Real World REX mpg

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RExingIT

Well-known member
Joined
May 11, 2015
Messages
49
Location
Chicago, Illinois, USA
I just did an MPG test for the engine.

Approximate Test conditions:
Battery level: 50%
Driving conditions: City, mix of 20,30,35 & 40 mpg roads.
Climate Control: Off
Air temp between: 40 & 65
Average trip: 2.6 miles

Filled the tank to the brim with 93 octane Shell gasoline. Ran vehicle for 31.5 miles. Used .732 gallons of gasoline (determined by filling tank back up to brim with the same Shell Gasoline.

MPG stats =~ 43 mpg.

Any other's gotten similar numbers?
 
I currently average 48.8 mpg over 3600 miles driven on the REx. Mostly dual carriageway (= US highway?) at around 60 mph. Temperatures varying between below freezing and 18 -or- so degrees C. UK gallons.
 
PhilH said:
I currently average 48.8 mpg over 3600 miles driven on the REx. Mostly dual carriageway (= US highway?) at around 60 mph. Temperatures varying between below freezing and 18 -or- so degrees C. UK gallons.

So if my math is correct, at highway speeds that works out to about 40 mpg US. (48.8/1.2)
 
Those numbers seem to be about average. I don't have a REx, but I think that that information is available in the app for both you and the community, at least averages. Because the rpm on the REx remains relatively static at certain load levels, once it is warmed up, the amount of energy it can produce will be fairly consistent. What can be determined is how much energy the REx produces at a particular RPM. It is somewhat disconnected with how far you can travel on that amount of energy, unlike in an ICE, the generator is not directly driving the car, the electric motor is and the batteries act like a buffer for momentary excess or deficit in output from the REx. IOW, since the REx is not directly connected to the drive wheels, and never drives the car, trying to determine a direct relation to mpg is tough.
 
Hi,

You've figured out my nefarious plan:
jadnashuanh said:
. . . once it is warmed up, the amount of energy it can produce will be fairly consistent. What can be determined is how much energy the REx produces at a particular RPM.
I've ordered Autoenginuity, an OBD based diagnostic package including their BMW codes. Hopefully it will give:
  • Mass Air Flow - for a gas engine, 14.7 gm air / gm fuel, the easiest fuel consumption metric
  • engine rpm - needed for hp calculation
  • engine torque - if available, need to look to find out
  • generator voltage and current - needed for net engine hp output, ~92% usual mechanical-electrical efficiency with expected engine-to-wheel efficiency the square, ~81%. The Prius transmission is twice as efficient via a parallel mechanical path.
  • 12V current - if available, need to look to find out
jadnashuanh said:
. . . It is somewhat disconnected with how far you can travel on that amount of energy, unlike in an ICE, the generator is not directly driving the car, the electric motor is and the batteries act like a buffer for momentary excess or deficit in output from the REx. IOW, since the REx is not directly connected to the drive wheels, and never drives the car, trying to determine a direct relation to mpg is tough.
Actually with the vehicle roll-down coefficients, it turns out to be fairly simple to calculate the 'drag power' as a function of speed. Fortunately, this is available from the EPA "Test Car Database". The unknown is the vehicle electrical overhead.

If we can read it out using Autoenginuity, problem solved. Otherwise, I'll have to install a clamp-on, DC amp meter after the 12V DC-to-DC converter to measure the load. In my earlier model, I used 1 hp, 746 W, as an estimate.

The only other major load is the pack environmental heating and cooling. I doubt it runs on 12V so it probably is fed directly from the pack. Not sure how to measure its load. So where does this end up?

Engines typically have a Brake Specific Fuel Consumption (BSFC), the amount of fuel burned to produce a specific amount of power. They also have an operating line, the path through the BSFC values that the car transmission and control laws attempts to follow. Along this line, efficiency can vary so we seek a speed that gives peak efficiency point and avoids any 'knee in the curve.'

