Wicking trouble at 150w.

[Bjorhyn]

Heya, folks.

After several months of exclusively using mech mods, I decided to splurge on a Sig 150 to let me experiment with my coils at higher power. With all that wattage at my disposal, I'm suffering from "because I can" syndrome and wanting to see what happens when I vape it at the max.

Typically I'm vaping around 75-100w at .25ohm on my various RDA, and my wicking has been sufficient to keep up with my chain vaping. I tend to use between 70-90 vg heavy juices.
When I've moved up to 125, I can get a good hit or two before I have to let the wick catch up.
At 150w, though, I can't seem to get more than a one-second draw without the wick tasting scorched. Anything past that second, and it's nothing but rotton cotton.

This one is .25ohm 26g (2mm I.D.) parallel coil, with a KGD wick.


I've tried angling the coil, raising the coil, and creating a cloud underneath. Nothing lets me run it comfortably above 100w.

This one is a .25ohm 24g (2mm I.D.) standard dual coil, same wicking method.


I just picked up this the other day so I'm still getting used to the chamber, but I've tried the same things. Raising, lowering, slightly tilting. No luck.
I do know I've got a bit too much cotton in here, but it was my last attempt at getting more surface area for the wick. It's not as snug as it looks.

When I get a new drill, I'll be trying more twisted coils to see if that makes a difference.
In the meantime, do y'all have any suggestions that may make a difference?

 

[State O' Flux]

Heya, folks.

Typically I'm vaping around 75-100w at .25ohm on my various RDA, and my wicking has been sufficient to keep up with my chain vaping. I tend to use between 70-90 vg heavy juices.
When I've moved up to 125, I can get a good hit or two before I have to let the wick catch up.
At 150w, though, I can't seem to get more than a one-second draw without the wick tasting scorched. Anything past that second, and it's nothing but rotton cotton.

This one is .25ohm 26g (2mm I.D.) parallel coil, with a KGD wick.

Hi Bjorhyn...

The above photo shown doesn't match the description... a .25Ω, 26 gauge dual parallel (2mm ID) would have far fewer wraps. Photo typo? ;-)

This photo below does match the description of .25Ω, 24 gauge - 2mm ID.

__________________________________________
​

Anyway... moving on to the more important bit - your issue is extreme "Heat Flux". The heat flux value represents the coil radiant heat, measured in milliwatts per millimeter squared.

Using the Steam Engine coil modelling program (see hyperlink below), with either of the builds described, at a median wattage output of 80 watts, the heat flux is (especially the 26 gauge) quite hot, at 708 mW/mm² and 353 mW/mm² respectively.

To maintain (or reduce) the current heat flux values, but at a higher wattage, you need to either increase the wire thickness, go up on the resistance or change from a dual parallel to a quad parallel build... or a combination of these variables.

For example, at 0.35Ω, using 24 gauge wire and an output wattage of 150w... your heat flux drops to 473 mW/mm². Still quite warm, but closer to the upper range of, what one might consider, normal temperatures.

Using 26 gauge, but a quad parallel build at 0.25Ω, you could deliver a full 150 watts and have a nicely warm, but not a wick cooking excessive, heat flux of 332 mW/mm².

So... take a look at Steam Engine when you get a chance, get familiar with how it works, and start playing with heat flux values.

 

[Bjorhyn]

Hi Bjorhyn...

The above photo shown doesn't match the description... a .25Ω, 26 gauge dual parallel (2mm ID) would have far fewer wraps. Photo typo? ;-)

This photo below does match the description of .25Ω, 24 gauge - 2mm ID.

__________________________________________
​

Anyway... moving on to the more important bit - your issue is extreme "Heat Flux". The heat flux value represents the coil radiant heat, measured in milliwatts per millimeter squared.

Using the Steam Engine coil modelling program (see hyperlink below), with either of the builds described, at a median wattage output of 80 watts, the heat flux is (especially the 26 gauge) quite hot, at 708 mW/mm² and 353 mW/mm² respectively.

