bluesman wrote:You're describing the benefits I got from using long line pressure PI without flow control. It would be very interesting and helpful to compare the effect(s) of each in isolation using the same machines and coffees to see the relative contributions.

I agree! I think it would take a lot of patience or someone with a DE to pull off the needed repeatable tracking to call this an experiment. My take is that line level preinfusion is great if line pressure is 2 bar or less. If higher, I'd personally go flow control or add a restriction of some sort. Flow control also has the benefit of allowing users to preinfuse thoroughly without plumbing or a flowjet setup.

I can add two things. Line level preinfusion has always sounded great (since I don't plumb) but now with flow control I'm actually happy I don't. The reason is that your line pressure and my line pressure are different so discussing it in a forum might be comparing apples and oranges. The other is that with using a pump for preinfusion I can control the pressure down to a very low level.

I did an experiment that seemed to help my extraction process. I can't see what's going on inside the puck but I have this picture in my mind that if the pressure is only, say, 2 bar then the water will slowly seep from the top of the puck to the bottom over several seconds. This means the coffee at the top of the puck is wet for longer, and the bottom for shorter. Instead, I programmed my pump to run full for 5 seconds then reduce to 1.5 bar for 10 seconds. This means the puck quickly gets wet then stops at the point that the coffee is just coming through the basket. The puck is thoroughly wetted, and then it sits while it soaks and blooms. The 1.5 bar is enough not to de-pressureize the puck (hopefully preventing channeling) but not enough to push much water through the grounds. This sequence makes more sense to me. From there, I do the normal ramp up to 9 bar with a trail-off to 7 bar.

The other observation is that I have been following the dogma of the 25 second shot for years. I'm finding that time isn't as important as I thought. First of all, with the preinfusion routine above the shot is not going to be done in 25 seconds. Plus, a gear pump ramps up slower than a rotary so it takes 5+ seconds to go from 1.5 bar to 9 bar. With another 15-20 seconds for extraction the total gets up to 40 seconds. Whether that is longer by 5 or even 10 seconds doesn't seem to make a difference. Has anyone else seen that time is less crucial with flow control?

I'm finding that time isn't as important as I thought. First of all, with the preinfusion routine above the shot is not going to be done in 25 seconds. Plus, a gear pump ramps up slower than a rotary so it takes 5+ seconds to go from 1.5 bar to 9 bar. With another 15-20 seconds for extraction the total gets up to 40 seconds. Whether that is longer by 5 or even 10 seconds doesn't seem to make a difference."]I can add two things. Line level preinfusion has always sounded great (since I don't plumb) but now with flow control I'm actually happy I don't. The reason is that your line pressure and my line pressure are different so discussing it in a forum might be comparing apples and oranges. The other is that with using a pump for preinfusion I can control the pressure down to a very low level.

This jives with my experience. Only as it happens, I am plumbed. But I don't use line pressure for espresso. My pump is rotary and I still use it through the needle valve for pre infusion.

The other observation is that I have been following the dogma of the 25 second shot for years. ...snip... Has anyone else seen that time is less crucial with flow control?

Agree here too. I've got a coffee I'm working right now where I have done 90s ristrettos, if you include long pre infusion.

Flow control changes a lot of things.

-Peter

MPantani wrote:Instead, I programmed my pump to run full for 5 seconds then reduce to 1.5 bar for 10 seconds. This means the puck quickly gets wet then stops at the point that the coffee is just coming through the basket.

Sounds like that would compress the puck more, requiring a coarser grind. Part of the reason for a low pressure pre-infusion is to be able to use a finer grind without choking the machine. Also, a full 9 bar should take more time to fully saturate the puck than say 4, assuming the flow is high enough with the lower pressure.

After buying my first lever machine I also felt that time was less important. Arguably you can get good shots with anything from 9 to 90 seconds.. but +-5 seconds can still make a difference in my experience, probably more so with faster shots.

MPantani wrote:...your line pressure and my line pressure are different so discussing it in a forum might be comparing apples and oranges.

That should not be the case. Along with many others, I've always believed that every plumbed machine should have a pressure regulator with a gauge in the line - there may be a reason not to use one, but I haven't encountered it. I've always put it after the softener and filter so that the last run of tubing is direct from regulator to machine (passing through a 1/4 turn shutoff ball valve). Manufacturers include a recommended line pressure in their specs, and I follow it. Interestingly enough, it seems that 2.5 bar is almost universally good.

Here's EricS's post on this from 8 or 9 years ago:

"If it were me, I would install [a pressure regulator] and adjust same to produce 2.50 bar +/- 0.25. Also install a shut-off valve (ball valve) as close to the machine as is reasonable. Now adjust your pump to produce 9.0 bar +0/-0.25 and you will be a happy barista. "

Sounds like that would compress the puck more

This keeps coming up in posts. Where does this idea originate? I don't agree that this happens. The puck expands (blooms if you like); I've never, ever seen a puck come out smaller than when it went in dry. Upon starting the shot, the water first displaces the air between the coffee particles. Then the coffee particles swell. This isn't compression of the puck. Water moves less easily through the puck than does air, so pressure at the group rises and eventually stabilizes at pump pressure, given a reasonable grind. I suppose if the grind is so fine as to choke the machine and if the water came in slowly enough that the top layer of coffee particles bloomed quickly while those below remained dry, some compression might take place in the lower strata of the puck. But this is theoretical; I doubt any of us intentionally runs our machine like this. <Mpatani> has simply automated what some non-plumbed e61 users do (me included) manually. Raise the lever for about 5-seconds, drop it to mid-position for a time or until a few drops of coffee come out then re-raise the lever. This is so obvious to me and is backed up by watching my group pressure gauge, that I wonder, what am I missing here?

As a Rancilio Silvia owner, I truly believe a significant upgrade will be a life-changing event, if, like me, you are a true lover of the craft itself! I wound up going with the Decent Espresso DE1+ not only because of true pressure and flow control but temperature control and stability that rivals, and likely surpasses high-end machines such as the La Marzocco GS3 that are way out of my price range! So, for me, it was truly worth the added cost of the ability to control pressure and flow control! However, paired with a good quality grinder, even a simple, relatively inexpensive HX machine such as the Rocket Appartamento will be an amazing upgrade for you; it's all a matter of what you want to do! Best of luck to you, I think you are going to be amazed whichever direction you go in!

All true. Just remember that with DE you get "program and let it run" type of control. The other side of the coin in flow control is "on-the-fly" control. So with DE you program, pull, taste, change program, pull taste, until you like it. With the other kind, you pull, watch flow, adjust as you go, taste.

The big thing that DE brings is data. And very interesting data at that. I have a buddy with a DE. I learn from his data. But I have on the-fly-flow control and prefer it. It's like a convertible car. Happy to ride in one as long as it's someone else's.

-Peter

Nunas wrote:This keeps coming up in posts. Where does this idea originate? I don't agree that this happens. The puck expands (blooms if you like); I've never, ever seen a puck come out smaller than when it went in dry. Upon starting the shot, the water first displaces the air between the coffee particles. Then the coffee particles swell. This isn't compression of the puck.

About puck compression, perhaps it's a poor choice of words, although I believe it does happen to some extent (especially with lighter tamping). The puck normally doesn't expand until after the pull is done, see the transparent portafilter videos.

If you release the pressure after pre-infusion and then ramp to full pressure, sure, there will be a real bloom and expansion.

In any case, whether it should be called compression or not, the puck becomes less permeable if hit with high pressure from the start, as far as I know. Depending on the machine, full pressure for the first 5 seconds might not translate to full pressure in the basket to be fair.