Quick question: When pulling a shot on an E61 HX machine, like my QM Anita, do you start your shot timer when you throw the lever up or do you wait to start it until after the pre infusion, when the machine reaches full brew pressure? My machine doesn't reach full pressure for about 3-4 seconds, I do believe.

I'm not usually too concerned about timing, but I tend more to watch the progression of my shot to know when to stop it, but when trying out a roasters recommendations, I like to be a little more precise. For example, I'm pulling Verve Coffee's "the Sermon" Espresso right now and they recommend 20g in the basket, 24-27g out, in 24-27secs... so when would you start the timer to hit the 24-27 second mark?

I read somewhere (I don't remember where) that you start the timer when you start the shot, but that you only count half time until first drip.

So if the shot runs 30 seconds, but first drip is at 4 seconds, the actual usable count would be 28 seconds.

I don't know how pre-infusion works into this.

Interesting. Yeah, I've never heard that. With the Crossland CC1 that I had, I would do 2 secs of Preinfusion, 4 secs wait time, and then start timing the shot.

I use a Acaia Lunar scale and have it set to start the shot timing in auto mode. This means I place my cup on the scale, it is auto tared and the timer starts, at the same time I raise the lever. The scale keeps weighing / timing until I stop the shot. What I've found is that there is an extra delay because of the pre infusion process. I haven't worried about it as I go by coffee in / out, and then taste keeping the shot time within reason.

I have my lunar set up so the timer starts when the first drops hit the cup

If I use another scale, I start the timer when the pump comes on, totally inconsistent

I think, it does not matter much. 20 to 30 seconds is only a guideline in the first place and used to be from the time we pulled the lever. As we've moved to other technologies in making espresso, especially weight-based shots, it's become less important. Most importantly, we fine tune for taste, not precise time...that should never change. It's what you get in the cup that counts.