It works thanks!

Thank you for the comments :)

THROTTLE VALVE IN DIRE NEED OF MORE MORE DIGITS

@Aoi Blue: That's a nice theory, but unfortunately it does not work, at least not with how the engine is implemented in this simulator. Unfortunately, the game does not display the water usage, so I have pulled out the good old Cheat Engine and fiddled around until I found the variables that store the water flow (although I don't know what unit it is in) and here's what I found out:

Following this guide, I was able to achieve the following numbers:
Throttle valve: 56%
Water valve: 100%
Temp: 300° C
Pressure: 90 PSI
Speed: 4692 RPM
Water flow: 1.0377

When I try out your method, then I have to open the water valve to about ~30% to keep the water level steady, and I get
Throttle valve: 100%
Water valve: 30%
Temp: 140° C
Pressure: 37 PSI
Speed: ~4000 RPM
Water flow: 0.9986

So it's not a big difference, but your method boils roughly 3.8% less water than the method described in this guide -- at least in this game.

I believe @Aoi Blue is correct because their system maximizes water flow and lower pressure environments will make the water boil faster at the cost of engine efficiency (which doesn't matter if you're focusing on boiling water as fast as possible). The guide's version trades efficiency for slower boiling times and the water flow isn't maximized.

To consume more water you will want the chamber to be at lower pressure.

To do this, fully open the throttle and steam vent, with the water almost off, slowly turn up the water until you are just over 50psi (over that will cool the boiler pan too much.) 

This will consume far more water as it doesn't have the back pressure of tons of steam in the boiler chamber. Notably, this won't get you nearly the RPM in the process, as you are letting off half the steam in the vent.

Gracias por la información amigo

0.1 L / 6 min = 1 L / 60 min = 10 L / 10 h, es el consumo a casi 4.700rpm, no pasar del 55% o el 56 % de apretura de vapor y con calidad al 11.1%,... yo confirmo al 54% 4688.6rpm, y al 55% 4692.6rpm es el maximo que alcance y roza la cifra dada, siento no conseguir la cifra que dicen.... Si tienes un 55% no pases al 57% caera, y si tienes el 56% no pases al 58% caera. Con solo pasar de las 4685rpm esten contentos.

thanks for the comment, I'm happy this was useful for you

4687.9 RPM max here. Thanks b94!