When shopping for a blower, vacuum or loader, you will undoubtedly run into the acronym CFM (Cubic Feet per Minute). CFM is the amount of air that is being moved. It is a measurement of volume, that is how many cubic feet of air is being moved for every minute of operation. More CFM is a good thing and means more air to push the dirt, leaves or debris you are trying to move.
Effective CFM: Calculation obtained by applying accepted engineering methods of measuring overall average airflow volume. This is the default figure published by Scag for all its blowers and truck loaders.
Here's how we collected the published CFM data on Scag products. An accepted engineering method of collecting CFM data is to take multiple readings at a distance of approximately 10X the diameter of the output tube. Example: if the output tube is 6" in diameter, we would extend the tube about 60" and take readings at the end of that tube. This is a good method as it gives the fast moving, turbulent air some time to settle down for more consistent, real-world, non-exaggerated readings.
Depending on the diameter of the tube, up to 24 readings are taken in different locations across the output of the tube (reference the orange dots in the illustration above as an example). As you might expect, the numbers can vary depending on where in the tube you take the reading, so we take an average of those various readings and that is the CFM rating we publish.
To be certain this was a fair method when comparing our numbers against the competition, we tested their equipment using the same method. In most cases we achieved the same CFM numbers they publish online and/or in their brochures (for those that publish their CFM ratings).
Theoretical Peak CFM
Theoretical Peak CFM: Figure derived by assuming the highest single-point measurement obtained during testing would apply to the overall airflow volume calculation. This figure is published by some other brands of blowers as their default "CFM" measurement.
This measurement is taken by finding the peak rating directly at the end of the discharge opening. This method does not use the test tube (shown above) which allows the air to settle down and represent a more real-world scenario. One negative to only reporting this CFM rating is the measurement is only taken at one small area of the outlet that doesn’t truly represent the airflow volume for the entire output nozzle.