Topic: slow start with several engines

I am developing an application with several modules, each module that needs to be an Engine (http://railscasts.com/episodes/277-mountable-engines).
In this case, will be around 100 to 300 modules scaffolds with an average of 10 each.
I performed some tests creating the 300 engine and a common application to include them.
I did the test with the 100 and 300, but is very slow to start the application.
Does anyone know anything to solve this problem? Thank you.