From what I gather there is a lot of factors that can be monkeyed with. How much pipe, what size pipe, where and how you measure cfm. I don't think any two manufactors measure them the same. Bill Pentz measurements are the only ones I really trust as accurate and consistent. I imagine that most manufactors numbers are accurate, just they sometimes measure it where or with a method that makes them look good.Originally Posted by Brian Gumpper
As for pipe, yes is make a big difference. Flex pipe is rough inside and that disrupts the airflow. Elbows disrupt the air flow. Smooth and straight is best but of course it's not usually possible to run it that way.