To maintain (or reduce) the current heat flux values, but at a higher wattage, you need to either increase the wire thickness, go up on the resistance or change from a dual parallel to a quad parallel build... or a combination of these variables.

For example, at 0.35Ω, using 24 gauge wire and an output wattage of 150w... your heat flux drops to 473 mW/mm². Still quite warm, but closer to the upper range of, what one might consider, normal temperatures.

Using 26 gauge, but a quad parallel build at 0.25Ω, you could deliver a full 150 watts and have a nicely warm, but not a wick cooking excessive, heat flux of 332 mW/mm².

So... take a look at Steam Engine when you get a chance, get familiar with how it works, and start playing with heat flux values.

Interesting!
I was very sure I had used 26g, although it could have been 28.
But it's definitely 2 strands of whatever gauge I used, wrapped 8 times around my 2mm bit, done up for a dual set at .25ohm.

I appreciate the break down!
Looks like I have some learning to do about heat flux. While I do use SteamEngine, it's mostly for the typical wrap/gauge/diameter relationship. I hadn't needed to bother with the heat flux, as my mechs can't ramp up like the box can.

I'll do some experimenting with some 24g, and some quad parallels and report back

 

[Bjorhyn]

Out of curiosity, any changes I should be making to the wicking?

 

[State O' Flux]

While I do use SteamEngine, it's mostly for the typical wrap/gauge/diameter relationship. I hadn't needed to bother with the heat flux, as my mechs can't ramp up like the box can.
No worries... we all started somewhere. ;-)

With mechs, how fast it "ramps up" depends entirely on the wire gauge and resistance. That's called "heat capacity"... just below heat flux. The smaller the number, the faster it will reach full temperature, and the faster it drops off when you release the button.
If you go back and look at your numbers... you'll find some slow (numerically high) heat capacity values.

Out of curiosity, any changes I should be making to the wicking?

On this last question... sometimes it can be hard to tell, but your wick looks to be pretty tight, in-the-coil. Pull-through cotton or rayon wick should pull through the coil with only a light resistance. If it's too tight it tends to restrict capillary action to the wick-in-coil

 

[Bjorhyn]

On this last question... sometimes it can be hard to tell, but your wick looks to be pretty tight, in-the-coil. Pull-through cotton or rayon wick should pull through the coil with only a light resistance. If it's too tight it tends to restrict capillary action to the wick-in-coil

I'll definitely give those numbers a bit more than a fleeting glance!
Heat capacity and flux are relatively new to me.

Regarding the wicking, with the amount I've been using I can stand the mech or box on the table, and tug on the ends of the wicks without toppling them over. I like to think I'm "flossing" the coil.
I do end up vigorously fluffing the ends right outside the coil, which gives it a pretty snug look.

 

[State O' Flux]

I do end up vigorously fluffing the ends right outside the coil, which gives it a pretty snug look.

And that explains it... although I'm not so sure I'd admit to being a "vigorous fluffer".

 

[Bjorhyn]

And that explains it... although I'm not so sure I'd admit to being a "vigorous fluffer".

Bahaha, yea.
I really should proofread before I put anything on the Internet.

 

[Bjorhyn]

Okey doke, trying something new.

I'm tired of owning a broken drill, so I decided to twist some kanthal up by hand.
I tried a few different builds, with a few different gauges, but ripped out most of them because size was becoming an issue.

This one's a .14ohm 24g (2mm I.D.) twisted dual. The hopes with this one was using a much thinker overall gauge, with more nooks and crannies for the juice to flow in.


I'm still not able to run it at 150w very well. I can get longer than the one-second draw I'm used to, but it's very unsatisfying.
Plus side, the flavor and vapor production have massively increased at lower watts.

