Dream T and Vivaldi Mini vibe pump sub-par?

[haroldo_psf]

Hello! Long time lurker here...first post I guess.
I purchased the Dream T and received it about 2 weeks ago. I have a question on the machine operation, and decide if it needs repair, or if it is normal operation, in which case I would return it (and spend the extra money on the plumbed Dream version instead).

Here is a the background... We have a La Spaziale Vivaldi S1 VII at work (plumbed, rotary). I operate it daily for the past year or so. I liked it so much, I decided to purchase the Dream for my home. Other co-workers who had the same machine (Vivaldi VII plumbed) referred me to Chris Coffee. To avoid plumbing, I went with the Dream T(tank, vibe pump).

Using the same beans as I use at work, and similar grinder (Mazzer supper jolly at home, mazzer mini at work), I cannot get a "normale" extraction at 9 bar with the Dream T at home. It simply won't do it.
The machine at work (Vivaldi VII plumbed) pulls 2oz in 25 seconds at 9 bar solid, no problem.

I collected similar data on my Dream T:
The following was done with doses of 18g to 18.5g on the triple basket, espro 30 lbs tamp:

1) With a blind porta filter, it takes the pump 13 seconds to come up to 9 to 9.5 bar (that seems way too long).
2) With a starting grind setting, 2 oz in 25 to 30s come out around 6 bar.
3) Setting grind finer, 2 oz come out in 38 seconds at 7.5 to 8 bars
4) Setting the grind finer, 1.8oz come out in 40 seconds at 7.5 to 8 bars.

I could keep making the grind finer and eventually get to 9 bars (and close to choke the pump), but the shots just take way too long, indicating the vibratory pump cannot keep 9 bars at 2oz in 25-30s, which is a "normal" shot range.

Anybody has any ideas, or is this normal? I emailed Chris Coffee this info in order to either repair it (if it isn't normal), or initiate a return and spend the extra money on the plumbed and rotary pump version of the dream.

Thanks for any input

[chas]

The most likely problems are all between the water tank and the output of the pump:

1) In tank water filter partially clogged (try removing filter)
2) Kink in plastic tubing between tank and pump inlet (will need to remove covers to check for this)
3) Bad pump

[jfrescki]

There was a thread on HB a while ago where someone with a vibe pump could reach 9 bar against a blind filter, but had problems during extraction. The problem WAS a bad pump. So it certainly could be your case here.

As far as the tank Spaz, I have a Mini Vivaldi and have no problems with my extractions. The machine design is not your problem. I'm about 8.5-9 bar against a blind basket, and am a little under that extracting unless is very tight. You didn't mention if you had a pre-infusion chamber on the DreamT. If you do, that's part of your slow ramp to brew pressure, but probably not all.

Brew pressure on vibe pumps is in direct relation to flow rate. Faster flow==>lower pressure. However, since we know you can reach 9 bar against a blind basket, and you're not reaching 9 bar with a super-ristretto, it does sound like a bad pump, or any of Chas' suggestions.

[haroldo_psf]

I think my problem my be related to channeling. I captured an extraction video. Notice a couple of things:
1) Is the ramp up time in the normal ball park range for vibe pumps? See manometer needle and how long it takes from pump start. (I have no pre-infusion chamber installed)

2) I also noticed that the pressure ramps up to 9 bars, and 2/3s into the shot, it drops to 7ish...When I see the puck, there was a hole...The only explanation I have, given flow rate didn't change (or increased slightly if anything), is that that slight pressure drop was due to the channel forming mid shot.

HEre is the video (any comments would be great!):
http://www.youtube.com/watch?v=DHpuGIhR3ik&authuser=0

[haroldo_psf]

I think my problem my be related to channeling. I captured an extraction video. Notice a couple of things:
1) Is the ramp up time in the normal ball park range for vibe pumps in these machines? See manometer needle and how long it takes from pump start. (I have no pre-infusion chamber installed)

2) I also noticed that the pressure ramps up to 9 bars, and 2/3s into the shot, it drops to 7ish...When I see the puck, there was a hole...The only explanation I have, given flow rate didn't change (or increased slightly if anything), is that that slight pressure drop was due to the channel forming mid shot.

HEre is the video (it takesa bout 40 seconds to fill the 2oz cup, but it looks pretty!):

http://www.youtube.com/watch?v=DHpuGIhR3ik&authuser=0

[jfrescki]

That does seem like an awful long time to build pressure.

[chas]

This is not right. With a blind PF the pressure ought to ramp to 9 bar almost immediately. If you have a softener cartridge in your tank, take it out and see what happens.

1) With a blind porta filter, it takes the pump 13 seconds to come up to 9 to 9.5 bar (that seems way too long).

[haroldo_psf]

Looking at my own video, it doesn't seem that long? Not sure why I noticed such a long time with the blind. Does the ramp up time in the video look ok? I searched YouTube for "la spaziale mini" and came across a few bottomless videos where the pressure gauge was visible. It doesn't seem I'm too far off. I'm confused...
I'm wondering if this is normal
For instance
http://youtu.be/oep-F-XmvG8
And
http://youtu.be/ve6VDw6z2GQ

They're pretty similar in ramp up, no?

[jfrescki]

I just pulled a shot to compare, and you're pretty much on. I don't have pre-infusion and I come to full pressure in 6 seconds. You can see a very slight decline from 9 bar to just below as the shot progresses from a slightly increased flow. Don't mind my aoogahh horn sound, it's the flow meter.

RedBird Shot

[haroldo_psf]

Thank you John very much for taking the time to make that video! I feel much better knowing my machine works normally!

Question, was there any sign of channeling in your puck? I attribute my increased flow (and decreased pressure) to visible pencil size (or sometimes bigger) holes in the puck which likely form mid shot. I was curious as to if you experienced this slightly increase in flow (and decrease in pressure) together with signs of channeling.

[jfrescki]

No channeling. It's typical for the shot to start running a bit faster as it progresses. You may have some. Try the Weiss distribution technique if you're not already.

[haroldo_psf]

So, correct me if I'm wrong, John. Given the amount of coffee and grind setting you have, you extract such volume at that time with close to 9 bars.

If you wanted to adjust your extraction by say decreasing extraction time, you would coarsen your grind while keeping the same dose (or decrease dose and keep same grind). Either way, you would decrease puck resistance.

By default, and from what I understand about our vibe pumps (or any vibe) you cannot extract at faster flow rate and keep it at 9 bars. Is this correct? Meaning, the pump has a sweet puck resistance spot for 9 bars extraction which will produce some flow rate. Changing the resistance in order to accelerate flow rate will bring you outside the 9 bars range for the pump.

Right?

[jfrescki]

I'm no expert, but yes, I think you're right. 9 bar is no espresso promised land, so I wouldn't worry about it too much. As long as you're in a reasonable proximity of it, you should be fine and have a reasonable flow.

Also keep in mind that the consensus on the La Spaziale group is that longer extractions are quite good if not preferable. Something to do with the geometry of the puck I guess. I usually error on the side of longer, and like that taste. I've never had a 58mm group to compare to though.