Frankly, I had given up on attempting to measure efficiency on my i3 until now. Either the battery thermal management was skewing results, or countless other factors that I could not really control for with how the car manages energy were. In an effort this evening to burn off some charge to verify that my DCFC system actually works (since the only fast charger within 50 miles was just completed last week 2 miles from my house), I decided to do some very informal testing with a throttle stop to that end.
Obviously, pedal travel limiting is the only way to do this, so I used a stack of washers taped under the pedal to limit my top speed to around 70 mph on the flats.
Fortunately the display provides relatively accurate feedback about throttle percentage, so I could see that it would peak and hold at the limit of travel. Doing so, I was able to verify window down drag at about +6% over a distance of just a couple of miles. Frankly, I was surprised to see my top speed drop by 4 mph just from that. Now I can get a little more serious with trying to improve the car instead of attempting to compile annualized data which can swing hugely with varied weather conditions.
I'd thought about doing a throttle stop before, but for whatever reason, just never bothered since nobody else seemed to talk about it.
This is a game changer.