I get the Arduino tie, Leo, and thanks for the thought and consideration to pull that in.
You are at least trying to tie a story or meaning to a symbol, which is necessary if it is to have any meaning or value without massive marketing. My question to those voting for simple logos (which are stylish and generated to be instant triggers for brands after massive marketing campaigns); which is what those symbols have to do with EFI, ignition, and DIY engine control? You know, our group project? Catch22. Simple and easy to remember needs marketing. No marketing needs visual info, description, or meaning. All of us here already know what Speeduino is, and simple style is fine for us if we plan to hold the user population at current levels, as it then needs no purpose except to please our eyes. But, we don't have much choice in these options if the logo is to be effective to the uninformed. Nobody said logo creation is easy, the voting is coming to a close, and we must keep in-mind the purpose of it.
PS: It would seem obvious, the most widely known DIY EFI system of global recognition is Megasquirt, which through its development life has used logos including relevant parts to make connection. Injector sprays, injectors, trigger wheels with flames, etc. Connections to what it does. Now that MS is so well known, they can use whatever they want—but not when they started—and they still use the injector spray on all their sites. The designs may have been somewhat geeky, but they served a more important purpose. Examples: