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Thread: Modifying Pressure on a Silvia

  1. #1
    Senior Member
    Join Date
    Aug 2004

    Modifying Pressure on a Silvia

    Gene Cafe Coffee Roaster $850 - Free Beans Free Freight
    Has anybody read this article;

    Be interested to hear comments from those who have. Silvia delivers 15 bar of pressure IIRC? By all accounts 9 bar is optimium.

    Comments anybody. ;D

    Warren -

  2. #2
    Super Moderator Javaphile's Avatar
    Join Date
    Dec 2004

    Re: Modifying Pressure on a Silvia

    Looks like a simple mod that will allow you to tweak the pressure to where you want it. By adding the additional gasket(s) you are reducing the spring pressure. A simple yet effective mod. :D

    Java "The Tinkerer" phile

  3. #3
    Senior Member
    Join Date
    Apr 2005

    Re: Modifying Pressure on a Silvia

    Behmor Brazen - $249 - Free Freight
    If you do a few searches on youll find the Silvia pressure mod is very popular. It simply involves adding an extra washer to the over-pressure relief valve, it effectively caps the machines pressure at 9 BAR (it seems almost magically so, as the washer is juuuust the right thickness to accomplish this). Other more adventurous mods are fitting an additional adjustable pressure relief valve (swagelok RL3) and dialing in the exact pressure you want (if you have a pressure gauge).

    For those with Gaggia machines, the over-pressure valve is actually adjustable, so with the help of a pressure gauge, you can set the maximum brew pressure without any mods to the machine.

    The reason for these mods is that the vibe pumps in home machines can apply up to 15 or 16 BAR when there is no flow. The actual brew pressure is then determined by primarily by the flow rate. So proper shot timing might not correspond to the proper brew pressure. In fact it is usually too high. However, by limiting the maximum pressure with a properly tuned pressure relief valve, you have a much greater chance of brewing at the correct pressure AND flow.

    As soon as I can get my hands on a portafilter pressure gauge, my Classic will be adjusted down to 9 BAR. Oh happy days...

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