nixter Senior Member Joined: 29 Jan 2008 Posts: 162 Location: Vancouver Expertise: I love coffee
Espresso: Giotto Evoluzione, Oscar Pro Grinder: Baratza Vario
Posted Sat Jun 19, 2010, 1:52pm Subject: Re: Installing an OPV in a Nuova Simonelli Oscar
I had an Oscar for the last 2 years and I did the cold water opv thing. I've concluded that there really is no need to do this mod. Brew pressure is self regulated by proper grind and dose. Dose/measure your grind to your preference, say 17g. Tamp and pull. Adjust the grind so that your extraction is in the golden window of 25-30 seconds and you will automatically have about 9bar brew pressure. Basically your grinder is the only opv you need. The vacuum breaker mod is a fantastic idea on the Oscar.
amish_hooligan Senior Member Joined: 12 Jun 2010 Posts: 7 Location: Colorado Expertise: I love coffee
Posted Sat Jun 19, 2010, 2:13pm Subject: Re: Installing an OPV in a Nuova Simonelli Oscar
Thanks.
Why do you like the vacuum breaker mod for the Oscar? I thought all it did is save the trouble of opening the steam wand after turning the machine on.
Using grind and tamp to regulate brew pressure makes sense but my grind is so fine I am getting some in the cup. If I coarsen the grind then I'll have to tamp extra hard. I was hoping the cold water OPV mod would make the "adjustment window" for grind and tamp larger.
nixter Senior Member Joined: 29 Jan 2008 Posts: 162 Location: Vancouver Expertise: I love coffee
Espresso: Giotto Evoluzione, Oscar Pro Grinder: Baratza Vario
Posted Mon Jun 21, 2010, 1:38am Subject: Re: Installing an OPV in a Nuova Simonelli Oscar
amish_hooligan Said:
Thanks.
Why do you like the vacuum breaker mod for the Oscar? I thought all it did is save the trouble of opening the steam wand after turning the machine on.
Using grind and tamp to regulate brew pressure makes sense but my grind is so fine I am getting some in the cup. If I coarsen the grind then I'll have to tamp extra hard. I was hoping the cold water OPV mod would make the "adjustment window" for grind and tamp larger.
Yes, cracking the wand works but then you must wait for the machine temp to stabilize again. Full stabilization can take a while. With a vacuum breaker you can put Oscar on a timer and she'll be all ready to go when you wake up.
Based on what you're saying, I don't think your problem is pump pressure. Most likely stale beans or poor grind quality. How long after the roast date are you brewing? What kind of grinder do you have?
amish_hooligan Senior Member Joined: 12 Jun 2010 Posts: 7 Location: Colorado Expertise: I love coffee
Posted Mon Jun 21, 2010, 5:49am Subject: Re: Installing an OPV in a Nuova Simonelli Oscar
I have a 9 year old Nuova Simonelli MCF. I get green beans from Sweet Marias and roast them weekly.
If I could just measure the brew pressure that would eliminate the guesswork. But I don't have the tools and the OPV mod looks cheap and relatively easy.
I'm all for the vacuum breaker mod too. It just didn't seem like my biggest problem at the moment. When you say full stabilization can take a while, how long is that roughly?
nixter Senior Member Joined: 29 Jan 2008 Posts: 162 Location: Vancouver Expertise: I love coffee
Espresso: Giotto Evoluzione, Oscar Pro Grinder: Baratza Vario
Posted Mon Jun 21, 2010, 6:25pm Subject: Re: Installing an OPV in a Nuova Simonelli Oscar
20 minutes give or take I'd say.
I know what you mean by "eliminating the guesswork" but you really need not worry about about the pressure. Get the grind/dose/tamp right and the pressure takes care of itself. Even with the opv the pressure it's a static 9bar. It would just be a maximum of 9bar. I did this mod and it didn't make life any easier. If anything it just created a couple extra points for potential leakage. The only real benefit of the mod is that re-routed cold water can go back to the tank instead of hot water going to the drip tray. This means more stable brew temps and less refilling. BUT! Again... in the real world if you have your grind and dose right then these benefits never materialize.
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