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Rear wheel steering re-calibration?

Old 06-01-2018, 05:09 PM
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Petevb
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Default Rear wheel steering re-calibration?

A close friend and 3RS owner passed on an interesting nugget: A Porsche experience center instructor mentioned to him the fact that they need to re-calibrate the rear wheel steering roughly monthly on their cars. Apparently the stepper motors that drive the RWS can lose counts under some types of heavy use/ load. This results in the rear toe alignment drifting off, which the service department then resets.

Has anyone else heard anything similar? It makes sense, and if true I'd like to understand the re-calibration procedure to see if that's something we can do ourselves... Any insight from the collective wisdom?
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Old 06-01-2018, 05:42 PM
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Yargk
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Originally Posted by Petevb View Post
A close friend and 3RS owner passed on an interesting nugget: A Porsche experience center instructor mentioned to him the fact that they need to re-calibrate the rear wheel steering roughly monthly on their cars. Apparently the stepper motors that drive the RWS can lose counts under some types of heavy use/ load. This results in the rear toe alignment drifting off, which the service department then resets.

Has anyone else heard anything similar? It makes sense, and if true I'd like to understand the re-calibration procedure to see if that's something we can do ourselves... Any insight from the collective wisdom?
Wow, great info and great question. Seems like it could become standard maintenance for the track driving crowd.
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Old 06-01-2018, 07:24 PM
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CAlexio
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Not sure if this applies, but this car hunts road imperfections and crowns like nothing I've ever driven.. it's all over the place. 2700 miles from now, a lot of European highway driving + switchbacks, Stelvio etc.

Alignment or rear steering calibration?
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Old 06-01-2018, 08:58 PM
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Mech33
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Originally Posted by Petevb View Post
A close friend and 3RS owner passed on an interesting nugget: A Porsche experience center instructor mentioned to him the fact that they need to re-calibrate the rear wheel steering roughly monthly on their cars. Apparently the stepper motors that drive the RWS can lose counts under some types of heavy use/ load. This results in the rear toe alignment drifting off, which the service department then resets.

Has anyone else heard anything similar? It makes sense, and if true I'd like to understand the re-calibration procedure to see if that's something we can do ourselves... Any insight from the collective wisdom?
I would be surprised if Porsche didnít have some sort of auto-zeroing mechanism built into the system though limit stops / encoder.

Last edited by Mech33; 06-01-2018 at 09:19 PM.
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Old 06-02-2018, 12:56 AM
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Originally Posted by Mech33 View Post


I would be surprised if Porsche didn’t have some sort of auto-zeroing mechanism built into the system though limit stops / encoder.
+1 (if they were Japanese) but then Porsche makes such stupid software engineering decisions that I would not surprised if they did not.
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Old 06-02-2018, 02:08 AM
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TRAKCAR
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How would you know?
shop sets toe, but the amount of RWS is different?

i havenít noticed anything.. Holds alignment well.
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Old 06-02-2018, 02:10 AM
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Petevb
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Originally Posted by Mech33 View Post
I would be surprised if Porsche didn’t have some sort of auto-zeroing mechanism built into the system though limit stops / encoder.
You would think. I’m actually hoping that the “slow figure-8 ten to twenty times” referred to in this post (I think) might be a re-calibration procedure based on end of travel limits:
https://rennlist.com/forums/991-gt3-...l#post15042102
However that’s a big stretch... But perhaps someone with access to a service manual might confirm or deny?
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Old 06-02-2018, 02:16 AM
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Originally Posted by TRAKCAR View Post
How would you know?
shop sets toe, but the amount of RWS is different?

i havenít noticed anything.. Holds alignment well.
My understanding is that it loses zero/ toe alignment, but it comes back to spec when recalibrated without any mechanical adjustment. They did suggest it wonít be an issue in many peopleís usage. Iím not sure if it requires very quick corrections to provoke, or maybe curb jumping? We use stepper motors extensively at work; they lose counts if they accelerate too fast or exceed their design torque.
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Old 06-02-2018, 05:17 AM
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Based on info from some UK owners, apparently manual and PDKs GT3s have different RWS calibration..Some Porsche engineers have said that RWS works better with PDKs as its able to communicate with the PDKs E-diff..On the manual GT3 with the fixed mechanical diff the re-calibrated RWS is dialled back to be less aggressive..A couple of pretty informed manual GT3 owners have said that their GT3s are pretty lively to drive..They move around more on uneven UK road surfaces compared to the PDKs..
I don't experience any of this movement on my PDK GT3 so there must be some truth in it..I have never driven a manual GT3(still waiting) so i can't comment on the differences myself, just other owners experiences..
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Old 06-02-2018, 05:19 AM
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Originally Posted by TRAKCAR View Post
How would you know?
shop sets toe, but the amount of RWS is different?

