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Gaggia Classic Pressure Modification

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  • Gaggia Classic Pressure Modification

    Hello there

    This is a short description of how to modify your maximal brew pressure on one of the newer models of the gaggia classic. Apparently the ESE pod certification requires that the machines overpressure valve (OPV) are set to a brew pressure of 11bar. Unfortunately i havent got a manometer, but this is also confirmed by the findings of quite a few tinkerers on the german Kaffee-Netz site and IRC also from people on CG.
    My motivation was that I permanently got a quite acrid taste out of my Brasil Santos (?) beans which should not produce this kind of taste (as they are not at all high grown). Furthermore there was also a really narrow margin between a grind setting which chokes the machine and one which results in a gusher (sometimes even less than one step on my MDF).

    be careful not to tinker on a machine which is running: you may void yourself - or was it the warranty :-?

    youll need:
    - a Phillips head screwdriver
    - 17mm hexagon screwdriver or just a gripper for those who doesnt mind a few scratches on the nut
    - 5mm allen key (=hexagon socket)

    how to:
    - unscrew the two phillips screws on the upper plastic cover (which has the water inlet)
    - before unmounting the cover completly: lift the plastic and the metal plate up a bit and unmount the male/female connectors which is
    connected to the downside of the metal part
    then youll see the OPV (red circle) which is located on the side of the boiler:



    - unscrew the nut with the 17mm hexagon screwdriver (or the gripper) the first few turns, until theres only just some minor resistance noticeable.

    - the remaining turns can be easily accomplished by turning the tube which is attached to the OPV

    then you see the allen nut inside the OPV which can be adjusted to limit the maximum brew pressure:



    use your 5mm allen key to modify the setting of your OPV: thightening (counterclockwise rotation) leads to a higher setting - losening to a lower setting. 1 turn approximately equals 2 bars of maximum brew pressure setting (source: http://www.kaffeewiki.de/index.php/G...til_einstellen)

    Since my modification (I backed it off 1 turn) the margin between choke and gusher has widened quite a lot and Im also able to pull ristrettos without producing an acrid/harsh taste.

    happy modding

    marco

  • #2
    Re: Gaggia Classic Pressure Modification

    Well worth doing for all you Classic owners out there

    Makes for a much smoother and more forgiving shot.

    Comment


    • #3
      Re: Gaggia Classic Pressure Modification

      Hi Marco and welcome.

      As noted - this is a very worthwhile modification to make to the Gaggia Classic.
      If you do a search in the Machines section - there is an old thread there called Classic Pressure.
      http://coffeesnobs.com.au/YaBB.pl?num=1143118905/0
      This thread also details how you can measure the pressure without using a pressure-meter equipped portafilter by measuring the flow against a blind filter.
      With this you can tune the pressure pretty accurately to suit. I think I was running mine around 8.5 bar.

      Oh - and there are also good threads on modding/changing the steam wand and even a PID mod.

      Cheers
      Frankie

      Comment


      • #4
        Re: Gaggia Classic Pressure Modification

        Thanks you both for the kind words and the tips!
        @ frankie I searched for the a thread like you pointed me out to, but didnt find it.. I knew one could determine the pressure by measuring the back flow; but IIRC it gives you only a ballpark value, so I prefered to do the adjustment by taste :P

        Originally posted by gz20tt link=1175171794/0#2 date=1175220683
        Oh - and there are also good threads on modding/changing the steam wand and even a PID mod.
        I saw those ones. Already PIDd my machine some while ago - as I had a chance to do it quite cheaply and I was getting really frustrated by temp surfing-hit or miss-action. but it still lacks of a properly modified steam wand! Ill probably either try out the wand bending or make one on my own like dsc described.

        greets
        marco


        Comment


        • #5
          Re: Gaggia Classic Pressure Modification

          Hello Marco!

          Good mod description

          You have a PID and you didnt even mention anything!!?? Quick take some photos and start a thread so we can all see how it looks and works.

          Ill probably either try out the wand bending or make one on my own like dsc described.
          Yes yes build one yourself

          Cheers,
          dsc.

          Comment


          • #6
            Re: Gaggia Classic Pressure Modification

            Hi Marco,
            Thats odd - the 4th line down in my answer above is the actual link to the thread. Laying your mouse pointer over it and clicking should take you straight there.

            As to the accuracy of the backflow method - I think it is more accurate than you might think - since the flow rates are based on the supplied specs by Ulka. I found that I was getting repeatable flow rates to within 10ml when I was checking the calibration.

            I took the easy option on the steam wand - I just bought a Silvia one and it bolted straight in. If I had to do it again Id consider making one - and threaded so that I could swap and play with different tips.

            Frankie

            Comment


            • #7
              Re: Gaggia Classic Pressure Modification

              Originally posted by gz20tt link=1175171794/0#5 date=1175474408
              As to the accuracy of the backflow method - I think it is more accurate than you might think - since the flow rates are based on the supplied specs by Ulka. I found that I was getting repeatable flow rates to within 10ml when I was checking the calibration.
              Not all Classics have an Ulka pump (mine included) and following the pressure graph from Ulka resulted in a MUCH lower pressure at the flow rate prescribed by Ulka.

