I didn't want to hijack another thread so I will tell my story here
OK heres the story....
During extraction cold water enters the relatively small boiler. This results in a 6-8 C drop in watertemperature during extraction. My idea was to preheat the incoming water to reduce this drop. The easiest would be to preheat the water before the pump, but after testing this by using hot water in the tank, I gave up this idea. The pump sounded strange working with hot water.
The idea was to use the large flat area on the front side of the boiler to attach a chamber that would hold enough water to get a stable temp during extraction. Since this chamber is placed after the pump it must withstand the high pressure and temperature.
The easies I think was to use an aluminum chamber built out of two halves shown below. The chamber holds 70 ml and is hold together with M3 bolts and aquarium silicone.
The chamber is inserted after the pump and before the OPV. Connections are made with PTFE tubings and pneumatic connectors. (quite cheap actually).
See pictures below.
I had to take away the switch in order to be able to place the chamber on the front side of the boiler. Luckily I had a broken switch that I could use as a dummy to keep track of the position of the cables.
On the frontside of the boiler there is a small edge that I removed to get better contact between the boiler and the chamber. I also used heat transfering paste to get better heat transfer.
The chamber is held in place with a hose clamp (is this the right word ??)
The result is shown in the graph below. Temperatures are measured with a probe on the probe on the top of the coffeepuck.
I should also say that I have already installed a PID to get the start temp right.