Then why is everyone complaining about not being able to adjust the pressure? How do you adjust this then to get the pressure down? I thought it only had the safety valve, others are going to great lengths then for nothing if this is factory installed and adjustable.

The OPV is designed to open I believe at 14bar. This is a safety issue rather than a brewing pressure control. Adjusting the OPV to open at a lower pressure is akin to adjusting brew pressure even if that's not what it was designer for. Some confusion happens because some of the older Oscar's OPV fitting is not adjustable whereas newer ones like mine, are. Now while you can adjust the OPV on SOME Oscars to adjust brew pressure it's not an ideal way to do so because the OPV is on the hot side of the water system. The problem with that is you end up losing a lot of hot water out the OPV which can result in a large fluctuation in your brew temp over the course of a shot. Ideally, the OPV should be on the cold water side of the system and funnel any excess water back to the reservoir. This is how I've set up my oscar and it works great. Now I just need to add a vacuum breaker and Im set.

a "mechanical preinfusion" doesn't mean an "automatic preinfusion" so could this be the process of pushing in the brew button half way? This releases water without activating the pump. So you could manually preinfuse to any degree before engaging the brew pump. I saw this little tid-bit on a very good CG Oscar review http://coffeegeek.com/reviews/con...lli_oscar/CuppaJay. I thought it interesting and was curious as to its application to this topic.

Interesting. I will look into this but I think it might be incorrect. I'm fairly certain the brew switch is purely electrical and connected only to the pump.

This potential "freebie" via the brew switch would ONLY be applicable if the particular NS Oscar were plumbed in vice taking suction from the onboard reservoir.

Personally, I would put a lot of faith in what Nanook said a few posts ago on Page 1. He works on these machines and others "up the scale" and spoke directly with a NS engineer.

iZappa wrote:According to one of Nuova Simonelli's head engineers that I talked to, the Oscar does not have any preinfusion. The only way to achieve preinfusion is by pushing the brew button for one second, release it, wait for a few seconds and then commence brewing. This is what he told me. The expansion valve on the group head only releases pressure when reaching 10 bar. The grouphead of Oscar does not have the preinfusion chamber as the Nuova Simonelli Aurelia.

This applies to the Oscar manufactured last year in Europe. Other models might have a different group setup that I am not familiar with.

nixter wrote:Interesting. I will look into this but I think it might be incorrect. I'm fairly certain the brew switch is purely electrical and connected only to the pump.

Actually, if you look at the wiring diagram at Nuova, it shows the brew switch connected to the solenoid, the ECM, and the pump, so I suppose the review at CG could be accurate. Perhaps I'm overthinking the concept of mechanical pre-infusion, but wouldn't it be possible for the solenoid to open part way for a few seconds to allow low-pressure water into the group head before opening completely for the rest of the brew?

Link to diagram (on the last page): http://nuovadistribution.com/images/Tec ... Manual.pdf

robnsac wrote:a "mechanical preinfusion" doesn't mean an "automatic preinfusion" so could this be the process of pushing in the brew button half way? This releases water without activating the pump. So you could manually preinfuse to any degree before engaging the brew pump. I saw this little tid-bit on a very good CG Oscar review http://coffeegeek.com/reviews/consumer/ ... r/CuppaJay. I thought it interesting and was curious as to its application to this topic.

I just did this and it does work. I had no idea but look forward to seeing how it works and if it improves the taste.

Yes, SOMETHING works - and that is the opening of the brew solenoid valve prior to pump activation BUT that gives you ZILCH pre-infusion UNLESS you have your NS Oscar hooked up to a positive pressure water supply, i.e. something other than the machine's reservoir.

I don't understand; none of the threads I could find explained preinfusion in so far as pressure/non pressure. Is preinfusion a low-pressure wetting as opposed to just a saturation process?