another_jim wrote:My own limited experience with levers attests to the conventional wisdom of selecting a grind so that an 8 to 10 second, 1 bar preinfusion results in a few drops, i.e. a saturated puck.

Ten second pre-infusion for the Pavoni produces different results than 10 second pre-infusion for the PV Lusso, at least in my experience. Which lever machine/machines are you referring to?

Pavonis, Mcals, and Peppinas all seemed to do best at that grind to dose setting

shadowfax wrote:In fact, I'd be interested to see a graph of the Speedster's pressure ramp-up. How long does it take for that preinfusion indicator to come out fully when you go straight to pump pressure?

Bit rough around the edges, but you get the idea. Front heavy extraction which seems typical with the Nino when I get a bit lazy with dosing.

Cheers, Chris

Wow, that's either a really small gicleur or a really big preinfusion chamber. That's about E61-level preinfusion. I wonder if that's what Kees was shooting for, mimicking his Mirages a little. I can see why you don't bother to preinfuse at line pressure on it.

0.6mm gicleur, chamber looks reasonably big, top left on below photo.

Hahaha, you're doing a "Slayer-like" shot with that drift back down to line pressure at the end.

Using an ExtractMoJo refractometer, I've been measuring extraction yields with and without engaging my Speedster's manual line-pressure preinfusion.

I think a subtle effect results from the fact that, to maintain a normal flow rate, one grinds a little finer when using an extended preinfusion. The finer grind increases the extraction yield at any given brewing ratio.

Practically, what does that mean? Well, it's all up to the barista. As the extraction yield increases, shots tend to go from sour, to tart, to sweet, to bitter. Or, if one keeps the extraction yield constant, preinfusion allows one to pull a slightly more concentrated shot.

We're not talking huge differences, perhaps a change from 19% yield without manual PI to 20% with PI.

Sometimes it also seems that preinfusion makes the flavors in the shot less distinct. It may be "smooth," but not as interesting.

Meanwhile, I don't think the "forgiveness factor" is relevant with the Speedster, since its spring-loaded preinfusion cylinder, along with the Robur's nice grind, are already pretty forgiving.

If I remember correctly (it has been a long time) I was running around 8 seconds of infusion with 2 or 3 bars of mains pressure to fully saturate a 16-18 gram basket. I had a delay on make adjustable relay on my two group Faema. On that machine, it had a positive improvement. I was having problems with off extractions. That tamed the beast and my shots improved quite a bit. When I went to my A3, I had another improvement in clarity and flavor. I had not real extraction problems other than the occasional up-dose which Elektra's dont like. When I did, it reminded me who was boss by squirting me with a spraying shot.

although i hate to admit it, i dont think i can tell a difference on my vivaldi S1 between using the programmable preinfusion or not

maybe thats because im talking about tasting a difference in the context of lattes

I've had my S1V2 for 19 months now, the last 12 with the programmable line pressure pre infusion; currently set to 38psi. As John stated you don't need p/i to get nice pours with the S1. What I've found is that I don't care for what it does to my low dose (13-15g) S/O shots as it seems to dilute/smooth out? too much of the flavor/intensity? as compared to a non p/i shot. For that very same reason I do like to use it with higher dosed(16-21g) commercial blends as it mellows them out a bit & makes them more enjoyable to me. Nothing scientific here just my personal taste experience.

Since I'm drinking mostly home roasted S/O these days the p/i stays off most of the time but I do like having the option to use it when I chose.