ELR Home   Create recipe   Resource page   My recipes/favorites

Recommend a coil - Asmodus Pumper 21 + Recurve

Hi there,

I got a wonderful present, an Asmodus Pumper 21 and a Wotofo Recurve. I love the kit, and the flavour with the Recurve is so intense… However, I am having problems getting it to work properly. I am getting too much spitback. Have tried different coils, going down to 0.25 Ohms. My guess is that the problem is related to the 21700 battery, too strong for these ohms. I tried using the Recurve in a wattage-regulated mod and I get much less spitback (or even none) at 40w. Perhaps I need to go even lower (0.12 Ohms?)

I would love if some expert here could recommend some solution.

Thanks!

5 Likes

How about something like a simple round wire, spaced, 8 to 10 single wrap, 26 or 28ga, 2.5mm ID coil? :thinking:

5 Likes

Spitback occurs when your e-liquid pools on the coil, being ‘cooked’ or heated rather than vapourised as it should.
It then bubbles and spits - just like a pot of boiling water would.
Things you can try:

  1. Increase wattage
  2. Don’t over-prime
  3. Fire before you inhale
  4. Check the wick
  5. Choose high-VG e-liquids
6 Likes

I use 4.5 wraps of 26/36 SS clapton on a 3mm rod and have no problems. Resistance is right about .2Ω.

.12Ω is getting close to the point where you blow your face off depending on the battery.

6 Likes

Thanks for the suggestions! I’ll come back to let you know how they are working. So far I’ve tried with the coil coming with the Recurve, with tight or loose cotton, and with my own made clapton coil (0.25 Ohm). Overwicking makes it worse, but spitback happens almost always. It only gets better when the battery is half way, what made me think there’s too much power coming in (I have to admit I don’t entirely understand the physics of batteries and resistance).

3 Likes

Maybe you need a coil with more mass. More mass takes longer to heat but also takes longer to cool. Try a larger diameter with more wraps. You’ll end up with a higher Ohms coil but you should be able to stay fairly close to where you original targeted.

Can someone who knows their stuff comment on my statement :stuck_out_tongue_closed_eyes: I may be talking out my arse

5 Likes

Try flat wire maybe? Had a spool of alien claptons that I ditched when I found flat-twisted, bought a bunch of that and flat/round-twisted mix. For whatever reason, alien claptons would pop quite a bit and since switching to flat wire, it almost never happens.

4 Likes

In addition to some of the other thoughts/suggestions above, the very first thing I would recommend is adjust your cotton.

Too much or too loose, and you end up with problems (of one sort or another).

Sometimes it takes a bit to dial in (read as: learn what a new atty prefers/demands. :wink:

If you have tried varying amounts of cotton in the coil, then use whatever worked the best for you, and move on towards adjusting the coil. JMHO.

5 Likes

The one I have is fused clapton. I remembered something that solved this for my wasp nano: using two fused clapton N80 (38ga) in parallel, 4.5 wraps each, 2 mm diameter (0.19 Ohms). It gets a bit noisy but the spitback is much better now. I still get some though, I think 21700 batteries deliver too much power. Indeed, in a wattage controlled mod at 50w I get no spit back at all.

I will give flat wire a try. I think it cannot be the cotton, already played with it

3 Likes

Quick update: that coil I just made is frying my cotton!

3 Likes

A 21700 depending on the make and model could be up to 40A, I think that’s 120W output. I’d try using:
https://www.steam-engine.org/ If you’re not already, and inputting various values until you find something that’s recommended to operate at that high a wattage. I never go above 40w, and prefer 20w, so good luck lol. Your best bet may be getting a low Amp, high MaH 21700.

5 Likes

The Pumper 21 is not a unregulated mech, it has a chip which provides safety features such as low voltage, reverse polarity, atomizer short and a few other things. You still take ohms law into consideration though to determine the output, it does not regulate the voltage output.

I personally love running a mesh RDA on mine at around 0.15 ohms. Haven’t used the recurve in a while but ran it on the Aspire Feedlink squonk mod which is basically the same as the Pumper 21, has a chip with protections but uses a 18650. I ran a multi strand Clapton in that setup, probably around 0.15 ohms as that is my preferred range for a quasi mech.

6 Likes

Disclaimer: I’m no expert and I just started building for unregulated mods.

With the disclaimer aside, if you like the performance with a 50W regulated mod, try building a coil for you 21700 unregulated mod to Target 50W @ 3.7V (3.7V because that’s what you battery supplies for most of the discharge cycle).

Using Ohms law calculator, punch in 3.7V and 50W.

Try 0.27 Ohms, 0.35 Ohms (4.2V @ 50w, see below), and a point or two in between the two(0.31 Ohms)

NOTE: running a 0.25 Ohm coil will have you vaping, starting at 79.56 W and between 54.76 W(see below) . Try putting your 0.25 Ohm coil into a regulated Mod set for 79.56 W and see if you get a similar popping/spitting. Set to 54.76 W and see. I would think you can zero in on a somewhat ideal resistance coil. This is how I will try building in the near term to see if my logic holds. Remember my upfront disclaimer. I’m not speaking from experience at this point.

5 Likes

Thanks everyone, this is very helpful! I’ll play with a regulated mod to find out the best wattage/resistance combination for the recurve, then reverse engineer the coil to use with the 21700 battery. I think I need to buy thicker wire and install one of those apps, look very useful :wink:

4 Likes

Ok, I think I understand now: P=U^2/R. So I got all wrong, if I am getting too much power (watts) what I need is to increase the resistance not lower it!! I’ll try 0.4 Ohms. Thanks again

5 Likes

I like a SS316L 28g parallel 7/8 wrap on 2.5mm or 6/7 wrap on 3mm for slightly restricted airflow single coil rda’s on a mech, ohms around 0.44ish and in the 40 watt range, and smaller gauge parallel wire heat up and cool down quicker, if it’s not a warm enough vape then you can always drop a wrap or add in a third strand.

7 Likes

Well done! :sunglasses:

Sometimes, I’ll do a twisted pair, 28ga @2.5mm, for a nice ridged coil. I won’t have to worry about changing it out for a while; the back and forth of wick changes tends to wear on the leads of a single wrap coil. :confused:

5 Likes

The only time I twist anymore is doing a chain link coil, @Cutlass92 has a tutorial on here somewhere on how to make them, I really like them over clapton coils when vaping something that gunks really bad, the flavor is near equal to a two core fused but easier to clean lol.

I’ve really been into mechs here lately, especially with the apocalypse on the way, next wire order from LV already has some odd gauge wire in it, 25g and 27g specifically, having 24-28g odd and even numbers should allow for very precise builds for mechs.

6 Likes

Just an FYI when I get spit back it’s usually a wicking issue… Too loose mostly… An ez fix might just happen to be the simplist. Try rewicking and snug it up to the point that it bunches on either side as you pull it back and forth. You want it in there pretty tight… I dunno maybe try this before messing with ohms law tweeks. Although if you do a simple .25 diameter 8 wrap of 24 Guage kanthal… you’ll get around .40ish., and coupled with tight wicking I’m sure that’ll solve your issue. Solved mine…! Spit - back sucks!

7 Likes

I am trying that, making the cotton a bit tighter, plus using simple wire (in parallel, 5 wraps… don’t know the awg but this gives around 0.3 Ohm). And is working wonderfully. Very happy!

3 Likes