Now I come from a Prius background and I have no expectation that the BMW i3-REx will have even similar data patterns. This is only an example using my earliest chart for the 2001-03 Prius:
epa.jpg

  • below 42 mph - the Prius control laws cycle the engine ON and OFF but when ON, always about 15 hp (~11 kW). The excess power is banked in the traction battery so the engine operates at peak efficiency. This behavior is NOT expected in the BMW i3-REx.
  • limit 65-70 mph - at this speed, the Prius drag moves the 1.5L engine out of the peak efficiency sweet spot. At 70 mph, we're seeing 39 MPG … not too far off from the BMW i3-REx reported efficiency.

Now I am not expecting the range extender engine to turn off automatically. But I suspect if I descend a steep slope, the regenerative braking will bring the battery SOC high enough to exceed the original set point. At that point the engine should go into an 'idle without power' mode. If it turns off by itself, I will be thrilled!

My curiosity is in range extender operation, its efficiency and relationship to the control laws managing the SOC. Having the numbers and running some experiments will give me insights to how to do long range trips. But if the BMW i3-REx achieves 39 MPG at 75 mph, it is no worse than our 03 Prius highway performance … my lead-footed wife will be pleased.

Bob Wilson
 
I don't own the REx version, but from what I've read, the engine does turn off on its own depending on the load and the SOC. In the rest of the world, you can put it into a charge hold mode, but if you had a lot of downhill, regen might let it turn off as well.
 
I have a 2015 REX and have made it charge up the battery enough to turn itself off. This was done driving at slow speeds and barely using actual brakes, just regen braking the whole time.
 
... arrived home with the BMW i3-REx:

Left 5:53 PM (EDT), Arrived: 5:10 AM (CDT, add one hour)

  • 9:31 - driving duration
    462 miles - distance
    4.6 mi/kWh
    49.8 mph - speed
    Starting SOC: 100%, Ending 72%
    Fuelings
    • $5.10 - 1.75 gal
      $4.35 - 1.50 gal
      $3.29 - 1.45 gal
      $3.65 - 1.48 gal
      $3.89 - 1.53 gal
      $3.70 - 1.55 gal
      $3.88 - 1.58 gal
      10.84 gal - 462 miles -> 42.6 MPG
    @65 mph - 1.48 gal - 60 miles -> 40.5 MPG, Knoxville to Cleveland TN
    @55 mph - 1.584 gal - 70.3 miles -> 44.5 MPG, Bridgeport TN to Huntsville AL
dynamic cruise control tripped out three times, two driving into sunset and one at ~10 PM
"Check Engine" light self-cleared with 10 miles
Put car on free, public charger while eating supper, added ~7% SOC
Commercial charger could not be made to work ... found credit card charged for no electrons (Green Mountain)

Still learning the car and systems. So far, no surprises. Taking a nap before trying Level 1 charging at home. Eventually, electrican for better home charger. Also test the Whole Foods and other chargers.
. . .
Reading the owners manual and just tested the automatic, parallel parking (car perfect, driver thought it was done ... car corrected driver.) Also mastering key-fob.
. . .
I've had our BMW i3-REx for a little over 24 hours and used these chargers:

EVgo (Green Mountain Power) - charging station did nothing and even failed to read two credit cards. Calling the 1(877)494-3833 support and giving credit card information failed to charge … but there is a $10.67 VISA charge. Apparently they are good about charging credit cards but not the car.
Public EV stations at Hilton - my first, successful charge, no fee while eating supper in Biltmore.
Huntsville Whole Foods - no charge, reported ~4kWh after over an hour
Level 1 charging at home - find the first outlet is not properly grounded. However, the second outlet works fine. Using the middle, 10A, charge rate, for now. Will investigate the dryer outlet. All will be thermally checked to make sure the new load is not causing other issues like setting the house on fire.

I have the car and know where the BMW dealer is. I'll figure out the 'last mile' problem and drop the car off for a charger checkout.

