Headala wrote:YEdit: your picture above might be showing a pressure regulator that drops the line pressure down to a safer pressure for espresso machines. I think this would cause pump cavitation if you tried to use this with your current setup, but maybe others can chime in. It depends on the maximum flow of the regulator.
Jake_G wrote:To do what you are after on an FB80 EE using a needle valve, I would install it right at the group. <image>
Which now I see is exactly what your picture shows!
At first the picture you posted had me confused, but now I see where the 4 water connections go:
-One above the needle valve that attaches to the group neck and can travel through the needle valve if the left solenoid valve (2 way) is closed (preinfusion), or it can bypass the needle valve if the 2 way valve is open (full flow).
-Two connections in parallel on the right solenoid valve (3 way brew valve) go to the group (U-turn) or up to the brew pressure gauge. When brewing, the three 3 way sends water from the 2 way or needle valve (depending on state of 2 way valve) and gives you a fairly accurate pressure reading since its after the needle valve but before the gicleur.
-One last connection at the discharge of the 3 way which purges the group like always after you're done brewing.
You would need 2 of these assemblies in order to have preinfusion on each group and the pump would be running the entire time.
As Alan noted, the most simple way to get a lower initial pressure is to set your mains pressure to wheat you want to use for preinfusion (3 bar) and then intercept the wire that goes to your pump to turn it on and put either a programmable "delay on make" switch inline (best to have this switch control a high current relay to ensure it has a long life) to have a consistent duration of preinfusion. I wanted more control with my setup, so I installed a simple rocker switch and I preinfuse until the entire underside of my naked portafilter is saturated. Then I kick the pump on. This takes anywhere from 12 to 25 seconds, depending on the beans, roast level and age. For me, having a set duration of preinfusion wouldn't meet my needs.
Also as Alan noted, this solution does not work if you want to pull a shot on the left group while pre-infusing on the right group. I don't really care on my machine, so i didn't do anything to address that. Long term, I will be going the needle valve route and will have full pressure control over both groups with the pump running.
9coffee wrote:1. In these assemblies, should I install a normal gicleur(0.8mm)?
Because I have already replaced an other part gicleur to 0.6mm one.
9coffee wrote:2. In this preinfusion, does the pressure raise from 3 bar to 9bar slowly or quickly?
Is it depend on adjusting the needle valve?
9coffee wrote:3. Where can I connect the wire of 3 way brew valve to?
Peppersass wrote:I use a high-quality high-flow Swagelok regulator to drop the line pressure down to about 1-2 BAR for long, slow preinfusion on my modified GS/3 (rotary pump replaced with variable speed gear pump.) It works, most likely because the regulator allows a high flow rate. The pump doesn't cavitate, but it's a little noisier. No problems with autofill, even though my Arduino firmware increases the gear pump speed for that. It's much happier at 3 BAR and up, which I use unless I'm pulling Slayer-like shots. [I probably don't need a regulator at all for normal shots because my max well pressure is less than 5 BAR, but it helps smooth out fluctuations in house pressure inherent in a well-based system.]
Note that lowering the flow rate before the pump works for long, slow pre-infusion, but it's not exactly the same as the Slayer, which runs the pump at full brew speed before the needle valve. This causes the pressure to go to 9 BAR almost immediately after the basket fills. In my case, the pressure tops out at 1-2 BAR, then my pump kicks in and raises the pressure to 9 BAR. In a sense my way of doing it is more flexible because I can do a "soak" or change the ramp up curve, but it's not the way a Slayer works.
Also note that putting the pump before the needle valve requires that the pump have a bypass rated for continuous operation (as rotary pumps do but gear pumps do not), or an external OPV between the pump and needle valve to bypass the excess flow. Brew speed is slow enough that it's possible a gear pump won't hit its rated max without an OPV, but it depends on how far down the needle valve is cranked and the brew speed. If I every install a needle valve after my gear pump I'll have to figure that out or use an OPV.
Another issue that's specific to my GS/3 is that the reduced flow rate causes water to flow more slowly through the HX, so it superheats and boils when it hits the cooler boiler water. This causes a few "bangs" in the pipes that are harmless but a little disconcerting. In a GS/3 the needle valve needs to be after the HX.
And remember that I have only a single group. In your case you should have a separate switchable needle valve for each group.
Jake_G wrote:I don't think it will matter at all. The gicleur will work in series with the needle valve to control the pressure ramp while filling the headspace, so leaving the 0.6mm gicleur in place will result in you cracking the needle valve open slightly more so than if you put the 0.8mm back in. Since your pressure gauge is upstream of the gicleur, you won't see any difference after the preinfusion on your brew pressure gauge, but the 0.6mm gicluer will tend to taper the pressure off towards the end of the shot as the puck erodes and the flow increases. The 0.8mm will also do this, but will do so less aggressively than the 0.6mm.
Good question. The short answer is that the transition from 3 bar to 9 bar will always happen quickly, because water is not considered a compressible fluid. Nerd-speak aside, the needle valve controls how quickly water is available to fill the headspace and permeate the puck. By slowing down the water debit, you can slowly compress the air and push it first through, and then out of the puck as you replace the air with water. To Dick's point above, you can do this with pump running and use the needle valve to control how long it takes to reach 9 bar, or you can preinfuse with the pump off and use the needle valve to adjust how long it takes to reach 3 bar. If you go the route of preinfusing with line pressure (like Dick does and I currently do), the transition from line pressure to pump pressure is abrupt no matter how you look at it because all the air is out of the system once you've taken up the head space and saturated the puck with water. There may be a transient response if you leave the needle valve in play, but we're likely talking about 10s of milliseconds to get from 3 bar to 9 bar, depending mostly on how quickly your pump gets up to speed.
The 3 way valve replaces your current 3 way brew valve. It would be wired into your existing harness. It is the 2 way valve that you would either wire into a 3rd party controller like a Sure Shot, or an external switch to control manually.
Jake_G wrote:All this said, bear in mind that preinfusion has a more subtle impact on flavor than you might think. I enjoy roasts that are a deep chocolate in color, but have no oil showing through the skin and I find that preinfusion allows me to enjoy the acidic brightness of these roasts without being overcome by it. It allows for a balance of these fruity varietal notes while maintaining the deep chocolate middle flavors and buttery mouthfeel that I prefer. 90% of getting the flavor you are after is in nailing the temperature and the grind. Pre-infusion is somewhere in the last 5% of the flavor, opening up a balance that temperature alone can't quite hit on my machine. I can get chocolate, while totally masking the varietal nuances by bumping the temp up a few degrees, or I can get overwhelming floral and fruity brightness but no chocolate or body by dropping it a few. The balance point without preinfusion ends up muted, with a nice aftertaste but not much else. Pre-infusion for me is a tool to achieve a layered and balanced flavor profile but it won't fix flavor defects. Good flavor starts with a good bean, processed and freshly roasted well to bring out the best that bean has to offer, freshly ground to the right consistency and brewed at the right temperature. Pre-infusion helps me take a really good shot and make it even more enjoyable to my palate. It won't take a bean or roast I don't like and make me enjoy it.