VW ID3 aerodynamics

[JulianEdgar]

If you want to see how to do it with an electric car, look at Vianney's thread:

150 samples per run - not 5! You can also see overall trends in his data very easily.

[Vekke]

Originally Posted by JulianEdgar

Then you have some big problems with your measurement of aero drag changes, don't you?

Katz lists changes in drag windows up/down for a variety of car shapes. In all cases, it's pretty major.

No my testing works fine to show the differences to 0.6% accuracy easy, fast and reliable enough at least me to trust them.

I just drive my windows up all the time. Lowering them down uses more energy as we're proved and the percentage is shown.

[JulianEdgar]

Originally Posted by Vekke

No my testing works fine to show the differences to 0.6% accuracy easy, fast and reliable enough at least me to trust them.

I just drive my windows up all the time. Lowering them down uses more energy as we're proved and the percentage is shown.

The point of lowering the windows is to see if the aerodynamic drag change that is measurable reflects what the literature shows actually occurs when a car is tested in a wind tunnel with its windows down versus up. When referenced against that literature, your measurements appear quite wrong.

Can you please explain how you have come to the conclusion that your on-road testing can show aerodynamic drag changes of 0.6 per cent? I can't see how that is possible in anything you have presented, but since you seem so confident, perhaps you can explain?

[Vekke]

https://youtu.be/QORPe_g0FOA

So 1 celsius change in outside temperature on my test route effects the engergy consumption of the car 0,6% on average. Due notice that at some points even your outside temps stay stabil the tarmac temperatures can still increase which effects (usually linear, but may depend on your tire) your cars tires rolling resistance


How I know the temperature is affecting the results?
On previous tests on summer conditions when temperature stayed constant the results stayed constant.

[JulianEdgar]

Originally Posted by Vekke

https://youtu.be/QORPe_g0FOA

So 1 celsius change in outside temperature on my test route effects the engergy consumption of the car 0,6% on average. Due notice that at some points even your outside temps stay stabil the tarmac temperatures can still increase which effects (usually linear, but may depend on your tire) your cars tires rolling resistance


How I know the temperature is affecting the results?
On previous tests on summer conditions when temperature stayed constant the results stayed constant.

Ok, you've lost me.

If you believe you can show changes of 0.6 per cent in aerodynamic drag, one obvious thing to do is to do back to back tests, with no changes to the car, and ensure the results are repeatable to far less than 0.6 per cent variation.

Can you show me where you have done this?

[Vekke]

One week old setup explained. https://youtu.be/iePbSCjmspg

[Vekke]

15.0kWh @100km/h speed. https://youtu.be/EywBNia5s10

[Vekke]

https://youtu.be/JhcDhwnwU0I

That 2nd run to east was off from start. Almost came to same result still.
5 times 16,4 and one time 16,3=98,3/6=16,38
4 times 14,1 and one time14,2=14,12
--> Average consumption in my test route 15,25kWh

What is the accuracy if you don`t take the temp changes into account?


On todays 100km test result 15,0kWh on more level and smoother road, but there was little wind.

All project pictures can be found here at facebook:https://www.facebook.com/media/set/?...76628169017686

[Vekke]

Originally Posted by JulianEdgar

Then you have some big problems with your measurement of aero drag changes, don't you?

Katz lists changes in drag windows up/down for a variety of car shapes. In all cases, it's pretty major.

https://porschecarshistory.com/wp-co...%20Edition.pdf

Is the famous windows up and down test dokument you are talking about this on page 223?

[JulianEdgar]

Originally Posted by Vekke

https://porschecarshistory.com/wp-co...%20Edition.pdf

Is the famous windows up and down test dokument you are talking about this on page 223?

No, wrong Katz book.