I understand that this is an interesting topic for people with that type of mentality, but at the end of the day, all we are doing is boiling a substance that's pretty volatile to start with...right?. Sometimes I think we lose sight of the practical aspects here.
Yes, we are trying to boil (vape) several substances in our oil that are quite volatile and easily degraded. But that's the point you may be missing,
we only want to boil it: we don't want to combust it or degrade it through pyrolysis. Doing that to our substances transforms them from lovely, tasty, therapeutic compounds into nasty, harmful, foul compounds.
Using TC makes it easy to only make vapor from your oil, and not burn it and make smoke.
Semantic backup: vapor is not smoke
Smoke has vapor in it, and also particulates, carcinogens, tar, etc
Vapor is just one of the forms of matter than nearly any substance can take: gaseous
I can speak for myself and several of the guys here: I just want pure vapor, not smoke
Using your mod in VW mode, or a poorly tuned TC setup will inevitably combust some or alot of your oil, not just boil it.
And your istick 100w can set max watts in TC mode
However, I really don't understand these values as the actually TCR value for pure Ni200 is about 0.006. That means that for every °C hotter a Ni200 wire gets, its resistance rises by (0.006 * <starting resistance>) in ohms. The 245 fits into the range allowed by my Eleaf, but not sure how this values actually equates to the Ni TCR of .006. I need to read the manual again, I think.
At the time I bought my atomizers, Matt said just us Ni setting which in turn sets the TCR value (although I don't know what value is used). Has this changed? Why manually set 245
From what I am told, the wire in DT donuts is nichrome, not nickel. And it does work fine in TC-Ni mode, which, depending on what brand / model / firmware your mod has, can represent a TCR # somewhere between 600-700, IIRC.
DT donuts work fine in TC-Ni mode, but our resident dab scientists fernand and OF have observed with thermocouples and infrared thermometers that the temperatures of our donuts on TC-Ni mode is much higher than what the display says, due to the functional mismatch of our donut's' materials and TC-Ni mode.
We only need to heat our oil to around 320F to vape it, but the wire must get much hotter than 320F to transfer enough heat through the ceramic disc and then to the oil to raise the oil's heat to vaporization range.
TC mods are intended to report the temperature of coil wires, but not how hot it makes your juice. The extra layer of ceramic insulation that we have on our coils helps explain why we need this extra heat to make substantial vape from our oil, and also why the donut+coil seems to work more accurately with a very low TCR that is closer to the titanium range rather than the nickel range.
I hope this makes sense...maybe OF can re-explain this if it doesn't?
Re-edit: we set TCR to 245 only so the numbers we see flashing on our mod during use are more accurate to the actual temp the coil / donut is reaching. I also feel we gain a little bit more fine-control over temps this way vs TC-Ni.
Why would it exceed 1.0 ohms?
Because as they age the DT atomizers increase in resistance. They start out around 0.8 ohms.
I'm not denying what you are saying here outright, but I have never observed this in my usage of dozens of donuts, some of them over the course of over a year. Mine tend to stay very steady, with only the slight variation of different mods measuring the same base differently, within a small margin of +/- 0.02 ohm.
The few "old soldiers" I have that actually did change resistance, actually went down a tiny bit.. no more than 0.02-0.03 lower.
The several instances I have observed of donut cold resistance very quickly going up was clearly from my overzealous and aggressive cleaning / scraping efforts with q-tips or metal dabs tools on the donut itself or the ceramic cup holding it.
Scrape or disturb the donut too much, or twist the ceramic cup too much, a 0.68 base may suddenly turn into a 0.90, or a 0.80 becomes 0.88. Left to sit for a while, it almost always settles back to its original, low resistance.
I can't be certain, but my guess is that this resistance change results from the contact that the wire leads of the donut makes with the metal base being moved/ distrubed / interupted. From making a nice solid contact, to having a less secure metal-on-metal contact.
The wire leads on the 2.0/2.5 donut are not soldered or screwed or firmly fixed to their contact points. Only a weak tuck-in with a silicon gasket holds the wire where it's supposed to be.
Poking around the donut appears to move the wire leads. Sometimes if will short out completely, reading 0.00, but you can bring it back by poking / twisting some more. Most of my donuts will always read the same no matter how harsh I am in cleaning it, others are more sensitive. I blame it on inconsistent assembly at the donut factory in shenzhen.
Matt started out not fully understanding Temp Control and why they'd drop out of TC mode. Meanwhile the technology has matured.
Yup, the emergence of massively available, affordable, functional TC mods on the market magically coincided with the release of the v2.0 DT donut. Matt didn't design these things with TC in mind, but this e-cigg'er technology has readily adapted to us kushers, with our extra insulation and more delicate compounds.
Barely a week goes by now when I don't learn something new about TC, or when I'm not trying to digest new TC mods and features
(and yea, scan back a few pages at the very least people, this thread is complete as far as Im concerned - its got all the info needed, except maybe some more DC discussion..and the off-gassing results) ::Cough:: until V3!
!
Right?
Maybe not alllll the info you need, but pretty damn close!!!
I think we can geek-on about TC stuff forever and uncover new stuff still.
The issue of oil leakdown has not been thoroughly disseminated, and can still be constructively discussed further, i think.
This (tendency to slip out of TC mode) is what keeps killing my efforts to run the DC herb atty in TC mode. Not done 'right' slipping into 75 W VW mode will light up a doughnut before you know you have a problem. No need to take the risk IMO. Stick with the mods that let you set a useful power protection level as a backup.
OF
OF, I'm really getting the idea that you are not reading my posts. Are they too long?
I shared my results of successful, repeated TC on the DC with us all here several pages back.
Erka renewed my interest in this atty, which could have stood for "Dust Collector"
Her idea of pre-warming the atty before switching to the TC mode you want to use is the key.
Try this: I bet you it will work: has nothing to do with high resistance, it seems.
25-35w or so - whatever you feel is appropriate
Start in TC-SS mode - 500F maybe? Hold the button down for 10 seconds, at least 3 times. For a 30 second or so warmup. It should hold TC here.
Immediately Switch to TC-Ti: Around 380-400 is a good minimum temp to start, and you can vape on this mode, although we can surmise the temps we are seeing on the screen has little to do with the temps of our flowers inside the oven
Lastly, after it is warm.
you can go from TC-Ti to TC-Ni, which is presumably where we want to vape on from the beginning? And maybe TC-Ni is the pre-set mode whose displayed temps might be closest to accurate for this atty?
Sometimes you can jump straight from TC-SS to TC-Ni, but other times you must do TC-Ti as an intermediate step.
I have repeated this dozens of times now, and the only way to make it fail is to not pre-warm enough in TC-SS, or to try vaping from TC-Ti or TC-Ni from the very beginning.
I have done this mostly on the pico, but also on the cuboid mini, where I recall seeing hot coil resistance rising to within 1.2-1.3 ohm with little fluctuation. This is clearly within the TC resistance limit of these mods, so I'm thinking the finicky TC performance of the DC is not caused by high resistance, or maybe partially caused.
This is also something I notice on all my TC mods. I get to hold them at arms-length from my face when I use them on any of my rigs so I can see the screens easily. After a fresh load, early in the hit, the watts are higher, and when the donut is more empty it usually cruises along at 7w or so.
but i've done that just to prove to myself the responsiveness of TC 
We're all trying to help you out here, but every single thing you've asked in the last few pages could be easily answered / looked up at:
