IMO, yeah! I'm sure everyone is aware of the situation. It would be weird, annoying, a lot of nerve, and total lack of class. They would be chatting behind your back for years, plus your parents would probably freak. If they have the extra cash and they are generous, maybe they will offer to help. If not, get it the old School way, work for it. Good luck!
Lets assume no one would think it weird and annoying that you ASKED. I believe it might be weird and annoying if you honestly EXPECTED to receive funding though. You can ask me for money if you want, expecting it from me is another matter entirely. What might really be weird is if you asked and actually RECEIVED enough to buy a satisfactory car especially without any stipulations attached. If that happens, I would like the phone number to your relatives as well. Thanks.
This is such a low budget idea. You would be ignored or you would be told to get off your bum and earn the money. You don't mention paying anyone back -- are you a child inside your head? Why would they give you money? Mommy probably told you that you are a very special boy, but that's not true.