Coil Diameter Pros & Cons

[DAVEAPER]

I've been vaping a few years and have recently started using box mods and rebuildable atomizers. (No mechanicals....)

Please educate me to the pros and cons or benefits of using small diameter coils versus larger diameter coils. For instance, would it produce more flavor to build a 3.5mm or 4mm ID .7 ohm coil with 28 gauge or use an additional wrap or two and make it 2mm or 2.5mm ID?

Which is generally regarded as being better?

 

[State O' Flux]

For a known net resistance, as determined by wire gauge, wire length and parallel coil count - regardless of the diameter and individual coil wrap count - the coil "surface area" remains the same, as does the wattage required to produce a desired radiant coil temperature ("heat flux").

Where it does matter, is in the wick, and it's cross-sectional "exposure" to heat. Small ID coils rapidly heat through and through the wick, and if the heat flux is high enough, and/or draw is long enough... will vaporize juice all the way to the wick axial center line... within the lengthwise wick-in-coil.

Larger ID/shorter length coils may take a longer amount of time ("heat capacity") to vaporize the same volume of juice... that time may be counted in seconds, but it's still added time, so if you start your draw as soon as you hit the button... for a given time, you may not get the same vapor density/flavor as you would with a smaller ID coil. within the same time period.

Flip side... you may have a much greater likelihood of dry hits with a large ID coil. Again, a variable that includes your personal vaping habits.

Think in these terms... first, know that there is always an optimal build for any given available wattage, and an optimal wattage for almost any build.
The coil must physically fit the atomizer and align well for adequate capillary function... other than that, you need to provide a minimum wattage to support the resistance/coil gauge/number of coils in parallel... to obtain a desirable heat flux value as well as heat capacity value.

More information about heat flux and heat capacity can be found in my second sigline below... to be used with the Steam Engine coil modeling program.

 

[Exchaner]

I am one of the few on this forum who likes his vape at 2.2 ohms and above - usually with 32 gauge wire and 2mm ID. Recently tried lowering it to 2 ohms using 28 gauge wire and 3mm ID and experienced first hand what State mentioned above. My lag time almost doubled. Had to take at least 2 prime puffs before I could even feel anything despite the lower resistance. But then the tape felt a lot harsher - so much that I had to go down to 5 watts. Checking the Steam engine calculator, the indicated heat flux was a paltry 44 mw. I was also surprised that the calculator indicated my total wire length at 111mm. So here is the question, is there an error on the calculator's part? And the second question is, I have vaped at 1.5 ohm with disposable atties with no harsh effects. Why am I experiencing such harshess at 2ohms with a kayfun? And BTW, I am using the Kayfun at half my regular nic strength.

 

[State O' Flux]

I am one of the few on this forum who likes his vape at 2.2 ohms and above - usually with 32 gauge wire and 2mm ID. Recently tried lowering it to 2 ohms using 28 gauge wire and 3mm ID and experienced first hand what State mentioned above. My lag time almost doubled. Had to take at least 2 prime puffs before I could even feel anything despite the lower resistance. But then the tape felt a lot harsher - so much that I had to go down to 5 watts. Checking the Steam engine calculator, the indicated heat flux was a paltry 44 mw. I was also surprised that the calculator indicated my total wire length at 111mm. So here is the question, is there an error on the calculator's part? And the second question is, I have vaped at 1.5 ohm with disposable atties with no harsh effects. Why am I experiencing such harshess at 2ohms with a kayfun? And BTW, I am using the Kayfun at half my regular nic strength.

Some of what you've stated makes sense... but I'm not clear on what you're using for a power supply. Is this a single 28 gauge coil, approximately 111 mm in length, 10/9 wrap on a 3mm mandrel for 2.0Ω even?

If so, and if you're "forcing" 40 watts with a regulated mod... then your heat flux is "very warm" 355 mW/mm2.

If you had an unregulated mech, with the above build, your wattage/current would be 8.8 and 2.1 respectively. What I'm saying here is that at 4.2 volts, your Ohm's law calculated wattage should be 8-9 watts.

This is an excellent example of why you shouldn't vape high resistance atomizers with a mech mod, and why mech mod users prefer low resistance... resistance determines wattage (via the constant of fully charged mech battery voltage at 4.2V), and by extension, heat flux.
Coil radiant heat, as a product of the Ohm's law formula where (V² ÷ Ω = C) volts squared divided by net resistance equals wattage... is pitifully low.

