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P85D vs GTR - PerformanceBox data vs drag strip slip data... help?

Discussion in 'Model S: Driving Dynamics' started by wk057, Apr 17, 2015.

  1. wk057

    wk057 Senior Tinkerer

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    #1 wk057, Apr 17, 2015
    Last edited by a moderator: Mar 13, 2016
    So, had some fun at the drag strip today. Put together a video of one of the runs.

    2014 Tesla Model S P85D vs 2015 Nissan GTR Nismo - YouTube



    And here is the PerformanceBox graph for that run:

    Run 3.jpg

    Here is the time slip (frame used for my video):
    2015-04-18 00.24.48-1920.jpg

    Now, I can't seem to reconcile the two sets of data. They seem to differ by about 0.5s (PBox always showing a higher time)

    I was posting about this in another thread, but I didn't want to derail it.

    At first I though the times were off by my reaction time on the slip (0.516s)... maybe this is the case, but I have another run with a 0.224 reaction time on the slip that has the same 0.5s difference from the PBox. The ~0.5s difference appears to be pretty consistent.

    For this run:

    60' Time

    PBox: 2.16s
    Track: 1.626s
    Difference: 0.534s

    330' Time
    PBox: 5.32s
    Track: 4.788s
    Difference: 0.532s

    1/8th Mile Time
    PBox: 7.96s (@ 94.82 MPH)
    Track: 7.356s (@ 95.003 MPH)
    Difference: 0.604s

    Now, I went and analyzed my video a bit. The reaction time appears on the board in the distance exactly 15 frames after the green light on the tree comes on... so, 0.5s, which matches my slip. However, my car has definitely moved several feet by the time this happens. PBox says almost 3' and almost 8 MPH at 0.5s.

    So... any ideas? Is the track wrong or is the PBox wrong...... they can't both be right.

    Edit: Some more Google searches landed me this quote: "
    Most drag strips will not start timing until your vehicles wheel fully crosses over the start line, which means the first foot of movement will not be captured in their official time." Guess that could explain it. PBox says at one foot I was traveling at 4 MPH after 0.4s.
     
  2. Puff

    Puff Member

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    Your times are like the 1/8 runs I've made at the strip. 7.3xx. Sounds like you got the answer you were looking for with google.
     
  3. mnx

    mnx 2013 P85

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    Yes, that is why the PBox has a setting for 1ft of rollout. :) (And why some car mags use that methodology as well)
     
  4. falconeer

    falconeer Member

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    If the difference is indeed due to 1ft-rollout, then I have one question:

    What is the true 0-60 time for P85D? From your run (which is probably not under ideal conditions) it would seem to be in the mid 3s range rather than low 3s.

    Is that true? When Tesla advertises 3.1s, are they taking into account rollout? If so that is highly misleading. 0-60 times should be ZERO-60 not 3-60. 1ft-rollout makes sense with the quarter mile since drag strips use rollout. But for any other metric it shouldn't be used IMO.
     
  5. fiksegts

    fiksegts Active Member

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    u need the 1ft roll out turned on for sure in the vbox.....

    that 60' in your P85D is awesome, you best my best 60', take it to the 1/4 mile and see how it does...


    BTW, I have the external antenna for my vbox as the coated windshield can block GPS sometimes and I was getting some weird readings on occasion, I run the antenna to the back of the car and tape it to the underside of the rear hatch window...

    - - - Updated - - -


    using 1ft roll out is the "standard"...... not misleading....



     
  6. wk057

    wk057 Senior Tinkerer

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    I definitely feel a bit cheated if the rated 0-60 times (3.2 or 3.1) are with a 1-ft rollout....

    At 1-foot the PBox says I'm already moving almost 5 MPH... I'm not sure exactly how thats zero to 60. More like 5 to 60.
     
  7. EarlyAdopter

    EarlyAdopter Active Member

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    If it's the standard by which all cars are measured, then relatively you're not getting cheated. :)

    FWIW, when I measured 0-60 at <18% SOC on my P85D, I used a 1mph trigger for Dynomaster+10Hz GPS, as I found using the phone's accelerometer to start timing added a 1.0s lag.

    Seeing as how I reported 3.9s - 4.0s for those runs with only a 1mph rollout, I should have actually reported them as 0.4s faster to account for a 1ft/5mph rollout.

    This means a fully depleted P85D is actually way faster than a fully charged P85 when comparing apples to apples (both with 1ft roll outs, or both from true dead stop).
     
  8. wk057

    wk057 Senior Tinkerer

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    I guess... heh

    Using the 1ft method... I got a killer 0-60 on the street in rain... 3.17s subtracting the time-to-one-foot, but only 3.47s on this run.

    Subtracting the time the drag strip used (0.516s, or about 3') I got 0-60 in 3.26s on this run.

    Really no idea what number to use at this point, lol.
     
  9. falconeer

    falconeer Member

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    Disagree. 1ft rollout is appropriate (and standard) for the quarter-mile, as that is the drag racing convention that has a technological reasoning: you need ~1ft to clear the beam at the start line.

    0-60 times do not have this convention... There is absolutely no standard whatsoever. Most american car manufacturers quote 0-60 times with rollout, but the germans and the rest of the world don't use it...

    There is also no consensus among magazines, MotorTrend tests using rollout, Edmunds tests without rollout. Edmunds wrote about it here. European mags also don't use rollout AFAIK.

    I also believe Tesla advertised the P85 without rollout (initially 4.4s, then 4.2s) while most magazines using rollout got 3.9s (motor trend). It seems Tesla has changed this policy with the P85D, where the MotorTrend times matched Tesla's claim.

