CarPlay/Android Auto doesn’t require a modem in the car. Your phone already has a modem in it.

I wonder if it’s not so much the density/opacity, but rather refraction. Significant difference in density meaning diffraction, and we’re seeing the comparatively dark sky refracted through the exhaust plume?

Would love to see some of the 3d models showing how this all fits together.

I do like how modular the shifting mechanism is in SRAM levers. I’ve seen aftermarket parts available for these sort of 10-11 or road11 > mountain12 swaps. Also easy to remove whole shift mechanism for 1x or singlespeed setups.