VW ID3 aerodynamics

[Vekke]

I will soon get my own first eletric car and it will be the VW ID3
Frontal area is 2,36m2 and announced drag coefficient Cd 0,267.

Cars oem tire size is 215/55R18 which is not super wide, but still not super narrow either.

Car is already pretty energy efficient, but ofcourse there is room for improvements as the drag is 0,267 which in my mind is pretty high.

Testing and changing will begin from tires. I already have bougth BMW I8 20" aerowheels and 195/55R20 Nokian Hakkapeliitta R2 winter tires which have A rolling resistance mark. Those wheels are almost fully closed.

I also have the 155/70R19 wheels and tires from A8 project, but for those I have only summer tires at the moment. But surely I will test also those when weather gets better. Will try also with wider wheels at rear like they are in the I3. Specs on these vehicles are pretty close as
BMW I3 CdA 0,714 vs VW ID3 0,63 The bmw is 400kg lighter so it consumes little less energy at lower speeds about 10% . But when speeds go to 140km/h difference is only under 4%.

Roofline of the ID3 matches perfectly the ASTII template so the bad aerodynamics come from wheels and underside of the car as the front already has a active grill block on all models. Will look closer is it full grill block or not when I get the car.

Disclaimer:

Don`t believe any of the results and ideas presented in this topic, you might save some energy. All the testing is highly questionable on the measurement reliability perpective. If you believe you can only measure road changes in the accuracy of 2% then just take that much lower figure down on the total savings percentage you have your value how much better energy consumption you migth get. Everything depends on your car setup and the outside conditions you are driving. I have tried to put the details here what you should take into account when doing mods like grill block. I don`t take any responsibility what you do to your vehicle.

[freebeard]

Wheels tires and underbody? Is that why they call it low-hanging fruit?

[aerohead]

Just looked at it online.
* L= 4261mm
* W= 1809mm
* H= 1552mm
* L/H= 2.745
* L/W= 2.355
* Cd 0.267
* Af= 2.36 m-sq
* CdA= 0.63012 m-sq
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* There's a 4-view Blueprint of it available online
* Lower rear quarters have little plan-view camber
* Beltline has healthy plan-view camber
* Roofline has healthy plan-view camber
* Tumblehome is healthy
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* Tighter front wheel arch gaps might be possible
* 'Tesla', long-strut mirrors might knock 0.005 off the Cd
* Rear skirts would be a setup for some later tail extension
* No view yet of underbody, so it remains an unknown quantity
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* Creating a perfectly-vertical, Kamm-truncated box-cavity, to take advantage of every existing millimeter of body length, would be a logical setup for a later boat-tail elongation ( that's where any significant drag reduction would come from )
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* The Blueprint side elevation would allow us to accurately locate the roof apex, and that would allow us to quantify the starting Verjungsgungverhaltnis ratio, to compare to bodies of known lower drag, from which one might more accurately predict a drag outcome from a specific degree of elongation.
* She looks like a great canvas from which to paint a masterpiece!

[Vekke]

I have thinked about the boattail. The oem spoiler has good angles so I just need to make it longer with clear 0,5mm thick plastic sheets.

What I have read the door mirrors like they have in the ID3 should be better than the long arm a corner piece mirrors.

Underside is pretty smooth due to battery, but around the a struts and before wheels you can do something.

[Vekke]

I have had the car now soon 4 days. So far I have got ~6% better FE

starting point calculation:
https://ecomodder.com/forum/tool-aer...ToStep=40-65-1

Current situation cd at about 0,24: https://ecomodder.com/forum/tool-aer...ToStep=40-65-1
done mods:
- 195/55r20 tires with BMW i8 wheels. These are 4% taller and increase ride heigth 15mm. Which is bad for FE. Savings 2,3%
- Grill block Savings 1,3%
- Rear suspension arm covers 1,3%
- Front suspension arm covers 0,6%
- Bigger Front tire deflectors 0,5%

Underside is pretty smooth from factory. Only the suspension and wheel areas is where you can make improvements.

