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P85D - Electric Mechanical Braking System

Discussion in 'Model S: Driving Dynamics' started by drewfabrics, Oct 10, 2014.

  1. vgrinshpun

    vgrinshpun Supporting Member

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    TDial, could you check your car manual - accessible from the center display in the car or "My Tesla" page on teslamotors.com - to see if the new brake system still includes hydraulics, or it is purely electromechanical (electromagnetic) brake system.
    Based on my review of the manual version associated with my car manufactured last July, the hydraulic brakes are mentioned on the following pages:

    p.93 - On the Maintenance page there is recommendation to change brake fluid every 2 years or 24,000 miles, whichever comes first
    p.109 - Includes instructions on checking the brake fluid
    p.126 - Includes brakes specs

    Thanks
     
  2. gpetti

    gpetti Supporting Member

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    Apologies if this is a dumb question, and I know this thread is about brakes, but was anything changed on the steering (as per Elon's comments at the reveal)? It seems that he was just reminding people about the car's electric steering rather than explaining something new or at least there was no indication that they did anything freaky like drive by wire. I'm assuming that if they have changed the steering, TDial would have noticed any changes to the feel.

    It is interesting to me that so many of us have signed up for new cars even though none of us has driven the new car. I guess besides the brakes and the seats, we all assume that the radically new drive train will just improve traction and raise our adrenaline a few extra points.
     
  3. Todd Burch

    Todd Burch Voltage makes me tingle.

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    I haven't noticed a steering change.
     
  4. CHG-ON

    CHG-ON Still in love after all these miles

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    vgrinshpun:

    Unfortunately, my manual on the site is still 5.9 (sloppy in my opinion). So it has the same instructions as you mention. I checked the in-car manual and it says the same thing. So I have no new insights. Though I can say that the brakes are absolutely amazing. I had to plant them very hard today due to sudden stop and they were linear, smooth and had outstanding feel to them.

    I will update if I get any new info.

    - - - Updated - - -

    I think I am too new of an owner to be able to tell if there is a steering change with 6.xx. But I can say that the feel is perhaps the best I have felt. I can feel every aspect of the road (every damn pebble, which I LOVE!) and sense that I know exactly where the car is at every moment. It's extremely predictable. It actually feels similar to the manual steering of old (ooops.. Just gave my age away) I let my good friend drive this past weekend, a Porsche driver and racer, and he said the same thing (when steering is in sport). I am still learning exactly where each tire is on the road, so I have some work to do. But I have three of the four down. The last is the right front. Seems to be a hard one for some reason...maybe the sheer width of this monster. Can't seem to relate fully to it yet. Not sure why. But I am being conservative until I have it down. Does that make sense? But when I get it, watch out! I tend to be a balls-out driver (and I'm still alive).

    And just to piss everybody off...I drive 51.7 mi each way on the top of a mountain ridge in CA to work and back every day. It is COMPLETE AND UTTER HEAVEN!!!!

    I am so blessed I simply cannot believe it!
     
  5. gpetti

    gpetti Supporting Member

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    So definitely not drive by wire then. I'm not clear on how it controls the steering if it's just electrically assisted. Might have to start a separate thread.
     
  6. Saghost

    Saghost Well-Known Member

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    I'm pretty sure it is a dual pinion electrically assisted system, like the Volt and some others.

    In a system like that, there are two gears turning on the steering rack to turn the wheels - one is connected to the steering wheel, the other to an electric motor.

    In normal operation, the car senses how you are turning the wheel, and it uses a little bit of motor power to help you until you stop turning (frequently a variable amount of power depending on your speed.)

    However, there's no reason the motor can't turn the wheels without your input, assuming it has enough torque to do do. The steering wheel would of course turn as well, and you could prevent it from steering by pushing the steering wheel the other way.
    Walter
     
  7. bhzmark

    bhzmark Active Member

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    Exactly. This new AWD and braking system could allow add'l regen in two respects:

    1) From the front wheels/motor. This will allow better balanced lift-off-the-accel-pedal braking that won't only come from the rear wheels. This is especially important on slippery surfaces and around corners. Braking with only the rear wheels around corners on slippery surfaces invites oversteer. There is a video someone driving a MS on slippery surface and making it fish tail (before the stability control can correct), because all the regen braking force can only come from the rear wheels.

    2) Use the brake pedal to signal add'l regen. I assume that the amount regen braking force from the accel lift off is limited by design to the safe amount of neg g's from merely lifting off the accel pedal. Even if the motor could generate a lot of regen, we wouldn't want the car to come to a screeching halt merely on lifting the accel pedal. IF there is any add'l regen ability left in the motor and battery capacity, and it isn't fully triggered by the accel lift off, then the brake pedal could be used to trigger add'l regen and have the car make more electricity and less brake dust.

    - - - Updated - - -

    Oh right. Since the auto engineers in Detroit and Japan haven't been able to do it, there is no way that Telsa will be able to do it. Nevermind...