              My pump is made by Invensys, and there is little to no info available regarding flow rate / pressure graphs. So alas I had to calibrate by taste as well.

              Still well worth doing though!!

              Comment


              • #8
                Re: Gaggia Classic Pressure Modification

                @dsc: thanks for the compliment tom - its all the more valuable to hear it from an experienced modder have a look at your pms..

                @gz20tt:
                Sorry, I guess my post was misleading.. Thanks for the link its working perfectly!! I just wanted to say that I searched for such a thread before I started thisone - but obviously I was too stupid or simply incapable

                Originally posted by gz20tt link=1175171794/0#5 date=1175474408
                As to the accuracy of the backflow method - I think it is more accurate than you might think - since the flow rates are based on the supplied specs by Ulka. I found that I was getting repeatable flow rates to within 10ml when I was checking the calibration.
                Ok, I dont doubt its precision (the quality of being reproducible in performance) but to compare it to given espresso standards (9bar or thelike) you would need accuracy (the quality of being near to the true value) which is about +/-1bar as I interpret ULKAs diagrams; the difference in pressure between the two dashed lines for a given flow rate.

                thanks again for taking your time to give some feedback



                Comment


                • #9
                  Re: Gaggia Classic Pressure Modification

                  I gave my machine a 180° turn and pulled close to 200mL in 30s. I then backed it off in 1/8th increments until I reached about 90° from the original setting which gave me 100mL in 30s pretty much exact.

                  Other things to note... pulling the hose off before trying to undo the 17mm hose barb will aid in using a socket. Dont try using a shifter or spanner that you cant get a good position on, you will just round the edges like I did. The material is soft so its not recommended in my opinion. If you dont have a socket, just get a cheap set from Supercheap Auto or from the market.

                  Anyway, machine should be just about warmed up, let me go see how she goes. Still using shitty beans (Lavazza) but I am hoping to get some fresh ones from Veneziano on Monday as I have taken an RDO, booya! Also going to see about getting a steam wand from a Silvia from somewhere and some steam wand knob springs for the Silvia for work, since its broken, again.

                  Comment


                  • #10
                    Re: Gaggia Classic Pressure Modification

                    More crema than before... now to get those freshly roasted beans
                    My espresso still tastes like crap though but better... need more money to get me a Pullman also.

                    So many toys... so little money.

                    Comment


                    • #11
                      Re: Gaggia Classic Pressure Modification

                      Just a little correction to the above instructions.

                      Marco said "thightening (counterclockwise rotation) leads to a higher setting - losening to a lower setting."

                      But i discovered (and marco confirmed) that tightening is actually Clockwise, not Counter-Clockwise.

                      Also, Did anyone find a drop in Steam pressure after this mod?

                      Regards, Aaron

                      Comment


                      • #12
                        Re: Gaggia Classic Pressure Modification

                        Gday Aaron,

                        Adjusting the OPV will have no effect on the Steam Pressure as the Brew Pressure relies on the Pump Output/OPV Setting whereas the Steam Pressure is reliant on the Heating Element of the Boiler and is downstream of the OPV and Pump,

                        Mal.

                        Comment


                        • #13
                          Re: Gaggia Classic Pressure Modification

                          I did this mod yesterday and im impressed. my opv was set so tightly that when initially testing my return flow the pump dead-headed against the blind filter and only released pressure through the safety release when the pump was switched off. I think this is important to note as this is an excellent way to destroy your pump if youre not sure of what youre doing - if you hear the pump struggle for >1-2secs and see no flow in the return line immediately stop the pump and decrease the setting of the opv to prevent damaging the pump.

                          There seems to be a significant variation in factory settings - my machine was set far too tightly to even operate correctly, but the other machine in my kitchen at the moment (a classic that im PIDing for a friend) was actually set perfectly direct from the factory.

                          as for performance, im very happy. Long gone are the gushers caused by a slightly imperfect tamp. im now in the process of dialing in my tamp on a smaller grind which is delivering much smoother, better smelling and tasting espresso with a far better crema than ever before. globs of the stuff - its great to watch the pour now

                          The crema does however seem a little more fragile than before - when making milk drinks i dont seem to have nearly as much time between pulling the shot and pouring the milk before the crema begins to thin. this could be perhaps down to the cool cups im using at the moment (bloody winter, i just cant keep them warm) or perhaps im just pulling the shots a little too long. im also on a new bean at the moment so it could be any number of variables, but im sure ill dial it out soon.

                          thanks to the contributors of this and the other thread on this topic, your help is greatly appreciated

                          Comment


                          • #14
                            Re: Gaggia Classic Pressure Modification

                            QUESTION:

                            i have a gaggia espresso. I noticed on partsguru the OPV valve on the classic and the valve assembly on the gaggia espresso have the same mounting configuration.

                            Does anyone know if these fit??....

                            I checked with parts guru schematics of the espresso vs. the classic and they look

                            identical.

                            I was considering buying the whole setup from the OPV to the classic elbow arm coming off the pump and replacing all the gaggia espresso parts with that to attain
                            a proper brew pressure on my gaggia espresso.

                            I have pics too add if anyone needs to see them.

                            Im almost 100 percent postiive its the same.

                            Comment


                            • #15
                              Re: Gaggia Classic Pressure Modification

                              i GOT PICS DONE.



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