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Discussion Starter · #1 ·
TLDR: Testing of wheel covers at 110km/h show a increase in efficiency by a little more than 7% in clear winter conditions (-12°c low windspeed and dry roads).

After stumbling over a mod for the Nissan Leaf, where some users have been fitting “leaf-petals” into the holes in the rims I looked at my winter rims that I got with the car, which are five spoke rims with very big gaps and thought it might give me a little extra range during the winter if I covered them up. So my quest was started in October last year prototyping and test-fitting to make sure they stayed on and could withstand the rotational forces. At the start of December I had a full set of 20 workable wheel covers. I installed them all and left them on the wheels until the end of January, they were very dirty but still intact after 3400km of Nordic winter driving through some pretty harsh blizzards and windspeeds upwards 30m/s.

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Here are the two setups, top one with the wheel covers and bottom one without.

Now came the time to start testing them, I started just doing a run of my commute with and without them but the weather, traffic etc chose not to be consistent and it was hard to draw any firm conclusions. I decided I did need to do dedicated testing but I did not have the time to do two back to back full discharge runs and devices a way to extrapolate the consumption from the power drawn from the battery and logged via (my cheap clone) ELM327 and Torque Pro logging at half second intervals.

The test is run on a 5km stretch of E18 west of Karlstad, Sweden where the speed limit is 110km/h. There are good turnaround points at either end. All 4 runs have been full (10km) loops to account for elevation and wind(about 2m/s NNE on all runs). The turnaround has been cut out of the data so that only time spent at 115km/h (110km/h GPS) has been included. I did the runs on two separate days(one of each both times) so neither would get the advantage of increased battery temperature/oil in reduction gear/engine temps etc from the previous run:
Day 1, wheels covered first then uncovered (run 1 & 2)
Day 2, wheels uncovered first then covered (run 3 & 4)
Both starting from the warm parking garage at work after 4h of charging and with 100% SOC to make sure the battery was not cold(was about ~6°c leaving) it then heats up ~2°c/run and about 2°c driving to the test area.
Since each run only takes about 8 minutes the climate control has been turned off, as has seat and steering wheel heaters to remove that variable.

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Most variables are consistent enough, speed is the same as is ambient temp, battery temp(almost) and tire pressure.

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This shows the histogram of all the values and the elevation profile of the test loop (travelled left to right and back again). A longer test loop on flat ground would be a better, but that would entail traveling at least 200km(which is more or less prohibited under the current corona restrictions).

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Here is the distribution of measurements plotted against speed, they create a good central blob so it’s a consistent result but it also highlights a clear weakness in that a lot of values line up at the same power interval(either due to slow polling of sensors or low precision in said sensors).

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The wheel covers are made out of 5 pieces of 3D-Printed PETG each for a total of 20 to cover all four wheels. They weigh in at about ~28g apeace.

What could have been done better?
*Logging interval would preferably be 10 times per second or greater, but my ELM327 clone can’t do that and I am unsure how fast the car can supply the data through the OBD port. The precision of the logging also seems a little low, a lot of the values line up on the scatterplot instead of distributing more evenly as would be expected.
*As mentioned above it would also have been advantageous to do a longer test on flat ground. Preferably both logging as this test but also testing the energy recharged after the test and the cars stated consumption, but that is a level of time commitment I don't have.
But you take what you can get and make what you can. I wanted to test at winter temperatures (as its my winter rims) so getting it done closer to home made sense as the weather changes quickly.

If you made it this far, I hope you enjoyed reading my little test. I'm still not sold on the 7% figure, it feels to high and I think a result closer to 2-3% would be more reasonable.
But these are the numbers I have come up with and I have been getting very good efficiency during December(178Wh/km) and January(183Wh/km) after charging losses which account for 15-20% in the winter on my charger due to low power(2kW average) and freezing nightly temps (-15-20°c) during charging). :)
 

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IONIQ Electric, SE (w/ CCP) 2018.
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Xiziz

I think your results are pretty good actually. I've read articles in the past where they claimed that "aero" wheel covers offer a 3% to 5% increase in efficiency, which is quite close to your value. I note also that your rims are very "open" without the covers and probably generate a lot of drag, and are very "closed" with the covers, so I can see how the effect might be more noticeable on your vehicle than the ones in the tests.

Car and Driver Test
Electrek Test

Cheers

Ou Boet
 

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2019 Ioniq 28kWh
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Great input!! I do 3D print for a living experimenting with foaming filament at home for lower weights.

Which dongle do you use?

(BTW, mine is a late 2019 Trend with chrome delete... a premium adds the unwanted chrome?!!?!)
 

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Great experiment! Thanks for sharing. I was thinking not getting my covers back for spring, but your data support the science behind it. Cheers!
 

