...is still very accurate for most vapers.

Okay, yeah, agreed. I think we're saying the same thing. I just worded it poorly.
These single-value TCR mods (like the RX) have to "tilt" that linear graph so that the sweet spot in accuracy is happening for most vapers (higher resistance builds).
So, what I was calling the "TCR" not changing for a given material really should have been worded "a proper, accurate TCR curve" not changing for a given material.
But a curve is not what we're dealing with on the RX200...it's just a single value inside it (I'm pretty sure)... so, you're right, the single value TCR does have to "change" (tilt) for dual.
In fact, I think this solves the mystery of the "dual coil" settings in some mods.
Because those mods have that linear TCR, and therefore aren't as accurate at halved resistances, they've created a workaround, a "hack" (a dual coil setting), that shifts that linear TCR graph to better work at lower (a.k.a. "dual") builds.
If this is true, I have newfound respect for Evolv's breakpoint curve approach. And newfound disappointment for how kludgey those "dual coil" settings are. But it least it solves the single-value TCR problem.
My brain hurts. I need a drink (and a vape).

Great report of very bad news. Whatever.... $44.95 flushed. I'll try SS on the POS and report back. Expecting delivery in a fee days unless Santa gets in the way.I recreated your build to within a hundredth of an ohm (.18).
Confirmed.
You don't have a defective unit. The RX200 doesn't seem to be well-optimized for dual TC coils (at that low of a resistance).
Temperature Protect, even with good airflow over the coils and snug (but not too snug) cotton, was triggered at 20 watts at 400F.
I was able to avoid the TP message at 20 watts at exactly 550F.
(20 watts was of course not enough to drive a build like this, it was just a test to see when TP would not be triggered.)
But, Temperature Protect doesn't seem to be a brick-wall limiter. Keeping it at 550F and upping the wattage to 45 watts was then producing a denser vape.
Going up to 60 watts seemed to get slightly denser, but there were diminishing returns above that (at 550F).
I was able to get a warm, more cloud-chasing vape at 600F, 75 watts, but this would not be enough for the true chaser (which is not me).
I then removed a coil, let it cool, reattached for "new coil" and the remaining single coil was delivering plenty of vapor in the below 500F range.
Conclusion: The RX200 is not optimized for dual TC coils (at these lower resistances).
Wismec should add a "dual coil" option in a firmware update, like some other mods have employed, to address the raw physics behind this issue.
Or, just deal with the lower resistances better, in general (it may not need to be a "dual coil" setting).
However, I think a flavor-chaser would still find a range that works with dual TC coils. 580F would have been fine for my taste.
In the meantime, I suspect a slightly higher resistance build (maybe dual 3.5mm 10 wrap) would work better.
Also, for what it's worth, this same build (single coil after I ripped one out) on my DNA200, same settings, was delivering an almost identical vape as the RX200. I should have tested when both coils were in, but didn't think of it.
The adjustable tcr update we have been hearing about will end this issue.....adjust the tcr a couple points higher for dual or twisted wire builds....easy peasyGlad to have helped at least remove the "defective unit" concern.
Regarding higher resistance, I think so, because it's not a raw power issue, it's just a TCR issue. A higher resistance build might fall within the sweet spot of the temp range better. Not sure though, would need to test.
Great report of very bad news. Whatever.... $44.95 flushed. I'll try SS on the POS and report back. Expecting delivery in a fee days unless Santa gets in the way.
I don't mind vaping ti in the .25 ohm range. Put the heat and watts on it and go.
Indeed. Its a great mod, that does what it is designed to do very well (see my temp probe report earlier [emoji14]).....and we know an update is coming for tcr adjustment, just dont know when.....that will make this an almost perfect mod IMOPOS?
You crazy..
Indeed. Its a great mod, that does what it is designed to do very well (see my temp probe report earlier [emoji14]).....and we know an update is coming for tcr adjustment, just dont know when.....that will make this an almost perfect mod IMO
Sent with one hand, the other is busy vaping.
I had read it in reddit....a reply from a joyetech rep that said they were "working on" a tcr update
Sent with one hand, the other is busy vaping.
Firmware is updated. Tried a new set of Ti coils. 3.5mm ID , 5-6 wrap 26awg. .17ohm.
