I have a PID from pidkits.com. Their recommended temperature is 109c, but I find many of my shots to be bitter at this temperature. In another post I read that the right temperature should he around where the machine stops flashing steam when brewing. On my machine this is around 102c. I tried a shot at this temperature and for the first time I actually tasted a sour flavor, and all of the flavors where brighter than I'm used to. At 102.5c there was already much less sourness and more balanced flavors. But I haven't run nearly enough shots in this temperature range to verify this. What temperature are you using on your pid'ed Silvia? Are there others here who have found the recommended temperature to be significantly off for their machine? Are there any known differences between Silvia models that could account for this?

I have made a test series using 105, 104, 103 and 106 deg celsius. I did the tests over two days time, using Mauro de Luxe.
Each test starting with a cold machine and flushing during warm up time. 1.2 sec pre-infusion, 2,5 sec wait and 25 sec brewing!

105 had more taste than 104 which had more taste than 103, which was getting duller.
106 deg gave the best drinking experience, but distinct bitterness instead of chocolate in the aftertaste!

I think that with different temp probing equipment and mounting, the temps is not really comparable. But test and find out.

Just so I don't misunderstand anything - Is it a "flash boil" when you hear a hissing sound and have some steam coming out of the group in addition to the water? And when you only see water and some steam, but no sound it is not? And is this known to be a reliable, repeatable and consistent way to find the PID offset on a Silvia? That would be great, because then it would be possible to know for certain exactly what temperature I was running without using additional measuring equipment.

I guess my problem is I have real trouble finding the sweet spot on my machine. I also have trouble differentiating between bitter and sour, so it's really hard for me to tell in which direction I should be making adjustments. I can make pretty good shots, but I can't seem to match the truly excellent ones I've had at good coffeeshops where there is a clarity and separation of flavors that seems to be missing at home. I also get a slight unpleasant aftertaste in the back of my mouth that is hard to get rid of no matter which adjustments I try.

My guests don't agree with me however, and frequently praise the espresso I make and tell me it's some of the best they've ever had. My wife tells me I've ruined coffeeshops for her because the coffee she gets at home is so much better. I seem to be the only one who really find anything lacking in the espresso I make.

The technicalities seem to be in order. I use the B-Vario which should be able to produce a decent grind. I use a bottomless and don't detect any obvious channeling problems or uneven extractions, and I always use high quality fresh roasted beans. So I'm pretty much left with dosing and temperature as the variables that I can adjust. Unless I've actually hit the limits of my machine and should consider an upgrade, but I consider it more likely that the problem is on my end somewhere.

Not sure if it's a good idea to add to an old thread, but here goes. I ended up with an offset of 20 F by taking 200 as the reference point using a digital thermometer in a styrofoam cup that substituted for the basket in a bottomless PF. I then tasted my favorite blend at temperatures (using the PID) from 212 F to 222F (subtracting 20 to get the "real" temperature. (For me, 198 F was best=218 F as the SV on the PID.) The old PID writeups gave a very high SV of 230 F and 225 F which suggests a larger offset. In the end you have to experiment to see which PID value produces the best result.
I suppose to be accurate, and take advantage of roasters' recommendations, we should use a procedure like Jim suggests, but I also don't understand what a flash boil looks like. And I'm not sure the thermocouple probe on the outside of the boiler is measure exactly the same as the water and/or steam coming out of the steam tip. I think you just need a ballpark value to begin your experimentation with a range of temperatures. I asked Chris Coffee about the Alex Duetto and they used 20 F as the offset so that may be a common approximate value.