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P85D vs. P85 Efficiency Testing

Discussion in 'Model S: Battery & Charging' started by wk057, Dec 29, 2014.

  1. wk057

    wk057 Senior Tinkerer

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    #1 wk057, Dec 29, 2014
    Last edited: Dec 30, 2014
    Edit: Results start here: P85D vs. P85 Efficiency Testing - Page 6
    Edit: Data entry here: P85 vs P85D Efficiency Data - Google Sheets

    So, the details around my upcoming efficiency head-to-head have been somewhat scattered around the forum in various threads. Tomorrow is looking like it is going to be the day to actually do the test since it should finally be clear all day weather wise. High temp is predicted to be a bit low, low 50s, but this shouldn't impact the test since climate control will be off on both vehicles and both will be preconditioned from wall power prior to setting out.

    As many of you know, both myself and my fiance have our own Model S's, which puts me in a somewhat fortunate but relatively unique situation where I can easily do side by side tests and comparisons.

    Test subjects, with notable differences noted:

    • 2014 Tesla Model S P85D, fully loaded except 3rd row seats
      • 21" Silver rims with Michelin Pilot Sport tires, 245/35/R21 in the front, 265/35/R21 in the back
      • Air suspension
      • Just under 1,000 miles on odometer and tires
    • 2014 Tesla Model S P85, my fiance's, also pretty much loaded
      • 21" Grey rims with Continental Extreme Contact tires, 245/35/R21 all around
      • Coil suspension
      • Under 8,000 miles on odometer and tires

    For the air vs coil suspension, for normal driving this should not effect efficiency. Since I believe the P85D is at an efficiency disadvantage based on my existing data I will have its air suspension set to always low for the test. The sport tires on the P85D are rumored to be less efficient than the tires on the P85. The P85D also has wider rear tires than the P85. I'll see how the final numbers come out. If a reasonable margin for error due to the minor differences makes it too close to call, then well, that is the result. Obviously these are not identical vehicles, but the differences should be minor enough to show any gross efficiency differences that can't be accounted for by the small differences between the cars.

    I have two GoPro cameras and a dash cam in each car. I plan on syncing the video from all of these and making a four-panel video of the test, possibly time lapsed on the boring parts. The dash cams will view the road ahead. The GoPros will be clipped on the center divider on the pano roof to the left of the driver and aimed at the dash display (this is the plan anyway, but I'll make sure it ends up somewhere that the dash is clearly visible... working on this now actually). The dashes will show the trip meters and the 5 mile energy efficiency graph as the two "apps."

    I'm still tweaking the details of the trip to make sense, but the plan is to take the same route that includes some non-highway, decent stretch of highway (~20-40 miles), some more non-highway, arrive at a destination, allow both cars to sit for the same amount of time while we're there (the plan is to meet and pick up a couple of friends while we're out that way, one to ride back with each of us), then do the reverse of the trip. The plan will be to use the cruise control on the highway set to various speeds for 5 to 10 miles at a time. I plan to follow the P85 with the P85D for both parts of the trip, also. Combined with the air suspension set to low, I think this should offset any potential differences caused by the different tire configurations.

    Some things that come to mind for setup for both cars:

    • Ensure cold tire pressures are correct before departure
    • No cabin climate control (jackets, gloves, and seat warmers only)
    • Range mode enabled
    • Sport mode setting on the P85D for acceleration
    • Traction control On on the P85 (should go without saying)
    • All windows closed
    • No cargo
    • Regen set to standard
    • Very limited use of friction brakes
    • No P85(D) shenanigans (ie: acceleration within reason)
    • Charge both cars to 90% overnight, then set both to 95% in the morning
    • After charging, precondition both cars via app at 75F until preconditioning automatically shuts off
    • FLIR pics before departing, at the destination, and when returning
    • If possible I'm going to have Visible Tesla logging for both cars, although the API hasn't been as predictable lately as it used to be for some reason.

    Should be a pretty fair test I think. Anything else simple to be added to my list to make it as controlled as possible?
     
  2. techmaven

    techmaven Active Member

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    Wow. Thanks for doing this.
     
