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What Wh/mi are you getting with AWD and P cars?
- Thread starter Thomas Edison
- Start date
AlanSubie4Life
Efficiency Obsessed Member
I plugged in the numbers again; I guess it's closer to 1650Wh per 1000ft for the P3D+ (depends on passenger weight and anything else you're carrying). So add 165Wh to your number and it's starting to look pretty reasonable (although quite good still).
One idea to improve efficiency with a downhill commute is to load up your trunk with rocks before leaving home in the morning. Then discard them when you get to work. Eventually you'll run out of rocks though.
One idea to improve efficiency with a downhill commute is to load up your trunk with rocks before leaving home in the morning. Then discard them when you get to work. Eventually you'll run out of rocks though.
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I have a P3D- with 18" rims (no caps) and winter x-ice tires. I'm at 265Wh/Mile for the last 5.6k miles. It's been dropping in the winter when I'm using the heater and driving in the rain. In the fall I was getting 220-240Wh/Mile going to work and back on the interstate in somewhat stop and go traffic 7 miles each way.
Right now just did 129 miles locked on 70mph the entire time on autopilot.
Current tire pressure 50psi
OAT 82F
Wh/mi 299
P3D
Disappointed.
Current tire pressure 50psi
OAT 82F
Wh/mi 299
P3D
Disappointed.
P3D? 20" wheels?
If so, you shouldn't be disappointed; that's expected. If you want sticky sports tires and "baller" wheels, you better expect to pay for it in terms of efficiency. Want better efficiency? At least put more efficient tires on it (yeah, you'll sacrifice a few tenths of a second). Ideally put aero wheels on it.
Or, accept the tradeoffs. Honestly, 299Wh/mi at 70mph is still quite good by most EVs standards. People on LR RWD with 18" aeros have spoiled everyone else's expectations, that car is an efficiency beast
Don’t state “current” psi, it’s useless, what is cold PSI?
It’s hard to know under your conditions what the pressure should be warmed up.
But that sounds about right for 45 psi cold.
Drove 70 miles today round trip. LR AWD Aero’s, 350 miles in car
70/30 freeway/city. 70-75 on freeway, 45-55 on city. Did get stuck in traffic jam for 20 minutes. Outside Temp 24F, climate at 67F, Two seat heaters on
320wh/mile
Turn the heat off for 3 miles and got in the 280’s at 75.
Pretty much limited Regen for 70% of trip
70/30 freeway/city. 70-75 on freeway, 45-55 on city. Did get stuck in traffic jam for 20 minutes. Outside Temp 24F, climate at 67F, Two seat heaters on
320wh/mile
Turn the heat off for 3 miles and got in the 280’s at 75.
Pretty much limited Regen for 70% of trip
I just did a 125mile trip in my AWD P. 18 inch wheels without aero caps.
Outside temperature: 36
Cabin temperature set to 70. Seat heaters off.
115 miles were strictly highway, drove with EAP @70 mph, had 4 complete stops to pay tolls.
10 miles were local roads, speeds between 25 and 40.
Left with 72% battery, arrived with 26%
Energy consumption was 272wh/m
Outside temperature: 36
Cabin temperature set to 70. Seat heaters off.
115 miles were strictly highway, drove with EAP @70 mph, had 4 complete stops to pay tolls.
10 miles were local roads, speeds between 25 and 40.
Left with 72% battery, arrived with 26%
Energy consumption was 272wh/m
This is actually a good result compared with EPA estimates for even a non-performance model 3. Remember this is unlike an ICE vehicle....efficiency happens in city driving not highway.
Actually this is a common source of fairly systemic confusion. All cars show declining efficiency as speed Rises. This is due to the fact that while at very low speeds rolling resistance and parasitic transmission losses are the biggest drains on energy, as speeds rise it is actually drag and air resistance that becomes the biggest consumer of energy, and this drag is proportional to the square of the speed. This is why the Tesla Model 3 shows roughly four times the energy consumption at 80 miles an hour that it does at 40 miles an hour. Anyone who is skeptical can easily repeat this experiment. Drive on cruise control at 40 and see that your watt hours per mile are under 200, and then do a stint at 80 miles per hour and you will see your watt hour per mile roughly double.
These relationships are obscured in ICE cars simply because they are only able to be efficient in their top gears. In other words the best mileage you can get in an ICE vehicle is at the lowest speed it will tolerate in its top gear. That rule does not apply to Teslas because of their single speed transmission, and this essentially means their most efficient speed is probably something like 10 to 15 miles per hour, and it's possible it's even more efficient at lower speeds than that.
