Peppersass wrote:But the effect from very long and slow PI by using needle valves or variable speed gear pumps, and the much finer grind required, is often dramatic. I'm talking about 10-20 seconds or more for PI, which can allow grind settings that would otherwise choke the machine (on the order of 4-8 setting marks on my K10 and Monolith Flat.)

This converts the profile into a kind of lever on steroids. After seeing how much easier it is to do light roasts on regular lever machines; I can see how this is true.

Perhaps this is dragging things a bit off topic, but I was curious what my porta-filter saw with respect to pressure ramp up vs the gauge indicated on my Pro-700. The gauge take-off is immediately downstream of the pump, more or less.
The gauge pretty much ramps to 9B almost instantly.
I knew that this ramp up was not indicative of the PF pressure ramp, but how much off was it?
I was surprised to see that the ramp up at the PF was more along the lines of my old Rocket HX vibe machine, that is, quite slow, as measured on a gauge equipped PF.
Obviously (or maybe not?) the gicleur orifice is working as the designers intended, so my previous comment re. installing throttling valves is moot at best.
Has anyone messed about with gicleur orifice dia. to observe its effects on the shot?

Yukonista wrote: Obviously (or maybe not?) the gicleur orifice is working as the designers intended, so my previous comment re. installing throttling valves is moot at best.
Has anyone messed about with gicleur orifice dia. to observe its effects on the shot?

I changed the gicleur on my Vesuvius - and without a change in the profile the pre-infusion time (or the time it takes for the first drop to come out of the portafilter at least) increased when the gicleur had a smaller opening. The following extraction rate/throughput however was higher.

So it took longer for the first drop of coffee to be seen, but the total time more or less remained constant when I went to a smaller gicleur.

Differences in taste/texture were so that I didn't go back (but I can't recall exactly in detail what I liked more).

I have owned Rocket HX machines with both rotary and vibration pumps, and I actually preferred the vibration pump machine because of the way it preinfused a bit longer due to the ramping up of pressure. Could I tell a difference in a blind taste comparison? I highly doubt it.

Rocky

The vibe pump on my Gaggia was still going strong after 7 yrs of daily use. I'm not worried about longevity.
My only complaint is the one on my Expobar Lever vibrates so much the shot glass wont sit still while I'm pulling a shot

ok here is my beginner and different look on rotary vs vibration in the cup.

i have seen the rave about pressure profiling how it start's slowly at 2.5 bar then it raises to 9 bar and then slows at the end again, and when I look at it from my novice eyes that's exactly what vibration pump does anyway, doesn't it?
it gradually raises the pressure until it reaches 9bar even mimicking the pre infusion in some respect with that build up and when you stop it earlier it does it again, so you can mimic the profiling with vibration,

rotary pump is more instantaneous and aggressive with build up making the whole process more of a shock to the puck,
so by this amateur logic I think that vibration pump is a bit of advantage to me...

other than that, i actually like the loud sound knowing that machine works its muscles....but yes, it's like listening to it expecting whether it's gonna break or not...haha

anyhow, can someone actually compare the taste? coz this topic such as all of them are diverted from its original subject very quickly and not answering the main question