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Tracking / Autocross / HPDE / Drifting What these cars were built for! |
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09-16-2020, 05:13 PM | #15 |
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With the fuse pulled there's enough front bias to ensure thhe fronts lock first, at least with the pads I'm running (CSG Spec C2 front, Winmax W5 rear). I didn't note any loss of overall braking so the built-in mechanical bias/balance must be pretty decent, i.e. forward-biased but not *too* forward-biased...
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09-16-2020, 08:37 PM | #16 |
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Well this is terrifying.
And at the Glen no less. Probably the last track Id want to have a wheel randomly lock up |
09-16-2020, 11:24 PM | #17 | |
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I went out a few times and was able to reproduce the problem. Brakes operated fine until the VSC light came on. After that the brakes went psycho next time the brakes were applied somewhat hard (like 80% max), aggressively and asymmetrically locking the fronts. I put the 40A fuse back in for the trip home today and the light never came on. I don't know if there really is a yaw sensor problem or if track usage made the car think there's a problem there. Anyway, I'll probably just pull the fuse for next track event. I get -1 points for that so can run 42 lb. lighter so why not... |
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09-17-2020, 03:52 AM | #18 |
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Not much related with yaw sensor glitch, but when few times ago i got handbrake signal on dash from time to time on track, first thing i'd check would be brake fluid level. Pads wear > fluid level dropped below normal > that light lit. Simple fillup to normal level to compensate pad wear "fixed", just had to remove excess when changing new full thickness pads and pushed pistons in, to not overflow.
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09-18-2020, 12:13 PM | #19 | |
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C1234 Yaw Rate Sensor C1237 Speed Sensor Rotor Faulty C1464 Front Speed Sensor RH Circuit C1465 Front Speed Sensor LH Circuit Went back out with no changes, after a few laps the light came on again and again at the very next braking zone, taking it easy (early braking at ~70%) the same early and asymmetrical front lockup happened. But no crash this time! Brought it in, plugged in and this time it only showed the "Yaw Rate Sensor" code. We think the speed sensor codes from the first occurrence might have been triggered by the massive front lockups and impact. Went out again with "pedal dance" instead of 5-sec hold on VSC "OFF" button, again fine for a few laps, then VSC warning light on and insane front brake behavior. |
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09-18-2020, 12:15 PM | #20 | |
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09-21-2020, 12:03 PM | #21 |
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When I bought my car it had a bad clockspring/steering angle sensor(long story). it showed bad wheel speed sensor as well but once I replaced the clockspring/angel sensor the wheel speed sensor error went away.
You mentioned you have(or have a friend with) techstream, have you tried to do the calibration?
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09-22-2020, 01:30 PM | #22 | |
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09-22-2020, 01:42 PM | #23 | |
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I think you have a failed part. Unlike many other Toyota's and subarus, the Yaw Sensor isn't external and easily replaceable like on other cars but these yaw sensors do fail. In our case the Yaw Sensor is integrated into the Speed Control Computer which is integrated into the ABS Block (Brake Actuator Assembly).
Ideally, you have a wheel speed sensor that is faulty (or getting a dirty signal) and it can be cleaned/replaced. Another ideal scenario is that the calibration is off and a recalibration with Techstream will set you straight (pun). Quote:
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09-22-2020, 01:50 PM | #24 | |
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Obviously you want to eliminate this as a possibility which means you do need (and should have) techstream and checking/resetting the calibration should be considered if you've ever had your steering wheel off. If you've never removed your steering wheel I think the likelihood of your Steering Angle Sensor (clock spring) being the culprit is low.
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The Following User Says Thank You to rice_classic For This Useful Post: | ZDan (09-22-2020) |
09-22-2020, 01:52 PM | #25 | |
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Given that the problem does give warning (VSC warning light), and given that the car performs great at the track with the ABS fuse pulled, and that pulling the ABS fuse gains me a classification point (42 lb. lower weight allowed), and that the failure doesn't happen on the street (not so far anyway), and that I'm about to be $$$$ out for body repairs, I think I'ma leave ABS module as is for now...
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09-22-2020, 02:30 PM | #26 |
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@ZDan a bit of topic, but would you say the car was better or worse to brake with after pulling the 40A ABS fuse pulled? Im doing a swap next season and car will be ABS-less and I had to return the nanny86 that I had borrowed so Im considering this option for my last TT this season. Thoughs?
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09-22-2020, 02:37 PM | #27 | |
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The Following User Says Thank You to NoHaveMSG For This Useful Post: | Icecreamtruk (09-22-2020) |
09-22-2020, 03:36 PM | #28 | |
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At this event, before the light came on, it seemed to me that the *outside* left front was kinda being overworked going into turn one, which struck me as odd. Then light came on and next brake zone left front, then both fronts dead LOCKED, quite prematurely at a much-lower-than-expected force applied at the pedal. With the 40A fuse removed, no ABS, braking was quite good and predictable, and modulatable up to and after front lockup (i.e. easy recovery and no wacky darting left or right during lockup). Without ABS, front/rear brake pad selection is going to be more important for ultimate braking and controllability. Again, I'm on CSG Spec C2 fronts and Winmax W5 rears. My impression is that this is somewhat front-biased but not excessively so. I wouldn't be averse to trying C2 rears with the C2 fronts, which has been recommended by the experts (i.e., CSG). But for sure I'd keep the W5s on hand just in case it got squirrelly under braking. I'd recommend having same/same front/rear brakes with no ABS but maybe have a lower-coefficient rear set on hand just in case... I have zero qualms about running without ABS for the last two events of the year and definitely *prefer* this to taking chances with malfunctioning sensors when the now KNOWN failure mode (excessive, premature, and asymmetric front lockup) is pretty dangerous! |
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The Following User Says Thank You to ZDan For This Useful Post: | Icecreamtruk (09-22-2020) |
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