Hi,

just upgraded my grinder to a Eureka Atom Specialty 75 which helped me a lot getting more consistent espressos on my Izzo Vivi.
But to be honest, I'm still wondering how people on YouTube can experiment with settings in the 1-2 grams scale. If the shot is this and that, try letting it run for another few grams in the cup.

I'm grinding 18,0 grams in and 30 seconds later getting somewhere around 27 to 42 grams out from first drip. Not very precise.
Also, if I hit the timer on my scale at first drip I can stop it at the 30 sec mark, but sometimes it drips a bit first, then stops, and then starts to drip again, leaving the shot overextracted. Next shot could be running more smoothly, which gives way more fluid in the cup.

My machine is an Izzo Vivi PID, I get around 9 bar during brewing. My shots are 18 grams in a 18-22 basket and gets prepared with a leveller before tamping. I use a bottomless PF and extraction seems to run pretty fine with little to no channeling. Pucks are a bit of a soggy mess, but from what I gather that shouldn't be a problem. My scale is a Hario Drip Scale.

I feel that my technique is pretty uniform from shot to shot but the results doesn't seem to be as consistent as I'd like, so experimenting is not really possible.
What could be my weakest point?

Just to clarify: how sure are you that the dose is always 18.0 grams exactly? Do you measure the input after grinding, or are you relying on the grinder's timer (or single-dosing but weighing before grinding)? Deviations as small as half a gram can translate into shot time differences of several seconds.

Are the results consistent taste-wise, if you always aim for the same brew ratio? I've largely stopped worrying about brew times as long as they're roughly in the right ballpark. Hitting the right brew ratio seems to be far more important. The deviations seen in the brew time could be due to a number of factors (puck prep; different proportions of different beans ending up in the portafilter, if it's a blend; other random stuff) but rarely seem to ruin a shot if small enough.

Yes, I weigh all shots before tamping.
The results taste-wise are as expected a bit all over the place...
Interesting to hear that you worry less about time. I thought the flow was more important than ratio. That a fast flowing 36 gram cup at say 25 sec would be sour and a slow 36 gram cup at say 35 sec would be bitter..?

People tend to care less about time nowadays, flavor is king. You can do a coarser grind turboshot in 15 seconds that will taste delicious due to even extraction (no channeling).

I will look into getting a scale that is faster than my Hario, maybe perhaps a Acaia Lunar. Then I can weigh while brewing at instead of stopping at exactly 30 secs I can focus on the brew ratios instead.

That's excellent advice, thanks. I always thought that time was important.

As an example: The general consensus was that light roast required quite a fine grind for espresso to be able to extract all the goodies. However, if your puck preparation is not on point, the chance of channeling are huge. This can be mitigated by techniques such as good WDT and preinfusion in the brew, but chances are that you will get areas in the puck that are over extracted and some that are under extracted. So, basically both bitter AND sour. By grinding a bit coarser you decrease the extraction potential in theory, but practical application shows that the flow of water is less likely to channel and hence giving a much more even extraction and yummy shot. A shot like this can typically be much faster than 30 seconds, and look quite "ugly" during brewing.

One of the better $15-ish scales is sufficient, in my opinion. Time is an output for me. It is the target weight I want to hit repeatedly. I find a 10% step in weight to often be significant in flavor. 36 g may be consistently "meh", but 40 g notably better, for example.

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For me, an expensive scale only starts to make a difference in the cup one you have an app that reports mass-flow rate. I've had a loaner Acaia Lunar 2021 on the bench here and I wasn't impressed by the flow-meter feature, especially compared to the app outputs I get from custom software. By the end of two weeks, I no longer had scale envy.