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IC to turn Traction Control (TC) off automaticlly without user intervention...

Discussion in 'Roadster' started by wiztecy, Oct 24, 2015.

  1. wiztecy

    wiztecy Active Member

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    I've found TC to be more dangerous in the Roadster than the safety its suppose to add, for example, when you hammer on the brakes and in the event Traction Control (TC) feels a loss of traction, it cuts TC off entirely which then makes you lurch forward in what feels and is now accelerated momentum forward rather than deceleration. Everyday, if its not raining, I'm always turning TC off for my own, others, and my Roadster's safety. By turning off TC in dry conditions I don't have this unexpected surprise that will take time off my deceleration time that essentially can help you avoid a collision or possibly loss of control in which the car could go off the road.

    With this I talked my my hardware engineer friends, discussed the issue and my requirements. The requirement being that I need to have a signal sent to the TC input, hold it high for at least two seconds, and then bring it back down to activate the TC off command upon every key-on event. Since the TC button becomes live on key-on, the key on can be taking from the live signal fed to the TC button, then bypassing the button, and sending that single back as a button hold. Also by pressing the button after the IC has set TC to off, I want to be able to disable this ON as we normally can by manually holding down the TC button. Lastly I want to shut-down this IC so that it does not automatically turn off TC but rather, allow it to fall back to its stock / always on state for the raining season where TC works its best and is a safety advantage feature.

    With that my friend turned me on to a "oneshot" IC. With that I can send a high signal after a specified period has elapsed. I also can bypass this IC circuit by putting a simple toggle / push-button which I can flip in the raining season.

    Just a rough draft at the moment, I have the IC, just need the time to build and test.
     
  2. smorgasbord

    smorgasbord Active Member

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    I believe what you're describing is loss of regen braking due to TC disconnecting motor from drivetrain. It feels like "accelerated momentum," but it's really loss of deceleration. It used to occur regularly for me on the Page Mill exit ramp off of Northbound 280 - but they may have paved that ramp in the past couple of years. It happens even when you're not applying the brakes, but relying on regen braking.

    TC was designed to prevent acceleration when the wheels don't have traction, thus preventing wheel slip. During deceleration, however, we have anti-lock brakes to module braking power accordingly. Contrary to your problem statement, I find the harder I'm physically braking the less TC engaging bothers me. I take that off ramp I mentioned with only regen braking (no brake pedal), and the braking literally goes completely away. If I'm braking hard on the pedal, then the loss of regen braking isn't as noticable.

    I'll speculate that the real solution would be to disengage TC while regen is active. This would be a firmware change. I think it would be better to suffer through some slippage of wheel to pavement on regen braking than to lose all regen braking, which is what happens today.
     
  3. wiztecy

    wiztecy Active Member

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    #3 wiztecy, Oct 24, 2015
    Last edited: Oct 24, 2015
    Interesting enough, when turning of TC you still have regen. I don't really understand that, but happy its designed that way. However when TC is spooked by an incorrect tire-size combination between the front/back, it shuts of TC and regen. At least that's what it does on the (my) 1.5 Roadster.

    I think what you're feeling and what the Roadster is exhibiting is the same issue I'm describing. Correct, you don't need to be braking for this to occur. However if you turn TC off with the button it won't occur. At least in my case. For my solution I won't need a firmware change or update, its doing what I do by disengaging TC which the user has control of.

    I just don't want to have one day that I forget to disengage TC and have TC do what it thinks best causing me to rear-end something or someone.
     
  4. BartJ

    BartJ Member

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    I must say I never saw the TC intervening when doing a hard brake on my 2.5.
    and it never turned of by itself.
     
  5. wiztecy

    wiztecy Active Member

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    If you don't push the car hard enough as well as not having the right conditions for it to kick on (or off in this matter), you most likely won't encounter it or if you do it won't be quite so significant to be noticeable. When it does I'm more focused on the road rather than looking at the dash indicator lights to see the TC light come on, but when you do feel it its quite scary and real.
     
