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Disengaging EAP Explored - Anyone else try these things?

Discussion in 'Model 3: Driving Dynamics' started by SOULPEDL, Jul 23, 2018.


    SOULPEDL Supporting Member

    Jul 25, 2016
    On Freeway, turning, if you steer into the turn during EAP, it seems that my torque on the wheel + car steering force was exceeding turning limit and disengages EAP. Sometimes you won't feel it disengaging if your force equals the force on the turn (balanced). So besides the chime, control is smoothly transferred to human - yikes. Slowing down helps eliminate for sure, I was going about 70 mph, but noticed it at slower speeds as well (road flatness, turn radius, and other factors also play a role here). Anyone else have this happen?

    When I first got the car, EAP was disengaging several times on the freeway in a single day. The Shop Service Report showed an Exceed Steering Limit error in the log that coincided with this event. I'm doing that "correction steering" less now and it's stays engaged, same roads and conditions (or maybe better control SW now, but still on 2018.21.9, Model 3).

    In hindsight, I'm thinking that error was more likely because I was helping it steer the corner a bit and my force was added to the controlling force at brief moments during the turn. In one area of the road, and consistently, it was also dip related (in the turn), which makes sense because the suspension dynamics would require the car to compensate to keep on track (coming out of the dip), right when I was pulling the wheel. Obviously the effect is brief, much like a wind gust would throw it off a bit. So the people that don't have this happen - I bet they don't add force on the wheel (or they are going slower...).

    So what's New?

    Call me crazy, but now I steer slightly away from the turn with a slight nudge (towards the ditch) and discovered something. The car will try to compensate and tighten the turning radius slightly. (Only recommended for the skilled driver because if it does let go, you might go off the road.) When I do this entering the turn, it tightens the turn momentarily so it doesn't come so close to the outside edge of the road. I also started doing it when I came up on cars/trucks in traffic close to my lane. Ya, I'm turning into the danger to get the car to pull away - briefly, and helps center it in the lane. It seems to help especially when the car wants to understeer on tight roads. Plus it isn't disengaging because I'm not helping it turn as before.

    I'm not sure if this is normal. Could the shape of my 19" wheels (vs 18" stock) affect the control system? My indicated speed is off for one by a few mph at freeway speeds, but maybe that's something else because I assume the overall height is the same for all tire sizes. I'm at 42 psi cold as spec'd. But I wonder if is Tesla is compensating for the dynamics of a tighter wall on the 19"? I wonder how 18" or 20" feel in comparison? If it matters, it's hot in Az and this happened on new tires, Model 3, from day one, ~400 lbs for passengers and bags total. Tires reach ~45 psi hot. Maybe there's more to Elons suggestion to drop pressure for a smoother ride. I think I'll try that next and see how EAP responds. Maybe worse right?

    Hopefully centerlane tracking improves and preferably to the inside of the lane rather than the outside. I'm sure they know and I can't imagine it's an easy thing to solve with so many variables.
  2. Oil4AsphaultOnly

    Oil4AsphaultOnly Supporting Member

    Mar 14, 2015
    Arcadia, CA
    I also disengaged auto-steer with my "help" at the beginning. From what I can tell, it "appears" the car is a split second "slow" in turning. Human drivers pre-empt the turn and hug the inside edge, while EAP tries to stay in the middle at all times, resulting in being closer to the outside edge at the start of the turn. It then corrects later in the turn. I've learned to trust EAP in turns when there are no cars next to it. With other cars nearby, I take over, because the other drivers are human and may occasionally veer out of their lanes (will ultrasounds veer away during a turn?).

    Edit: So how I compensated is to literally "hang" my hand on the steering wheel. That way EAP senses that my hands are still on the wheel, but there isn't too much pressure for EAP to overcome.

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