How does Oscar's HX differ from typical e61 HX

[nixter]

Given that the NS Oscar isn't an e61 type group that most of the HX articles and threads written here are about, how might the temp cycles and flushing be different? I've been playing with flushing and trying to zero in on a good routine but I still seem to be all over the place. I'd really like to get a permanent temp gauge or something but the only thing I've seen is erics device which is for e61 machines. Any suggestions?

cheers,

nik

Dan, if you feel this should be part of another thread feel free to move it.

[cafeIKE]

Since typical e61 HX does not refer to any known device, the best procedure is to set aside a few hours, get some great coffee and make notes.

Let the machine warm up for 1 hour. Time and measure the flush water volume until the flash boil stops. Leave the machine for 30 minutes and repeat 3x. The time and volume should be very close. This is your start up initial flush.

On the last flush, have a PF ready to load and pull. Note how the shot tastes. Probably bitter. You don't have to drink the whole thing, just get an idea. Be consistent with the cup temperature and how long you wait from pull to tasting.

Wait 30 minutes and repeat, but go 5 seconds longer if shot was bitter or 5 sec less if sour.

Iterate until shots are consistent and tasty.

[nixter]

I've read the articles but how do I know when the flash boil has stopped? I don't quite understand what this water dance is that's mentioned.

n

[cafeIKE]

The end of the flash boil is when the water stops sputtering from spontaneously turning to steam and simply 'rains' from the group.

[nixter]

Ok That's what I thought. It's more of a sound than anything visual with my Oscar. I get some hissing and some steam which I'm guessing is the flash boiling. The hissing only lasts 3-4 seconds I'd say. Does this sound about right?

I'm going to do some testing tonight. I'm kind of leaning towards some kind of permanent thermometer or gauge though. Can this be done with the Oscar?

n

[caeffe]

Nikolai-
I've got an Oscar also.
There are a couple of ways to see the "water dance"
1. W/O Portafilter: you'll see steam and hear hiss coming out of the grouphead. 3-4 seconds sounds about right.
2. W Portafilter with a double spout or single spout: water will come 'gushing' out and spill all over the place
3. W Portafilter w/o spout: this is when it gets hard to tell - I wouldn't recommend doing it this way until you figure out a time/volume aspect based on method 1 or 2.

Since I make cappuccino's for the wife every morning. I tend to flush into an Illy Cappuccino cup until its 3/4 full. Loosen the portafilter and more water will come out so the cup becomes full. This is about 4-5 ounces.

[cafeIKE]

Not as easily as with an e61.

You may want to review Oscar's Parts Manual

You could attach a TC to the group above the water outlet or on the Thermosyphon Inlet and / or Outlet to the group. Neither will be as accurate as Eric's Adapter, but may give some useful information.

[danetrainer]

It's helpful to read an earlier thread on "'Flush and go' technique suitable for smaller HX machines?":

flush-and-go-technique-suitable-for-smaller-hx-machines-t666.html

Here is what Dan wrote that I have been using with great results on my Oscar:

Most mornings I move pretty leisurely behind the machine, so it's not unusual that I do a second "mini flush" before locking it. Not to get all Zen on you, but there's a definite intuition for the particular machine. An eight degree drop sounds like a lot, I would expect more like four degrees F. Let me toss out this idea: Let it rebound a second time, but only for 10 seconds. Remember that the HX is fairly small -- on the order of 110ml -- and easily exhausted. Specifically I'm proposing the slow man's routine:

1. Flush to usual brew temperature (~six ounces)
2. Leisurely prepare your basket in around a minute
3. Flush barely two ounces, just a teenie bit past the water dance end
4. Lock in the portafilter. Face towards Seattle and say a short prayer to the Espresso Gods (10 seconds have passed since step 3)
5. Go.

Oh, with all this flush minutia, I forgot to ask: How's the espresso taste?

I have found my step "3" is usually less than 2 ounces before the water dance ends, maybe only 3 to 5 seconds worth and is easy to tell with a naked portafilter. I do have the Pstat cranked up over stock as my temps were measuring consistently low (I use a Fluke with a probe in the portafilter basket).

