Dynamic *steering* on the track


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Thread: Dynamic *steering* on the track

  1. #1
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    Dynamic *steering* on the track

    I am close to ordering a 2020 R8 v10, and have a choice of either getting Audi dynamic steering, which varies the steering *ratio* with speed and steering wheel input, or the standard (fixed ratio) power steering.

    Does anyone have any experience on the track with dynamic steering?

    How did it go? Is it predicable enough to hit apexes consistently?

    This option has been around since at least 2017 on R8s, and in other Audis going back at least a decade.

    Note dynamic steering is *not* about varying the power steering boost with speed (all R8 steering systems do that). Dynamic steering changes how much the wheels turn with a given steering wheel input.

    This video explains what it does, and how the three modes, comfort, auto, and dynamic, work:
    https://www.youtube.com/watch?v=Ge7huVZANC4

    I tracked my last R8 about 10 days a year for 7 years, so have gotten to the point where I am reasonably precise, and fast, around the track. I was good enough that I could run with ESC all off, and still keep the car on the track :-), I ran R compound tires on dry days.

    If you really want to understand how dynamic steering works, read this technical document. Dynamic steering is an interesting use of two strain wave gears (harmonic drives), one to step up turning angles by about 50X or so and the other back down again, then adding a coaxial motor to move the "static" part of the step down gear so that it effectively slows or speeds up the turning rate of the front wheels relative to the steering wheel turning rate.
    https://www.scribd.com/document/3405...c-Steering-pdf

    This description and video are another take from Audi:
    https://www.audi-technology-portal.d...namic-steering

    This shows how strain wave gears work. They are kind of magic: notice the deformed ring (three highlighted teeth) spin at a much slower rate, and backwards, relative to the inner spinning shaft.
    https://www.youtube.com/watch?v=tMh-Axar3o8
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  3. #2
    Senior Member steve9's Avatar
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    Re: Dynamic *steering* on the track

    I have not tried dynamic steering on the track, only on the road. I have the standard steering and had no issues with it on a track day. Tyres at 80C were a different story.

    I'm fairly certain that if you select dynamic mode from the drive select then the dynamic steering reverts to a fixed ratio. you should also be able to do this from the Individual mode where you can select the setting of the various components individually i.e. engine, suspension, exhaust, steering etc. Hopefully an owner can confirm this.

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    Re: Dynamic *steering* on the track

    Thanks Steve: I did find this German reviewer (in translation) who said he felt the 2019/2020 R8 dynamic steering would be a *better* option on the track than the fixed ratio standard steering.

    "A direct comparison [of dynamic and standard steering on a track] shows the incredible precision of the optional dynamic steering. Let me put it this way: It’s a scalpel, while the normal steering is a very good Santoku kitchen knife."

    https://www.motor1.com/reviews/28756...-power-hitter/
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    Senior Member natetheskate's Avatar
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    Re: Dynamic *steering* on the track

    I have had 2x 2nd gen v10 plus's, one with and one without dynamic steering. I leave my car in Dynamic all the time and on the track I usually drive in Performance Dry or Wet which will also give a fixed ratio. I honestly can't say I feel a whole lot of difference with dynamic steering. If I changed drive modes often I would notice it more but I like a heavier steering input and a more fixed ratio so I stick with what I know in Dynamic. For my money, if ordering the car, I wouldn't add it.
    Last edited by natetheskate; 03-29-2019 at 12:08 PM.
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    Re: Dynamic *steering* on the track

    Thanks Nate for the info. Am I right that you are saying you cannot tell the difference with dynamic steering on the track, so you would save the money and not get it?

    A separate question about "performance" ESC mode (dry or wet) on the plus:

    How is performance ESC mode different from dynamic ESC mode?

    In particular, is it an explicitly different mode for dynamic steering, or does the steering just go in dynamic mode?
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  8. #6
    Senior Member natetheskate's Avatar
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    Re: Dynamic *steering* on the track

    Quote Originally Posted by R8Someday View Post
    Thanks Nate for the info. Am I right that you are saying you cannot tell the difference with dynamic steering on the track, so you would save the money and not get it?

    A separate question about "performance" ESC mode (dry or wet) on the plus:

    How is performance ESC mode different from dynamic ESC mode?

    In particular, is it an explicitly different mode for dynamic steering, or does the steering just go in dynamic mode?
    Correct, I'm saying in my opinion you don't need to spend the extra money on Dynamic steering. A lot of the earlier reviewers shared the same opinions but at the end of the day YMMV.

    ESC to my knowledge stays the same no matter what mode you are in. When you switch to any Performance mode, the first level of ESC is disabled by default. You can press the ESC button once to turn it back on or hold the button down to disable it completely. I don't believe the nannies are changed from Dynamic to Performance with ESC on.

    Bottom line, my current V10+ has Dynamic steering and I drive in either Dynamic mode or Performance mode and don't notice the steering ratio change at all under these 2 settings. I believe if you run in Comfort or Auto you will feel the variable ratios kick in (or in Personal depending how you have it set up).
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    Re: Dynamic *steering* on the track

    I ended up buying a used 2017 R8 v10 plus that came with dynamic steering.

