Like DeS I was thinking it had to be fake. E.g. the tires rolling up the ramp, the exhaust pipe rotating balanced on the spring, etc. But it seems it really isn't. They just pulled tricks like weighting the wheels to make them roll up hill. Whether there wasn't some other trickery involved, I can't say.
[link|http://www.dailytelegraph.co.uk/news/main.jhtml?xml=/news/2003/04/13/nhonda13.xml|Daily Telegraph] story on it.
Nissan's [link|http://cars.ign.com/articles/385/385397p1.html|The Run] through Prague is neat too, in a very different way.
Cheers,
Scott.