[nixter]

Great help guys, I have lots of experimenting to do now! I'll let you know how it goes.

nik

[RE*AC*TOR]

Hey Nixter, I'd be concerned you are losing hot water into the drip tray following your OPV adjustment. This could be throwing the repeatability.

[nixter]

Funny you mention this reactor. I was thinking the same thing this morning. My opv is pretty much letting a steady steam of water through during my shots now. I think I will recalibrate it with the portafilter loose enough so that I drip 2oz of water around the sides in 30 seconds or so. I wondered this after doing a very brief initial flush and a long grind prep and still my shot was a tad sour.

Thanks,

n

[RE*AC*TOR]

Hi Nixter,
My OPV also lets a steady stream of water through, but the difference is that its cold water, and its going back into the reservoir.
In your case you are losing hot water into the drip tray.

I don't think you need to allow water through to set your OPV, at least not in a vibe pump machine.
I may be wrong but I think that only applies in a rotary pump system.

[nixter]

I didn't actually set the opv to specifically let water through. I set it using a PF with a pressure gauge screwed to the bottom. I adjusted the opv so that it opened at 10bar. However... this testing procedure may not have been ideal though as it's essentially "blind" meaning that there's no flow through the PF as there would be with a puck in there. If I go back and adjust to 10bar while loosening the PF enough to get some leakage to simulate flow I think I might be better off. Ever since I loosened my opv I've been a little on the sour side I think. Although I'll admit I'm not always sure of the difference between sour and bitter. I'm sure if I was tasting side by side I'd know but my taste buds have a terrible memory for this sort of thing.

n

[RE*AC*TOR]

An OPV sets the maximum pressure, so your procedure is correct, you do not need to set it higher (in fact you should set it lower than 10bar).
The sourness I would say is because of the temperature loss due to the location of the opv.

[nixter]

Yes but I'm not about to move the opv, it's more modding than I care to do. Let me put this to you.. If I'm getting a steady stream of water from the opv (set at 10bar blind) then I'm creating a puck that has too much resistance. For ideal brewing I want to create a puck that by nature of it's own resistance creates a pressure of around 9 bar correct? So how do I reduce the resistance of my puck while keeping my flow rate the same??

It could then be asked, "why mess with the opv at all if the puck should be dictating the 9-10bar?" The way I see it, a more sensitive opv is a tool to let me know when I am just over where I want to be pressure-wise.

n

[cafeIKE]

You need the OPV because the flow rate of the pump at 9 bar is too high, on the order of 200ml/minute.
http://www.ulka.it/eng/e4_gra.htm

[RE*AC*TOR]

It depends on the pump and the pump flow rate (as cafeIKE has said).
I don't think you can say that it is all down to your puck.

I measured the output of the OPV (at 9.5 bar) pulling a 60ml double shot at over 100ml. This tells me that the Oscar pump is trying to push far too much water through the puck, which equates to either (a) too high a pressure or (b) too high a flow rate. So unless you set the OPV to a level which limits the pressure you cannot really get either to an ideal level.

I hope this is somewhat clearer. It is a complex consideration.

I will say that I have adjusted my OPV down to 8.5 bar. I am no longer experiencing the brew problems I had previously been having trouble with (channeling, premature blonding). The difference is night and day.

[caeffe]

nixter's question is more -why does NS put in an OPV if it's not adjusted for 9-10 bar? I found that my Oscar had it's OPV installed such that it didn't regulate the pressure at all - same as what nixter and others on this thread have discovered.

[RE*AC*TOR]

nixter's question is more -why does NS put in an OPV if it's not adjusted for 9-10 bar? I found that my Oscar had it's OPV installed such that it didn't regulate the pressure at all - same as what nixter and others on this thread have discovered

As I said already (maybe on the other thread) NS does not use this as a traditional OPV. Mine was set to 16bar, and is apparently only a safety release valve. In my mind it is a bad design issue, and along with the lack of vacuum breaker, lack of hot water spout, I would say it was done to save money - hence why the machine is cheaper than the competition.

[nixter]

Interesting, so perhaps I can't achieve perfect flow rate via puck resistance alone as the pump rate is too high? I'd like to dial it in as close as possible. I'll have to experiment more, maybe shorter flushes are required given that I'm losing hot water through the opv. I guess there's no way to dial back the pump rate?