  3. pgiralt

    pgiralt Active Member

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    This should be a great test. Only other thing I can think is to maybe set some limit on the max power you will use when accelerating (say maybe 60 or 80 kW) so that both drivers will use similar acceleration profiles. Also, maybe to offset any driver differences, swap drivers on the reverse trip. I would think these things should be minor compared to the long stretches of driving. I think for road-trips, the most important piece of data will be the wh/m usage on the expressway. Maybe do separate 5-minute stretches at 65 mph, 70 mph, 75 mph, and 80 mph. A 5 mile stretch should give you a good enough period to get a wh/m number for each of those speeds.
     
  4. wk057

    wk057 Senior Tinkerer

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    The route I have planned should allow for most of this. Speed limit is 65 and 70 MPH. I probably won't do a test at 80 MPH since that seems to be the police-attention-getting threshold. 78 MPH is likely though. There is a ~2 mile work zone on the route that I'll probably drop us to 55 or 60 through, but other than that it should be pretty clear on a Tuesday afternoon.

    Swapping drivers on the way back actually isn't a bad plan, although my fiance has expressed her annoyance at the reversal of the turn signal and cruise control stalks between our cars... which hopefully wouldn't foul the tests. I'm still not 100% used to it either.

    For acceleration, I was thinking keeping acceleration below 1C (85kW) would be reasonable. This would keep resistive losses in the battery low as well.

    The highway is not perfectly flat on this route, so, averaging out over 5 to 10 miles per speed setting will make sense. Net elevation change between here and the destination is only about -50 ft. So, +50 ft on the way back. However, that doesn't tell the whole story. EV Trip Planner shows the total Up Feet and Down Feet to be just under 2000 ft. Decent bit of hills on the highway. This is real world stuff, not a test track. These are the results that actually matter.
     
  5. Bighorn

    Bighorn Member

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    #5 Bighorn, Dec 29, 2014
    Last edited: Dec 29, 2014
    When the P85+ came out, the staggered 21" set up was supposed to provide improved efficiency, (3%?IIRC) vs the P85.

    Does the P85D have an Ideal mileage setting? Seems like it shouldn't since it was a throwback to the 2-cycle EPA testing. (Edit--on further review, it's likely based on 55 MPH testing; the 2-cycle test yielded 320 miles)

    I've been curious what the Wh/rated mile rate constant is, which you'll have good documentation of if you're videoing the Trip Meter and rated mileage. Should be 275+/-5 for the RWD and 310+/-5 for the P85D.

    I would abbreviate any stops for changing drivers, etc so that any unrecorded energy usage is minimized.
     
  6. wk057

    wk057 Senior Tinkerer

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    #6 wk057, Dec 29, 2014
    Last edited: Dec 29, 2014
    Well, looks like the hardest part is going to be finding a good place to mount the GoPros!

    Turns out clipping it to the center beam there is way to far back to see any detail on the dash... so, need to find a good close place to mount it that still allows safe driving... hmm.

    Edit: Yeah, tried a few places... not really any good places to put the camera that has a good view of the entire dash without obstructing that view for the driver... going to mount it on one side at an angle probably with the sticky tape and get half of it at least (trip meter plus speedo). The graph is visible, but the numbers aren't readable.
     
  7. darthy001

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

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    I also clearly remember claims from Tesla that the plus-package for the P85 actually was supposed to slightly increase range. It actually said so in the design studio. So according to Teslas own claims a P85+ should have better range than a P85.
     
  8. wk057

    wk057 Senior Tinkerer

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    This doesn't make me feel more optimistic about the P85D claims, since AFAIK the P85+ was not actually more efficient...

    - - - Updated - - -

    Found a decent GoPro position, but requires using one of the sticky mounts on my CF trim... not 100% sure about that. Anyone with any experience?
     
  9. dan-l

    dan-l Member

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    To largely eliminate rolling resistance as a variable you might consider swapping the front wheels for tomorrow's test.. Although I also recall reading that the TPMS has been updated so maybe the better idea is just to try and find the RR specs. (I looked but only found a tirerack write up based on a 400 mile consumption test.)

    If one of you follows the other I'd actually recommend the same driver follows after the car swap. This should help minimize some of the differences resulting from aerodynamics (drafting) and driving style (as follower vs leader) differences.

