This is huge and so so good! You did a fantastic job of coming up with a concept that's scoped well enough to fit into a game jam while also being able to make an absurd amount of content. I adore this game.
A couple things to note though. One, it doesn't seem like the shield does much to protect from the mud. I still got muddied even with the shield up. And two, I'm not sure bombs do anything but hurt me. They certainly didn't slow down my opponents, at least not noticeably.
All that being said, if you give this a few weeks worth of polish and maybe even add in local multiplayer racing, I'd put this up on Steam for a couple bucks. It's that good.