Thanks, the more water = more energy. 10 liter isn't actually enough
. Energy is needed to heat the engine block too. The engine weight is about 100 kg which is mostly iron that has specific heat capacity of about 1/9 of water. Not calculating the oils and such materials.
I would have put more, but the plumbing to the back needs to be of small diameter to stop heat loss. => The pumps cant generate enough pressure to pump all of the water though in time.
The hood is factory insulated... There is also a small factory belly pan. The tank could fit into the engine bay but the box is about 30 liters in size and i would have to make the insulation thinner to make it fit too. There is also the possibility of the styrofoam catching fire when the engine is hot.
The control system as of now is still me
. I can see the temperatures on my gauge and control the pumps manually. I have planned to put a Attiny 85 to do the job for me but I first need to experiment. The pumps run at the same time for now so i don't get a lot of pressure or level change in the reservoir.
As to the cracking issue, the hot water is mixed with the cold water before getting into the block. The picture might be a bit misleading.
The weight increase is still less than 2% of the cars weight so I think it won't affect my mileage seriously. This is also a "luxury" mod because I can start driving almost straight away without waiting for the windows to thaw. And running rich for a few minutes less will surely have an effect.