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Hyundai Ioniq premium -19, 28kWh ~52k km
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Discussion Starter · #5 ·
Ou Boet: Yeah I thought my results would a land closer to 3%, which would have been good to. Ofc I belive the difference should be lower at the country road speeds I mostly travel (80-90km/h).

Superhero: cool, sounds advanced but would probably be better for these kind of things. I printed these with a .5mm layer width in vase mode, they are 1mm thick so the two layers attach. This makes them flexible enough to bend and pop in but I had to make a lot of small design changes while prototyping to make them strong enough.
A thicker more rigid part would be better for covering the stock wheels that have screw holes and attach under the bolts.
I use an old Elm327 from Kjell å Co, don't think it's sold anymore, it's a Chinese clone with v1.5 firmware. I used it to clear error messages on an old Volvo but it works for this too, I'd buy a proper one now if I bought a new one (one that works properly with ev-notify/canioniq etc).
Yes, a whole bunch of unwanted chrome, didn't think of the trend not having it, might be possible to source black trims then!

Blackfly: Keep em on, the oem rims look really ugly with them off. The inserts on them are screwed on and the holes are visible if you remove the inserts. :)

Now, it would be fun to design one for the oem rings too, if I have time to design and print them before it's time to put the summer wheels on.
 

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That's huge! Before I opened this thread, I was going to say 3% myself. I suspect longer runs and more of them will bring your number down a good bit. Also, open spokes is worst case scenario (yours are not the worst configuration though). I have no doubt that full coverage "normal" hubcaps will be much closer to manufacturer aero hubcaps and that may be why 3% difference is quoted so much. Would be nice to get real numbers from manufacturer's wind tunnel tests or computer modeling, but I think such real numbers are too small to advertise - it is the accumulation of many small aero enhancements that add up to big improvements.

There are many reports here of owners simply taking off their hubcaps and noting zero observed difference in efficiency (most of these owners are likely far more focused on looks than efficiency though). At 3% change, I think that most owners wouldn't notice. At 7%, I'd think most owners who pay sufficient attention will notice.
 

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While im here to find the URL to link it i might just leave a image of a new project too.

View attachment 34126
Can these black parts be removed from the wheel trim and just be replaced by those?
The brakes also need some air to cool down, but that shouldn't be a problem if you drive normally and use regeneration. My guess would be that the rear brakes are hardly used, so installing these kind of covers wouldn't be an issue.
 

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Discussion Starter · #9 ·
Can these black parts be removed from the wheel trim and just be replaced by those?
The brakes also need some air to cool down, but that shouldn't be a problem if you drive normally and use regeneration. My guess would be that the rear brakes are hardly used, so installing these kind of covers wouldn't be an issue.
Yeah, exactly, the grey/black oem trims are attached with two screws and the wheel nut so its a simple replacement (wheel does need to come of though).
Brake cooling is a going to be slightly compromised, but the brunt is taken from regeneration as you say, unless driving very aggressivly. In the relative cool Swedish climate i doubt its going to be an issue, there is still airflow on the inside of the rim that will cool, just not as fast or effectively, the heat will also dissapate into the rim and knuckle metal.
Normal driving should not be a problem anywhere i think, especially the Eco driving most of us electric car owners do.

Printed the last one today, still got some post processing to do ofc.
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Can't wait to see the final result
Yeah, exactly, the grey/black oem trims are attached with two screws and the wheel nut so its a simple replacement (wheel does need to come of though).
Brake cooling is a going to be slightly compromised, but the brunt is taken from regeneration as you say, unless driving very aggressivly. In the relative cool Swedish climate i doubt its going to be an issue, there is still airflow on the inside of the rim that will cool, just not as fast or effectively, the heat will also dissapate into the rim and knuckle metal.
Normal driving should not be a problem anywhere i think, especially the Eco driving most of us electric car owners do.

Printed the last one today, still got some post processing to do ofc.
View attachment 34397
 

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Discussion Starter · #11 ·
I thought I'd have a little more time att hand, but they are all printed now atleast, two of them might need to be reprinted but I won't know until Ive done the coarse sanding with the machine how deep it runs.

To be continued :)

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Discussion Starter · #12 ·
Well, I ran out of clear coat and still have some issues with the quality of my prints(think i have some underextrusion or a need for some overlap). But I decided to put them on the car and fix whatever during the winter instead. Not yet got a feel for how they affect efficency, I only did a quick test around the "block" at 80km/h to see that they stay on without any noise or imbalance

Will be uploading the files to thingiverse soon if anyone wants to try printing them or remixing a better version.


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In hindsight black or gray would probably have been nicer colours.
 

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Nice effort! I agree a darker color would be more like stock but having them painted with the proper car paint would probably be cool too.
 

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Discussion Starter · #14 ·
Yeah, maybe I will revisit them in the future. For now I'll put this project on the shelf for awhile and start a long test period of them(until the winter tires are due to go on).

I posted the files to thingiverse if anyone is interested(including the .blend file).
 
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