So now that 1.9 has dropped with the new Drain Valve, I found out and experimented with a few settings with it.
Here's what I found out -
The Drain Valves can run on air. No joke, if you can attach them to an intake, you can drain and produce thrust magically.
The Isp of the Drain valve is independent of atmosphere, so its the same on Eve and Vacuum.
The Isp is dependent on the flow rate, but during normal operating ranges, it doesn't vary much.
The thrust generated is dependent on the fuel tank attached, so if you want a higher thrust you need to attach them to larger tank. When I attached just 2 to a Kerbodyne large tank, it shot up in the air, and built up massive acceleration towards the end.
So, to pass the time, I did some tests to prove that the Isp is dependent on the flow rate, by creating a craft to test stuff out. There are two versions. Both comprise of a Kerbodyne large tank, a Remote Guidance unit and 2 drain valves at the bottom of the tank. The second version also included a KAL-1000 controller, the use of which shall be seen below.
The first thing I did was to teleport them to Minmus's flats to test their DV (The new position cheat is very very good, 10/10 Hyperedit actually is worse) and fired the drain valves with a drain rate of 20 (Corresponding to a drain time of 5 seconds and a fuel flow rate of 2880 units/s). This resulted in a delta-v of 107.78 m/s (used F3 and crosschecked using KER and math). Running the numbers (Wet mass - 81,120 kg, Dry mass - 9,120 kg), I found the Isp to be about 5 seconds (5.027s), which matched up with reports from other players I talked to over discord. I then lowered the Drain rate to 10, which created a marked difference in max altitude(14.7 km to 14.2 km), which I initially attributed to gravity losses due to the increased drain time (10 seconds).
The second thing I did was I took the second version with the KAL-1000 editor, and overclocked the Drain rate to be 98161.52 (The track editor has no cap on the curve, so by changing the tangents of the curve, an arbitrarily high parameter can be attained. This bug is stock, no File editing or craft editing was used to change the drain rate, and the same trick can be used to get negative drain rates, or overclock any other parameter like the thrust limiter for example), and fired the drain valves again. This time, I managed to get up to 387 m/s (I used F3 only since I got up to Escape Velocity and hence wasn't able to cross check). Running the numbers on that (Wet mass - 81,130 kg, Dry mass - 9,130 kg), I got an Isp of 18 seconds - a marked improvement.
Of course, in normal ranges, the difference in Isp isn't probably great, but useful to know.
Ofcourse, these results look trash, but considering their powerful exhaust (do you think 2 Ant engines could lift that tank?), their independence from Atmosphere and the fact that even ignoring the overclock boost, they can be used to run on air (apparently the thrust is about 2.5 kN) by draining the intakes, I'd say the new Drain valve is quite OP. You could say its Krakentech, but eh, that's for you to decide.
What else is there to know of the new part? Is there something wrong with my math by any chance, or have I interpreted the results incorrectly? Have I made any other mistakes? Discuss!