1)
http://www.soundsofnascar.com/
2)
http://audio.mpix.org.uk/lemans2007/2007_lem_fx.mp3
That's from Radio Le Mans (original link, not rehosted so no copyright infringement). ~17 MB, 192kbps stereo MP3, 13 mins in total. Most of the time there is only crowd noise but the whole pack of cars go past the recording point two times. First time (sounds like actual race start) @ 6:50.
Since it has excellent sound quality, you can really max the volume.