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Pressure Profiling on Lelit Grace PL81T (and other VIP Machines?)


antinwales
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When I make shot on my Grace, I can get 40g from 18g in 25-30 seconds as expected, but the pressure is way too high. Usually around 11bar.
Speaking to Lelit, they confirm this is normal - they said they aim "to 10.5 +/- 0.5bar".
I think this is too high - higher than the optimum 9bar - and I suspect it's so coffee pods work.

There's a video on YouTube about changing the OPV on the Victoria, but it looks complicated, tricky and warranty-invalidating.

I read somewhere about opening the water/steam handle to reduce the pressure, and this certainly worked. I could drop the pressure down to 9 or 10 bar.
And I certainly seemed to have a more rounded espresso - less bitter, with more of the flavours coming through.
Which means I've blundered uninvited into "pressure profiling"!

I'm thinking of combining this with the pre-infusionto start low (8-9 bar) and build up to 10 and then back down again.
Does this sound sensible?
Does anyone else use their water control this way?
Am I over-complicating things?
 

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I very briefly tried this on my gaggia classic before I upgraded. 

I have no scientific evidence, but I was finding that I could grind finer when I started the shot with the steam valve open, then gradually closed it through the first ~10 seconds of the shot. 

Grind settings that would choke if it went straight to 9 bar would work perfectly. So it did make a difference. 

Could I tell the difference in a blind taste test? Not a clue, I didn't experiment enough! But I'd definitely did... Something... 

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The main benefit of preinfusion is to reduce channelling/choking so you inadvertently get to taste via being able to use a finer grind.

I played with different parameters on my GCP too, noticed no real difference at all. I had also modded the OPV.

The easiest (and least wasteful) way is to set OPV to the desired max pressure (the intended function of the OPV) on the GCP you open the case, unscrew a hose and change a spring - easily reverted if the machine goes back to base. But is pressure even a limitation to your coffee tasting good or is it because conventional wisdom says 9bar?  If you like what you are drinking you can probably stop there.

 

PMA all day!

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10 hours ago, antinwales said:

@Kjk OPV adjustment is pretty difficult on the Lelit "VIP" machines. I need to do some A/B testing tomorrow ...

Actually I wouldn’t try to mess with the OPV at all, given you’ve got the LCC.

I back flushed my machine (Elizabeth) last night and noticed my OPV is set around 10.5 as well. I’ll try and take note of the max pressure from the machine when I pull shots later today although you can read into the fact that I’m unaware of the max pressure displayed when I’m pulling shots!

One thing that is worth having a play with is turning on and adjusting the preinfusion on the LCC - press the minus button to toggle through the menu and turn it on and set a preinfusion time which is divided between an initial pump run (typically set in the advanced menu) and the total preinfusion time (total seconds from you pressing the button to turning on the pump for your main extraction). For example you could set 4s initial pump run against a total time of 10s, which equates to 4s of pump on (ramp up pressure), 6s off (gradual pressure drop as the water saturates the puck) and then the pump cycles on to complete your extraction. You can change parameters to control for max and drift off pressures before the main extraction.

Treat pressure as an output that informs you how much water is pushing on the coffee - the goal is that the puck is fully saturated with water before you unleash your main extraction flow. If you have a bottomless portafilter a great visual cue is that liquid coffee beads and begins to cover the bottom of the filter during the preinfusion (in practice I get a few drops in the cup during this preinfusion). You should note that your extraction time will be faster following the PI and to measure your total shot time from when you first press the button.

I wasn’t able to find the most exhaustive explanation of the PID menu for your machine online but a basic walkthrough can be seen here. While you are at it you can toggle the display to show current boiler temperature (seems like factory default is to display target temp - useless) and verify E (temp offset) value (10 on my machine, which means I set the PID to my desired brew temp but the boiler is actually 10degrees hotter in the understanding that the water will lose that temperature by the time it gets to the coffee puck).

Edited by Kjk

PMA all day!

