It is a mechanical, the resistance is to high to work well I bet at 1.8 its almost anemic. I would suggest anything over 1 ohm is not going to be very productive, in a mechanical the battery voltage is the usage voltage. Our batteries only stay at 4.2 for maybe 10 minutes then slowly goes down.
Meaning each puff you take is getting worse and worse
The recommended range 3.3 to 6 is for a regulated mod