Thank you for your input, Márcio and Cannonfodder.

The injector for the Appia is the same as the Aurellia. I discussed this issue with the tech manager at ECM in Vancouver (love those people), and he mentioned that steam pressure, water level and gicleur RATIO are significant factors towards adjusting brew temperature. I was definitely schooled in this lengthy phone conversation. Here is what I learnt.

Obviously, increasing the steam pressure through the pressostat is an immediate way to control brew temperature. However, if you drop it too much steam pressure/quantity will suffer. Second, adjusting the water level will change the HXs internal temperature (more water in boiler will reduce the temperature in the HX). I am sure there is a balance between water level and pressure that will keep the HX cooler and still produce enough steam.

I knew that the water in the HX circulates through the thermosyphon loup through natural convection. Reading posts about changing the upper gicleur from 2.5mm to 1.75-1.5mm will alter the flow of water through the grouphead when idle (convection) as well slow the pressure build-up.

blade69 wrote:a new flow restrictor that makes the pressure buildup more soft...I have Got Info from a technician at Nuova Simonelli that you Can replace a restrictor controlling the amount if hot water going to the grouphead and thereby reducing temperature with 3 degrees celsius.

I didn't know that when the pump is initiated both lines are pressurized (top and bottom). The cold water from the lower line is mixed with the hot water from the HX in the group head during the brew cycle. The ratio of hot to cold water is determined by the gicleur sizes. 2.5mm:3mm which is stock produces a 45%hot:55%cold while the optional WBC gicleur ratio (which I installed) is 1.5mm:3mm or 33%:67%.

I understand that reducing the size of the restrictor at the hot end (either really, but I only changed the hot end) will reduce the thermosiphon flow, which will create a cooler grouphead. Even though there will be less heat dissipation from the brew water through the grouphead, since the boiler/HX are kept at a relatively constant temperature will this actually cause a significant difference in brew water temp? Even though the water in the boiler acts as a buffer between the brew water and the heating element, is it possible that there can be a significant change in brew water temperature through heat dissipation in the grouphead? I was clearly under the impression that the thermosyphon loop was designed to keep the grouphead hot, and that the huge mass of the grouphead was to keep it hot without much added heat from the circulating water.

What I am really trying to do is to get this machine back to what it was designed to do, brew with water the proper temperature. I understand that all HX machines need a flush routine. However, mine should not need a 12oz flush to even approach a reasonable temperature.

Those are great recommendations Eric. I will check out the accuracy of both my thermofilter and the thermometer the way you described. It makes perfect sense.
I will also take a look for a high quality pressure gauge to check out my steam pressure from the steam wand and relate it to the gauge installed.

Thanks for the great advice.

Troy.

As far as I know, the group at Appia and Aurelia are designed to dissipate heat during the shot. That whay, you have to find the balance so the thermosyphon loop keeps your group at a reasonable temperature and with a small flush it will get to the point you want. During the shot the group head will absorb heat at the same time the HX looses some heat as cold water is entering, that's why the temperature profile keeps flat.

Márcio.