    Bottom line, it is definitely misleading, by using rollout you aren't actually measuring 0-60 are you? It is more like 3-60 or 5-60. The rest of the world doesn't have this asinine 'standard'.

    I'd be willing to bet that if you polled the viewers of your DragTimes P85D 0-60 videos (which I appreciate a lot BTW), they would think the car is actually going from ZERO-60 in 3.1s, when its in fact more like 3.5s. Most people (including buyers of the car) have no idea about this cheap trick to make the numbers look better than they are: how is that not misleading?

    - - - Updated - - -

    See my above post.

    - - - Updated - - -

    Are you sure? It seem like the graph already started at 1mph (makes sense for 1ft speed in rain to be 1mph IMO) so the graph already account for 1ft rollout and the 0-60 should be 3.46 + rollout time. That makes the most sense to me, but if the data shows otherwise then idk.

    So far no one has shown 0-60 faster than 3.3s. @fiksegts got 3.45s (3.17s with rollout) from his pre-6.2 100%SOC run (from this graph). Considering he managed 3.05s with rollout post-6.2, I'd say the record is no faster than 3.33s.

    Maybe the '2.8s' update will get the car to a true 3.1s.
     
  10. wk057

    wk057 Senior Tinkerer

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    Up until yesterday, I was in that category. :(


    Well, not trying to beat any records. Just throwing data out there. ;)

    The drag strip clocked my 60' time on this run at 1.626s. In the PBox non-rollout data from 0, at 60' I reached 60' in 2.16s. This tells me the rollout cheat the drag strip used was about 0.534s. The 330' time was also off by about the same (see first post).

    So, if I subtract 0.53s from the PBox's @ 60MPH time of 3.79s from an actual 0 MPH, that'd give me 3.26s.

    Granted, that's assuming the drag strip is the metric.

    The PBox shows stats for 1' being 0.32s @ 4.41 MPH. Subtracting that from 3.79s actual 0-60 gives 3.47s "0"-60 with 1' rollout.

    Which number is right?

    (All above data is referring to this particular run vs the GTR)
     
  11. falconeer

    falconeer Member

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    I think it's probably the latter. Usually 1ft rollout is ~0.2-0.4s, 0.53s seems like too much. PBox is more reliable IMO.
     
  12. Andyw2100

    Andyw2100 Well-Known Member

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    Until 60 seconds ago, I was in that category.

    Seriously. And I consider myself pretty well-informed about the P85D. And wk057 is certainly more knowledgeable about the car than I am. I've read about the term "1-foot rollout" but didn't really know what it meant, and didn't have any idea that it meant my car really took more like 3.6 or 3.7 seconds to get to 60 from a dead stop.

    On the other hand, as far as "things I would have liked Tesla to have been more clear about before purchase", this is well below the range issue. I really don't care a lot about this, as this isn't what I bought the car for, and it's certainly fast enough and powerful enough for me. Still, it would have been nice to have had the distinction explained.
     
  13. darthy001

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

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    This whole 1ft rollout was new to me before I started reading US-tests of the model s, and I didnt understand it before reading this thread to be honest. The whole concept is unknown/unused in europe I believe. And makes me wonder a bit about relevance when comparing Tesla specs vs european car specs.

    This all leaves me a bit bummed if it turns out the times are so much slower in real world. Only due to feeling a bit fooled. Car is plenty fast enough for me in real-life, but I like getting what I paid for. Especially in this price-range.

    Anyone know what the "record" 0-60 is measured with proper equipment _without_ this 1ft-nonsense?
     
  14. loco

    loco Member

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  15. darthy001

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

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  16. loco

    loco Member

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    Oh, sorry. Didn't catch that. Never used 1ft on my PBox. I get 4.1s 0-100kmh, btw.
     
  17. qwertzy

    qwertzy Member

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    #17 qwertzy, Apr 19, 2015
    Last edited: Apr 19, 2015
    2015款 特斯拉 Model S P85D 性能测试4—在线æ’*放—优酷网,视频高清在线观看

    The actual 0-62mph/100km is 3.7, and 0-60mph most likely 3.5 seconds. After the performance update, they get bumped down by .1 seconds.

    ÆñÖ¹Óڿ죡 ÌØ˹À*MODEL S P85D²âÊÔ_Æû³µÖ®¼Ò

    EDIT:Actually nevermind the results were botched by battery not in optimal temps.
    According to google translate -
     
  18. Andyw2100

    Andyw2100 Well-Known Member

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    I feel a little guilty even asking this question, but is it safe to assume that when Elon Musk was comparing the P85D to the McLaren F1 it was an apples to apples comparison? What I'm asking is was he comparing the 1-foot rollout times of both cars, as opposed to comparing the 1-foot rollout time of the P85D to the true 0-60 time of the McLaren F1? I really expect that is the case, (because to do otherwise would really be disingenuous) but I'd just like someone who knows about this stuff to confirm.

    Thanks!
     
  19. wk057

    wk057 Senior Tinkerer

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    This was actually one of the first things I thought of... and I couldn't find any definitive info on it. :(

    Perhaps someone has better Google-fu than I and can find a drag time slip from an F1?
     
  20. dsm363

    dsm363 Roadster + Sig Model S

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    Since all car company advertise like this it makes sense for Tesla to do the same. They could put at footnote on the website explaining the 1 foot rollout and how other car companies do it maybe but for advertising purposes not doing the rollout would put them at a disadvantage in comparisons to other cars.
     

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