Frame rate low and jumping in daydream project (Google VR)

Hi,
Recently i start to migrate my project to google daydream and when i try to run in Nexus 6p ("The Nexus 6P is the only phone supported as a headset phone for a Daydream development kit at this time" say google in https://developers.google.com/vr/concepts/dev-kit-setup) the frame rate are jumping between 45fps - 60fps, this is very unconfortable to final user.

I read the documentation to unity and i can't improve the frame rate, i think don't use the correct setting because i don't specific in any sites i develop to daydream and not to cardboard vr.

Any idea to help me?

thanks