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Wh/km with 5.9 and low

Discussion in 'Model S: Driving Dynamics' started by Mario Kadastik, Apr 6, 2014.

  1. Mario Kadastik

    Mario Kadastik Active Member

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    So I wasn't quite sure if to put this thread here or in Battery and charging, but as it's directly related to suspension changing I thought here more appropriate.

    So my question as someone who's never experienced the low setting (still not gotten my 5.9 yet) is how much of an impact it has on the actual usage of Wh/km (or Wh/mile). The reason I ask is that running on my 21" wheels in 5C weather I'm getting on average 220Wh/km, which is about 8% worse than the typical range (EU model) and far far worse than one would expect to reach the actual 500km that Tesla advertises. And I'm driving at their spec speed of 88-90km/h on a flat road with close to no wind in any direction. And I know another Model S owner (S85 unlike my P85 and on 19" wheels) who also got 220Wh/km on the same route yesterday and the weather is almost identical so the 21" vs 19" probably have close to no real impact.

    I know a big part of it is the temperature and while the HVAC has no true impact (I turned it off for ~10km and the chart remained unchanged) I'm guessing battery might be getting some heating though I had been driving for well over 150km by that time. The air resistance of +5C humid air is probably far higher than +20C dry air so that will account for some of it, the 21" should account for another ~5% if I've understood it about right, but how much of an impact does it have of driving on Standard height instead of Low? Those with 5.9 could easily test it on a straight road dropping the car to low and seeing on the 10km chart how the usage changes.

    Oh and my tires are inflated to just above the spec (3.1 atm) and the car is ~4 months old with 10 000km on it. Just trying to figure out what the various impacting conditions are as I plan a 450km trip in a month where time is of the essence and I need to figure out if I can somehow make it without charging or if I should stop for 2h and charge (got single charger only so ~40km/h typical range increase). Today I did 368.3km using up 79.4 kWh averaging 216Wh/km. I ended with 4% SOC and I charged at my interim stop ~4% so basically arrived with empty battery had I not charged. And 216Wh/km is ca 350Wh/mile so it's not utopically high. To make the 450km in 80kWh usage (pretty much maximum I would dare) it takes 177Wh/km or basically I need to reduce my current usage by 20%.

    IMG_6073.jpg
     
  2. jerry33

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

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    There's a big difference between 19" and 21" (at least in the Teslas I've driven). I'd guess that either he was driving faster, alignment was out, or the tire pressures were lower than yours to get the same numbers that you experienced.

    To reduce consumption by 20% on a trip: Aero wheels 5%, 19" tires 5-8%, Driving skills 10%, pre-warm 5-10%, pano insulation 5%, etc.

    However, I'd stop for the two hours.
     
  3. FlasherZ

    FlasherZ Sig Model S + Sig Model X + Model 3 Resv

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    Tesla says 21" wheels are a ~6% penalty. In practice I've found that to be the rough case. I was averaging ~400 Wh/mi last winter and ~375ish this winter. Granted, a small sample size and there is a difference in that this is year 2 and I'm not giving 1 kWh/mile test drives anymore, this winter is considerably colder, etc... definitely a difference though.
     
  4. cwmenne

    cwmenne Member

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    The 21" wheels are definitely part of it, but the temperature is likely the biggest part. The difference from summer to winter is staggering. Even from +5C to +15C will be quite noticeable. Frankly, I'm surprised you are getting that good at that temp.
     
  5. Mario Kadastik

    Mario Kadastik Active Member

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    To be fair I have no clue how good it can get considering that since I got the car the weather has never been above +8C for more than a couple of hours :) I did drive the car in -20C and saw 230-250Wh/km numbers or even lower and I did see 180Wh/km average on a long trip at 0C for >50km, but that was on winter wheels...

    I guess I just have to hope that the weather turns warm by May 5th ;) but it is looking like I need to plan a stop :/ The crappy part is that I'm leaving the country in that trip to a country with exactly one EV charger (which as it happens is on my route at 380km distance) which I have no clue if it'll work ;) So I guess I'll have to charge at the last charger in Estonia or at the last bigger town (so I'd have something to do) ;) too bad the car is still limited to 3x13A, that's a 10km/h difference in charge speed :/
     
  6. AoneOne

    AoneOne Member

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    One minor note: as water vapor has a lower molecular weight than nitrogen, humid air is actually less dense than dry air at the same temperature and pressure. I presume that this means it will also have less aerodynamic resistance, but that's not my field.

    In practice, at cool temperatures, the amount of water in the air is limited and so the effect on aerodynamics will be ignorable.
     
