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Tracking / Autocross / HPDE / Drifting What these cars were built for!


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Old 06-27-2017, 10:49 AM   #15
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My bet is due MY2017 among changes listing fixes/improvements to electric powersteering to not overheat with sticky tires on track, that this is the reason for loss of powersteering on older models.

Things that may affect powersteering more - ones that make it work more/counter larger forces. Yes, sticky tires included. Other things that may imho impact - things like wheel spacers/higher wheel offsets (changing scrub radius, heavier steering/more load on power steering), extra caster (also will make steering heavier and more straightening forces to wheel in turns). Don't know about camber impact on steering/power steering.

I somewhat doubt in ability to retrofit MY2017 power steering to older ones and also doubt Toyota doing something to "fix" it on older ones. It works fine on stock spec suspension/tires and during daily driving within legal limits, it works when you ask reasonably more (like interim tires between slicks and stock) and on track .. i doubt Toyota will see it as "bug" to fix. Not even majority of all the twin owners/drivers had been to track even once, so why should Toyota loose money on that for older ones?

Hmm .. on second though, if it's due overheating .. i wonder if some extra cooling mod of it may help? People seen other cooling limits for engine oil, tranny oil, diff oil and implemented track worthy mods/rads/cooling for those .. why not think of something for powersteering?

I myself most probably will never use slicks but at most something like MPSS or AD08R of reasonable width, so again very probably i won't care about it
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Old 06-27-2017, 12:25 PM   #16
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Power steering is electric and is under the dash. Why would an electric power steering in the cab of the car need additional cooling?

Actually thinking about it, since process of going into a high G turn is braking, downshifting etc which also has the RPM's dropping has anyone ever tried putting a voltage meter on the power to the electric motor to see if a voltage drop is causing the issue?

Last edited by Azzudien; 06-27-2017 at 12:32 PM. Reason: Add to it
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Old 06-27-2017, 04:09 PM   #17
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Power steering is electric and is under the dash. Why would an electric power steering in the cab of the car need additional cooling?
?
Under heavy usage the electric motor generate a lot of heat, and it overheat, and cut on thermal protection.
But I've seen people in other thread saying that they had PS issue on the first lap of a session, so it's not overheating in those particular case.


I've not had this problem on my 2017, but only used RE71R in autoslalom.
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Old 06-27-2017, 11:20 PM   #18
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what about trying to pull the fuse or power connector to the PS and see if it steering manually will feel the same. If it feels different than the motor is the issue.
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Old 07-14-2020, 07:49 PM   #19
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BUMP.
This is still an issue for with my track car and getting worse with addition of a splitter giving some downforce. It happens under hard cornering, especially when the front is loaded at the bottom of a dip or cambered turn

Has anyone come across a fix for the EPS system being overpowered and momentarily shutting off the power assist?
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Old 07-15-2020, 02:37 AM   #20
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EPS overheating? Yes, recall posts about that. The grippier the tires, the more there is downforce, the higher offset, the higher caster, bits that make EPS working more, may trigger overheat of EPS resulting in temporary disabling to cool off. Haven't seen yet if anybody managed to fix that (except dialing back some of things that make EPS work harder (eg. caster)).
IIRC one of things fixed in MY2017 from change list. Haven't seen if someone was successful retrofitting restyle EPS either.
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Old 07-15-2020, 11:27 AM   #21
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BUMP.
This is still an issue for with my track car and getting worse with addition of a splitter giving some downforce. It happens under hard cornering, especially when the front is loaded at the bottom of a dip or cambered turn

Has anyone come across a fix for the EPS system being overpowered and momentarily shutting off the power assist?
My solution is to grip the wheel harder through corners I know may cause it to cut out

Have seen no fix.
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Old 07-16-2020, 09:20 AM   #22
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Make sure it really is EPS shutting down and not your tire contacting the inside top of your fenders. Check the plastic to see if there are scratching marks in it (any marks at all means you are touching up top).
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Old 07-16-2020, 03:38 PM   #23
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Wasn't EPS switching off due overheat (so far haven't experienced by myself) indicated as red steering wheel light on dash?
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Old 07-16-2020, 05:02 PM   #24
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Wasn't EPS switching off due overheat (so far haven't experienced by myself) indicated as red steering wheel light on dash?


I can't see my factory dummy lights. My aftermarket gauges are in the way.
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Old 07-18-2020, 09:51 AM   #25
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Thanks for the replies. Yes I reduced caster and it helped a bit but its still a problem.

My guess is that this is some safety circuit to keep the motor from overheating, not actual overheating , because it happens on the first lap not just after a long session.
I bet if we had an electronics expert or some inside information this overheat safety circuit could be disabled. Maybe with just a snip of a wire or a resistor. I would risk a motor burnout to possibly fix this issue.
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Old 07-18-2020, 02:13 PM   #26
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If it happened on first lap and possibly is not temperature triggered .. then i guess it might be rather from what strength/torque from EPS is asked to turn a wheel. Not sure it's that simple of a fix, it might be also some programmed firmware logic. I'd rather explore possibility of retrofit of EPS from MY2017.
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Old 07-20-2020, 11:10 AM   #27
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@ROADRACER did you actually went and checked your fender liners inside on the top? It sounds very much like you are just hitting it with your tires and it "locks" the steering into place while it rubs. Just check it, takes no time and you can at least write it off the list if its not that (but it does sound like it is to me).
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Old 07-27-2020, 11:03 AM   #28
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@ROADRACER did you actually went and checked your fender liners inside on the top? It sounds very much like you are just hitting it with your tires and it "locks" the steering into place while it rubs. Just check it, takes no time and you can at least write it off the list if its not that (but it does sound like it is to me).
Yes, I have checked. It is definitely not from a clearance/interference issue.
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