Ive had the Divine Miss S for nigh on two years now during that time I have done some mods along the way. First a Synesso ridgeless double basket then the countersunk centre screw mod. Next up was monitoring the boiler temperature by fitting a thermocouple(gronking). All low cost mods *which worked quite well. Like most Silvia owners I longed for a PID, but which PID to fit between the 2 kit suppliers or roll my own. I felt it was better to stick with a kit, with there matched components designed for the application rather than the DIY approach. Of the two I did not much care for the Aubers mounting position beside the group head, to much going on down there for my liking. That left Jim Gallts PIDKIT as my preferred choice. I did not feel the need for steam control, if Im going stand by the machine to tend the boiler creating headspace by blowing off steam then I may as well just watch the PIDs temp readout, I did however order the shot timer kit and I installed the 1/32 size 935 into a 1/16 enclosure.
AND THIS IS IT
Looks a bit different eh, you see I also desired a preinfusion system shown Here thats what that button is for, the shot timer is used to display elapsed time. Operation is simple press the set button for the shot timer display, press the down button to start the pump there is a second delay before the pump actually starts more than enough time to move the finger down to press and hold in the PI button when the desired PI time has elapsed just release the button and pressure ramps up to 9 bar, timer is currently set to stop the shot at 28 seconds but can be set to whatever. PI pressure is currently set at 3 bar Ive had it down to 2 bar, I can just adjust PI pressure to whatever I want.
UNDER THE BONNET
Lots of extra bits shoe horned into here. A three way fitting is attached to the pump on the end is the original right angle fitting which the original braided hose attaches to, on *the side of the 3 way fitting is the 2 way solenoid then a right angle fitting to the isomac OPV which has the other outlet plugged OPV water line goes back to the tank. On the back wall is the solid state relay for the shot timer and on the right hand side is a small relay to cut power to the element during the shot, more about that later.
The OPV spring had to be cut down to get the pressure down to PI range I couldnt source a softer spring but a local spring works had a identical stainless steel spring to the original so I just kept cutting loops off that till I got down to 2 to 3 bar, the original is still untouched.
Fitting a PID is THE Silvia mod there is so much info out there re the benefits of PIDd Silvias. But it wasnt as straight forward as I thought. Initially I was getting a overshoot not a problem as Jim suggested a parameter change to correct it, Jim tests his PIDs before shipping but I feel our Silvias get hotter quicker with our 230v supply compared to the 110v models, Jim suggested I try the kill relay as it might help as well, so one was on the way. As it turned out the kill relay wasnt the answer as I had to further change the PID parameters to compensate for overshoot due to the increased temp drop, but it remained in place. I felt I was getting better results pulling shots on a falling temperature while using the thermocouple than with the PID, strange, as most are happy with the results after fitting a PID. Jim Suggested the PID would cause a slight temp rise at the end of the shot, and that using the relay to cut power to the element during the shot would result in a slight temp drop, more like the thermocouple I thought. A bit of research turned up This at the end are Silvia graphs showing temp measurements with a kill switch fitted, anyway I feel if 110V Silvias exhibit a temp rise then it will be more so for our 230v machines. So the kill relay has remained.
So thats the story so far, its getting late so Im off to bed.
Special thanks to Jim Gallt(PidKits)
And Renzo at Di Bartoli who supplied the solenoid and OPV
Also a thank you to Mal for his kind assistance[/edit]
I will add more details later on if CSrs are interested