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Letter To Elon Musk Regarding P85D Horsepower – Discussion Thread

Discussion in 'Model S: Driving Dynamics' started by Andyw2100, Aug 20, 2015.

  1. dsm363

    dsm363 Roadster + Sig Model S

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    4.4 seconds so still a 0.9 second difference using 3.5 seconds for P85D.
     
  2. Dennis87

    Dennis87 Member

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    85D is 4.2 sec to 60 mph so 0.7 sec difference.
     
  3. omarsultan

    omarsultan Active Member

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    See, I do not understand this thinking.

    I would assume you got your P85D, and found it was fun to drive and faster than your prior Model S. As far as I can tell, the performance of the actual car has not changed (IIRC it got a hair better with an OTA) so I do not understand why you would suddenly feel differently about the car.

    Looking at the 0-60 time, it is as advertised, all that has changed is a bunch of people have gotten an education as to how acceleration historically gets measured in the US. To be honest, I don't think anyone can feel the difference of 0.3sec introduced by a 1-ft rollout, and no, you did not pay for that 0.3 sec, you paid for a car that goes from 0-60 in 3.2 sec per customary testing practices in the US.

    As far as the 691 hp goes, I don't think we can resolve this until we see Tesla's test methodology. The two-motor drive train is pretty unique in automobiles and I have not seen any standards on how to appropriately measure it. As I noted in another thread, the closest analog I could find was multi-locomotive trains, where the power is additive. If you do the math, 400 V * 1300 A = 520,000 W ~= 697 hp at max draw. Both of these seem defensible ways of measuring total system power. Are they legit? I dunno, but I do trust the guy trying to land rockets on the decks of ships to not wing it.
     
  4. Dennis87

    Dennis87 Member

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    The voltage is only about 350-355 at full throttle because of voltage drop. So that is not correct.
    Also the old style melting fuse cant run on 1300A
     
  5. WarpedOne

    WarpedOne Supreme Premier

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    Yes, and black is now white.

    Any customer who believes he did not get what he payed for, has clear set of options:
    - demand and receive what was promised or
    - receive a refund

    You are not the first who believes he did not get what he payed for so legal paths are well oiled, should be no problem reaching good result.
    If of course, what you are saying is real. Why are you not going that way?

    Why are you rather choosing a smear campaign? Love? It ain't no love.
     
  6. heems

    heems Member

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    I think anyone that signs is keen on ruining a great company. Tesla is not a perfect company but it is a great company. Anyone can make mistakes. True supporter don't cry foul and jump up and down asking for entitlements. They acknowledge the amazing feat it took to start a car company let alone make an amazing car on the first try. To top that they are -as we speak -in the middle of trying to pull another miracle out of the proverbial hat with the X. Yet instead of support for the final push they have to deal with distraction and noise by the self professed supporters. I call this for what it is. Getting something free. I am not fooled for one. Unhappy supporters give feedback. Maybe even sell or return the car. They don't ask a cash strapped company for hand out.
     
  7. tom66

    tom66 Member

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    Assuming a range-charged pack (~403Vdc), that's implying a drop of about 50Vdc at 1300A, or a power loss of 65kW. In the pack alone. That is unrealistic.

    I would be surprised if the voltage drop is more than about 5V.

    It should be easily possible to get >500kW at 1300A.
     
  8. neroden

    neroden Model S Owner and Frustrated Tesla Fan

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    It's actually a great way to accomplish it. I've tried to explain this to you before...

    See, the best way to accomplish it would be a private contact to the management, and to have the management *actually fix the problem*. That's been tried. It didn't work, because management didn't respond. (This is not the first, not the second, and not the third time this has happened with a screwup by Tesla. It's far from the worst, actually. Management has made a long series of screwups on communications, and so far it hasn't fixed most of them. Some are actually getting worse over time.)

    The second-best way is to publicize the factual negative information and pressure the management in public to fix the problems NOW, while the media message can be controlled by people who want Tesla to succeed -- people who consistently say "We love the car, we want the company to do the best, we just think it's making this mistake".

    If this fails, what happens is that the negative information comes out LATER, in the hands of less committed people who are really angry at Tesla and actually want Tesla to fail, and Tesla gets accused of a coverup on top of everything else.

    It's much better to have your friends pointing out your flaws in public and asking you to correct them, then to have your enemies pointing out your flaws, and your friends saying, "Yeah, that is a flaw, we were keeping quiet about it".

    - - - Updated - - -

    The undiagnosed drivetrain failures, the rampant copyright infringements, the paint quality, the reneging on Ranger service, the refusal to support salvage cars, the refusal to release maintenance information?