At the Whole Foods charger, I just needed a few things, ~10 minutes which is not long enough to get a good charge. Since my wife told me I needed a hair cut, I asked the clerk and she had no idea. So I had a nice walk around the area and found a salon that had an opening. I began to realize a free public charger now defines my 'neighborhood.' Over time, I will learn what services are in walking distance. I'll also investigate using my inline skates to expand the area.
. . .
This article led to:

  • About a month into ownership last year, I authored two posts dedicated to my initial likes and dislikes.​

Under "likes" I would add two strangers have admired the car: (1) a gas station attendant Friday afternoon, and (2) a man in a car stopped aside me at a light. Contrast that to what happens when driving a Prius. So I've taken an open attitude to showing off the car. I'm not selling it but letting folks know there is an alternative.

The "dislikes" are amusing as some I found but others won't surprise me so much:

  • under 100 miles EV - since it was under 100 miles, he bought the REx version only to discover, it is very handy. I bought the car because of the range extender which is 'right sized' for cross-country drives. It exactly matches standard day driving at 75 mph. At 70 mph, perfectly fine without eventually draining the traction battery and I'm happy with cruising at 65 mph, the usual posted speed limit which fully preserves the battery SOC.
    No SOC - fixed as I drove with a three digit, SOC, 99.9%
    No Battery Temperature - still a problem but driven like an 11 year Prius owner, not critical for my purposes.
    Glide - not a problem for me because the cruise control is great! I don't operate use the accelerator except to get over 20 mph when the cruise control takes over. But then that is how I drive our Prius too.
    glare - I drove west into the sunset. I never noticed it.
    no AM radio - heck I'm a podcast guy as AM/FM and satellite have been bought and sold to folks with an 'agenda' and lack of imagination and character. I prefer to choose my content on the Internet.
    thin tires - really a function of roads. I'm more concerned about the replacement cost. Also there are both 19" and 20" versions and the front and rear tires are different. I will be looking at alternatives and a full-size spare. I don't like one flat trashing the tire and pressure sensor with 'goop.'
    key fob functions - it is what it is and don't choose are car because of the fob … heck I'm Ok with a physical key. However, I do like holding the unlock will roll down the windows.
    regen braking - finally that d*mn creep I've been pissed off at Toyota for is GONE! It does regenerate to a complete stop and is non-linear. I plan to measure it with an accelerometer so I can better predict where the car will stop.
    locking connector - when I pulled up to the free charger, there was a guy eating ribs at a bench. He mentioned a 'joke' of disconnecting the charging cable. At the time, I did not realize locking the car would lock the connector but when I got back from supper, he was gone and the car still charging. I like the lock even if it means not being 'friends'.
    Regen stops on fast turns - hummm, good to know. I've not experience it but on my first cross-country drive, I'm trying to reach home, not shake-off a tailgater. But I drive on cruise control so I'm not likely to experience this.
    software bugs - at work I have to use a Windows laptop management by another government contractor.
    charging - I had always planned to use a home L1 while investigating options.

As for the technical details about the car, I found a link to the BMW technical information service. For $250 I can get 30 days access and start downloading the service manuals. So far, sounds like regular integration and test.
. . .
My first test drive and take it home:

  • 462 miles (740 km)
    • 710 ft (216m)
      2786 ft (849m)
      680 ft (207m)
    trip speed of 50 mph (80kph) (door-to-door)
    • included an hour supper break
      multiple, 1.5 gallon refills every hour (also wife's bladder range)
    42.4 MPG (Plus grade, 89 octane)
So last night, I parked with ~42% on the battery and range remaining just under 40 miles. So I used the 110VAC wall outlet cable and a 25ft, 15A cable ($40) to plug into the utility room outlet. I lost two hours because I didn't notice the power fault, the ground and neutral problem, of that outlet.

I re-ran the extension cable into the back, kitchen outlet leaving the door cracked and got a solid 12 hours, 92% SOC and range of 82 miles. Now this reading will soon decay because when charging a battery stops, the battery voltage soon decays to a steady state value, true value. Given the EPA lists the battery range as 72 miles, '90% isn't good enough, it is PERFECT!' (former GE manager Dick Hicks when a software manager tried to report progress,'90%, next week 92%, 93%, 94%, setback 92%').