  6. ElectricLove

    ElectricLove Member

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    I think you are exactly right... I've experienced this loss of deceleration and you are right Tesla needs to do a firmware update to fix this... How do we as owners go about encouraging them to make this update for all the Tesla Roadsters? (1.5 and 2.0/2.5)
     
  7. wiztecy

    wiztecy Active Member

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    #7 wiztecy, Oct 24, 2015
    Last edited: Oct 24, 2015
    Smorgasbord has a point that TC should only be on when accelerating, and off when decelerating but regen still active. Can anyone understand why it was decided to be spec'd to be in the "on" state while decelerating? Truly makes no logical and real world sense to me and a serious hazard since the Roadster was marketed as a "Supercar". Out of the showroom it was a "Supercar" accelerating, but a "Super-Scary-Car" when you needed to perform a sudden stop.
     
  8. smorgasbord

    smorgasbord Active Member

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    Makes perfect sense: TC disengages the motor from driving the wheels. Just as Anti-Lock Brakes disengage the brakes from stopping the wheels. Unfortunately, ABS disengages/engages many times a second, whereas TC disengages for what seems like more than a second.


    But then you lose the advantage of TC when stepping on the accelerator. My solution gives you TC when it helps and disengages it when it doesn't help. The downside is that it's a firmware change for Tesla, and that seems pretty unlikely to happen.

    - - - Updated - - -

    In 2008, Tesla published this blog post on Traction Control in Roadster.

     
  9. wiztecy

    wiztecy Active Member

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    #9 wiztecy, Oct 24, 2015
    Last edited: Oct 24, 2015
    Thanks!

    I've never had an issue in dry conditions where TC off became a problem or a hazard. There's too much weight over the rear wheels to brake free of traction if you're aware of your dry driving conditions. Yes, if there's some gravel or the road is off-camber, a person who's not in-tune can and will break traction and possibly spin out. With my solution, when it rains I *will* have to remember to re-engage the TC. But I don't (try not to) drive aggressively in those far from ideal road conditions, especially after the 1st few days of a 1st rain. But there still is a possible of an incorrect input which I could give the car in the wrong conditions that could be catastrophic to myself, others and the Roadster due to this limitation in order to correct a performance flaw that was overlooked. Possibly make a sensor that picks up humidity of the road to automatically engage it :). Over-engineering where over-engineering does not need to be. For myself, the sooner I implement my solution before waiting on Tesla Time's clock if they do agree to address this, I'll be in safer hands just like we came up with solutions to the *very* under-par Roadster brakes.

    I'm down for pushing a firmware fix to Tesla with a petition on this one, and request a quicker rather than later fix. My life is in the hands of the Roadster every day.
     
  10. Doug_G

    Doug_G Lead Moderator

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    Just wait until you hit a hard bump while braking strongly. You will be scared at the result.

    I automatically turn off TC when I start the car, unless it is raining.
     
  11. jeremyz

    jeremyz Member

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    I agree that the regen going away on heavy braking/rough surfaces is terrifying and dangerous. It's especially dangerous because the brakes on the Roadster aren't that good when they're all you have to stop. I've never experienced anything like this in any other electric car that I've driven.
     
  12. MLAUTO

    MLAUTO Member

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    This whole problem is due to the abysmal rear brakes. They are terrible when the regen is on, and almost nonexistent when it is off. If anyone wants to duplicate this situation, just do a medium brake from 55 MPH. Just after you hit the brakes, put the car in neutral to kill the regen. You will feel the "rush" of the lack of rear braking. While I was fine tuning the caliper piston sizes on my 4 piston brake setup, I originally tested it with the ABS disconnected, which kills the regen. After reconnecting it, the car became "tail happy", setting off the traction control/regen and ABS with ease. I had to reduce the rear caliper piston size to eliminate the issue. Now the loss of regen during braking is just a little hiccup. To state in numbers how mismatched the OEM calipers are, I had to increase the rear caliper piston area by 300%, but the fronts only needed 20% (with 8mm larger rotors). The car now has some of the best brakes I have ever driven, and the regen loss is a non-issue.
     
  13. wiztecy

    wiztecy Active Member

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    #13 wiztecy, Oct 24, 2015
    Last edited: Oct 24, 2015
    There is evident wear of the rear pad and warping of the rear rotor compared to the front. With this, the Tesla Roadster is rear biased. Elise is front biased. Tesla messed with the rotor geometry as well as the weight distribution of the car with what I feel with inadequate engineering in braking, hence why I've been flagging this issue. Honestly it is safer to have more rear brake bias over the front, but it may not be optimal in the performance of braking.

