How can I protect an official idea from others?

Describe your idea in writing - and you can protect it by copyright registration and/or by filing a patent application. These are US protections only. Each country has its own rules for protection of ideas - so if you are on the Internet - everyone will see your idea. GOOD LUCK!

You keep your idea secret by not sharing it with anyone else. If you have to hire someone to develop a concept or manufacture a part for you, make sure they sign a nondisclosure agreement and an agreement that anything they develop belongs to you before you give them the job. You won't be able to apply for a patent until you can prove that the car you envision actually works as designed.