I've found this to be highly influenced by the roast. the darker the roast the shorter the time of the preinfusion you want to use in my experience. Even if it hasn't started pushing through the basket like the slayer videos show.
I also found that with lighter roasts, I was confusing overextraction and underextraction due to the higher acidity than what i was used to with my 'ol comfort blends. If you still have a refractometer, try it out.

Something doesn't sound right. If you can get a good shot (i.e., not sour) using a traditional profile, then the roast isn't suitable for the Slayer technique. The Slayer technique is primarily useful for very light roasts that pull sour with a traditional profile, or when you want to experiment with light-to-medium brew roasts pulled as espresso.

It takes practice to dial in a Slayer shot. If you grind too coarse, the long slow preinfusion will break up the puck and you'll get channeling or gushing, and likely the shot will be sour. If you grind too fine, then the long slow preinfusion can't break up the puck and it resists water flow to the point of underextracting (two minutes is way too long.) There's a place in the middle where the grind is fine enough for the preinfusion to loosen the grounds without causing the puck to break up but enough so the machine doesn't choke. You have to do some experimentation to find the right combination of preinfusion flow rate and grind.

It's possible that your roast is too dark for the Slayer technique, which might cause you to hunt around in vain for the sweet spot. Best to try a brew roast, if you have one handy, or buy an SO espresso roast from George Howell.

Your flow rate works out to 106 ml/min, which is about 33% higher than Slayer's recommended flow rate of 80 ml/min. But I think that should work for most light roasts. It's been a while since I measured the flow rate when I'm doing a Slayer-like shot on my modified GS/3, but since I can only get the line pressure down to 1.5-2.0 BAR it's probably similar to your flow rate.

spressomon wrote:Generally, when using the IMS single baskets (all things 58mm basket related ), I find I can down dose without adjusting the grinder setting.

Same here.

Peppersass wrote:Something doesn't sound right. If you can get a good shot (i.e., not sour) using a traditional profile, then the roast isn't suitable for the Slayer technique. The Slayer technique is primarily useful for very light roasts that pull sour with a traditional profile, or when you want to experiment with light-to-medium brew roasts pulled as espresso.

This is most likely the correct explanation for what I noticed since the espresso I pull using traditional machine settings tastes perfect. The roast isn't all that light. It's an Ethiopian Guji roasted by my local West Palm Beach Subculture Coffee Roasters. They are using standard LaMarzocco machines that don't have pre-infusion at all, so they are roasting for that profile.

I'll probably revisit this after I get a few months of practice under my belt. It's challenging enough to dial in the nuances of a standard espresso let alone trying to eek out good flavors from an unforgiving, bleeding edge roast!