[atmosphericM]

My advice is bump that number up to the under $100 range. Check out Amazon for reviews, there were a surprising amount of reviews left by people that used their mics for just this purpose. Off the top of my head, there were some nice Rode shotgun mics that worked well for what you're describing, and then also a smaller Olympus mic that wasn't a shotgun style that would work for being mounted inside or near the engine bay. You'll want a 'shotgun' mic if you're wanting to 'aim' it at an exhaust tip or car to capture the sound. They block out most of the ambient noises that come from behind the camera. Even the traditional type of mic that clips to a shirt can work well, depending on what you're doing, and those are more common thus less expensive. The type of mic needed really depends on your use though. Check out Rode VideoMic line. Also bear in mind the connection type. Phones, etc. use connectors with more contact points. A quick google search will explain what I'm getting at.