Knowing my weekly driving habits, I expect to have no problem with the reduced rate (1 kwHr). One advantage is charging efficiency since the electrical losses house-to-car vary by the square of the current. A faster charge rate is less efficient and tends to induce more heat. For the summer and fall, no problem, giving more time to design a better home charging system.

Our kitchen is closest to our car parking area and has a 40A circuit breaker protected oven and electric range. So I'll install a junction box with a current detector on the range/oven side that operates a solid-state, relay on the 220VAC lines. However, I'll also wire a 110 VAC plug for Level 1 when cooking. The operational scenario:

  • stove and oven OFF - Level 2 charging available to an installed, external box, and Level 1 outlet
    stove or oven ON - Level 2 charging turned off but Level 1 continues to work, car set to reduced mode
    default charging when home - Level 1 at 1kWhr mode. In exceptional cases such as planning more errands around town, turn off the stove and oven and use the Level 2 charger

So far, I have only one suggested enhancement. When the car is off and the windows are down, the rain sensor should trigger rolling up the windows. Also hitting and holding "Lock" on the key fob should roll up the windows. This way in Alabama if no shade around to park, we can keep the interior dry while letting the solar heat out.
. . .
i3_rex_030.jpg

The data suggests there is an unexpected drag, likely rolling, with this particular car. The service history shows the passenger side front tire was replaced and the driver side, inner tread, is down to the wear bars. Before taking it to BMW, I'll buy a lifetime alignment contract from Firestone and have the measure everything. Then I'll head over to BMW to see what sort of pro-rated tire replacement I might get. I'll also have the Firestone alignment metrics.

I could find no evidence of an accident repair in the vehicle history but ...

The adventure continues ... still grinning.

Bob Wilson
 
bwilson4web said:
... arrived home with the BMW i3-REx:
Congratulations on your new purchase!

bwilson4web said:
Reading the owners manual and just tested the automatic, parallel parking (car perfect, driver thought it was done ... car corrected driver.)
Unfortunately, Parking Assist is not always perfect. Several owners have reported that their wheels have been scratched when Parking Assist parked their cars against rather than close to the curb. I have found Parking Assist to be so slow that using it is not worth the risk of scratching our wheels. I am perfectly capable of parallel parking faster than Parking Assist, usually without scratching our wheels myself :)

bwilson4web said:
No SOC - fixed as I drove with a three digit, SOC, 99.9%
The 4 charge level bars indicate the charge level to a level of accuracy sufficient for many people allowing other information to be displayed where the %SOC can be displayed.

bwilson4web said:
No Battery Temperature - still a problem but driven like an 11 year Prius owner, not critical for my purposes.
With a temperature-controlled battery pack unlike some EV's, battery pack temperature extremes shouldn't be a problem. Battery pack temperature can be displayed in the hidden service menu should you want to see it, but probably not while driving.

bwilson4web said:
thin tires - really a function of roads. I'm more concerned about the replacement cost. Also there are both 19" and 20" versions and the front and rear tires are different. I will be looking at alternatives and a full-size spare. I don't like one flat trashing the tire and pressure sensor with 'goop.'
The only alternative so far are 19" Bridgestone summer tires (same model as the standard 20" summer tires) rather than the standard all-season tires. I'll consider those when the time comes since our year-round summer driving conditions would never benefit from all-season tires.

I would like to exchange my rear wheels and tires for someone's front wheels and tires so that we could both have a square setup that would allow proper tire rotations and hopefully longer tire life. Unlike the REx, the base BEV is equipped with the same narrower wheels and tires all around, so I would not be concerned about reducing the width of our rear wheels and tires. Apparently, the wider rear wheels and tires will fit on the front with wheel spacers.