    If Tesla isn't careful, the latter three issues are going to nail Tesla badly after the warranties start expiring, and Tesla's acting completely insouciant about the problems. Better that they have a fire lighted under them to fix the problems preemptively *before* the warranties expire and the masses start complaining, rather than after...
     
  9. wk057

    wk057 Senior Tinkerer

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    #129 wk057, Aug 22, 2015
    Last edited: Aug 22, 2015
    Not unrealistic. It's actually probably conservative. I suggest you study up on battery internal resistance. A 5V drop is more like super capacitor territory...

    - - - Updated - - -

    For fun I'm going to run the math again from scratch without looking at any of my previous posts and see if I come up with the same data.

    The internal resistance of the NCR18650B, the closest cell we have data on that is comparable to the Tesla 18650 cells, is 55 miliohms. I believe in previous calculations I gave Tesla the benefit of at 25%+ improvement in this area (seems unlikely, but OK) and went with 40 miliohms internal resistance.

    Let's go with a 1300A draw. We know that the pack is configured with 96 cells in series with 74 cells in each group of cells. Amperage in a series circuit is constant, so we can divide 1300 by 74 to get the amperage per cell. That gives us 17.57A per cell load at 1300A. We'll assume the pack is 100% charged, so 4.2V per cell. Theoretically that'd be 4.2V * 17.57A = 73.794W per cell = 524232W, right? Yeah, if the battery were a superconductor and had zero internal resistance, sure, that'd be awesome. Unfortunately this is the real world. Lets factor in internal resistance using the very conservative 40 miliohms.

    At 17.57A and 40 miliohms, Ohm's Law says that we'll get a voltage drop of 0.7028V at the cell level. Extrapolating that out that comes out to a 67.4688V drop at the pack level. For a fully charged pack at 1300A load that is an output voltage of 335.7312V @ 1300A = 436,450W. This is ONLY accounting for voltage drop at the cell level and not in the pack bus bars, wiring, contactors, current shunt, external connection to the pack, etc etc etc.

    So, let's not just multiply A*V with batteries to get impossible numbers, folks.

    Edit: lol, so I dug up my previous post that did the math on this and... yeah... pretty much the exact same thing I said previously. Except from that post:

    I'll point out that the 436kW number I came up with is less than a 5% difference than what we actually see as a max on the P85D (~415kW / 556HP)

    ---

    For more fun, lets figure out how much heat is actually generated due to internal resistance assuming a 1300A draw for 30 seconds (say, a top speed run?). We know 1kWh is about 3,412 BTU. So how many kWh are lost as heat due to internal resistance in 30 seconds? Let's do more math.

    A 67.4688V drop at 1300A is about 88kW lost as heat. So that comes to about 2,631,283 joules of energy lost to heat in 30 seconds. 1 kWh is 3,600,000 joules. So, in 30 seconds 0.731 kWh will be wasted as heat at 1300A draw. We'll do the math and round that to about 2,500 BTU.... spread across the entire 1,500 lb battery pack. Overall, with the cooling loop and such this is pretty negligible.

    ---

    Edit: Rolling with this a little further, a 1300A draw for 30 seconds will drain at least 5% of the pack power (output plus heat loss), dropping the cell voltage down even more. If this rate could be maintained until the pack was dead (it can't, batteries would explode... lol) it would be drained in something like 9 minutes.
     
  10. dhrivnak

    dhrivnak Active Member

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    To me the issue is Tesla said they are to be a new car company that does things different and to be better. Stretching the truth sounds like an old style car company. Is the P85D a fast car YES. But why over estimate the HP? It seems to me they are only asking for egg on their face.
     
  11. AnOutsider

    AnOutsider S532 # XS27

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    I may have missed it in all the back and forth, but Tesla did say that torque sleep would be worked on to achieve the range originally quoted right? Someone above said that P85Ds did indeed get faster with an update. Has Tesla said they are done working on it? If not, then perhaps they are and the issue just reverts back to one that Tesla knows well: failure to communicate?
     
  12. WarpedOne

    WarpedOne Supreme Premier

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    It did get faster, just not faster enough for some.
     
  13. dsm363

    dsm363 Roadster + Sig Model S

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    You're right. I thought it was 4.4 seconds at launch before the software update. Anyway, still a nice bump in 0-60 time.
     
  14. bareyb

    bareyb Active Member

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    Well if any good has come from all of this, it's that the vast majority of the World has turned a deaf ear to all the Tesla whining that goes on. None of my friends on other car forums have even mentioned this latest one. That's a huge and positive change in my opinion. I got so tired of all the crap from here leaking out to the real World.