i havenít noticed anything.. Holds alignment well.
Is yours manual or PDKs..?
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Old 06-02-2018, 08:34 AM
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^His is 991.1 RS
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Old 06-02-2018, 09:21 PM
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Larry Cable
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Originally Posted by Petevb View Post

You would think. Iím actually hoping that the ďslow figure-8 ten to twenty timesĒ referred to in this post (I think) might be a re-calibration procedure based on end of travel limits:
https://rennlist.com/forums/991-gt3-...l#post15042102
However thatís a big stretch... But perhaps someone with access to a service manual might confirm or deny?
+1 that was exactly my thoughts also!!!
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Old 06-13-2018, 02:51 AM
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I have a 991.1 GT3 and have been trying to solve a high speed speed vibration that starts at 120mph. I had the car aligned last month and after the alignment felt the vibration at the track. I thought I had thrown a wheel weight or possibly had a bent wheel so I rebalanced the wheels with no help. I have been scratching my head trying to figure this problem out. Was it the conversion I did from PCCB's to Steel, do I put the PCCB's back on and see if possibly this is the source. After reading this thread I got to thinking about the RWS as a possible source of the problem. I had the car realigned today and prayed the RWS was centered Key On. There is no way of checking unless you go through the PIWIS procedure which only the dealer has. I tested the car on the way home at 145mph and the problem is solved. RWS was the cause of the problem and induced toe into one of the real wheels causing the vibration. FYI
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Old 06-13-2018, 03:02 AM
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Mech33
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Originally Posted by SmokinGTS View Post
I have a 991.1 GT3 and have been trying to solve a high speed speed vibration that starts at 120mph. I had the car aligned last month and after the alignment felt the vibration at the track. I thought I had thrown a wheel weight or possibly had a bent wheel so I rebalanced the wheels with no help. I have been scratching my head trying to figure this problem out. Was it the conversion I did from PCCB's to Steel, do I put the PCCB's back on and see if possibly this is the source. After reading this thread I got to thinking about the RWS as a possible source of the problem. I had the car realigned today and prayed the RWS was centered Key On. There is no way of checking unless you go through the PIWIS procedure which only the dealer has. I tested the car on the way home at 145mph and the problem is solved. RWS was the cause of the problem and induced toe into one of the real wheels causing the vibration. FYI
Sorry, what did they do differently for the 2nd alignment vs the 1st alignment with regards to the RWS?

Also, how does the toe being at a different set point cause high speed vibration?
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Old 06-13-2018, 11:17 AM
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Originally Posted by SmokinGTS View Post
I have a 991.1 GT3 and have been trying to solve a high speed speed vibration that starts at 120mph. I had the car aligned last month and after the alignment felt the vibration at the track. I thought I had thrown a wheel weight or possibly had a bent wheel so I rebalanced the wheels with no help. I have been scratching my head trying to figure this problem out. Was it the conversion I did from PCCB's to Steel, do I put the PCCB's back on and see if possibly this is the source. After reading this thread I got to thinking about the RWS as a possible source of the problem. I had the car realigned today and prayed the RWS was centered Key On. There is no way of checking unless you go through the PIWIS procedure which only the dealer has. I tested the car on the way home at 145mph and the problem is solved. RWS was the cause of the problem and induced toe into one of the real wheels causing the vibration. FYI
thanks for sharing your experience !
your bold text do you mean to say that you were praying (hoping) that the rws was aligned with the key (ignition sw ) on ?
was the toe out on the rear wheels on the second alignment ? was that not checked on first alignment ?
Anyone here know if it's possible to unplug (in the aligned position ) RWS electric power each side and the car will function without throwing codes ?
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