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[lolachampcar] Performance Upgrade Efforts

Discussion in 'Model S: Driving Dynamics' started by lolachampcar, Apr 24, 2013.

  1. lolachampcar

    lolachampcar Well-Known Member

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    Dennis,

    I've been mulling over a few different approaches to the problem. Regretfully, it would really take doing the two side by side (or using my car as one of the solutions) then comparing them.

    My car has P+ front dampers, standard air rear dampers (I did not see any difference between the standard and P+ rear air dampers) all using Tesla coil springs with the ride height set to slightly less than air Standard. My car is no M5 but is acceptable as my daily driver.

    The other option would be a coil P85 lowered with rims and tires to achieve the best grip. You would loose the super thick sway bars which, for me, would be a plus as I do not think roll control is an issue on MS. You should also do better in the grip department as there are better choices for ultimate grip than the Pilots on the P+. You are likely to loose range as other tires may not be as efficient. The rub in this approach, and thus the need for testing, is (1) the standard coil dampers do not have the same bump and rebound valving as the P+ dampers and (2) their operating range or ideal operating stroke is further up the shaft thus testing is required to make sure there are no issues using them lowered.

    The P solution is the most cost effective as it is bloody expensive to buy the P+ package only to have to buy a full set of coil units (parts not sold separately, you have to buy the whole damper assembly) to get the coils and perches. You then have to disable the air suspension.

    Either way you go, you will be machining spring perch landing grooves so you can set your ride height.

    Belgium is a long way away. If you find yourself on a family vacation to Disney or otherwise in South Florida you are welcome to drive mine to see if it meets your expectations.

    As for developing an aftermarket set of dampers for the car, I've checked with Bilstein aftermarket and they do not have these types of dampers available. It is a shame because a few weeks and a stack of shims would permit coming up with a very nice solution. I'm not up for wandering over to other manufacturers although that is always an option for those that like to experiment. The MS supports both upper spring perch mounting stud spacings thus BMW strut mounts will work.
     
  2. 3mp_kwh

    3mp_kwh Active Member

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    Awesome thread! So, just confirming two major upgrades, the standard ‘S’ coil spring (for air susp) and the evolved lower control arm (with critical new bushing), post-spring ’13. It would be good to get that arm part number, or price? I’d appreciate more subjective opinions on just the arm changeover. Also, lolachampcar, I didn’t understand what looked like a dual-function Force / Displacement graph, in trying to establish what you implied were higher damp rates in the front of the P85+. Is that data comparing complete assemblies (strut w/air, vs strut S85 coil)? The comments were on damp rates, but I though the function looked like spring rates (showing displacement, not velocity)?



    I’m coming from a GT3 997 and this thread sounds quite familiar. I’ve found, at the track, a lot of 997 owners do similar upgrades. Specifically, the inboard rear LCA bushing is too compliant, giving an uneasy wandering feeling around undulating sweepers. When a bushing like this deflects, it can produce changes in toe (left/right steer) as the other arms deflect at different rates, or not at all. One look at Tesla’s multi-link rear and you can see there’s lots of bushing going on. I don’t plan to track a Tesla, but since F=MA, the increased “M” suggests benefits from the arm evolution/upgrade. I came to the thread looking for solutions to reported left/right wander, under acceleration.

    For prospective MS buyers, seeing air suspension limits, etc, it seems cheaper may be better, with value perhaps in pre’13 coil cars and an arm swap, or simply a new S85 and maybe an upgrade from the rear 8.5”, to the offered 9.0” wide wheels?
     
  3. lolachampcar

    lolachampcar Well-Known Member

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    I've got two different plots attached. One is the classic "football" damper plot while the other is the classic "V". I normally only use a shock dyno to confirm rebuilds and troubleshoot suspect units. I've never gotten to the bowels of revalving dampers as it eats up too much time. Applying all this to your question about the axis and it is my experience that one axis is velocity while the other force generated by the damper. This has proved out when doing sweeps of low speed and high speed damper settings (on adjustable race shocks, not MS shocks). Having not used a shock dyno in many years, I simply approached the task to build tooling to mount the Tesla dampers (without spring other than the gas charge) and get a qualitative comparison. I did not research axis or otherwise relearn anything else about the dyno apart from my immediate needs.

