How to calibrate for head adapter?

[The Silver Bullet]

I now have FP1 and directions state to calibrate with plate on top of bench because head adapters causes skewed readings...
When I calibrate to the top of the bench, I am seeing a 20 cfm difference with the head adapter.
What I am confused about is it seems I would want to calibrate utilizing the head adapter since the head will be flowed utilizing the adapter.

Am I missing something here...lol

Thanks for all your help,
Richard

[86rocco]

The head adapter doesn't effect the way the FP1 unit measures the air flow rather it effects the way the air would enter or exit the calibration plate thus effecting how much air flows throught the plate. When calibrating the FP1 with a plate, you need to make sure the plate is flowing at it's designed rate so that you get an accurate calibration of the FP1 sensor.