    Personally, they failed to do proper performance system testing here in braking, due to lack of expertise, hence the issue, and moved more towards the realm that is safer due to the added rear end weight with the ESS. They also were concentrated in range and batteries, hence their expertise focus and blinders. But upgrading to the custom rotors, I'm not seeing rear brake bias anymore. I've been looking at the polishing of the discs over-time and the fronts polished subtlety first over the rears with the initial black oxide coating I requested to be put on. They cleaned off the black oxide a little faster, and in a ratio of a front to back bias that I'm VERY happy with. I don't want to mess with what I've found dialed in and what works for this car at the moment at all. I push braking and acceleration of my Roadster in this current setup where every day I push the Raodster 100% with full acceleration and braking on twisted off-camber roads going up and and coming down from a 3000k ft. elevation on a two lane road every day with daydreamers constantly being random obstacles. Its quite the stress test on performance of a vehicle. The car is performing as what I'd want a performance sportscar to perform in acceleration and braking (now I modified it). I was looking at playing with the front to back bias, but yet that's a science in itself. Only way to get this right is with dual brake boosters. Tried to get data from Tesla on the bias, but that was a no-go, after I pointed out a safety concern. You can see this on rotor and front to back brake wear if you have new rotors with some coating, like the black oxide we put on the customs. I have disagree that changing the bias/piston is a solution. TC should NEVER be engaged upon braking, period.

    Honestly, I just got lucky putting in time, finding the right people, information, and expertise that has put the braking on par where it should have been from the beginning with the Roadster.

    Honestly wish I was on the team at the time to give real world feedback. And now its a bigger company, and I'm a start-up type of guy. So patching is our game.

    Again, braking is a true science that's quite involved. I want to state here I / we got lucky dialing it in with what I have asked for. The CarboTech AX6 brake pads and CRF's 2 piece slotted rotors. Its very rare nailing it.
     
  14. hcsharp

    hcsharp Active Member

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    Actually Lotus did most of the mechanical brake system design and engineering. They worked with Tesla to some degree to get information about regen. Lotus was quite familiar with the weight distribution of the car.
     
  15. wiztecy

    wiztecy Active Member

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    #15 wiztecy, Oct 24, 2015
    Last edited: Oct 24, 2015
    So why the huge difference? Elise / Exige front biased vs Tesla Roadster rear biased? Let those out there be clear that I'm the only one who's publicly stating openly of any evidence of rear brake bias due to warped rotors and rear brake pad wear vs the front. I have others who personally confirmed, as well as a Tesla shop to also confirm that the Roadster is rear brake biased over the time of maintaining these cars. These are just samples and inquiries. When I make people aware of it, there is more and more support of it.

    This makes no sense to me as an engineer unless they were pushing for safety. But why the front bias for which the Elise, which Elise groups / forums complain about? Wouldn't you think a company would stick to their known braking guns, making the Roadster front brake biased? But hard core racing enthusiasts strongly agree that the Lotus Elise/Exige was setup with too much front bias. Why not just have an even bias between the front/rear, or a bias that matches the weight distribution ratio of the car which would make perfect sense? For myself (Tesla Roadster wise) I'd like a little more in the front vs. the rear. The rear calipers are very wimpy as well as the braking surface area is not all significant, hence why I want a little more up front with the stock configuration.

    Testing Testing Testing should have been done in multiple real world conditions / setups / weight distributions of the car to find the ideal bias. Again, this is a science.

    Why couldn't a well known performance car company provide the right information to Tesla to get the Roadster's braking right? How was this missed? Its a huge safety issue and I have not seen any red flags raised by anyone on it earlier on. Who tested and test drove these cars? Did they really push them like a SuperCar? If so, braking should have been evaluated and criticized as much as acceleration. I really can't see how this was missed for so long and never discussed. A full-fledged performance driver would have flagged this issue instantly.

    We know that Lotus / Tesla opted for safety with the laxed configuration of the front camper, to float the front rather than grip & spin. But why would they want to spin out the Elise/Exige customer base on braking alone but not with the Tesla customer base? Did they think regen/TC was to save them? It was not a huge number of people really.... 2.5k vs 35k. Martin E. noted to me that they went larger on the rotors to take on the extra weight of the Roadster. Still it was under-par. I don't think Lotus had input of the test data honestly.

    I'm still frazzled why Lotus chose a front brake bias for the Elise / Exige and Tesla went rear under (if that's true) Lotus's consultation to go rear bias. I personally think something was overlooked here.
     
