lane centering or returning the wheel to straight ahead after a turn. Nor will it ever counter-steer for you at the stability-control system's behest. And while the rack ratio is still variable, the wildly variable Active Steering will not be offered. The engineer tasked with tuning the new M3/4 steering set the E92 (fourth-gen) M3's hydraulic-assist rack as his personal benchmark. I look forward with guarded optimism to discovering how close he came."

Excerpt of http://www.caranddriver.com/reviews/...ntended-page-2
The electric power steering that he so effortlessly wields might end up as the M division’s greatest triumph regarding these new models. Engineers and executives know the shift from hydraulic to electric assistance comes with enough stigma to fill an X6, and they claim to have taken great pains to ensure they got it right. The M3 and the M4 use bespoke hardware from supplier ZF that makes their steering systems closer to that of the 5-series than the 3-series, but whether it passes judgment ultimately comes down to the calibration. “We don’t use EPS [electronic power steering] to cover up deficiencies,” says Albert Biermann, head of development for M GmbH, meaning the power-steering motor won’t compensate for understeer, oversteer, a crown in the road, or a coarse road surface. In fact, the lines of code that BMW deleted might be as important as the code that was included. Even though virtually all electric steering systems use the motor to help unwind the steering wheel, BMW has omitted this function in the M3 and M4. The steering wheel will return to center by the natural self-centering forces of the suspension geometry, just as God intended.
So BMW has altered the recipe with the new M3 and M4, but we like the big torque, that the cars have lost weight, and that M engineers pledge the steering system will become the industry standard. We can’t render a complete opinion, however, until we wrap our hands around the steering-wheel rim and whack some cones for ourselves.
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      09-26-2013, 01:30 AM   #7
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Thanks, I read those mag. comments already. I would still like to know some more of when the non assisted return to center forces are allowed. Any time the wheel is not actively moved away from center? I.e will the PS only be used when the wheel is turned away from center and be deactivated when the wheel is held still, turned towards the center actively or passively? I'm very curious to know more and try this out.
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      09-26-2013, 10:03 AM   #8
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Quote:
Originally Posted by solstice View Post
Anyone who want to take a stab at analyzing how this unboosted return to center system works? Is it always in effect or only when the wheel is not turned etc. Here's a piece from car and driver comparing the E90 and F30 that highlights just how important and how much potential this feature has for steering feel.

10] The slip angles producing cornering forces at the tire patches create what’s known as aligning torque—essentially, the tire trying to return to straight-ahead running. This aligning torque is fed back through the rack-and-pinion steering gear to the steering wheel. It’s part of the information the driver uses to learn what’s going on where the rubber meets the road. The K&C machine reported that aligning torque is 64 percent lower in the 328i than in the 335i. While the switch to electric power steering may improve mileage, it’s a bummer for Bimmer driving satisfaction.

Source: http://blog.caranddriver.com/a-tale-...-so-different/
EPS commonly use ball screw mechanisms to drive the rack. Ball screws can be reverse driven. So at a guess it is a case of dropping control voltage to the EPS motor when torque is removed from the steering wheel, allowing it to be back driven by the wheels centring action, rather than trying to drive it to the steering wheel position.

The problem is, bumps mid corner can 'simulate' the driver removing torque, which if simplistically done would cause a whole new problem. How does the system differentiate a bump from driver input?
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      09-26-2013, 10:08 AM   #9
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Quote:
Originally Posted by M3 Adjuster View Post
i just posted this in another thread. Electronic steering has been improving as the enginners figure out proper algorhithms for the servos.


X3 < F30 < X1 .... go test drive an X1 and see what you think of the steering. Then realize that it will be better in the 1M.
Ive had an x1 as a loaner and thought the steering feel was awful.

Quote:
Originally Posted by M3 Adjuster View Post
Excerpt of http://www.motortrend.com/features/p...m4_first_ride/
"Speaking of cornering, you'll be ordering that up via electric power steering. But fear not, we're assured, the team has sweated the road-feel details like never before. Exhaustive testing of zillions of combinations of racks, ratios, electric motors and rack "transmissions." The end result is a unique rack using the 5 Series' transmission with a smaller electric motor that's quicker to rev. And to keep the steering feel pure, the EPS motor does one thing and one thing only: Helps you dial in exactly as much steering as you wish. It never assists with quotidian tasks like lane centering or returning the wheel to straight ahead after a turn. Nor will it ever counter-steer for you at the stability-control system's behest. And while the rack ratio is still variable, the wildly variable Active Steering will not be offered. The engineer tasked with tuning the new M3/4 steering set the E92 (fourth-gen) M3's hydraulic-assist rack as his personal benchmark. I look forward with guarded optimism to discovering how close he came."