    Put differently, I could be completely out to lunch on the data :) That being said, I felt the increased bump and rebound on the front of my MS when I changed out the standard front dampers to the P+ front dampers (both with the coil conversion).

    Moving onto your other points, I've mused elsewhere about the value of the P+ package. I personally do not like large sway bars when not needed and I feel the MS, with its incredibly low CoG, does not require a lot of bar to control roll. You can achieve the same feel in turn in by adjusting spring rate without getting the head snatch associated with larger bars.

    Moving back to value, I think a lowered coil 85 with P+ front dampers would be ideal when paired with low weight rims and sticky tires. The choice of staggered or not for me is a function of looks as I do not feel balance dictates the need for stagger. Street cars typically have way too much understeer designed in for safety reasons; removing a little by not using staggered rims/tires is not likely to change that equation much.

    The choice between S and P is a personal one but it is worth noting that you loose the rear bar altogether on the S (if memory serves me).

    Lastly, lower a-arm part number is ViN specific as very early cars had a different sub-frame. Anything with the newer sub-frame gets the stiffer bushing a-arms as these are the only ones available through Tesla. IIRC, they were about $550 each but do not hold me to that.
     
  4. hans

    hans P631

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    I tried to get my S60 upgraded with the new lower control arms with the stiffer bushings. The new control arms are Rev C and I think my car has Rev B control arms. However, the Rev C control arms require the correspondingly newer subframe because the mounting point has changed. I'm not a suspension guy so I'm just relaying a layman's understanding of what they were saying. The service center said they could not put the new arms on my old car. So I asked them for a quote on upgrading the entire subframe as well, expecting it to be too expensive but still worth considering a "S60+". They said they couldn't upgrade to the "plus" subframe because my car has a 60kWh pack, and the weight difference would make the whole setup unstable and not necessarily an improvement. At that point I quit trying to make them do something they either can't or don't want to do. After driving my old BMW 540 Touring for a week, I just wanted to get back into the Tesla and my suspension felt much better anyway.
     
  5. 3mp_kwh

    3mp_kwh Active Member

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    Thanks. Words for the wise. I'll probably stick to considering newer sub-frame cars, then. I did notice some Signature cars don't seem to be going for a "collectable" price. One more reason, perhaps?
     
  6. dennis

    dennis P85D

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    Its hard to get a "collectible premium" when 1000 (1200?) of something are made.
     
  7. lolachampcar

    lolachampcar Well-Known Member

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    For those with early, but not too early, cars who were interested in Lower Control Arms with stiffer bushings, here is the part number....
    LCAs is 6006774-00-B RR SUSP LCA ASSY $318.60
    There is no difference between the Right Rear and Left Rear... They are the same part.
     
  8. Laurent

    Laurent Member

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    I was interested in getting those lower control arms to remove that floaty feeling in the back of my P85, but I was told that they couldn't install them on my car without changing the subframe as well. In the end, I chose to go for it anyway and to upgrade the other suspension components while we're at it. Here are all the parts that were installed:

    Rear subframe
    Rear lower control arms
    Rear upper link
    Rear toe link p+
    Rear integral link p+
    Rear stabar passive suspension p+
    Pilot Super Sport 245/35ZR21 tires

    Total out-the-door cost: < $6k

    I decided not to upgrade the air spring modules. It would have cost close to $10k (for parts, labor, and tax) and I wasn't sure I wanted the firmer ride anyway. This is my daily driver and I like the comfortable ride of my P85.

    For wheels and tires, I chose to go with a square setup with Pilot Super Sports instead of the staggered setup with PS2's. I couldn't justify spending between $6k and $9k (depending on whether I could keep the existing front wheels) for tires that are almost twice as expensive, that you can't rotate and that provide little additional grip (at most 7% based on tire section width calculation).

    I’ve only been driving the car for a few days but so far I’m happy with the retrofit. The car definitely handles better in the turns and under heavy acceleration. It feels more planted and goes where you point it without getting squirrely. I did notice an increase in noise though but that could be partly due to the tires being brand new.
     
  9. lolachampcar

    lolachampcar Well-Known Member

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    I suspected the changes you made would make a big difference in the way the rear feels. All that slopping around under hard acceleration should be gone and the car should feel more stable under acceleration and cornering. I would think there is a long line of people that would be looking at exactly the same types of modifications as they represent good bang for the buck.

