After a few problems with the printer, I’ve finally finished making the control unit and fitting all the components inside; I can say that the car is now working. But there’s another problem: to connect the car’s Arduino R4 to the R3 – which I ended up having to use due to technical issues with the ESP32 – I’ve used a 433 MHz RF transmitter and receiver module that has a very short range, and as I want to fit it inside the casing on both the car and the remote control, the distance is practically zero. So I’ve already bought an NRF24L01 PA+LNA, which is another bidirectional transmitter with a much greater range and comes with an antenna; the next step will be to fit it and carry out the final test before installing the DRS and the casing.