Idle energy consumption is 2-2.5kwh when car is warm when outside temps are +4 to +7 celsius. Thats a lot in my mind.

Pictures on my facebook page: https://www.facebook.com/media/set/?...76628169017686

Weird results in tire pressure tests.Lower pressures gave almost better results. On first tests I have thinked that the warm up takes about 20km, at least then the idle consumptions is around that 2-2,5kwh range. Maybe bearings and oils take little bit longer any experience and better data on EV warmup times?

[freebeard]

- 195/55r20 tires with BMW i8 wheels. These are 4% taller and increase ride heigth 15mm. Which is bad for FE
- Grill block
- Rear suspension arm covers
- Front suspension arm covers
- Bigger Front tire deflectors

All in four days?

[JulianEdgar]

Can you explain the mechanism by which you are measuring changes of 0.5 - 0.6 per cent, please?

[Vekke]

Yes all in four days. I am renovating my one house so mods are done in 6 hours time frame. Testing has took also about 8 hours.


Testing:
Same warm up route about 20km. After that test runs A B directions about 5km each direction inside forest covered road sections where is up and down sections. Not that much level road in this.

On first time when did tests checked how accurate were the results and cars own obd computer was 0,1kwh accurate on the end results. To verify car is fully warm

After that on the mods if easily possible take on and off the mods for each runs. sodoing ABA. I measure consumption figures on few points on the course and in the end also. Measuring points on the course will give little bit more accuracy for the results and from those you can see if something likeheavy wind migth have happened during testing. Also other diretion is little bit more uphill. On diesel testing I have noticed that some mods work better to other direction than other due to heavier uphill driving. On the EV that should not be so big problem as I cannot change the ECU programming on this like on the diesel.

I know its not easy to measure such a small changes and migth do more verifying when I am more get used to the car. Outside temps have been 4-6 celsius so pretty same. Road temps I havent measured but during each test they are pretty constant as it takes under one hour to finish.

Battery slow charge times make testing little bit more difficult than with diesel cars, but on the other hand on my own gas pedal use I was not able to save nothing compared to cruise control.

[JulianEdgar]

Originally Posted by Vekke

Yes all in four days. I am renovating my one house so mods are done in 6 hours time frame. Testing has took also about 8 hours.


Testing:
Same warm up route about 20km. After that test runs A B directions about 5km each direction inside forest covered road sections where is up and down sections. Not that much level road in this.

On first time when did tests checked how accurate were the results and cars own obd computer was 0,1kwh accurate on the end results. To verify car is fully warm

After that on the mods if easily possible take on and off the mods for each runs. sodoing ABA. I measure consumption figures on few points on the course and in the end also. Measuring points on the course will give little bit more accuracy for the results and from those you can see if something likeheavy wind migth have happened during testing. Also other diretion is little bit more uphill. On diesel testing I have noticed that some mods work better to other direction than other due to heavier uphill driving. On the EV that should not be so big problem as I cannot change the ECU programming on this like on the diesel.

I know its not easy to measure such a small changes and migth do more verifying when I am more get used to the car. Outside temps have been 4-6 celsius so pretty same. Road temps I havent measured but during each test they are pretty constant as it takes under one hour to finish.

Battery slow charge times make testing little bit more difficult than with diesel cars, but on the other hand on my own gas pedal use I was not able to save nothing compared to cruise control.

Interesting. Do the test with the windows down. I have data for a Tesla Model 3 windows up /down.

[planetaire]

Hello, All

There are very interesting aero infos here

There is a mobile shutter (red in the picture), so no need to add a grill blocking :


You have the underbody:


I don't understand why there are so big holes between "cladding rear end" and "cladding axles". These part, "cladding axles" is not flat, it as a double curvature.





Cladding center is not used with the high size battery (77-82 kWh)