Moar Steam! Gotcha.
Yeah I see that with the efficiency now. I always assumed that was whatever steam you put in get's converted to KU at 50% efficiency.
One bug I noticed is sometimes when a tool breaks halfway through a stack (like saw etc.) stuff disappears. Either the scrap or sometimes even materials. I can't reproduce it every time though.
Edit2: Forgot to mention that that pic was taken after it was already cooled down. I had it running through almost a stack of charcoal and nothing happened. No explosion either. I fired it up today again and left it running for a good 15 minutes. The engine turned green but the squeezer wouldn't work. On closer inspection I noticed the engine was flickering slightly. The boiler stayed level so all steam was being consumed. The steel steam boiler should be enough, shouldn't it? It produces 64l steam/t and the steel engine takes 64. If I add another boiler to this setup then I'll have an overproduction of steam and one of the boilers will explode.