    I only have one track day so far, and have the following impression:

    Running in "dry performance" mode, the dynamic steering is predictable with speed and steering input.

    I am not convinced this mode is a fixed ratio - it feels a little faster than that when parking in the paddock - but, whatever steering ratio changes are made at track speed, they are very predictable.

    On one lap, it felt like the dynamic steering/ESC (electronic stability control, also called ESP and ASR) kicked in and counter-steered, when I was turning in on a sharp hairpin turn on the track (turn 3A at Pacific raceway outside Seattle, Washington, USA).

    This is a place where I like to trail brake and corner hard, so the backend can get loose.

    It felt like less than a second of correction, a brief counter-steer. I may have hallucinated it, rather than it actually happening. :-)

    On the road, this is exactly what ESC and dynamic steering is supposed to do, when too much input is given by the driver that might cause a rear-end slide.

    Does anyone have a reference to a manual that could answer whether counter-steering is possible in the dry performance mode?

    Next time I am at the track, I will hold down the ESC button, turning ESC fully off, and see if this still happens.
    Last edited by R8Someday; 07-10-2019 at 10:43 AM.
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    Senior Member RNLabas's Avatar
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    Re: Dynamic *steering* on the track

    I don't know how it is possible for the Dynamic steering to produce ANY kind of automatic reverse or counter-steer adjustment because that is not within its physical operation. The links above and Audi's own description show it to be basically a self-adjusting amount of output for input set of variable helical gears within helical gears, with NO outside influence on the DIRECTION of adjustment whatsoever - so whatever DIRECTION is being fed, remains the DIRECTION of output.

    Further, the entire arrangement was meant to be an improved electro-mechanical system to better mimic the Gen 1 mechanical steering. I have driven both on and off track and there is a significant feel difference to me. The Dynamic Steering is more sensitive and precise, and a little heavier-feeling particularly at speed. I own a Gen 1 car and order almost every new R8 with this option as I believe it is easily worth the extra cost compared to the standard new steering. None of our customers (a few also track) have ever complained or regretted the choice. My 2 cents.
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    Re: Dynamic *steering* on the track

    Quote Originally Posted by RNLabas View Post
    I don't know how it is possible for the Dynamic steering to produce ANY kind of automatic reverse or counter-steer adjustment because that is not within its physical operation. The links above and Audi's own description show it to be basically a self-adjusting amount of output for input set of variable helical gears within helical gears, with NO outside influence on the DIRECTION of adjustment whatsoever - so whatever DIRECTION is being fed, remains the DIRECTION of output.
    This is not true. As described in the full technical description linked above (also link below), the coaxial electric motor is capable of running in either direction, at any time, with or without input from the steering wheel.

    When this electric motor turns, it turns the front wheels, even if the steering wheel is held still. The car is physically capable of doing all steering with *no* movement of the steering wheel.

    This ability of dynamic steering to steer the car without driver input is used by the "lane assist" feature in several Audis, though not in the R8, which doesn't have this feature *in software*, because the R8 lacks the cameras to tell where the lane is.

    According to the description of the "electronic stability program" (ESP, sometimes called ESC or ASR) part of dynamic steering, it is explicitly intended to reduce the input (counter-steer), the driver's input to prevent fishtailing. See page 4 "Over Steering the Vehicle" in the technical manual.

    While the graph is a little hard to understand, with dynamic steering, the motor in the dynamic steering module runs counter the direction of steering wheel input, reducing the turning of the front wheels relative to the steering wheel input, and potentially even making the front wheels turn in the opposite direction of the steering wheel input, in order to counter-steer and prevent a fishtail (section 2 on the graph).

    Page 6, "Braking on road surfaces with different friction coefficients", shows the ESP using dynamic steering to turn the front wheels, even as the driver keeps the steering wheel straight.

    The dynamic steering ESP features described on pages 4 to 6 are all ones a gen 2 or later R8s could use, because these R8s have the required wheel spin sensors and accelerometers to tell if the car is about to fishtail, is having differential braking effectiveness because of different road surfaces, etc.

    I don't believe dynamic steering was ever offered on Gen 1 R8s.

    The dynamic steering system is physically capable of steering the car with no driver input. The questions I have are what is enabled in software on the R8, particularly as part of the "electronic stability program" system, and in which driving modes.

    https://www.scribd.com/document/3405...c-Steering-pdf
    Last edited by R8Someday; 07-10-2019 at 11:10 AM.
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    Re: Dynamic *steering* on the track

    I have a physics PhD, worked for 15 years in highly computer-controlled physics research (experimental high energy physics), and the last 20 years in the commercial software industry.

    I understand the difference between what hardware is capable of doing, and what is enabled by the software that controls it.

    However, as the 737 Max has shown, sometimes even the engineers who design the software don't fully understand what the system will do when it gets bad input from a sensor. In that case, the software drove the plane into a steep nose-down attitude.

    That was something the hardware was capable of, and the software was not supposed to do, but did by mistake. Oops...
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