In my quest to find a decent car motor loop for Trigger Rally, I discovered recordings ofa graphics card and a hard drive from my personal library, which I mixed into a rather weak engine loop.
Also posted at FreeSound.
You might find some of these useful if you want to make a deeper engine noise or need other noises as well:http://soundbible.com/suggest.php?q=motor&x=0&y=0 (my search)
your sound is good but there seems to be a lot of background noise?
hopefully you might find one or some of the links useful :DScribe