Set to TC in TI mode. 4 clicks to set watts low. Ive tried 20w....still temp protection, went all the way down to 1w lol.... wouldnt get up to temp. Played around with wattage....it either doesnt get hot enough to vape or it goes into temp protection and stops firing instantly.
A buddy at work got his rx200 today, he tried his in TC with Ni wire.... he has same exact issue.
What a waste.... i should of went with the fuchai. I wanted this for my first TC mod and it only works in power mode.
Also....battery life isnt that good.
Using a married set of new lg he4's it barely makes it a whole day of moderate vaping at work.
I really love the feel of this mod and it works great in power mode.... ive tried 3 different Ti builds using Unkamen wire. It always hits "temp protection" and wont fire at all. Same exact issue with buddy at works rx200 bought from a different seller and using Ni
A .14 titanium Clapton dual coil in an Aromamizer RDTA works perfectly for me. Will do about 70w with a hard enough draw.I recreated your build to within a hundredth of an ohm (.18).
Confirmed.
You don't have a defective unit. The RX200 doesn't seem to be well-optimized for dual TC coils (at that low of a resistance).
Temperature Protect, even with good airflow over the coils and snug (but not too snug) cotton, was triggered at 20 watts at 400F.
I was able to avoid the TP message at 20 watts at exactly 550F.
(20 watts was of course not enough to drive a build like this, it was just a test to see when TP would not be triggered.)
But, Temperature Protect doesn't seem to be a brick-wall limiter. Keeping it at 550F and upping the wattage to 45 watts was then producing a denser vape.
Going up to 60 watts seemed to get slightly denser, but there were diminishing returns above that (at 550F).
I was able to get a warm, more cloud-chasing vape at 600F, 75 watts, but this would not be enough for the true chaser (which is not me).
I then removed a coil, let it cool, reattached for "new coil" and the remaining single coil was delivering plenty of vapor in the below 500F range.
Conclusion: The RX200 is not optimized for dual TC coils (at these lower resistances).
Wismec should add a "dual coil" option in a firmware update, like some other mods have employed, to address the raw physics behind this issue.
Or, just deal with the lower resistances better, in general (it may not need to be a "dual coil" setting).
However, I think a flavor-chaser would still find a range that works with dual TC coils. 580F would have been fine for my taste.
In the meantime, I suspect a slightly higher resistance build (maybe dual 3.5mm 10 wrap) would work better.
Also, for what it's worth, this same build (single coil after I ripped one out) on my DNA200, same settings, was delivering an almost identical vape as the RX200. I should have tested when both coils were in, but didn't think of it.
In which way do dual coils change the tcr? The material is the material, the number of coils doesn't matter.Problem is that with duals you are changing your TCR...... No way around it unless you have the ability to adjust the TCR directly (crosses fingers).
My eVIC VT worked ok with twisted kanthal and ni200 or with ni200 duals, but it just wasn't the same without some moderate to major temp adjustments.
You have to consider what TC is for. To prevent dry hits from single coils of materials that the device is calibrated for. You deviate out of this specification and welcome to uncharted territory.
0.02 and best of luck.
The difference you're seeing is due to initial resistance, not due to number of coils. In terms of percentage the resistance increases equal.View attachment 515956
Baseline 0.3 ohm single ni200 coil at 20 degC.
FWIW the ni200 coils I usually roll are around 0.12 ohm each. Just used 0.3 ohm for graphing purposes.
Single coil nets about 0.438 ohm delta from 0 to 300C
Dual coil nets about 0.234 ohm delta from 0 to 300C
Assuming perfect matching coils. Perfect wick saturations. Perfect coil heating.
This is a linear temperature/resistance curve for ni200 with a TCR @ 0.0052. Could be off some but is a rough guesstimate.
Great report of very bad news. Whatever.... $44.95 flushed. I'll try SS on the POS and report back. Expecting delivery in a fee days unless Santa gets in the way.
I don't mind vaping ti in the .25 ohm range. Put the heat and watts on it and go.

I wouldn't worry about it too much. I'm using dual SS coils in TC on my MT RTA and the RX200, and it works well. I have to set the temp up about 30F from where I am at on a DNA200 with the same build, but I figure that is most likely due to a different TCR vs what I have set on my DNA200.0 chance.
And the Aromamizer is probably the easiest tank to wick, all that matters is the cotton is fluffed.
And that's disappointing, I have an RX200 otw and was planning dual SS coils in TC in my Aromamizer. Hope they release an update soon.