I understand your desire to have a spare tire, but I'd hate to lose the storage space that a spare tire would require. You'd also need to buy and carry a BMW scissor jack that would properly fit into the i3's plastic jack points without damaging them. I consider the BMW jack point design to be inferior to other cars I've owned.

bwilson4web said:
key fob functions - it is what it is and don't choose are car because of the fob … heck I'm Ok with a physical key. However, I do like holding the unlock will roll down the windows.
…except when this happens unexpectedly due to accidentally pressing the unlock button (e.g., when in one's pants pocket). I have never experienced this myself, but quite a few i3 owners have. One solution is to install a BMW fob cover mounted backward so that the buttons are covered. They can still be pressed purposely but not so easily accidentally.

bwilson4web said:
As for the technical details about the car, I found a link to the BMW technical information service. For $250 I can get 30 days access and start downloading the service manuals.
Please report what you have been able to download. I have been frustrated by the lack of purchasable i3 service manuals. I've had service manuals or CD/DVD's for all of my previous cars.

The BMW technical information Website's system requirements are Internet Explorer 5.0+ with an Adobe PDF Reader plugin installed. That's a pretty archaic requirement especially when many people have avoided IE due to its insecurity. Hopefully, these PDF documents can be viewed and downloaded by current Safari, Firefox, or Chrome browsers.

It would be nice if these PDF documents include imbedded links that would support easier navigation of these PDF documents. Our Mitsubishi i-MiEV PDF service manuals included such links.

bwilson4web said:
Now this reading will soon decay because when charging a battery stops, the battery voltage soon decays to a steady state value, true value.
Although we don't know for certain, it's likely that the pack's charge level is not determined by its voltage which is quite constant over most of the charge level range and is also temperature-dependent. Coulomb counting is used by some other cars with battery packs to keep track of charge level with voltage at "full" and "empty" charge levels used to correct the coulomb count, if necessary. So I wouldn't expect you to see a drop in the charge level after charging is completed. Some have reported a drop in the charge level during cold months, but cabin and/or battery pack preconditioning is likely the cause.

bwilson4web said:
Given the EPA lists the battery range as 72 miles, '90% isn't good enough, it is PERFECT!'
Some of us who have experience with batteries and who want to extend the lives of our battery packs as much as possible try to avoid allowing our cars to sit with a full charge any longer than necessary typically stopping charging at 90% or even less when maximum range isn't required. Most i3 owners feel that the charge level buffer that BMW and all EV manufacturers maintain at the high and low charge level ends is sufficient to maximize battery pack life, or they don't plan to keep their i3's more than 3 years so long battery pack life isn't worth the additional effort required to stop charging before full.

bwilson4web said:
Knowing my weekly driving habits, I expect to have no problem with the reduced rate (1 kwHr). One advantage is charging efficiency since the electrical losses house-to-car vary by the square of the current. A faster charge rate is less efficient and tends to induce more heat. For the summer and fall, no problem, giving more time to design a better home charging system.
What you say is true, but it ignores the considerable overhead of the charging electronics in the car that is continuous while charging and apparently independent of the charging power. Test results on i3 charging indicate that lower charging power is less efficient overall from wall to the car's battery pack.

These tests don't seem to indicate the reduced charging efficiency caused by battery pack cooling should it be required because the battery pack is too warm and/or charging occurs at a sufficiently high power. I try to avoid charging when cooling is needed. If I begin charging and hear the A/C compressor start, this usually means that the battery pack is already too warm, frequently because driving has occurred recently. If I can delay the start of charging, I do.

It's more difficult to detect a charging power that is sufficiently high to warm up the battery pack such that cooling begins sometime after charging has begun because I cannot hear the A/C compressor from within our apartment, and I'm usually sleeping when charging. Because our JuiceBox EVSE allows the charging current to be adjusted in 1 amp increments, I could theoretically reduce the charging power enough that cooling would no longer be needed. However, it would likely take some time for the pack to cool and the A/C compressor to turn off, and I would be guessing how much to reduce the charging current, so I've never done this.

bwilson4web said:
default charging when home - Level 1 at 1kWhr mode.
If maximum charging efficiency is your goal, you might want to reconsider, or at least measure your charging efficiency at various charging power levels.
 