Excerpt of http://www.caranddriver.com/reviews/...ntended-page-2
The electric power steering that he so effortlessly wields might end up as the M division’s greatest triumph regarding these new models. Engineers and executives know the shift from hydraulic to electric assistance comes with enough stigma to fill an X6, and they claim to have taken great pains to ensure they got it right. The M3 and the M4 use bespoke hardware from supplier ZF that makes their steering systems closer to that of the 5-series than the 3-series, but whether it passes judgment ultimately comes down to the calibration. “We don’t use EPS [electronic power steering] to cover up deficiencies,” says Albert Biermann, head of development for M GmbH, meaning the power-steering motor won’t compensate for understeer, oversteer, a crown in the road, or a coarse road surface. In fact, the lines of code that BMW deleted might be as important as the code that was included. Even though virtually all electric steering systems use the motor to help unwind the steering wheel, BMW has omitted this function in the M3 and M4. The steering wheel will return to center by the natural self-centering forces of the suspension geometry, just as God intended.
So BMW has altered the recipe with the new M3 and M4, but we like the big torque, that the cars have lost weight, and that M engineers pledge the steering system will become the industry standard. We can’t render a complete opinion, however, until we wrap our hands around the steering-wheel rim and whack some cones for ourselves.
Industry standard? LOL, not so much. And its already been done to a point where everyone will be trying to emulate what Porsche has done.

Last edited by Wolfinwolfsclothing; 09-26-2013 at 10:14 AM..
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      09-26-2013, 10:47 AM   #10
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Quote:
Originally Posted by solstice View Post
Thanks, I read those mag. comments already. I would still like to know some more of when the non assisted return to center forces are allowed. Any time the wheel is not actively moved away from center? I.e will the PS only be used when the wheel is turned away from center and be deactivated when the wheel is held still, turned towards the center actively or passively? I'm very curious to know more and try this out.
Solistice, you and I have discussed my two biggest beefs from my old F10. Number two right behind the throttle insanity was the steering at higher speeds. The wandering, constant need for correction. I believe that this was always a fault of the EPS unit.

The engineers try to get too clever with EPS, primarily because they can. That motor acting on either the rack or shaft can be made to do many things that a traditional steering (hydraulic or even unassisted) cannot do. They can make that motor turn the column to do whatever they want. Like self park. In some cars, they are making it keep your lane now (S Class, Acura RLX). Etc.

BMW hasn't said much, but I have always suspected heavily that they had cross-wind correction built into the steering, and it always felt like I was fighting the car. Same with this "assisted unwinding" action. They're not just using the motor to assist you in turning the steering, they're using it to turn it back, etc., which feels entirely unnatural if you are used to ANY car with a modicum of steering feel.

I think this is all intentional. Look at BMW's mission with the F10...a mini 7, no longer a larger 3. Very intentional and it has boosted sales tremendously. Car and Driver's article on the E9X vs. the F30 was awesome, as it showed the "what" behind the "why" of the reduced steering feel and dynamics.

BMW's comment of "leaving the steering alone" to me speaks volumes. It means a more traditional role for the EPS motor....simply turning the wheel to the driver's command and not allowing it to do more funky stuff. More natural feel, and it won't damp out as much feedback as previous. I think THAT is how they're going to get it to feel good. That and the new hardware, which is probably stiffer and more direct than before.

I remember a while back I started the thread that "My hope for the S55 comes from....Porsche? It referenced the interview with 'Mr. GT3' Andreas Preuninger, and was mainly about the engine, but my thoughts were also on the steering as well. He speaks quite vehemently about that in the video.

I believe that my predictions in that thread are coming home to roost. Mr. Preuninger may have been discussing the GT3, but I think the M3 engineers were thinking the same thoughts.
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      09-26-2013, 12:21 PM   #11
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Thanks decaf, I agree with that and it should help with a more natural feel and better on center feel.

With steering you have forces applied from you the driver on one end and from the tire contact patch on the other end and then the PS in the middle. For good feel PS need to let the forces from the contact patch to come through all the time even when you actively turn the wheel ( which is when you need feedback the most ). I wonder if this return to center by natural function will help letting more feedback through all the time?

A prime example is when you enter a corner and start turning the wheel, you want to feel how tension is building in the steering wheel as the forces increases on the contact patch and if you say hit an oil spill the reduction of force should be transmitted as an immediate drop in steering wheel tension. Now you will counter steer to regain grip. Here you turn the wheel fast and vigorously and you need maximum feedback. Will this new function help at all? I don't know but I'm curious.

Last edited by solstice; 09-26-2013 at 01:07 PM..
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