  7. AndreyATC

    AndreyATC Member

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    Are we talking 21 vs 19, Pilots (from P85+) or regular 21s?
    TM site mentions performance and millage improvement for P85+ in 6-12mil range from regular 21s

    P.S. My current average is 330wh/m on PS2 tires
    Lot's of hills around me though
     
  8. Brass Guy

    Brass Guy Member

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    Wow, I just did the math to see what you're trying to accomplish. About 280 miles.
    You'll need the temp to be above 10C, no HVAC, and will have to set the cruise control at 90kph maximum, and if it's not raining, windy, or very hilly - you've got a good shot at it. I once beat the ideal range of 300 miles this way. 19", but coil suspension I think is slightly higher than standard height with air.
     
  9. Mario Kadastik

    Mario Kadastik Active Member

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    The speed limit here is 90km/h max anyway so most of the time I'm cruising at 90km/h or 88 km/h and if there are slow cars it can drop to 80km/h. That is not a problem. Temperature I'd hope to be in excess of 15C, but if I have to start real early, then it may still be cold in the morning :/ No hills essentially as the whole damn country is a flat pancake with biggest elevation difference being 300m and that's from one end of the country to the other so anything beyond 20-30m elevation change is not going to happen ;) Now wind and rain is something I can't control as well as the weather on the day of the drive. The good part is that I just heard I might have access to a charger in Riga, which is about 320km along the way, by that time I should already know if I'm going to make it or need a fillup.

    The 21's are standard P85.

    But noone's so far answered the main original question. What's the difference in relative terms of standard vs low in the 90km/h driving speed to the Wh/km. As I would assume you'd test it in identical conditions (i.e. wind, temp etc), then a relative correction should be derivable quite easily.
     
  10. Alysashley79

    Alysashley79 Member

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    I just did a road trip this weekend it was 187 miles each way. I had a supercharger to stop at mid way through the trip. I had my mom with me snd she just had shoulder surgery so I had to drivers very conservatively vs my normally spirited driving. I had the lowering ability when I first got my car but never tested anything. On the way there I drove 187 miles and used 196 miles and my avg Wh/m was 276 this was with the car lowered at 50mph. I was driving 80mph with the cruise control on and hvac on.

    Return trip. Set the car to never lower same 187 miles drove 187 miles used 203 miles and my avg Wh/m was 328 same conditions cruise and hvac.

    Nothing changed coming mint home no extra weight in fact less since there was no food it was all left at the summer place as were most of the clothes. Next time I will reverse what I did and see if the data changes. And once my 14-50 is installed I won't supercharge and will go thrill way and not stop.
     
  11. Kraken

    Kraken Member

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    tailwind on the way out would be a headwind coming back and could be he difference.
     
  12. Mario Kadastik

    Mario Kadastik Active Member

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    Yes, such long distances and doing it in different directions has too many changing conditions to be a viably good benchmark. What I would like to see is someone intermittently lowering and raising the car every say 5-10km and measuring the average power draw. If the constant settings yield ~constant power draw, then the averages of each the two periods (low vs standard) should be usable for the ratio to determine the effect of lowering itself. The other conditions should cancel out as I would assume unless the conditions are extremely biased (5km of hills followed by 5km of flat followed by 5km of hills etc). Then again I think the lowering also has higher and higher impact the higher the speed.
     
  13. Brass Guy

    Brass Guy Member

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    Need 2 cars with drivers. Benchmark both driving the same direction (no drafting!) at the same speed and height. It's the only way to verify identical conditions. Repeat with different heights. If 2 in my area want to do it and someone wants the coil comparison, I'll join the experiment.
     
  14. Mario Kadastik

    Mario Kadastik Active Member

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    Actually that would only be true if the experiment itself proved that while both were driving at standard setting they were getting the same Wh/km. There are a ton of things that matter like tire pressure that may well show a systematic shift towards one car and therefore nullify the experiment. That's why I mentioned doing it intermittently with the same car on a reasonably straight and flat road over distances of 5-10 miles per setting (this way any short term effects like gusts, minor hills and other such things average out). If I were to magically get 5.9 soon I'd probably do the experiment myself immediately, but am still on the list of people on 5.8 ;)
     
  15. Alysashley79

    Alysashley79 Member

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    mario
    i know you aren't in the US and not sure how far you are from a service center but can you. Pop by one they will load 5.9 for you onto your car....
    I know you mentioned raising and lowering. I'm not positive but if I remember correctly ill test it next time I drive the car but I think the car has to be stopped to changed between standard and low it'll give you an error like before if you try to do it while moving you can set the parameter again while stopped etc.
     
  16. huntjo

    huntjo Member

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    He's pretty far
     
  17. Mario Kadastik

    Mario Kadastik Active Member

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    Yeah, between me and a SC there's a whole sea or 2000km ;) Then again, a ranger is also joining the test drive event in 2.5 weeks so if I don't get the OTA update before, then I get the FW then at the latest :D
     

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