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Testing Silvias pressure without a gauge

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  • #31
    Re: Testing Silvias pressure without a gauge

    Yeah Sparky, but why does my Brew Water Temp change during a pour? :P

    Mal.

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    • #32
      Re: Testing Silvias pressure without a gauge

      Originally posted by Mal link=1143622054/15#25 date=1174382808
      Quite apart from a range of other factors, a spring coil does not compress/extend in a linear fashion beyond a small proportion of its overall length (as per Hookes Law), it does so exponentially over its total length. Other things to keep in mind is the resonance of the reciprocating mass including the spring. While it might be possible to control the output of the pump to an output pressure basis of control, unless the full stroke of the pump is maintained flow rates will vary enormously with input frequency. It would be an interesting experiment to undertake though so keep in touch with how it turns out.
      Although youre quite correct that Hookes Law is an approximation, exponential formulas likewise model only a portion of the stress/strain curve. However, since the section of the curve that is typically exploited is fairly linear, this discussion is mostly academic.

      Nonetheless, yes, it would be interesting to see how much of the damped harmonic behavior the designers took into account and to what degree it influences the brewing process. Even so, I venture to say that there are so many variables, the largest ones being the coffee "powder" itself, that the overall effect of the pressure exerted by water is likely negligible. Since I dont design espresso systems, my time is probably better spent on other things.

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      • #33
        Re: Testing Silvias pressure without a gauge

        Fair nough

        Mal.

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        • #34
          Re: Testing Silvias pressure without a gauge

          Apologies for the thread revival, but I just wanted to thank Robusto for the OP. Using this test I managed to diagnose and fix the ailing pump on my Silvia.

          Big props!

          Caff.

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          • #35
            Re: Testing Silvias pressure without a gauge

            While attending the Di Bartoli Home barista course last night, I was lucky to get assigned with the Silvia 2008 at their shop (Great class btw: Thank you!).  I was able to pull a super loaded creama 25 seconds shot with a perfect tasting espresso (unseen from my machine before).  However, when I came home and try to reproduce the same shot on my 2009 model, the espresso tasted the same as what I had before - Bitter and Burnt!!  The grinder setting was the same when I was at the shop, (I took my grinder into the work shop and had beans left over for 2 shots).  Something is not right!!

            Thank you to this thread I was able to measure the pressure setting without having to buy the pressure gauge attached PF.  And correctly as I have predicted, the factory setting was above the 9 bar…. How much over, I have no idea...

            Below is the picture which I believe is the over pressure valve (OPV) – I think so please correct me if I’m wrong!  I’ve tried turning counter clockwise to loosen it, but it feels so tight as if I turn it any harder the whole machine is going to break.  Obviously my spanner is a bit too big for the job as well…

            So, for those that had successfully adjusted their Silvia pressure setting –

            • Is that the OPV nut?  

            • Do I need to wait for the machine to cool down completely before adjusting the screw?  (Heat seems to expand metal making it harder to turn?)

            • When measuring the Pressure, does the temperature need to be at the brew temp or can I just switch the machine on and brew to measure?

            • How did you do it!!!??


            Thanks!

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            • #36
              Re: Testing Silvias pressure without a gauge

              I was able to pull a super loaded creama 25 seconds shot with a perfect tasting espresso (unseen from my machine before). However, when I came home and try to reproduce the same shot on my 2009 model, the espresso tasted the same as what I had before - Bitter and Burnt!!
              Did you replicate exactly what you were taught re temperature control?
              It doesnt sound like a OPV issue to me but I have got to where I am following my on path.
              • Is that the OPV nut?
              Yes
              • Do I need to wait for the machine to cool down completely before adjusting the screw? (Heat seems to expand metal making it harder to turn?)
              I would let it cool down
              • When measuring the Pressure, does the temperature need to be at the brew temp or can I just switch the machine on and brew to measure?
              No, I measure at a cool temp, but the gauge I use is not rated for brew temp.
              • How did you do it!!!??
              With a gauge attached tom the PF and needle valve below to replicate puck resistance.
              If your going to play with the OPV I think you need a gauge to attach to your PF there are threads here describing how to assemble one.
              PS dont take this as gospel its just my opinion based on my experiences.