Just so we're on the same page here... if you've not read my SE user guide, take a review of it, just to make sure we're, ah'... copacetic. ;-)

 

[Exchaner]

I'm not clear on what you're using for a power supply. Is this a single 28 gauge coil, approximately 111 mm in length, 10/9 wrap on a 3mm mandrel for 2.0Ω even? If so, and if you're "forcing" 40 watts with a regulated mod... then your heat flux is "very warm" 355 mW/mm2.

I am using an Eleaf iStick variable device with a 20 watt capacity. I did a 9/8 wrap on a 3 mm mandrel and My iStick and ohm meter both read the resistance at 2 ohms. With the iStick set at 4.2 volts, the wattage reads 8.8. Heat flux according to Steam engine is 80, not the 355 that you mention. Perhaps I do not know how to use the calculator. Meanwhile I will be reading your SE user guide.

 

[93gc40]

355 refers to being fed at 40watts.

28 awg wire is thicker, takes longer for it to heat up. Now being at 2ohms vs the 2.2 of the 32awg, the 32 should be a bit hotter. BUT the 28 has more surface area and more potential for making steam. Once it gets going may even vape HOTTER than the 32. mainly cause the 32 is easier to cool with juice and airflow.

 

[Exchaner]

355 refers to being fed at 40watts.

28 awg wire is thicker, takes longer for it to heat up. Now being at 2ohms vs the 2.2 of the 32awg, the 32 should be a bit hotter. BUT the 28 has more surface area and more potential for making steam. Once it gets going may even vape HOTTER than the 32. mainly cause the 32 is easier to cool with juice and airflow.

It sure does feel more hot with the 28 - but probably because I lowered the ohms to 2 ohms from 2.2. I am going to make a 2 ohm with the 32 and compare with the 28.

Still don't understand why I can easily vape 1.5 ohms with a small disposable atty but not in my Kayfun. Could be because the disposables use extra thin wire shaped into micro coils. My own coils are not micros.

 

[Libbydude]

I've been vaping a few years and have recently started using box mods and rebuildable atomizers. (No mechanicals....)

Please educate me to the pros and cons or benefits of using small diameter coils versus larger diameter coils. For instance, would it produce more flavor to build a 3.5mm or 4mm ID .7 ohm coil with 28 gauge or use an additional wrap or two and make it 2mm or 2.5mm ID?

Which is generally regarded as being better?

I am relatively new to rba's myself. I have wondered the same things and spent too much time researching it.

It's all generally regarded as subjective. The answers you receive will be as varied and numerous as the orifices of their owners.
I, personally, have found better better flavor using 2-2.5mm coils in a kayfun. I use drippers as well and haven't bothered to seriously venture into anything larger. I am not interested in large amounts of vapor or heat. I just like good throat hit and pure flavor. I use 28awg kanthal, as little JOC as it takes to get the job done and regulated devices

 

[darckeen]

Flip side... you may have a much greater likelihood of dry hits with a large ID coil. Again, a variable that includes your personal vaping habits.

Isn't it the other way around where a small ID gives you a greater chance of dry hit? Would think that large ID allows for thicker wicks which can move more juice to the coil faster.

I've found that one of the more important things for me if is the width of the actual coil. Essentially the number of wraps or surface area seems to create better flavor.

After lots of experimenting my optimal build thus far is: single coil 26g wire 10 wraps on a 7/64 ID, comes in at 1.4 ohms. Gives me a heat flux of 190 at 30 watts, surface area of 155 mm. Good wet vape with great flavor and wicking on a istick 50 with a magma.

I guess if i'm wrong about the wicking and dry hits relation to ID then I should try something with similar flux and more wraps on a smaller ID.

 

[astronomicals]

Isn't it the other way around where a small ID gives you a greater chance of dry hit? Would think that large ID allows for thicker wicks which can move more juice to the coil faster.

I've found that one of the more important things for me if is the width of the actual coil. Essentially the number of wraps or surface area seems to create better flavor.

After lots of experimenting my optimal build thus far is: single coil 26g wire 10 wraps on a 7/64 ID, comes in at 1.4 ohms. Gives me a heat flux of 190 at 30 watts, surface area of 155 mm. Good wet vape with great flavor and wicking on a istick 50 with a magma.

I guess if i'm wrong about the wicking and dry hits relation to ID then I should try something with similar flux and more wraps on a smaller ID.

i didnt get dry hits on macros but I do on micros. However, my experience is pretty limited. My micros dont give dry hits if i allow them some "prime time". If I take a lot of draws in rapid succession im guaranteed a dry hit. The build is 30awg, 1.6mm, 9/8. My macros had a lot of other issues though.

 

[Das Auto]

Where did the op go? Did he disappear? Or was this a Threadjack?? LOL