PHPFiwa delete range and edit interval

Good morning,

I'm still new in emoncms and I'm trying to build my system. I'm using phpfiwa for realtime values, and phpfina for daily values.

Everything is fine, except phpfiwa use a lot of disk space. I'm interest on a month of values for phpfiwa, but I can't delete a range with this engine. I've read the documentation and searched in forum, but without luck.

Can someone help me to delete a range of values in phpfiwa?

Another question is: i've set up a wrong interval for phpfiwa; basically, it's 30s, and I want to set this value higher. I can delete and create the feed, but, can I edit the interval if I already created the feed?

I want to keep my values if it's possible.

Thank you everyone

Github issue: https://github.com/emoncms/emoncms/issues/265