Hi all! I’ve owned an Oscar II for some time now and I’ve often looked for information on the interweb and it was not always accurate. As for other machines, I thought I would create a thread that could help future owner. Facts (please correct me if I’m wrong): 1. The Oscar 2 is a heat exchanger machine. 2. The steam is very powerful but temperature stability may be affected as for all HX machines. 3. Some version have a flow restrictor to reduce the pump noise. Latest version don’t have the flow restrictor and therefore a much noisier. The flow restrictor was creating flow problem with some flushing routines. 4. There is no OPV on the machine so the pressure is extremely high (approx. 14 bars!!!). Popular modification (at your own risks) 1. OPV installation (to limit the pressure to something more common) 2. Pump change (for a quieter pump) This what I have so far. I’ll add other messages below to talk about the mods I just made! Matt P.S. I’m currently trying to figure out if I should upgrade my machine or not. These mods were made in order to see if I would be worth keeping my machine a little bit longer if they were noticeable difference.

The General Simonelli Oscar II Thread

Snooze

Hi all!

I’ve owned an Oscar II for some time now and I’ve often looked for information on the interweb and it was not always accurate. As for other machines, I thought I would create a thread that could help future owner.

Facts (please correct me if I’m wrong):

The Oscar 2 is a heat exchanger machine.
The steam is very powerful but temperature stability may be affected as for all HX machines.
Some version have a flow restrictor to reduce the pump noise. Latest version don’t have the flow restrictor and therefore a much noisier. The flow restrictor was creating flow problem with some flushing routines.
There is no OPV on the machine so the pressure is extremely high (approx. 14 bars!!!).

Popular modification (at your own risks)

OPV installation (to limit the pressure to something more common)
Pump change (for a quieter pump)

This what I have so far. I’ll add other messages below to talk about the mods I just made!

Matt

P.S. I’m currently trying to figure out if I should upgrade my machine or not. These mods were made in order to see if I would be worth keeping my machine a little bit longer if they were noticeable difference.

Snooze

Pump replacement

After having tried a Lelit MaraX and noticed how much quieter it was than the Oscar II (without the flow restrictor) I considered changing its pump after someone explained to me that almost all vibration pumps are interchangeable (someone correct me if that general statement is not accurate).

I then replaced the Oscar II pump (Ulka) for the Lelit MaraX silent pump (PN: 4000040).

At first I kept the Oscar pump rubber bracket and while there was a noticeable noise reduction, it was not as good as for the MaraX. I then installed the Lelit one and the improvement was massive. Not as good as with the MaraX but it was quite impressive.

So far I’m quite impressed with this modification. The pressure ramp up seems quite gradual but not as slow as with the MaraX. I think this is because of the E61 group that has an internal preinfusion chamber and maybe something else (@DavecUK and other here may be able to provide clarification on this). Also it is hard to notice since the Oscar II doesn’t have a pump pressure gage like the MaraX so my impressions may be wrong.

Snooze

OPV installation

Companies like Elektros sell OPV kits for the Oscar II that can easily install if you are just a little bit handy. https://www.elektros.it (No affiliation).

I installed another valve (an expansion valve found at my espresso machine repair shop) and added the tubing to direct the water into the pump intake.

It was quite easy to do (and fun!) but after having adjusted the pressure to 9 bar at the group head with a manometer on a portafilter (with a filter!), there was a weird sound coming probably from the valve. Edit: I found this awesome article (http://coffeetime.wdfiles.com/local--files/opv-over-pressure-valve/OPV_Valve.pdf) from @DavecUK and I think the noise in hearing is temporary. Also I may need to look at the valve spec since it is quite small (similar to this one but with a nut to adjust and it is written 12 bar on it since it is already adjusted at 12 bar I guess! - https://coffeeaddicts.ca/products/nuova-simonelli-expansion-valve-1) but it is all brass should be of quality but it’s a straight one that I had to add a right angle fitting

I’ll have to dig a little bit since the expansion valve was one marked 12 bar on it so maybe it doesn’t like being adjusted to 9 bar. Anyone has any thoughts on that?

But all in all, it’s an easy mod and I’m sure with the proper valve (or adjustment) it will be a nice addition.

I feel like my coffee have more sweetness post the “silent” pump and the pressure limit at 9 bar installation but I’ll need to run more test to confirm.

Since I’m looking for another machine, I can comment that so far the Espressos from the MaraX with the same coffee never had the little acidity that I get from the Oscar II. The acidity seems a little bit tamed post modifications but the sweetness really seems to be the improvement. But note that I’m no taste expert neither objectives since I didn’t do blind tests.

Annex ( :)): I installed the valve right after the pump and redirected to the water tank out / pump intake like Elektros are suggesting to do with their kit. Their valve seems a bigger but maybe this is only because it includes the right angle and the pass through. In my case à added the right angle and pass through to a straight valve.