As intended I have written an appendix3 to my CVT article - this covers the internal operation of the 4 way valve.
I will post it in the Tech section but I will post here first to allow comments, additions and or corrections. It is a long time since I had one apart but I think it about right.
Im still trying to learn CVT so cant comment on the accuracy of the comment but given Macs work at Volvo Im sure this article to 100% spot on... looks very clear and well explained
thank you mac for another excellent article for the site