    :rolleyes:

    But seriously, the Toyota/Lexus versions of combined regen and friction brake on their brake pedals are perfectly seamless to me after after over 300k miles (With never a brake pad change). Combining some add'l regen and friction brake on the same brake pedal is not hard at all. And this has already been done by Tesla to some extent on their work on the Toyota RAV4 drivetrain which does do that.

    I heard that there was some mild dispute between Tesla and Toyota because they wouldn't share some of the tech details with each other on this very issue.
     
  8. gpetti

    gpetti Supporting Member

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    I must be missing something. I assumed that the Tesla system already increased regen as part of the actual braking process (in response to the brake pedal). I'm pretty sure I can see my regen increase dramatically as I apply brake, prior to or while the actual brake pads are adding friction braking.
     
  9. vgrinshpun

    vgrinshpun Supporting Member

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    Thanks, TDial!

    Not to be too pushy, but you can verify if brakes are a hybrid hydraulic system, or trully Electromagnetic design by checking if there is actually a brake fluid reservoir under the hood on the driver side.:wink:

    You'll just need to remove a plastic cover that is attached with a few clips, as shown on the figure from the manual. If brake fluid reservoir not there (right next to the windshield washer reservoir), that would meen that new brake system is purely electromagnetic.

    Brake Fluid.png
     
  10. Dave EV

    Dave EV Active Member

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    The new brake system still uses regular hydraulic calipers and brake fluid to activate the friction brakes.
     
  11. CHG-ON

    CHG-ON Still in love after all these miles

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    I'd be happy to. I'll check this Saturday and report back.
     
  12. scaesare

    scaesare Well-Known Member

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    I'd also expect this to be true.

    I imagine that the new system is mechanical/hydraulic brakes with electric assist, rather than mechanical/hydraulic with vacuum assist.

    In either case, the hydraulic components will still be there...
     
  13. bc17101

    bc17101 New Member

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    I have a recent (Sept 29th delivered) S85 with all the autopilot hardware features including the new braking system.
    I recently went on a 3500 mile road trip (it was fantastic) but coming home I got a brake warning indication. Since I was right by Fremont, Tesla service had me drop off the car an pick up a loaner. Tesla diagnosed the problem as an intermittent iBooster. They replaced the unit, paid our hotel bill, and delivered my car to my home in Southern California. Tesla service was FANTASTIC!!.

    Long story short...... The braking system is a Bosch iBooster system. I have taken the internal Frunk plastic cover off to inspect the brake booster, and it is a Bosch iBooster unit in my car. Take a look at the Bosch website for a full description of the system, but bottom line is that is is fully programmable, is capable of programmable pedal feedback, full automatic braking via computer, and failsafe pass through mechanical actuator from the pedal to the master cylinder. The power assist is via a built in motor that is much quicker to react than the older vacuum style assist.
     
  14. vgrinshpun

    vgrinshpun Supporting Member

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    Thank you, bc17101, this is very helpful.

    So the new brake system is hydraulic, but is using electromechanical booster in place of vacuum booster.
    Intelligent control boosts braking power Bosch in Japan

    [​IMG]
     
  15. Kbsilver

    Kbsilver Member

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    Then if I'm not mistaken, this will eliminate the need for any vacuum and the corresponding electric vacuum pump.
     
  16. bc17101

    bc17101 New Member

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    That is correct. There is no vacuum pump noise in my auto pilot ready S85. I can only discern two unique motor noises from the front car area. The heat pump motor which is very loud at times and variable speed, and the air compressor for the suspension system (which I have on my car).
     
  17. wycolo

    wycolo Active Member

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    Electo-mechanical as opposed to vacuum boost brakes have been in use in medium trucks for over 20 years. Nice small powerful units.
    --
     
  18. EarlyAdopter

    EarlyAdopter Active Member

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    #78 EarlyAdopter, Oct 25, 2014
    Last edited by a moderator: Mar 13, 2016
    Nice product video here from Bosch on the iBooster. It does indeed eliminate the need for a vacuum source.

     
  19. EarlyAdopter

    EarlyAdopter Active Member

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    I was able to dig up a little more information. This slide presentation is a good read. There is a mechanical linkage from the brake pedal to the gearing. It is not a drive-by-wire system.

    Untitled.png


    Original system on the left, with an electric vacuum pump (EVP). New system on the right with the iBooster:

    Untitled 2.png


    Photo of the internal gearing:

    bosch-ibooster.jpg


    Also, this Wards article has some good information on the fail-safe aspects of the system.
     
  20. Saghost

    Saghost Well-Known Member

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    Interesting. So unlike the Volt and 918 systems which keep a high pressure hydraulic fluid reservoir/accumulator, this system uses an electric motor to directly drive/assist on the mater cylinder. That's good for instant response and tunable assist, but may mean less room/ability to tune it to include regeneration, if the pedal is driving the master cylinder directly and without slop.

    (But the Bosch material specifically talks about putting regen into the brake pedal, so I'm a little confused.)
    Walter
     

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