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              • #37
                Re: Testing Silvias pressure without a gauge

                Back again
                the espresso tasted the same as what I had before - Bitter and Burnt
                Could be a number of things channeling maybe are you using the same tamper and basket that was used at the school?
                Burnt, take a look at this thread Here scroll down to my contribution re temps and times Im still starting the shot between 112 & 114 so try starting the shot 3mins 50 seconds after the brew light goes out and see if that helps.

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                • #38
                  Re: Testing Silvias pressure without a gauge

                  Originally posted by 607F756479777B7364160 link=1143622054/36#36 date=1243150119
                  are you using the same tamper and basket that was used at the school?
                  OH!!! true... they let me use their SS tamper, it was easier to use than my rosewood tamper I think... the basket at the course should be very similar to mine but who knowss.. Im still waiting for the Pullman and the Synesso basket to arrive, hopefully that can change thing a bit..

                  Originally posted by 607F756479777B7364160 link=1143622054/36#36 date=1243150119
                  try starting the shot 3mins 50 seconds after the brew light goes out and see if that helps.  
                  OHHHHHH!!!!!....  Ok, maybe this is why, I temp surf twice before pulling the shot... one was before grinding, then another was before Im ready to pull the shot... waited about 20 seconds after the light goes out and then pull...  Ill try temp surfing only once before grinding tomorrow... Time should be about right when I finish the grinding.

                  Thank you veryyyyy muchhhhh!!!!!  I nearly gave up on this 09 Silvia and thought of put it up for sale. ROFL. I wanted the 08 model instead hahaha....Also the 3 holes steam wand was a real let down comparing to the power I saw out of the old one hole wand!!!

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                  • #39
                    Re: Testing Silvias pressure without a gauge

                    SPL.G where are you?
                    I have a pressure gauge or maybe you could ask Renzo to do the adjustment professionally.

                    Comment


                    • #40
                      Re: Testing Silvias pressure without a gauge

                      Hi TG.

                      Im in the eastern suburb area.... true, maybe I should get it professionally adjusted by Renzo, but was trying to DIY and save $60 after splashing my cash so quickly in the past few weeks on the machine / accessories.  Plus, it sounded easy to just turn the nut on the new OPV...

                      BUT I still cant work out how to get the nut to turn LOL (so darn tight)

                      Comment


                      • #41
                        Re: Testing Silvias pressure without a gauge

                        just a tip - warranty may be voided if you dont do it right ! get Renzo to do it

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                        • #42
                          Re: Testing Silvias pressure without a gauge

                          Originally posted by 382C2A2A303C3B2C3E3E3838590 link=1143622054/39#39 date=1243163631
                          I still cant work out how to get the nut to turn
                          I agree then with dino.
                          Get the professional to do it.

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                          • #43
                            Re: Testing Silvias pressure without a gauge

                            Yep if its under warranty then a professional adjustment would be the best thing. Otherwise Ive got a gauge for hire that should fit any portafilter with a 3/8" thread and get it exact. Details in the Pullman sponsor area.

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                            • #44
                              Re: Testing Silvias pressure without a gauge

                              Greg do you get any flutter with the oil damped gauge?

                              Comment


                              • #45
                                Re: Testing Silvias pressure without a gauge

                                After a bit of research I’ve found someone (from C.Geek website) mentioned that the new batch of Silvia (since 2007) has a factory setting of around 10-11 bar pressure.  (To increase the machine lifetime and to meet some industry standard etc).

                                Anyway, this morning, I Temp surf just once and waited a while before pulling a shot (3.5 mins).. the coffee still taste quite bitter.  So please enlighten me as I’m getting a bit confused now:

                                • Does changing the brew pressure have any effect on the bitterness of the shot or simply the bitterness depends on the brew temperature/over extraction?  (Why / Why not)

                                My thought is it would affect the taste (using my stupid logic), as pushing water through the grind having higher water pressure than the grind resistance would cause the water to flow too fast.  Resulting in over extraction, early blonding, and hence the bitterness?

                                Never thought the learning curve needs to be this high in order to  use the Silvia lol….

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