Short form of a long story is that the single speed transmission and the very broad torque curve in an electric vehicle allows you to see actually how your energy consumption works in a clearer way than an internal combustion engine with its narrow torque curve and limited efficiency, and multiple gear ratios. If you're skeptical this take your internal combustion engine car and just keep it in first gear and drive around town. Your mileage will be staggeringly bad, way under any EPA City number.
And all of you that are complaining about the declining range as your speed advances in a Tesla, same thing happens to your mileage in an internal combustion engine car. It's just not as visible because range is less of an issue and because internal combustion engines are incredibly inefficient unless they are geared up so that they are under high load which is essentially what a Top Gear does
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StealthP3D
Well-Known Member
Factory recommendation is 42 PSI, so he's not that low. I run 40 PSI in mine. Sure if you're trying to hypermile your range you can gain a small amount by increasing it, but at the cost of increased tire harshness, noise and perhaps longevity. I'm guessing the EPA used 42 in their range calculations.
I couldn’t wait for it to get warm and turned off the heat for fun anyway. And got 200 wh/mi for the whole week (AWD, Chill, Areo’s and still with lots of limited Regen). All around town driving.
Heat gets real expensive in traffic and stop lights.
That's part of it but it's actually the smaller part, has even without regen EVs are more efficient, particularly at low speed around town. As for your notion that understanding the physics of this is over analyzing, I'm not going to take the bait
the tires must probably take most of the blame. Higher weight and 4x4 also impacts a bit. A comparison with my Model S. I have the S60 and I have driven the P85 and S85 av loaners. In general, with same temp, same tire, climate off etc consumption is generally 5% higher on P85 and 3% on the S85 than 60. They weigh over 100 kg more and the engine probably accounts for the extra 2% on P85 vs S85.
Now to the interessting part: Tires!
Stock tires on my car is the Goodyear RS-A2 245\45-19. They have an efficiencygrade of F (A is best, G is worst). My wintertyres are the Nokian R2 245\45-19, they have efficiencygrade B. With same tirepressure, tested multiple times on the same day consumption on the R2 is always 5-10% lower than RS-A2. At low temps, around 5C the RS-A2 gets really hard and the consumption is even worse. I have a route in the city that I drive 3-4 days a week and the R2 on average uses 38-55Wh\km due to going slightly downhill at the start of the trip. the lowest I have ever managed with identical driving with the RS-A2 is 62Wh\km, usually I get around 70Wh\km. On a longer trip I do 10 times a year (160km total) the R2 on average uses 140-148Wh\km and the RS-A2 uses 150-164Wh\km when temps are the same, average speed are the same and climate is off.
I would consider changing tires if I were you, you will probably get slightly worse performance from 0-60, but with the right tires, 5% improvement in range or more is possible.
Is there anything that could be wrong with the car that would negatively impact efficiency?
I got a P3D- in August and the average for the first couple months was around 280Wh/mi. I know cold affects things, but it has been ~40F for a while here, and it seems to just be getting continually worse. My commute to work is 7 miles on mainly side\country roads with reasonably heavy traffic, chill mode on and not huge accelerations and i have been getting 450Wh/mi, sometimes even over 500.
I got a P3D- in August and the average for the first couple months was around 280Wh/mi. I know cold affects things, but it has been ~40F for a while here, and it seems to just be getting continually worse. My commute to work is 7 miles on mainly side\country roads with reasonably heavy traffic, chill mode on and not huge accelerations and i have been getting 450Wh/mi, sometimes even over 500.
AlanSubie4Life
Efficiency Obsessed Member
Pretty short commute. If you want to debug it, prewarm the car and then turn off heat during the drive. See how you do.
People really should quote these efficiency numbers in terms of Wall-to-wheel, since that is the bottom line.
There’s a rough formula you can use, assuming you don’t use any preheating, and charge at home (no supercharging!; that will improve charging efficiency (AC-DC conversion loss is carried by Tesla) and make things a bit better actually):
Wall-to-wheel Efficiency = ( Displayed Driving Efficiency + 60Wh/mi * (440kWh/ miles driven per year) ) / 0.87
For example, if I drive 10k miles per year, at 270Wh/mi (displayed):
Efficiency = ( 270Wh/mi + 440kWh / 10k mi ) / 0.87 = 361 Wh/mi
In the end, that’s the number that matters and what you should compare to for the 290Wh/mi (for AWD) EPA rating. Don’t compare to EPA for the P3D+ with 20” wheels, of course (it would be closer to 310Wh/mi if they rated it). It’ll just make you sad, though the tires should make you very happy. The good news is that the static losses can make the efficiency gap vs. AWD with MXM4 a little less significant than it appears.
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