Does anyone know how Oscar's pre-infusion works. Promotional material says it uses a "Mechanical Pre-Infusion System'" I cant see it or a gicleur on the on-line parts list, I am curious to know how it works.

I haven't used the Oscar, but out of curiosity looked at the Oscar Parts Breakdown (PDF) on Nuova Simonelli's website. Part #73012002 is listed as "fitting 1/4 - 1/4" and it could house an orifice, but otherwise I found no likely candidates in the schematics. The problem is that the term preinfusion is used quite broadly in marketing literature and may entail some "creative license." In the actual implementation, it could mean an orifice (small hole to slow water flow or gicleur in Italian) between the pump and grouphead, expansion chamber, or even the naturally slower ramp up pressure of a vibratory pump.

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

My old Oscar bought and sold this year (EU) did most certainly have preinfusion. I have no idea how it operated but there was about a 5-7s part at the beginning of the extraction where the pump noise was lower and nothing emerged from the group, then the pump would kick in in earnest and stuff would emerge.

That doesn't necessarily mean that it had preinfusion. Could just be from the changing noise of the pump, from no water above the coffee puck to full pressure.

RE*AC*TOR wrote: . . . there was about a 5-7s part at the beginning of the extraction where the pump noise was lower and nothing emerged from the group, then the pump would kick in in earnest and stuff would emerge.

By that definition, my Gaggia Coffee had pre-infusion.

I was looking at one a while back and the dealer told me NS engineers had incorporated pre-infusion in the design but I can't figure it out, so I thought I would ask here, you're a knowledgeable lot on this sort of thing.

lolercats!

You guys are so funny.

Judge for yourselves (listen to change in tone around the 30s mark)

The squeaky sound in the video around the 30 second mark sounds like the OPV complaining.

That sound begins at 32s.
I'm referring to the change at 30s.