    Thanks for stepping out front on this one!
     
  10. bluetinc

    bluetinc Member

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    Laurent,

    What VIN do you have, I'm trying to get an idea of at what point the subframe needs not to be changed.

    Peter
     
  11. Laurent

    Laurent Member

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    My VIN is 34xx (built Dec. 2012) so P01766 very likely has the old subframe as well.
     
  12. lolachampcar

    lolachampcar Well-Known Member

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    my first (4288) was a newer sub-frame if that helps.
     
  13. tezco

    tezco Sig P85

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    For the unlucky early adopters with the early subframe, it is possible to press out the OEM soft bushings and replace them with something more durable?
     
  14. lolachampcar

    lolachampcar Well-Known Member

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    The very first thing I did when I started looking into the suspension was attempt to identify the bushing supplier. Tesla made the decision to deal in assemblies only so they do not stock things like bushings (or dampers or springs or,,,,). I found several bushing manufacturers but all require OEM volumes to even start a discussion on fluid filled suspension bushings. I briefly considered doing bespoke units but quickly gave that up once I confirmed that the bushings are used for isolation and as the pivot point for suspension movement. It was not as simple as cutting something like sway bar bushings.

    One thing I did find a bit interesting but have not confirmed 100%. I believe the physical dimensions of the lower control arms may be identical between the "old" and "new" sub-frames based on some LCAs I received from a Sig update. I did not look in exact detail but they appeared to be the exact same geometry as the new LCAs I purchased for my wife's S. If this is the case, then Tesla is insisting on changing the sub-frame bushings (by way of the sub-frame) before using the newer LCAs. It might be worth confirming the geometry of the new and old LCAs and, if identical, trying a set of LCAs without doing the sub-frame.
     
  15. tezco

    tezco Sig P85

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    I guess I'm confused. Are these bushings part of the LCA's, or part of the subframe?
     
  16. BP_Tesl@

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    Subscribed to thread, lots of good information!
     
  17. lolachampcar

    lolachampcar Well-Known Member

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    tez,

    Sorry. Two different bushings.

    I'm going out on a limb here has I have not examined the two sub-frames side by side so take this as a guess-

    I suspect the only difference between the first sub-frames and the current ones are the four large bushings that isolate the sub-frame from the chassis. I base this on a cursory examination of old versus new Lower Control Arms which appear to be the same geometry (which indicated to me that the sub-frame pick up points where the LCAs mount is the same between both sub-frames).

    I investigated changing out the bushings in the LCA on ViN 4288 because of the "wind up" I was feeling in the back of the car under hard acceleration. It felt like each rear wheel would load up, move forward slightly then snap back when it lost a little grip. Both sides were doing this and not at the same time which killed feedback from the back of the car. Tesla fixed this by changing out the bushings in the LCA and using them first in the P+ package then in all current production.

    I suspect, but this must be verified, that the only difference in sub-frames are the bushings as well. Tesla replaces older sub-frames and LCAs as a pair. Given that the sub-frame is the expensive part to purchase and R&R, I was musing about simply trying the new bushing LCAs on the old style sub-frame to see how much could be had with just that change.

    If I am correct on the sub-frame, these bushings would be much easier to design a drop in replacement as they do not act as an angular bearing (unlike the LCAs which pivot on their bushings). New sub-frame bushings are a regular thing in the BMW world. The down side is there are not enough early sub-frame cars to interest someone in the design effort :(
     
  18. swegman

    swegman Active Member

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    How can one subscribe to this thread? It contains much useful information. Thanks.
     
  19. palmer_md

    palmer_md Member

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    At the top of every thread there is a button toward the right side labeled "Thread Tools". Inside there is a "subscribe to thread" button. Also, when you post, you probably had the option of subscribing, and whether you subscribe to threads when you post or not is setup on your user control panel.
     
  20. tezco

    tezco Sig P85

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    Thanks Lola. I guess the squirreliness I feel on hard acceleration is due to play in the subframe as well as slop in the control arms. Seems to be getting worse in my S. I'm going to have the alignment checked next to see if that's a factor as well.
     

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