Improving the Model 3 Aerodynamics (for range)?

[TexaCali]

You don't need fancy equipment. Just do this test a thousand times for robust data. Satisfying your own curiosity is payment enough, let's go!

LoL! But there is more truth in that statement than many realize. Check this out:

I have a 30 mile test loop that I run - 15 miles out, 15 miles back, run late at night so no traffic, 70mph with Autopilot, reset the trip meter after stable at speed and crossing a set marker, measure at end at another set marker, only run when the wind is clam, tires always at 50 psi, etc, etc. But there is more variation in the data than one would expect:

Run A: 50F temps, climate was off, 245 wh/mi
Run B: 60F temps and had just finished supercharging, left AC on at 68F by mistake, 232 wh/mi

What factor was most important in the variation? Was it the outside temp? The fact I had just finished charging and the battery was warm? Or was it some other factor I completely overlooked? It will take a while, but slowly, very slowly, I'll get the data and have some answers.....hopefully before the Model 3 reaches EOL and becomes obsolete

 

[jackmott]

Doing the test tons of times would be great if these were easy to swap configurations, but they arent.

 

[Pjcliffo]

Note that the drag coefficient is a meaningless and is inherently misleading number which often means the opposite of what you might think it does. The term "coefficient" means that it has to be used in a formula with at least one other number to have any meaning. That number in this case is frontal area.

So the reality is that a gigantic car like the BMW 5 (Cd=0.22) might have 30% more drag than a normal car like the Insight (Cd=0.25) despite the 12% lower coefficient.

And if you made a huge BMW-sized Insight but kept the mirrors and wheels the same, the Cd would likely drop into the teens simply from being bigger - that's why Cd values taken out of context are often opposite of what you'd expect. It's easy to make a big pickup truck with a low Cd but hard to do on a compact car.

That’s why I’m surprised that model 3 has a blunt nose rather than sleek.

 

[Gauss Guzzler]

Unintuitive as it may be, the back of the car typically has more impact on drag than the front. Note how the air flows nicely around the front of any shape.

 

[Pjcliffo]

Unintuitive as it may be, the back of the car typically has more impact on drag than the front. Note how the air flows nicely around the front of any shape.

View attachment 817178

True but put your hand out the window at speed then turn it horizontal the difference is enormous.

 

[jackmott]

True but put your hand out the window at speed then turn it horizontal the difference is enormous.

That changes the frontal area. The nose of the car being blunt (it isn't really blunt, either) doesn't change the frontal area of the car.