I think the Nuova Simonelli Oscar has its OPV on the hot side as well...

Fullsack wrote:For me, it is easier to identify the end of the water dance when I have a single spout portafilter attached to the group.

RapidCoffee wrote:Really? I find it much easier without the PF attached, or with a bottomless PF.

For a second I thought maybe it depends on the machine, but I'm starting to think I just agree with John. With the Vetrano (John's HX machine I believe), I had a great handle on flushing with the bare group as in the video. It was easy to hear and see the water dance. On Valentina, which has a vibe pump, it's more difficult to hear, and about the same to see. I found on both machines the single spout portafilter just muffled the sound and made the end of the dance more difficult to see.

It worked great on the Elektra T1, though. Technically, it didn't actually help identify the end of the dance, it just helped the dance from getting all over the place, without muffling or hiding it. Maybe my machines were just wonky, but I never found the smoothed flow of water out the single spout to be a hugely consistent indication on my smaller HXes... For me they just weren't consistently smooth to flow out the spout even with the water dance well over--they would cover the exit hole occasionally and bubble regardless.

Nicolas,
I was just playing around with it on the brand new to me T1 and agree with you about the end of the dance sound, but there is more splatter without a spout and I agree with myself about the visual aspect of spout vs. bottomless. I haven't tried this out on smaller machines yet.

thanks guys for your suggestions!

I've my OPV now set at 1.2 bar upper limit...and tried the strategy flush for 5 seconds after flash-boil, wait 10 seconds and go...so far I'm getting consistent shots...so this weekend I'm going to play with longer and shorter flushes...

...do I understand well that by flushing less and waiting shorter the temperature profile is flatter and with a longer rebound time there's more "hump"...are there general rules, e.g. a SO favours a flat profile and a blend a humped one...or a lighter roast versus darker?

...surprisingly, if I only flush to end of the "water dance" and lock & go...shots are not burned at all...looking at the naked PF there are no burning signs in the beginning of the shot as well...

...interesting, sometimes when the machine has been idle for a long time there is hardly any flash-boil and sometimes I've to flush for about 10 seconds to arrive at the end of the "water dance"...

I'm convinced that a group head thermometer will make life easier...on the other hand it feels nice to operate the machine intuitively

best regards,
Bas

Just FYI,

You set your pressurestat for the boiler pressure(which is 1.2 as you noted)

The OPV is for Pump Pressure on a Vibe Pump.. and works as a Safety on a Rotary pump.

thanks for your correction...you are absolutely right...my brew pressure is set at 9,5 bar (OPV) and my boiler pressure is at the moment 1.2 bar (pstat upper limit)

Snip...

bas wrote:...do I understand well that by flushing less and waiting shorter the temperature profile is flatter and with a longer rebound time there's more "hump"...are there general rules, e.g. a SO favours a flat profile and a blend a humped one...or a lighter roast versus darker?

best regards,
Bas

That could be a general rule, but more likely it is a point of debate, and some research. Not bad, fourth post and you have located one of the central bones we like to chew.

The first call was that just about any blend would benefit from a flat profile. The number of great shots I get out of the La Peppina, which is temp stable as you can ask for, there could be something to be said for this argument. That same flat profile also pulls some great SO shots.

On the other hand the S27 can give me either 'u' or 'n' shaped temp profiles on a shot, depending on the flush and how long the machine has been idle, but hardly ever flat ones. It's just the nature of the beast.

I find with the larger basket and the faster pressure ramp that I grind a bit coarser and tamp a bit harder than with the spring lever. The coffee that I get while different can be just as good if I can temp surf the same average temperature area as I am pulling from the La Peppina.

To make this long story not so much short, but to get it to go away. The take home is if the average temp of your shot is near the 'sweet spot' for that roast/blend/bean you may like the flat temp taste, or you may find that a bit of wiggle room gives you a more interesting taste.

Have fun messing with the rules Bas.
-Cecil