I was about to open a new thread but since this one is quite recent and my question is pretty simple, I didn't want to pollute the forum more than needed:
What is the real difference between a dual and a single coil build?
Well, the easiest real difference is 2 coils instead of one. Simple as that. What I think you're asking if I read your right is what is the
qualitative difference. Thats a longer answer that is partly subjective, but I will try and address it.
I find the sweet spot is as a prior poster says, .28ga kanthal, 8 wraps for each coil. I use cotton and I am careful not to over wick and I don't micro coil.
If it comes out to around 0.6ohms, you've got the resistance right. Second, you do need a decent mod to power the coils as you don't want a long heat up time. When I use the 7-22 with a fresh battery, it goes up to 22.5W and then drops to around 17W-19W. You can probably look at a chart to figure out the wattage or voltage you need to power that coil setup.
The difference (and I am no engineer either, this is my experience, YMMV), is really surface area. If you get it wicked properly it will give you more surface area exposed to a hot surface, which vaporizes more juice with a single hit. One word of warning, it will cut into your juice supply as you vaporize juice faster with the additional heated surface area.
The result is a higher density and volume of vapor, and possibly hotter. I find it also improves flavor delivery but it may vary from juice to juice. Keep in mind it will also (theoretically) deliver more nic in one pull, so if you're a 12mg'er on a normal setup, you may suddenly find yourself getting a nic-buzz. If you don't like that, dial it back to 8mg or 6mg until you feel you're getting the right amount. Or you may not like it at all, and go back to single coils like some people here mentioned. Vaping is so subjective, when someone asks "why" you do something, its usually to obtain a result that you subjectively enjoy - it doesn't necessarily mean its "good" or "better".
Just to address the hotter. I like a warm vape and I hate getting seared. This has to do with your rebuildable and the mod. My 7-22 and my manhattan are heat sinks. The ZNA30 and the eVics are not. If the tank has good surface contact with a metal mod, it helps dissipate the heat better. I also have a tall drip tip I can use that helps with that, but, it also loses some vapor as it condenses against the longer travel of the inside diameter of the tip.
My latest addition is a Big Buddha which I love for tank size, ease of dual coil build and the sheer mass of the tank as a heat sink - there is just more of it. If I did that build in a Kayfun or the Russian, I have to ensure my mod is a good heat sink or I am using the long drip tip. Again, some of this is subjective but, if you build it and get a hotter tasting vape than you like, those are my solutions.
The nice thing about rebuilding, is if you're organized and patient, you can experiment and find what you like through multiple builds. I keep a build diary and rate it so I can go back to what worked, and more importantly, logged the failures so I don't forget and repeat it.
Most of all, have FUN with it. If its not fun, there are better things to do with your time.
