The flamethrower has something called Preparation range. If you look at them, when an enemy get close, do you notice that it turn towards incoming enemies despite not yet in range to start fireing. This is this preparation range. And the reason it doesen't work is because this preparation range NEEDS to be larger then the range. And this mod affects only the range. Also, ensure that the preparation range and range are a close value since the preparation, if very large, will eat up compure resources since it constantly gets the turrents ready to fire.
anyways. using the ai (free, no need for paid version) i modified the script. Here is the instruction: install something that can open zips and rar, an one that opens lua files. I use notepad++ since it free, and has everything you need, and very fast. As the ai or look online how to find the mod folder. There, look for this file, open the zip, drag out the data.lua file. Open the data.lua and replace the WHOLE text with the following: data.raw["ammo-turret"]["gun-turret"].attack_parameters.range = settings.startup["gun-turret"].value
data.raw["electric-turret"]["laser-turret"].attack_parameters.range = settings.startup["laser-turret"].value
data.raw["electric-turret"]["laser-turret"].attack_parameters.ammo_type.action.action_delivery.max_length = settings.startup["laser-turret"].value
data.raw["fluid-turret"]["flamethrower-turret"].attack_parameters.range = settings.startup["flamethrower-turret"].value
-- Adjust prepare_range slightly above actual range so turret can start preparing
data.raw["fluid-turret"]["flamethrower-turret"].prepare_range = settings.startup["flamethrower-turret"].value + 2
Save (don't close if you use notepad++, since it does NOT automatically save, so ensure you save before closing it), drag that file back from where you got it, and yes, replace it if asked. Start game, if any error for whatever reason it means it's either another mod that infears with this mod (but that should happen even without this change, sooo...) or it means you messed up something and i strongly suggest to ask the ai because you know, i have no IT or mod maker, all i did was follow the instruction it gave me plus telling it what works, what i have, and so on. And yes, now it works with no issues.