  16. MLAUTO

    MLAUTO Member

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    #16 MLAUTO, Oct 24, 2015
    Last edited: Oct 25, 2015
    I will have to disagree with almost everything you state except for your comments about Tesla and the fact you love your brakes.

    Wear and warping are an indication of faulty brakes-either by design or by their use. The weak rear brakes overheat, wear faster, and warp rotors because they are undersized. This is not an indication that they are doing more work than the front. Your relating "polishing" to the efficiency of your brakes is incorrect. Larger, more efficient brakes will wear less. Since all the components are different from front to rear, you can't even begin to compare brake bias from the rotor wear. Reading about your black oxide coating wearing off has me wondering if you bed in new pads, or just swapped the rotors. It takes me over an hour to bed in a set of pads, and all coatings are long gone by then.

    While traction control should not be activated while braking in a normal car, the Tesla has to deal with the regen while braking, which must be disengaged when the rear wheels start to slip. If not, the car will spin.

    Brake science is not that complex. There are just numerous ways to increase the actual braking force and efficiency.

    While your custom rotors will work better from the slots when damp, and may look pretty longer, once fully broken in, they will perform almost like any other cast iron rotor. They might not overheat as quickly, but the Roadster isn't a track car that needs to deal with that issue. You probably have increased your performance, ride and handling by a very small amount from less mass, but during braking the results will hardly be different from any other slotted cast iron rotor.

    Your initial post indicates an issue when the regen kicks off and the brakes fully take over. This itself would indicate a problem with your rear brakes. My 2.5 has the KW gauge for power and regen. Under normal braking I get full regen. Under heavy braking the gauge never moves from zero. I don't have the original issue that you are reporting. I assume the regen only will allow a certain rate of deceleration, and I can easily surpass that rate.

    The biggest benefit of larger calipers is the feel in the brake pedal. Much easier to modulate. The car does exactly what I want, with none of the touchiness of the original calipers. They always seem to hit a "brick wall", and pushing harder did nothing. Mine now feel like my foot is pushing directly on the back for my head.

    While you are knocking Tesla for not doing enough to develop the brakes, all you have really done is change the pads to a more aggressive compound, and now they are perfect?
     
  17. wiztecy

    wiztecy Active Member

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    #17 wiztecy, Oct 26, 2015
    Last edited: Oct 26, 2015
    You're right, we will and continue to disagree. As for the brake bias, you're correct that there is no real way to gauge brake bias by eyeing it. The only real way is putting a guage in the meter the brake line pressure between the front as well rear brake lines running to the caliper. And trying to dial in brake bias with a single brake master cylinder, one really can't get it write. The pressure of the front/back lines are not consistent, ever see testing of this and the pressure curves? The only way to dial in brake bias correctly is running dual brake master brake cylinders so that the front does not affect the rear and visa versa due to differences in line runs and pressure differentials of the lines. The Roadster is what I feel not front bias, I never got the front end to ever dive hard enough which I feel is should show some indication of a front bias. I agree, the rear braking is lame, but when Tesla went larger on a rotor size but stayed with the same pad size which does help out due to leverage, why would the Roadster still show bad wear / warping on the back? Yes the Roadster is running some heavier weight back there, but if they stayed with the same bias as the Elise, shouldn't we also be seeing more wear on the front pads than what we have? The fronts look like they barely wear with the stock setup.

    As for just the slots helping out, its more than that. Its a lower unsprung weight we saved per wheel as well as the FNC coating we put on. Just slots alone may have helped some, but it was not going to do the full job needed. I also put close to an hour of driving, hard braking, allowing things to cool, and repeat to bed the pads/rotors. The FNC coating is quite hard creating a porous rotor surface which also helps out with wet/dry braking. and the black oxide filled inside these holes, so it was not just a smooth surface like the EBC rotors which have the black oxide. I've bedded in those rotors too in my truck and yes, that can come off quite quickly alone.

    I disagree with you and stand that braking is a science. You just can't go throwing on large calipers, changing the brake bias, or anything that's integral with the car's braking system and believe you didn't affect something else that also may need to be adjusted.

    As for regen, Doug knows the issue I'm describing with regen/TC. Its a serious flaw.
     
  18. Doug_G

    Doug_G Lead Moderator

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    It's definitely an issue. It's not an issue with the Model S, so I guess Tesla eventually figured out how to manage it.
     

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