Stiff shot straight from the trailer

Here's another phenomenon which may be observed in some users' Londinium I machines when they do measurements and see a dip in group temp. For quite a while I've been convinced there must have been air in the TS then, by pushback or any other way like insufficient greasing or just taking apart the hot group to check the lube situation.

A flush of a 'nut bleed' helps get rid of air and when this indeed helped cure the 'dip', I assumed my assumption was right.

Over time I've noticed a different pattern though. My machine, when idling an extended time, can tend to 'dip' in group temp if I pull a shot and then do nothing. There's a certain stiffness in the system. The flow of the TS is there but as everything was hot enough, rather than overheat, the TS slowed down more and more and after the pull it needs some time to speed up again.

Any of 3 possible solutions work here:
1) pull another one
2) do a short flush (as if you need to quickly clean the group screen) or
3) use the Scace to do a short jet/fake pull.

It's like a horse coming from the trailer after idling there for a while on the road. It needs to stretch legs, get going, before going into the ring to jump or do dressage.

In the graph below, you see a long period of idling, then a pull, then a dip and it's healed instantly by (in this case) a Scace pull, then a period of idling and another pull with real coffee with the group behaving perfectly normal afterwards.

Low in the graph you see the Scace, first lying around, then heating up during use. I quickly left it back on the counter again, and locked the hot PF back in, so as not to introduce a 'heat sink' effect of the cold mass of the PF holding the Scace.

I remember Kfir in Israel having developed a habit of a short quick flush after every shot. Although it's not standard, it certainly doesn't hurt the group and excludes the need for a corrective use of it after a long idle time.