CNC Mill Mark Removal in Intake Port

One final thought. IMO, 1 cfm change from test to test can be ignored. 2 cfm change might be real. 3 cfm change and something is really going on. A small change to the entry plate can easily cause 3-4 cfm change.
I was going to ask you earlier about this. What would you say your machine is capable of for precision and repeatable accuracy for the CFM measurement? For instance can it determine to a tenth (0.1) of cfm? Then for a test repeated on the same port under same conditions say five times stepping through the lift range, what would you expect to see for variation for at a given lift number? I'm just trying to baseline the changes I see people reporting, vs machine capability. Changing something that on the next run results in a 10 CFM change may or may not be reality. I am/was an engineer and know that when examining test data, the capability of the measurement system needs to be factored into the analysis.

BTW...I'm enjoying your journey through these tests. Very interesting for me and your methodology seems pretty solid. I don't have room for a full flow bench but this Fall I'm hoping to see what I can cobble together with some controller HW and fans I have laying around from old work projects.