Factorio Forums

Boilers can only boil steam to 235 degrees, but steam engines require 275.

Mk2 Engines produce 2.1 mW at 275 degrees.
If your boilers only heat to 235, you're running at 85% Capacity.

So your actual max power produced is 1.8 mW (roughly)

But from what I can tell, it works in reverse for higher boiler Temp.
1 Mk4 Boiler heats to 375 degrees
Mk1 Engines use up to 165 degrees

So you can use more Mk1 Engines than the ratio works out for.

I'm doing some testing with it at the moment.


I placed a set up with 10 Engines per boiler, and (while running at game.speed = 20) removed one at a time until the power levels stabilised.
With 0.15 because cold water can't get through to the Engines, there is no harm over shooting the amount of engines to the boilers.
Quite a few of these run at reduced capacity.

For example:
1x Mk4 Boiler and 3x Mk2 Engines run at 6.8 mW
1x Mk4 Boiler and 4x Mk2 Engines run at 6.9 mW

Or,
Mk3 Boiler with 3x Mk2 Engines = 4.5 mW
But if you use 4x Mk2 Engines = 4.9 mW

But there isn't any reduced capacity. The only cost is the resources to make the extra Engine.


I haven't tested any mix/match with different levels of Boiler/Engines in the same setup.
Or combining 2 sets (2x Mk3 Boilers with 7x Mk2 Engines may be more efficient)

Basically...
4 tiers of boilers, 3 tiers of engines.
MK1 and MK1 are tuned to each other, MK4 boiler and MK3 engine are tuned to each other.
This means that the MK2 and 3 boilers and the MK2 engine are mismatched.

I recomend upgrading the steam engine first, then the boiler, because otherwise you end up wasting fuel heating the temperature of the water above what the steam engine can make use of. Fortunately, if you at least go with the MK3 boiler and MK2 engine it's minimal.

The reason I went with the values I did was to try and force you to make descissions between space and efficiency. The maximum efficiency you can gain from boilers and steam engines is 96%.

If you want to do further tests, here's one I sugest:

Place an accumulator next to the steam engine. You only need to feed 1 accumulator from 1 steam engine from 1 boiler.
Accumulator must be fully discharged.
Insert a single peice of coal, burn it, and record the accumulator charge. This gives total fuel efficiency.

Also note: a MK4 boiler can power about 1.9 MK3 steam engines. I have tweaked the numbers a little to make it an even 2, but not released the update yet.

When do you plan to release that tweak that will make MK4 boiler able to supply 2 MK3 steam engines?

yoh1612 wrote:When do you plan to release that tweak that will make MK4 boiler able to supply 2 MK3 steam engines?

I'm starting my Pass two right now (Pass 1, make things work. Pass 2, tweak values, and add basic new features), so the plan was to update it either if the mod needed a critical update (Which it hasn't), or after I've gone through and made sure everything else in the mod makes sense.

I can look at power next if you like, I was actually between mods right now, you could say taking a break. I can make power mod the next one I go through, then release it later today.

Well it isn't a big issue for me.

Okay, I did some calculations and it seems like 2 Mk2 boilers can feed 3 Mk2 engines at a reasonable efficiency. If I'm understanding the math properly, that should produce 5.27 MW (lesser of 2.1MW * 3 * 0.85 for engines vs 3.1MW * 2 * 0.85 for boilers.) You can get another 0.085MW by using 4 Mk2 engines. The Mk2 boilers are 60% efficient, but you also have to consider the 85% thermal efficiency, so I think you still burn coal at 6.2 MW/0.6 or 10.333 MW coal, which works out to 1.292 coal/sec at 8 MJ/coal. If you only go for three Mk2 engines, this means a total fuel efficiency of (5.27 MW / 1.292 coal/s) = 4.079 MJ / coal or 50.99% This isn't much of an increase in fuel efficiency, but you can potentially make your layouts more compact (3:2 instead of 4:2 engine:boiler ratio.) Going to four Mk2 engines only gives you another 0.01% efficiency. I'm not sure if there are any losses as a result of the pipe required to share the steam output from two boilers.

Does the above actually make sense or am I misunderstanding how the power calculations work?

I'm not sure where the 0.85 comes from.

Base game:
1.8MW from the boiler.
0.2kW per unit of water, 165 degrees output, minus starting temperature of 15 is 150.
150*0.2kW = 30kW per unit of water.
1.8MW / 30kW = 60 units of water turned into steam per second, or 1 unit per tick.
Steam engine consumes 0.5 units of steam per tick, or 30 units per second, multiplied by 30MW per unit is 900kW per second.

1.8MW/900kW or 1 unit per tick / 0.5 units per tick both add up to 2 steam engines to 1 boiler.
Temperature is important too.

Okay, to work out how many MK2 engines can be used on MK2 boilers, you need the basic values.
Boiler MK2 produces 3.1MW of heat, and had a target temperature of 235 degrees. Minus 15 is 220 degrees
220*0.2kW means 44kW is needed to produce unit of water.
3.1MW/44kW = about 70 units of water per second.
A MK2 steam engine consumes 0.625 units of water per tick, or 37.5 a second. This means 70/37.5 = 1.8666 steam engines per boiler. at MK2 boiler temperatures you'll also get 1815kW (1650kW from consumed water * 1.1 efficiency) from each MK2 steam engine too.

Also for this maths, you can figure out that, if you had 10 boilers, it can power 20 steam engines, or 16 MK2s. working out how many MK2 boilers that equates to is a little harder, but I know the best ratio to use is 9 MK2 boilers for 16 MK2 steam engines. The numbers actually come out to about 8.6 MK2s = 10 MK1s, but it rounds up to 9 boilers.

Thanks, that's very helpful; I didn't understand how the water/steam and per-tick stuff worked, but that makes sense. I got the 85% from the ratio of the temperature to the ideal temperature (220 / 260 = 0.846). I was basing things on the reported values in the tooltips and trying to work it out from there. In any case, thanks for the ratio; now I just need to see how many MW I can compress into a Factorissimo building. I need a lot to power my ridiculously long chain of Angel's Smelting buildings.