What tends to kill batteries is constant charging, not just charging them up to their maximum. Once the i3 detects things are fully charged, they remove the input voltage...no more charging, unless later, it drops past the hysteresis point to cause it to turn on again (this typically can take days).

Cell voltage leveling can cause the EVSE to turn on again after awhile, but it usually doesn't seem to stay on all that long...it levels some by dropping the rate significantly as it approaches what it thinks is full. By keeping the heat down with the liquid cooling feature, overheating the batteries should not be an issue.
 
Table tags are a little verbose but I wanted to share some initial results:
mphmi/kWhrmodelRoute
19.99.39.01.1 mi loop, x10
29.97.58.11.1 mi loop, x10
39.15.86.83.4 mi loop, x3
52.65.15.56.5 mi Cajun Cafe to DQ
These data suggests we may have a rolling-drag issue with this particular car.

The lowest speed, 20 mph and highest speed, are showing better agreement with the model. This suggests the vehicle electrical overhead is not as high as the 746W I'd estimated earlier. When I download the manuals, I should be able to locate the DC-to-DC 12V source and measure how much the car draws and then use 8% (assumes 92% efficiency) as the converter overhead.

On the highest speed test, the aerodynamic drag begins to dominate and approaches the model. This points towards the rolling drag disagreeing with the model. But I've having second thoughts about the Friday appointment for the four-wheel alignment. I would like better data.

The most likely result of a rolling drag problem would be excessive tire temperature and we are seeing inner tread wear. So I may push off the alignment to run some high-speed runs and measure the tread temperature quantify it.

The protocol is to put the car at a high speed, 70-75 mph for 5 miles; stop rapidly and measure the tread temperatures across each tires. Because of how fast the tires cool, I usually get just one tire with each run. But I may see if I can find an affordable, tire temperature probe. They were pretty expensive years ago.

Bob Wilson
 
So the car went in the shop and here is their initial check:
i3_rex_040.jpg

Then I got a call on the way over that they are replacing two, rear tires. So I told them to do the front tires too. This and the alignment should keep us good to go.

FYI, this is consistent with my earlier metrics that showed there was indication of a rolling drag problem:
i3_rex_030.jpg


Bob Wilson
 
bwilson4web said:
Table tags are a little verbose but I wanted to share some initial results:
mphmi/kWhrmodelRoute
19.99.39.01.1 mi loop, x10
29.97.58.11.1 mi loop, x10
39.15.86.83.4 mi loop, x3
52.65.15.56.5 mi Cajun Cafe to DQ
These data suggests we may have a rolling-drag issue with this particular car.
. . .
Last night, I repeated the 29.9 mph test:
mphmi/kWhrmodelRoute
29.97.58.11.1 mi loop, x10
29.97.68.11.1 mi loop, x10
This is after:
  • 4-wheel alignment
  • four new tires
  • inflated to maximum sidewall pressure

Even the "N" roll-down test on the track was disappointing compared to our 2010 Prius. Regardless, I have more metrics on our 2003 Prius and will continue to investigate what is going on. I want to eliminate any maintenance or other hypothesis. Meanwhile, I will be adjusting the roll-down coefficients to get an accurate model for our particular BMW i3-REx.

Updated table:
mphmi/kWhrmodelRoute
19.99.39.01.1 mi loop, x10
29.97.68.11.1 mi loop, x10
39.15.86.83.4 mi loop, x3
52.65.15.56.5 mi Cajun Cafe to DQ
54.94.95.2+85F 6 mi Rideout Rd, 78F A/C
64.93.84.2+85F 6 mi Rideout Rd, 78F A/C
74.93.23.5+85F 6 mi Rideout Rd, 78F A/C

Bob Wilson
 
FWIW, a new vehicle verses one with lots of miles on it will have different results. It can take awhile for bearings and seals to 'loosen up'. Also, the choice of lubricant and the temperature can make a difference. Test the same car after 10K miles or so, and you are likely to get different values as surfaces get polished and seated. Now, once you get LOTS of miles on it, things could start to go downhill again, as things wear more.
 