I think I'm still a little lost on heat flux, as Steam Engine looks to need me to input it. Default seems like 10?
The heat capacity is 105.74 mJ K-1, which seems like coordinates for space travel. I'm not exactly sure what the threshold I should be in is.

Next experiment: twisted 28g, .75ohm. Maybe that will make a difference.

 

[State O' Flux]

Okey doke, trying something new.

I'm tired of owning a broken drill, so I decided to twist some kanthal up by hand.
I tried a few different builds, with a few different gauges, but ripped out most of them because size was becoming an issue.

This one's a .14ohm 24g (2mm I.D.) twisted dual. The hopes with this one was using a much thinker overall gauge, with more nooks and crannies for the juice to flow in.
I'm still not able to run it at 150w very well. I can get longer than the one-second draw I'm used to, but it's very unsatisfying.
Plus side, the flavor and vapor production have massively increased at lower watts.

I think I'm still a little lost on heat flux, as Steam Engine looks to need me to input it. Default seems like 10?
The heat capacity is 105.74 mJ K-1, which seems like coordinates for space travel. I'm not exactly sure what the threshold I should be in is.

Next experiment: twisted 28g, .75ohm. Maybe that will make a difference.

Lets run the numbers, Bjorhyn...

Gauge - 24.
Number of strands in twist - 2
Estimated twist pitch - 2mm (looks like 2mm to me... but a measurement from you would be better)
Setup is - dual parallel coils.
Target resistance is - 0.15Ω (hope you have an accurate ohm meter at that low a resistance)
Wattage applied is 150w

Heat flux is - a nicely warm, but not excessively hot, 276mW/mm²
Heat capacity is - a ridiculously high 113.3. (takes a bit to heat and cool down, does it?)

Moving right along....................... ;-)

 

[Bjorhyn]

Lets run the numbers, Bjorhyn...

Gauge - 24.
Number of strands in twist - 2
Estimated twist pitch - 2mm (looks like 2mm to me... but a measurement from you would be better)
Setup is - dual parallel coils.
Target resistance is - 0.15Ω (hope you have an accurate ohm meter at that low a resistance)
Wattage applied is 150w

Heat flux is - a nicely warm, but not excessively hot, 276mW/mm²
Heat capacity is - a ridiculously high 113.3. (takes a bit to heat and cool down, does it?)

Moving right along....................... ;-)

Ooh, numbers! My favorite.
Sarcasm aside, that's pretty much spot on. I came up with 1.8mm for the pitch, but it could easily be 2mm if I measured wrong.
My meter isn't the best in the world, but I have two I use to cross-reference each other, so I'm confidant about the reading. I appreciate the concern! At least I'm not the only one who cares my face.

It's definitely a warm vape, I have to use all the available airflow I've got.
How do you arrive at that number for flux? Is there a calculation I'm missing? I'd like to be able to do that myself so I'm not relying on you to do it for me.
You came up with a different number than I (or SteamEngine) did, am I missing something there too?
It doesn't seem to take very long to heat up, but it does cool down very slowly.

From that breakdown, it does sound like that coil and wick should be able to support the full wattage, but I'm still not getting the performance I was hoping for. My guess is I'm still using too much wick. I'll pull that one out in exchange for a smaller one, and resist the urge to over-fluff, and see how that goes.

 

[State O' Flux]

Looking back at my numbers, I used 0.15Ω rather than 0.14Ω. At that low a resistance, it can make quite a difference.

Running the numbers again, with 0.14Ω... I get a HF of 296 mW/mm2. Better? ;-)

 

[Bjorhyn]

Looking back at my numbers, I used 0.15Ω rather than 0.14Ω. At that low a resistance, it can make quite a difference.

Running the numbers again, with 0.14Ω... I get a HF of 296 mW/mm2. Better? ;-)

Okay, I feel stupendously dumb.
The little box for heat flux is where I put what wattage I'm using. Took me way too long to figure that out.