    I guess people have finally accepted that Tesla is here to stay and that there will always be tons of detractors on both sides of the issue. It's just not even news any more. So for those of you who seem to feel the need to start multiple threads whilst you wring your hands and cry publicly over every little thing, I thank you, because nobody outside of this forum is listening anymore (bows at the waist). ;)
     
  15. lolachampcar

    lolachampcar Well-Known Member

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    What you fail to attempt to understand is that there is the possibility you are making a very big deal over a very small thing that you really should have known better of. Some people tolerate this type of behavior better than others and you are simply taking offense at someone that turns you off because they are tired of listening to the complaining (about something that, in their opinion, does not deserve anywhere near as much O2 as is being expended on it).

    Value other's opinions as much as you have entrenched yourself in your own and those comments will hurt less and make more sense.
     
  16. bonnie

    bonnie Oil is for sissies.

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    Thanks, Lola.

    As Andy and I have discussed privately, I haven't been saying much NOT because I don't want to be critical of Tesla. I've criticized Tesla's communications multiple times. I have deliberately kept my personal opinion quiet on this issue because 1) I have no skin in this particular game, and, 2) because people do have a right to pursue something where they feel they've been wronged. My only comment here has been that if people think that they are helping Tesla avoid bad publicity, it's maybe not going to work out that way. Unintended consequences and all that.

    Anyway, I clearly hit someone's button. Life is too short for that kind of drama on a car forum.

    Carry on. :)
     
  17. rns-e

    rns-e Member

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    On paper, yes.

    Good for bragging rights, but not showing in the real world, at least not on my P85D when driven by myself or by Tesla when they tested it. But to be fair, we may all be doing it wrong, as Tesla sales and marketing is telling us it can.

    Should have been 1.1s so 0.4 short, so missing more than 40% of promised performance. Which is a lot
     
  18. Auzie

    Auzie Tree Hugger Member

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    Main issues with the letter, as I see them:

    1. Lack of supporting data or evidence. Statements about car power and car marketing must be supported with some form of data or evidence.

    2. The letter takes a broad brush approach, listing few issues in order to attract more signatures or attention. Such broad-brush approach dilutes its effectiveness. Sharper focus on a single issue supported with evidence would likely be more effective.

    3. There are some irrelevant statements that distract from the main issue and clutter the letter (references to TMC, the number of posts etc).

    4. The letter seems unactionable to me. It does not specify in clear unequivocal terms what signatories consider to be an acceptable response from Tesla and what they plan to do if Tesla fails to meet their expectations as outlined. Instead, the letter states that different customers have differing views on what they consider to be the acceptable response. If that is the case, then these differing views may have a better chance of success if negotiated separately.

    5. The letter achieves some negative attention from the media and most likely from Tesla. Negative attention is not what I would choose as the effective way of negotiating in the given circumstances.

    6. I doubt that Tesla will give free Ludi mode upgrade to calm down the noise created with this letter. Such act would set an unsustainable wrong precedent. It would reinforce undesired behaviours - placating noisy customers with a freebie. Good luck with such business strategy.

    7. The correct approach is to establish the facts and determine the validity of the claims. The onus is on the claimants to provide evidence that supports their claims. If the claims are valid, Tesla owes them to make the car good to the specification as advertised or give a refund for the car.

    Let's suppose that the claimants can prove the validity of their claims and are entitled to a refund. It could be that the signatories do not wish to pursue that option, they prefer to keep a car and get a freebie. Freebie may not be an option for the reasons listed in 6.

    It may be that the only options available to claimants is to prove the validity of their claims and then to either negotiate a refund, or demand it through a court, or to leave things as they are and enjoy their car as it is.

    It is really up to each individual to choose what works best for them.
     
  19. dsm363

    dsm363 Roadster + Sig Model S

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    #139 dsm363, Aug 23, 2015
    Last edited: Aug 23, 2015
    If Tesla offered to buy the car back from the people who sign this letter but you had to sign something saying you would never buy a Tesla again and wouldn't talk with the media, would that be acceptable? You would get a full refund and would get out of this situation with a company you don't trust and could move on to a car that you would enjoy better.
     
  20. darthy001

    darthy001 Love my car, hope Tesla can get as great!

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    Not something I would want. I want to keep my car. I am still considering a X if it isnt to big for my garage, and a model3 or a nextgen roadster looks very interesting in a few years as well.

    Best case for me they "fix" the car and deliver on what they sold or worst case they at least admit to overselling and stop advertising wrong numbers and features etc in the future. Maybe give me a discount on the next car...

    Still showing numbers with rollout in europe, no hp-number and present-tense autopilot must be fixed.
     

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