There appears to be no way to set the Request charset.

Although a charset of ISO-8859-1 was specified both in the HTML, and in the jQuery contentType parameter, this form is submitted with: Content-Type tapplication/x-www-form-urlencoded; charset=UTF-8

Use Firebug to check the Request Header, look at the Content-Type.

However, if you apply only a charset to the contentType parameter, you get: charset=ISO-8859-1; charset=UTF-8