[Rails] Rails 3.2 and Streaming using response_body

I am working on a streaming download (CSV) from Rails 3.2 and am coming up
against an issue of the initial page request taking a long time. The
following controller code illustrates my issue:

       self.response_body = Enumerator.new do |y|
         10_000_000.times do
           y << "Hello World"
         end
       end

With the above, the response does seem like its streaming (from a server
than can support it... Unicorn, in my case). That said, before it starts
streaming it hangs for a much longer time than I'd like. If I change it to
the following, it starts much faster:

       self.response_body = Enumerator.new do |y|
         1000.times do
           y << "Hello World"
         end
       end

My understanding is that the response should begin with the first iteration
of the loop, but it seems the larger loops are causing that initial load
time to lengthen. If each iteration is output as it happens, shouldn't it
take the same amount of time to kick off the streaming process, regardless
of how many total iterations there will be???
Here is an explanation of the technique I am attempting. Maybe I am
misinterpreting or missing a step?:
http://facebook.stackoverflow.com/questions/3507594/ruby-on-rails-3-streaming-data-through-rails-to-client/4320399#4320399

Thanks for any insight you may have!