The set 8365 Tuneable Racer has tunability as its main feature, meaning the motor's parameters can be changed by adding, removing or swapping certain additional elements. However, these parts seem to be purely cosmetic, and not in any way mechanically or electronically relevant.
The instructions illustrate their intended functionality:
And similarly with the B-Model:
Based on these images, the functionality of the individual parts seem to vary in different combinations, as the last two setups for the A model hint on
having better performance than
but the B model seemingly has it inverted.
So how does this set work? My current best theory is that there are buttons inside the technic holes used to connect these parts and their states affect the motor's characteristics somehow, but I'd like to know if someone has better insights into its workings.
The first two images for the B model suggest different capabilities for the same setup, which must be an error on TLG's side, or is there something I have missed?
This Polish forum has a review of the set with an image depicting the switches inside the Technic holes:
The text states (as translated by Google):
it can be seen that in the places where the pipes are to be finally inserted, there are buttons that control the engine's operation.
can be tuned using regular pins, using them as jumpers
This eliminates the "rotating pins providing resistance" theory, but I'm still looking for any experimental results, authoritative information or preferably a full analysis of the different combinations regarding speed and torque.