Autoblogging Question

I have a single site and from what I have read, Google likes to see fresh content on a site, so I'm thinking of setting up Auto Blog Samurai. I don't really want the blog to be part of the site though and don't want people to see it from the main landing page.

Can I put a WP installation in a folder and have it churn out keyword related articles without it being linked to the site? Would it work if the blog had links to it from comment spam only, to get it indexed and crawled, with only links back to the main page to link everything together? or would Google see something a bit odd about it?

Is there any way to set this up? Any method at all? I want the content, but I don't really want garbage from it being visible.

Make a sub domain....

How does that work? How does the content get indexed?

Can someone explain that in a bit more detail?