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Thanks @Kjk, but there aren't as many LCC option on the Grace - just temperature settings (water and steam), timer, and a (useful but short) pre-infusion. No options to tinker with pre-infusion.

If yours shows 10.5 when backflushing, that's correct, as it is a bar or so over then. Mine shows 12bar when backflushing.

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1 minute ago, antinwales said:

Thanks @Kjk, but there aren't as many LCC option on the Grace - just temperature settings (water and steam), timer, and a (useful but short) pre-infusion. No options to tinker with pre-infusion.

If yours shows 10.5 when backflushing, that's correct, as it is a bar or so over then. Mine shows 12bar when backflushing.

Is it just on/off? That’s a shame. Some is better than none.

PMA all day!

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23 minutes ago, antinwales said:

Thanks @Kjk, but there aren't as many LCC option on the Grace - just temperature settings (water and steam), timer, and a (useful but short) pre-infusion. No options to tinker with pre-infusion.

If yours shows 10.5 when backflushing, that's correct, as it is a bar or so over then. Mine shows 12bar when backflushing.

So made two coffees and they both hit 10.5/11 bar. Both tasted excellent. How are yours tasting? If they are sour - grind finer, bitter/ashy - grind coarser, sour/bitter - look at puck prep in a bottomless PF for signs of channelling. If they taste good, change nothing!

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PMA all day!

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I tried making two coffees - both came out similar volumes using Black Cat's Signature blend.

Pressure surfed one noticeably paler but - my tasting was very poorly executed!

My work laptop was bleeping "You have messages!" all through. They did both taste good. But I was pretty wired as these were my second and third Espressos of the morning. I'm totally wired. I try again tomorrow.

 

PXL_20210225_093657722.jpg

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8 minutes ago, antinwales said:

I tried making two coffees - both came out similar volumes using Black Cat's Signature blend.

Pressure surfed one noticeably paler but - my tasting was very poorly executed!

My work laptop was bleeping "You have messages!" all through. They did both taste good. But I was pretty wired as these were my second and third Espressos of the morning. I'm totally wired. I try again tomorrow.

 

PXL_20210225_093657722.jpg

There is the other bit of guidance “don’t get into a shot pulling frenzy” good to know you’re liking the signature blend, that is next in the hopper once I finish my Chocolate Point. Feb has been a Black Cat month...

PMA all day!

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19 hours ago, Kjk said:

There is the other bit of guidance “don’t get into a shot pulling frenzy” good to know you’re liking the signature blend, that is next in the hopper once I finish my Chocolate Point. Feb has been a Black Cat month...

I also really noticed the change in the espresso taste as I went down it, becoming more bitter.
I'm definitely not stirring adequately.

I think I'm on Choc Point or the new Twilight next.

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  • 1 month later...
On 24/02/2021 at 18:26, antinwales said:

@Kjk OPV adjustment is pretty difficult on the Lelit "VIP" machines. I need to do some A/B testing tomorrow ...

I have done this recently with my Grace and its not too difficult. The worst thing is that they apply a bit of a glue at the valve so you need some heat (I used a lighter but a blowtorch is better) to turn the OPV. The taste is a lot better (added body and sweetness) and there is definitely less channelling. This will also depend on beans used - dark Italian probably won’t benefit as much as medium/light single origins which I prefer.

I think I turned OPV about 270 deg to have the static pressure at 9.5-10bar. When brewing it sits on 8.75-9 but obviously depending on the grind and dose.

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  • 1 month later...

I have the Victoria PL91T and that's set pretty high as well.

Tried to adjust it with a bit of heat from a blowtorch but didn't get much movement out of it with the glue on the thread. Probably got it down to about 9.5 bar. Ended up damaging the screw head as it's made out chocolate/brass.

Bought a new valve hoping it wouldn't have the glue..no such luck 😞
Will have another go when I get time and will fit an OLAB pump while I'm there. Supposed to be quieter?!

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  • 3 weeks later...

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