I am trying the intelligentsia black cat classic espresso, follow their recommendation 18g 5 sec preinfusion and 23 to 28 sec.

but I have encounter this ... I am using Kees speedster, when I switch on preinfusion it takes 10 to 12 sec to see the first drop, and finished around 25 sec.

my question is are there anyway to pre infusion only 5sec? should I switch on regardless whether I see the first drop from speedster?

Thanks

PI time has little to do with how long will it take for the first drops to appear, that depends more on the pucks resistance (dose and grind).
I don't know specifically about the Speedster, but I would guess it operates at approximately the same (4-5 secs) PI time, as most other PI pump machines.

If you have a recent version of the Speedster the combination of the remote .6mm jet & the PPIC gives a full 12 second ramp to a 3 bar line pressure when you select manual P/I. You don't have to wait for drips to show or for the P/I pressure ramp to complete. Try the shorter 5 second P/I & see which one you prefer.