296 sounds more like the coil is getting too hot for the wick to keep up, does that seem right to you?

 

[State O' Flux]

Okay, I feel stupendously dumb.
The little box for heat flux is where I put what wattage I'm using. Took me way too long to figure that out.

296 sounds more like the coil is getting too hot for the wick to keep up, does that seem right to you?

Won't know 'til you try, eh? ;-)

In truth, not really that hot. I run .40Ω, 27 gauge dual coils fairly regularly (8 wraps, 1.6mm ID, 5mm leg total) with RDAs and mech mods... Ohms law value for that, with a fully charged battery, is around 44 watts, but more importantly, an HF of 345.

Saying that, a few quick calculations indicate that my "most common" HFs fall into the 250~300 range.

 

[Bjorhyn]

Won't know 'til you try, eh? ;-)

In truth, not really that hot. I run .40Ω, 27 gauge dual coils fairly regularly (8 wraps, 1.6mm ID, 5mm leg total) with RDAs and mech mods... Ohms law value for that, with a fully charged battery, is around 44 watts, but more importantly, an HF of 345.

Saying that, a few quick calculations indicate that my "most common" HFs fall into the 250~300 range.

True that!
I'm all for experimenting. That was pretty much the whole purpose behind getting a box. Well, that and a bit more battery life. But mostly the experimenting. Getting to tinker with the coils and wicks was the last kick in the pants I needed to drop analogs completely. I've lately moved into RTA's because dripping on the go is tough, and that's opened up a whole new world for me.

Still, with the few builds I have, I'm struggling to keep up at 150w. The common denominator are the wicks, I'm generally using the same wicking method each time, so I'm starting to believe that's where my fault lies. Time for more experimenting! I've kept most of the coils I pulled out over the last few days, so I'll have some baseline comparisons.

The current coil does sound like it's in the average operating temperature, at least when looking at what you usually use, and some of the other builds I've seen on the forums, now that I understand a bit more about flux and capacity.

I'll keep ya updated!

 

[State O' Flux]

If you've not tried it, you might want to look into rayon... there's a gi-huge-ic thread on it in this sub-forum. A good bit faster than cotton, capillary action.

As I've mentioned more than a few times... vaping, especially high wattage and/or low resistance vaping does have it's rules - but it remains an "ongoing experiment", where we serve as both mad doctors, and lab rats".

Have fun!

 

[Bjorhyn]

If you've not tried it, you might want to look into rayon... there's a gi-huge-ic thread on it in this sub-forum. A good bit faster than cotton, capillary action.

As I've mentioned more than a few times... vaping, especially high wattage and/or low resistance vaping does have it's rules - but it remains an "ongoing experiment", where we serve as both mad doctors, and lab rats".

Have fun!

I'll have to look into rayon. It's one material I haven't tried.
Was a fan of yarn for awhile.

Agreed! There are times I feel I'm using enough electricity to make my own Frankenstein. Maybe I'll find a mod with "neck" bolts to play with.

You know I will!

 

[granolaboy]

WOW!



I have to say it's very refreshing to see a post titled "Wicking trouble at 150w" that actually got a very intelligent and helpful discussion going (rather than the typical "turn down the watts" and ensuing flaming)

I never knew what that value was for in steam engine. Now I do!

Just so nice to tune in on discussions like these. Bravo!

 

[jersey_emt]

There's some good advice and discussion here. Another thing I would consider trying is stepping up to a larger diameter coil. A 2.5 mm coil will wick quite a bit faster than 2 mm.

 

[Bjorhyn]

WOW!



I have to say it's very refreshing to see a post titled "Wicking trouble at 150w" that actually got a very intelligent and helpful discussion going (rather than the typical "turn down the watts" and ensuing flaming)

I never knew what that value was for in steam engine. Now I do!

Just so nice to tune in on discussions like these. Bravo!

Completely agreed!

Mr. Flux has been a huge help.