Air Flow Data For Filters in Canisters

This page shows air flow in CFM for air filters when used in a remote filter canister, all measurements were taken while using a 100mm enty and exit snorkel. Optimal CFM measurement is taken at 1.5 inches of water, this is considered an acceptable pressure drop across a filter. 1.5 inches of water equates to aproximately 3.73 mbar.

1 inch H2O = 2.49 mbar

Graph comparing flow rates of different remote filters

The graph below shows flow rate in cubic feet per minute (CFM) against pressure loss across the filter measured in inches of water (Inches H2O). Measurements were taken for each remote filter with 100mm entry / exit snorkel, however as the larger air boxes are not designed for use with a 100mm snorkel flow graphs with their optimum snorkel size have been included. The larger Suzuka Pro is designed to use a 127.5 mm or a 152mm allowing it to flow much more air.

1 inch H2O = 2.49 mbar

Snorkel Sizing

An inlet that is too small will cause a pressure drop inside the air box restricting performance. The Snorkel sizing guide shows the minimum recommended inlet and ducting snorkel size for a power output category. The larger the power output of an engine the more air it will require to run at peak efficiency, therefore a larger snorkel is needed as power increases. Multiple smaller snorkels can be used to achieve the same open inlet area as a larger snorkel for example if a larger snorkel won’t fit on the air box multiple smaller snorkels  or oval exit snorkels could be used to create a comparable open area. High flow alloy straight trumpets can also be used as intake snorkels.

On typical engines 150CFM is required for each 100BHP

On high performance engines 130CFM is required for each 100 BHP

The formula below shows the formula for required airflow to the engine in cubic feet per minute.

CFM = Engine Capacity (Cubic Inches) / 3464  * Max RPM

1L = 61.0237in³

For example a 5.7 litre engine requires 703CFM of air at 7000rpm :
703 CFM = 347.84CI / 3464 * 7000RPM

Or if supercharged...

CFM = (CI * RPM / 3456) * (boost [psi] / 14.7 + 1)