Motor or Efficiency Loss over time

I have searched the TMC forum for answers on this subject, and while I have mentioned this concern on several work orders, I have never gotten a satisfactory explanation or resolution. Here is the issue: I purchased a Signature 85, its serial S2108 for Canada - so early days. I got used to being able to carefully drive pretty close to the average of the 'rated range' line of the trip graph, in Si units: under 200Wh/km, often far less. Then my drive unit was replaced about a year ago - and ever since - my efficiency tanked. The drive unit was 'upgraded' to a P85 motor, as I was told the early S85 motors in the lower HP range were discontinued. Now I can no longer come close to the 200Wh/km number, and since the new drive unit was installed, I have gotten an average of 220Wh/km (equal to 354Wh/mi over 37,600miles) - which is on the high end I understand from reading the lifetime efficiency thread, and I live in a very flat area with moderate continental temperatures.

On speaking with other Signature P85 owners that travel the same routes I do - we have shared stats, and mine are always higher - and this is less related to driving style, because we are often stuck in the same weekend traffic. So I was determined to get to the bottom of this. Last time I was in for service, the loaner was a P85 with the same wheels I have, same everything, just a newer car. I drove it home like a bit of an animal, lots of fast starts, I was trying to get a high number like with my sig - not even possible.

My 71km trip consumed a total of 13.8kWh, for an average of 192Wh/km. the next night, almost identical empty road, same 22degree temperature, I drove like a little old lady in my car, and used 16.4kWh or 229Wh/km. A good 15% difference. And 15% of a 400km trip - as you all know, is the difference between arriving at your planned destination or not.



Loaner P85



My P85

I would like to understand what the issue could be here.

a) driving habits - I ruled this out after I did my test with the loaner.
b) temperatures - same - ruled out after loaner test.
c) wind and hills - ruled out.
d) roof rack/sunroof/windows - nope.
e) drag in wheel bearings - Tesla service checked - nope - rolls normally
f) tire inflation/type/wheel type - same tires, same inflation (checked w. pocket guage, 42psi & 42psi)
g) inversion issue - maybe
h) regen issue - maybe

At first Tesla said it was because the motor was a higher wattage model, but W=v*a, so if I am not *making* the motor work harder, why would it use more than the current supplied - it didn't make sense. I am starting to think my inverter is not paired to the new motor - could that be the issue? Where would the lost power go? Heat? Is my inverter getting unusually hot? I have no idea. I would be very grateful for any of you technically savante owners to offer your enlightened opinion here, as I am flummoxed to say the least, and I would like my car to perform as specified - and to do so, it seems I need to explain to Tesla what is in fact going on here.

Thanks all!

Thanks, alignment - brakes - I will ask them to check, but I've replaced my rims and tires since due to dings/rash, I figured alignment would have been part of it. In fact my rotors and shields(?) were just replaced - but I'm getting the same lousy numbers. You might both be right, mechanical drag of some variety rather than some electrical issue. Coast test - good idea thanks, will try w. a service tech.

freeewilly said:

Do you get P motor performance now?

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Zero difference from what I could tell at the time of the swap. I never felt a huge difference from S85 to P85 to be honest. P85D hell yes. I think I recall them saying the 85kW cars got the upgrades but not the 60s, if that makes any sense? PS - the 60kW loaner I borrowed at the last service got only 178Wh/km for the same 71km trip to my house.

SmartElectric said:

...it might be worthwhile to balance that concern with driving enjoyment and stop looking at the efficiency.

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I hear ya, but the thing is, before my drive swap I was getting 180-200Wh/km - for my first 80,000km. Then drive swap - and I can't do better than 220Wh/km. That's what bugs me the most...
and in Winter this is so much more pronounced. With all heat off - only enough to defrost - I am going up to 270, 320Wh/km - whereas my first Winter - I'd never go over 220... same roads, same temperatures... it just seems buggy. When compared apples to apples last summer in my little test - and from everyone I've talked to, the numbers seem off for my sig.

It's not the couch change I'm concerned with. We have very few superchargers and cold temperatures up here. The 10-20-30% difference is enough to not make it to our cottage, or to require not turning on heat. Which makes the spouse call this a 'stupid car' - it wouldn't be an issue with the 30-80km extra margin I became accustomed to in the first 1.5yrs. There's no way we will be buying an X or any future Tesla if I can't win these small battles. I think it must be some kind of drag. More wind when I drive the car - hehe, exactly! Thanks for the stats above jpet - handy reference. My latest tires are worn 5000km by now.

jpet said:

From the stats you can see that 220 Wh/km is not an unusual figure so that's probably the reason Tesla does not really want to invest a lot of time in your "case".
But... if you have a clear reference point from the past, something's going on if that suddenly changes by 10% IF the conditions (especially temperature!) are the same.

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That's just it. My past experience, and other local drivers with sigs, and my 'test' against a identically configured P85, driven in identical circumstances and weather, indicates a minimum 15% difference, that's why I'm taking issue with it. On average, I think most people drive MS as if they are enjoying it (hence 220Wh and not 200Wh as an average) - I do too, but with lots of long distance driving, I drive to arrive. PS - Have you compared your Battery Survey with data from the US/Canada lifetime efficiency thread? I seem to recall 330Wh/mi down to 300 was a standard range for my area, flat terrain.