# Need technical help with e91/e97/e98 group



## MikeHag (Mar 13, 2011)

OK, so I need to slow down the flow of water on my faema. Pump pressure is fine. I understand that the gicleur acts as a flow restrictor, and that a smaller orifice slows the flow, but my machine ships with a 0.5mm orifice which should be slow enough, but I'm getting around 240ml in 10 seconds, whereas I want around 75ml (with an empty basket in).

I'm drawing a blank everywhere I turn. How can I slow the flow? Can I modify the machine to have an additional flow restrictor, for example?


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## jimbow (Oct 13, 2011)

That does sound fast. Do you know if that flow rate is usual out of factory?

Bear in mind that changing the flow restrictor will affect brew water temperature and the function of the thermosyphon, so you may need to adjust boiler pressurestat or cooling flush routine to compensate if you go down that route.

I do not really know much about these things but I would take a look at the water pressure of the plumbed feed and the power supply the machine is running on (I am wondering whether the pump might be operating at a high frequency and pushing more water through).


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## lookseehear (Jul 16, 2010)

Does it actually matter when there's a puck there? Surely the puck would have a for bigger effect than a gicleur on restricting the flow - the biggest difference would be a quicker ramp up to pressure (at least in my head).


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## MikeHag (Mar 13, 2011)

I'd like to ask Faema what the factory volume should be, but having tried the UK distributor Mulmar and not had any success, I'm not holding out much hope at the prospect of communicating this technical stuff directly to an Italian.

You're right, Luke, once the water has saturated the puck then the puck itself will act as a flow restrictor, but in the time between hitting the brew button and the headspace filling/puck saturating, the water is coming in at a high rate. That could create channelling if the puck has any imperfections. Although it works fine, my research shows that if I can get it down to around 75-90ml in 10 seconds then it will act like an e61 pre-infusion, which should lead to better shots. Currently the pump pressure goes up to 9 bar as soon as I hit the button, and I'd like it to ramp up slowly. Restricting the flow should achieve that, and on other machines the gicleur does that job.

Someone on twitter suggested fitting a second restrictor, which I'm looking into. Would prefer to find a solution that doesn't involve modification tho.


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## jimbow (Oct 13, 2011)

Still not sure whether it will help but I wonder whether changing the jet might help. Reading up on water debit it seems some people have changed the jet size where they were not able to change the gicleur. There is also some speculation as to whether the jet might wear and increase in diameter over time.


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## MikeHag (Mar 13, 2011)

Yeah, my thoughts too but the ones in there are alrrady 0.5mm. I've inspected on and it looks fine. The jet and gicleur are the same thing


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## jimbow (Oct 13, 2011)

Ah, not seen it called that before. Thanks.

You have probably already read these but thought I would pass them on in case:

http://coffeegeek.com/forums/espresso/machines/74535

http://coffeegeek.com/forums/espresso/machines/308286

It seems the E91 does not have a pre-infusion chamber like the E61 but instead uses a piston inside the group to buffer the pressure at the start of the shot. Could the spring in the piston be replaced with a newer, softer spring?

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## MikeHag (Mar 13, 2011)

Thanks jimbow. Hadn't seen the first of those links so that's great and helps me understand what is going on inside the group. It's amazing what you can learn from people's forum posts 8 years ago, and just goes to show how much more there is to learn about espresso than I will ever be able to take in. If this is how the gicleur works then I'm amazed that so much water can be injected through such a small aperture so quickly. The pressure at that hole in the gicleur must be huge, I'd think. This makes me start to question my pump gauge a little more. I think what I'll do is:

1. Speak to Mulmar again and try harder to get through to someone who knows the e91 really well

2. Depending what they say, buy new gicleur assemblies just to be on the safe side. They are fairly cheap.

3. Buy/make a grouphead pressure gauge (since a Scace is out of my price bracket)

Regarding the spring... I'll pull things apart and have a look at its condition. Good idea worth following up on!


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## fatboyslim (Sep 29, 2011)

Would love to see pictures if you are taking things apart.


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## jimbow (Oct 13, 2011)

Perhaps the piston could even be failing where the o-ring has worn or jammed against the piston walls through scale, etc.

If you are having difficulty with the UK distributors might contacting Faema in Canada/US be any use?

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## MikeHag (Mar 13, 2011)

Ok. Finally found an engineer with the type of knowledge and attitude that's needed. There is a preinfusion chamber in the e91 grouphead, which gives a short (1-2) second soak at lower pressure. This is good as it makes lowering the flow rate less important to me. But I still want to get it down if possible. I now have the part number of new jet assemblies and will see if that helps. My machine came from a cafe in Edinburgh and it's possible that soft water has slightly eroded the jets. Worth a try as they cost under a tenner. But another idea is to get a very small disk of metal made, with a precision-drilled hole in it, and put this in the assembly to act as another flow restrictor. Just need to find someone who can make it.


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## MikeHag (Mar 13, 2011)

Further update, as I've been playing around. I removed both assemblies and to cut a long story short I swapped them over. Perhaps the act of removing them has freed up the threads on the nut a little, because upon replacing them they screw in further, and if screwed in far enough they completely shut off the water from the thermosyphon to the grouphead. By gradually unscrewing I've been able to find the point at which the water throughput is around 90ml in 10 seconds. Great! Now to see what impact there is on extraction, temperature, taste and whatever else!


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## jimbow (Oct 13, 2011)

Great news Mike

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## MikeHag (Mar 13, 2011)

Early results. The slower flow had a big impact on brew water temperature and stability. I'm now seeing a much flatter L-slant temperature curve when measured with an empty basket. The flush time has had to be extended from around 3 seconds to around 9, which makes perfect sense considering the flowrate has been reduced to around a third of what is was previously.

I pulled two shots of HasBean Rwanda SACOF, which I haven't had any success with previously - always too bright & tart. These two were more fruity, less citric, a slightly browner crema and generally much more pleasant to drink. My hope was that a bit of preinfusion would swell the grinds, allowing me to grind a little coarser to reduce fines in the puck. Early results are looking promising.


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## garydyke1 (Mar 9, 2011)

Good news Mike.


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