jadnashuanh said:
FWIW, a new vehicle verses one with lots of miles on it will have different results. It can take awhile for bearings and seals to 'loosen up'. Also, the choice of lubricant and the temperature can make a difference. Test the same car after 10K miles or so, and you are likely to get different values as surfaces get polished and seated. Now, once you get LOTS of miles on it, things could start to go downhill again, as things wear more.
Indeed and I've done such testing with our 2003 and 2010 Prius and found 'regression testing', retesting after some service time, is useful for diagnosing problems. It actually dates back to my first car, a used, 1966 VW MicroBus.

I was keeping track of each MicroBus tank with a 'blue book'. When the tank came in at 28 MPG, life was good. But when tank MPG fell below, it was time to:
  • Check tire pressure
  • Check and change oil
  • Swap spark plugs and use the grit cleaner
  • Adjust the valve backlash

I just needed some basis of estimate, a credible reference, that allows me to plan my trips. Especially the longest ones. But I also want a baseline so if I should ever suspect a problem, I can run a quick benchmark and adjusting for temperature, know if something might be wrong.

Bob Wilson
 
Range on an EV will vary by a fairly wide margin, much more than on an ICE, based on the ambient temperature and trip length. Maybe the best idea of 'normal' is from the i3 app, where you can compare your data to the community's. Driving style, as on an ICE, also can make a huge difference in expected overall range. Keep in mind that the car's estimate is based on the last 18-miles or so of travel, so cannot be relied on if your next trip will be under different conditions (temperature, time of day necessitating lights, etc.) or type of highways and expected speeds.
 
Sorry, I should have been more precise:
jadnashuanh said:
. . . Maybe the best idea of 'normal' is from the i3 app, . . .
A private pilot, we use the concept of a 'standard day' which I mislabeled 'normal.' In aviation, we define aircraft performance by reference to:
  • For Pilots: At sea level, Altimeter:29.92 in/Hg at 15 °C (59 °F) The "standard day" model of the atmosphere is defined at sea level, with certain present conditions such as temperature and pressure.

    Private pilots have density altitude charts (old school, today apps) that incorporates temperature, humidity, altitude, and air pressure to calculate the change in aircraft performance. More sophisticated engine management systems also calculate these impacts on performance. Aviation accidents continue to re-enforce why paying attention to these environmental factors can be life or death. In cars, it is a question of trip planning to reach our destination.

I've had to hold off on the BMW i Remote App and related apps because the car is not yet titled in my name. Happy day, Saturday the letter came from the DMV that the title arrived and I can now register my car. Then the service center will enable the owner connection options.

BTW, I do my mph vs mi/kWh charts for my own purposes and appreciate suggestions to adjust for differences in temperature, wind, and altitude. If others are able to use them, good. If not, ignore them. But a funny thing happened in the Prius community with my similar mph vs MPG charts.

Every now and then we have a Prius owner claim 'my Prius is broke because I get <xxx> MPG.' Now we have a standard list of questions that help people understand how to improve their MPG which works for 80-90% of them:
http://priuschat.com/threads/fuel-economy-complaints-queries-please-copy-paste-answer-these-questions-esp-if-youre-new.77074/

Yet there remains a hard core, 10% who continue to claim their Prius is broke. So I ask them to replicate my benchmark data, two points using cruise control for 10 miles with one below 40 mph and a second above 50 mph. For good measure, I replicate two points and compare them to my original chart. Their car could be broke but most of them go away and the problem is solved.

There is one individual who refused to run any benchmarks (long thread: http://priuschat.com/threads/latest-software-update-safety-recall-resulting-in-8mpg-less.139758/.) Eventually the local Toyota dealer and a Regional trouble shooter drove him in his car and demonstrated standard Prius MPG. For Toyota, case closed, but this same 'complainer' posted again two months ago and I had no choice but to put "Larry Schnack" on my ignore user list.

Bob Wilson
 
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