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  • Classic Pressure?

    Hi everyone

    Just wondering if anyone knows if/how to adjust brew pressure on a gaggia classic?? Thought it might be a good thing to play with to see if I can make any improvements to my shots. No idea what my brew pressure is at the moment as I dont have a gauge... but it cant hurt to experiment, can it?! :

    Ben

  • #2
    Re: Classic Pressure?

    Hi Ben,

    I know Sparky has done a lot of work with Gaggia Classics, and he is the man I would recommend you contact for this sort of info.... just drop him a PM or scout the site via the Search option ,

    Cheers,
    Mal.

    Comment


    • #3
      Re: Classic Pressure?

      Yep I can help with this one. The adjustment is hidden inside the OPV. You first have to identify the OPV which is attached to the inlet of the boiler. The pump feeds directly into it. There is a pipe that comes off the top and feeds back into the reservoir. That return pipe (silicone rubber) is attached to a hexagonal nut that you must remove to reveal the OPV adjustment. Then youll need an allen key (either 3 or 4 mm) to adjust the OPV setting. I used a 270 degree turn anti-clockwise. That lessens the spring tension. I didnt have a pressure gauge at the time, so I used a blind filter basket and calibrated the OPV setting using the return flow rate when the pump is on. It should be about 100 ml in 30 sec. You can check the ULKA site for their pump specs, the flow rate vs pressure curves are there. After you get it about right, you can tweak it until you get what you want.

      The result of my modification was amasingly thick crema, coming out like treacle, sometimes in globs. I know from my Faema Family, that this pressure corresponds to about 8.5-9 bar. This was the biggest difference in the Classic vs Silvia shootout I found. The Silvias higher brew pressure made thinner crema for ristretto pours (30 ml in 30 sec from a double basket).

      I hope this helps.

      Mark.

      Comment


      • #4
        Re: Classic Pressure?

        Thanks Sparky!!

        Thats very useful info there... you are truely a prince amongst men. I dont have any allen keys, so I will have to borrow some from family, but when I give this tweak a go, Ill report back! Thanks once again.

        Ben

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        • #5
          Re: Classic Pressure?

          Well I did the mod tonite... went well, and I got the same results as you Sparky... very thick crema. Shots seem to taste alot "fuller" as well, very happy with the improvement!

          Ben

          Comment


          • #6
            Re: Classic Pressure?

            Group pressure was one thing I never got around to on the Classic.
            Sounds like it has made a big improvement.

            Glad your enjoying it Ben. very happy to see it go to a fellow coffeesnob.

            Craig A

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            • #7
              Re: Classic Pressure?

              Sure am enjoying the machine Craig - very glad to have it thats for sure!! Shes got a good home, thats for sure mate.

              Comment


              • #8
                Re: Classic Pressure?

                Hi Ben,
                Im thinking of doing this mod myself.
                Did you end up measuring with a pressure guage or did you calibrate against the flow return or just "wing it" with the 270 degree turn?

                With the reduced pressure, did you have to make a large change in grind (coarser?) to get back to the "golden rule"?

                Thanks
                Frankie

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                • #9
                  Re: Classic Pressure?

                  Hi there Frankie

                  Id encourage you to do the mod, its quite easy and low-risk as far as I can see (insert usual disclaimers). All I did was use sparkys guide of 100mls in 30 secs flow. First step was the 270 degree turn, but on my machine I was still getting around 280mls in 30 secs!! so more tweaking was needed. One thing I noticed... to get the right spot required very very small adjustment. In one position, I would get 160ml in 30 secs, turn 45 degs and it was 30mls in 30 secs. Makes me think that the setting my machine was on before I fiddled must have been very very very wrong..... which I kinda suspected (hence the interest in doing the mod!)

                  Not sure if I needed a change in grind as I changed blends I was using at the same time, so the change I had to make could have been because of either (or both) of the changes.

                  Hope this helps!

                  Ben

                  Comment


                  • #10
                    Re: Classic Pressure?

                    Thanks!
                    I mainly want to do it because I think my grind is way too fine at the double shot 25 to 30 second "rule".
                    Its getting very close to fine powder and I sometimes notice what I think is some grinds in my cup.
                    The pours also look quite thin when compared to the many videos Ive seen here and there.

                    When you were setting it up - you had the suction pipe in the water tank and the return pipe reattached (after turning the adjustment screw) and pointing at a measuring cup?

                    Im trying to work out how best to do it.
                    I may end up doing it outside or in the shed anyway in case I make a mess.

                    Frankie

                    Comment


                    • #11
                      Re: Classic Pressure?

                      Yep Frankie thats exactly what I did - return pipe into a measuring jug.

                      Good luck and make sure to let me know how it goes!

                      Comment


                      • #12
                        Re: Classic Pressure?

                        Damn! Im busy at work a few days, and look what I miss out on! Im definatly doing THIS mod - tomorrow!!

                        Double checking a couple of things. Is the OVP thingie the RED circle here? Im assuming so, not the blue one right?


                        Also, once youve made the mod, do you test the water flow from the group head for 100ml in 30 - or do you get water coming out of that pipe where the red circle is??

                        Me and my no-mechanical brain.

                        Cheers in advance guys - looking forward to Rich Thick Crema already.

                        Comment


                        • #13
                          Re: Classic Pressure?

                          The OPV should feed the pipe circled in red. Now this picture rings alarm bells. I seem to remember the Carezza not having an adjustable OPV. The Classic set up is quite different with the OPV on the cold water feed to the boiler, not on the steam valve like in your picture.

                          This is a question for Greg Kaan, who knows his way around all things Gaggia.

                          Sorry for spreading possible bad news.

                          OTOH, the pressure mod sure does make a noticeable difference. Ive been using the crema to guide my setting OPV pressures in my other machines. It really works.

                          Cheers,

                          Mark.

                          Comment


                          • #14
                            Re: Classic Pressure?

                            Gday all.

                            My name is Jim and as my post count will show, Im new.

                            Ive owned a Gaggia Classic for approx 5 years now, and I hadnt enjoyed it until last year when I returned from the Coffee Expo held at The Rocks in Sydney.

                            I got some great tips including the need for a grinder for beans instead of pre ground supermarket coffee.

                            Lets just say, since then Ive been hooked.

                            Every day Im trying to perfect my shots and steaming/frothing technique.

                            Ive been reading through the forum for approx 24 hours (with breaks in between) and I can honestly say my shots have improved further.

                            The topic of Gaggia Classic modification has interested me.

                            Does the adjustment change the flow or the pressure.

                            Im ready to carry out the mod, but I just want to make sure that my shots will improve in taste and texture before I do this.

                            Has any one else tried this mod and what results were achieved?

                            Thanks in advance.

                            Jim

                            Comment


                            • #15
                              Re: Classic Pressure?

                              Sorry all.....just another question.

                              Do you start timing the amount of water that comes out from when you turn the pump on or from when the water starts coming out of the hose?

                              Thanks

                              Comment

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