    - - - Updated - - -

    I think the claim was in comparison to the original 21" setup. Another thread here..

    http://www.teslamotorsclub.com/showthread.php/22009-Increased-range-of-P85-over-P85
     
  10. CHG-ON

    CHG-ON Still in love after all these miles

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    I think doing three round trips might get better numbers. It could bring up some variables that you didn't see before. Clearly the more you do, the more accurate you will be. Not sure if you have the time for that.
     
  11. Andyw2100

    Andyw2100 Well-Known Member

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    Really? How did you pick three instead of two or nineteen?

    I think wk057 is doing way, WAY more than enough already. He is trying to provide a level of detail and precision far in excess of what the disparity in numbers we all expect he will find warrant. Here's what I see as a fitting analogy: wk057 is trying to provide data good enough for us to tell which of two fast runners trying to beat out an infield grounder for a hit was out by half a step and which was safe by half a step, when in reality you've got two runners, running the bases as fast as they can, starting at the same time, and one is going to cross home plate while the other is rounding third.

    I think he is doing more than enough with what he has planned. Any more is just overkill at this point. That's my opinion, anyway.
     
  12. AWDtsla

    AWDtsla Active Member

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    You have a FLIR camera? In that case you are making this way more complicated than it needs to be. Rent an hour of AWD dyno time, run the cars in cruise control at the same speed for x minutes. Use the FLIR camera to check the temperature of all electronics and moving parts. You can roughly integrate temperature over volume to get a comparison of wasted energy.

    100Wh/mi WILL show up somewhere, it's a massive amount of heat. If it's in the tires, then the tires will be hot, etc.

    edit - you will know EXACTLY where the extra energy is going, whether it be in the inverter(s), battery, motors, tires, bearings, transmission, etc. At 65mph on a dyno that's 6.5kW of heat being dissipated. Hell you could probably do it by feel alone.
     
  13. wk057

    wk057 Senior Tinkerer

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    #13 wk057, Dec 29, 2014
    Last edited by a moderator: Mar 13, 2016
    That's actually not a bad idea. I might do that next.

    - - - Updated - - -

    Mounted one GoPro in the P85D so far. Decided to brave the sticky tape mount on the CF dash trim. Using that plus a plastic bendy snake gopro mount extension.

     
  14. Bighorn

    Bighorn Member

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    I don't know about others' experience, but when I use evtripplanner, my P85+ is better modeled by using data for 19" rather than 21" wheels.
     
  15. Chris_WDO

    Chris_WDO Member

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    Why not use the suctioning mount on the left side window? Should be easily removable and adjustable. Of course, there shouldn't be driving situations where you have to lower the driver window ;)

    Sounds like a well thought, reasonable test setup! I'm curious what findings you will get!
     
  16. CalDreamin

    CalDreamin Member

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  17. Vger

    Vger Active Member

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    I saw this posted somewhere earlier, but I had the same thought:

    In addition to the comparison testing, it would be interesting for someone with a P85D to do a test to try to determine, in reasonably "average" conditions (no huge headwind, very cold temps, etc.) how much one has to hyper-mile the P85D to get it to show a) the 380 Wh/mi the EPA range implies; b) the 300 Wh/mi that an S85/P85 needs to do to get its EPA-rated 265 miles.
     
  18. jerry33

    jerry33 S85 - VIN:P05130 - 3/2/13

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    Every permutation you use needs another pair of runs, so it gets to be quite involved. And sometimes--even when you know what the outcome should be and have only one variable (e.g. tires)--you obtain the opposite results (temporary wind condition that wasn't picked up on but lasted for a few minutes during one of the runs).
     
  19. NOLA_Mike

    NOLA_Mike Active Member

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    My recollection on that was the P85+ with 21" wheels had better range than the P85 with optional 21" wheels due to getting Michelin Pilot Sport PS2 tires versus the tires that came on the P85.
     
  20. wk057

    wk057 Senior Tinkerer

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    Tried this... it doesn't seem to want to stay for some reason. Actually, I think my suction cup mount is broken, and I only have one. :(
     

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