It's confusing for sure, real 'can't tell your players without a program' country. Let's see if we can put some of this chaos in order?
First off, Gen 2 is the herb cart. It looks like this:
http://ineedhemp.com/product/generation-2-dc-ceramic-rebuildable-dry-herb-atomizer/
V3 and 2.5 are concentrate carts. V3 is 'rebuildable' (owners can replace the heaters and do other work), V2.5 is glued together and is a 'one shot' deal. V2.7 is a V2.5 with a different MP.
You can run them a couple of ways. If you go in VW (variable power) you have a problem in that it takes energy (heat) to make vapor meaning when that changes (like you stop hitting as hard) the temperature is going to go up since that energy has to go somewhere. It's a bit like picking a gas peddle position that makes your car go a constant 70 MPH despite winds, up and down hills and so on.
Enter cruse control for your car? TCR is cruse control for vapes. TCR uses a property of most metals to sense temperature (instead of say a thermistor like in Solo). TCR is "Temperature Coefficient of Resistance", a number that describes the change in resistance (in percent) for a given temperature change (typically one degree C). The metal used has an apparent TCR of about 2450 parts per million (1/10,000ths of a percent), about 1/4% per degree C. If we start at say .7 Ohms at 20C and want to go to say 200C we need a 180 degree C rise? So we can expect 180 times .245%, a 44% change give or take. Since it's a positive TC (most metals are positive, some materials are negative (like glasses)). A 44% rise on .7 Ohms is an additional .31 Ohms for a total of 1.01. If you had a mod like the Mini or Basic you can watch this resistance reading change as it heats. This change is 'translated back to degrees' and is displayed as the temperature. That displayed value goes up because the sensed resistance goes up. And it goes up at the rate (% per degree C) you told it to expect by the 'm value' you entered. Change that m value and the displayed temperature changes even though the real temperature is the same. Or, conversely, the real temperature changes even though the displayed one doesn't?
Enter TCR mode. Here the mod uses that resistance change to determine how close it is to the selected temperature, therefore how much power it should deliver. Just like you car feeds fuel to the engine trying to get the driveshaft speed (and therefore car speed) to match the target. When a hill comes along it senses the drop in speed and applies more gas. Thus a 300 HP car can be made to say under the speed limit and keep you ticket free. Likewise, TCR mode can keep the temperature from 'running away' and yet provide 'plenty of power' to get to temperature fast.
Your mod has several preset m values, the one for Ni (which you're using?) is generally in the 600 to 700 range (.6 or .7% per degree C). So the mod will 'run hot' with the right number on the display but since the math is off the actual temperature will be higher by a fair bit. That is it will 'misread' the real temperature. It will work, but you have to frig the temperature selected.
You're allowed 3 custom m values. Use any one of the 3 you want. I put 170 in m1 (for big doughnuts) and 245 in m2 (for everything else). All my mods are set up this way to avoid accidents. Just select the m 'channel' appropriate to the load.
Now to powers. If you remove the controls and put fixed power into the V3 (or 2.5) you either 'never get hot enough' or 'get to good vapor in a reasonable time'. Or worse still go overtemp and cook your oil. And again in this mode if it's the right temperature and you hit it hard it will end up too cold. So we pick a base heat that will reach temperature in a reasonable time (say 5 seconds or so?) without overdriving. You don't slam on the gas when the light turns green, right? Well, maybe if you're young and don't know better, but most of us apply power to get to the speed limit without annoying those behind us or getting a ticket for laying rubber off the line. That's what got me to the power levels I suggest. I ran them up and up until I got to 'temperature limit' after a few seconds (with a lightly loaded bowl, since that heat load can confuse things no end.
So that's the scheme. For the small doughnut you tell the mod to expect a 44% rise, display it as a temperature that makes sense to you and hold that resistance value by controlling the power. Automatically, like cruse control. And we tell it 'apply 12.5 Watts until you reach temperature', not the 75 Watts possible.
Confused enough for a Wednesday night? Great, ready for the test?
Here's a page that describes the same sort of stuff in other terms:
http://guidetovaping.com/2016/07/16/what-is-this-tcr-mode/
OF