Hi
@Megan Reeves
First of all, please provide us more information on your car, like software version, as that sometimes makes a difference. Below, I'm assuming 2021.04. Also battery "mileage" and supercharger usage will affect your charging rate.
You will never ever see charges above 150 kW, but you should get close. You can check what others get on
Fleet Charging MAX (Firmware)
I don't see an X P90D in there, but X 90D should be close enough.
Some people suggest that the 90 battery is no longer limited by high supercharger usage (used to be 90 kW max), but it's unclear to me whether that is the case or not.
As you'll see from the graph, 40 kW @ 79% is about right.
The best charging speed will be with a warmed up battery and low state of charge (SoC).
I have a 2016 S 85D. To warm it up at low SoC, I will accelerate by flooring it to about 70mph (speed limit), then regening until about 20-30 mph (depending on traffic conditions). I'll do this 7-8 times while close to the supercharger. I've only had to do this a couple of times, but worked perfectly. I also have the advantage of a hill between 2 roundabouts that's right next to the supercharger. When I did this, I tried charging with 3-4% while coldish. Didn't go above 30 kW. Charged a few percentages, did the high acceleration / high regen "procedure", came back with about 4%, got the max for my car at the time of 118 kW. I did have the navigate to supercharger on, but not sure that did anything as it was only a few minutes that it was on before returning.
As always, your results may vary. And be prepared for the acceleration at low SoC to be sluggish (totally normal). If the power limit goes too low, your battery might be uncalibrated / unbalanced and your car might shut down, so first try this at a higher SoC than what I did.
Hope that helps and congratulations on your purchase!
tl;dr: Repeating high acceleration followed by high regen at low SoC with navigate to supercharger on will get your battery quickly warmed up. Do this while close to the supercharger.