Compute CFM for Two-Stroke Engine Air Filter Requirement

[97K15004WD]

I'm looking at a specific two-stroke application and have computed CFM requirements for the air filter to confirm adequate flow. I have several questions, as I would like to confirm my numbers.

Application: chainsaw
Engine: 121.6 cc
Bore: 60 mm x 43 mm
BHP: 8.7 bhp at 8,500 rpm
Max RPM: 11,000
Computed Ve: 0.5841435966524767

I come up with around 28 CFM, but this site comes up with 15.67 CFM

Air Filter Calculator - Calculate air filter size for BHP/Power - StrikeEngine

This air filter calculator will tell you if your current air filter is big enough and if not, what size of air filter you need for your power level.

strikeengine.com

I have 47.2368985 CFM at 11,000 RPM as the maximum possible airflow with the above information.

What am I missing?

 

[wag123]

2-cycle vs 4-cycle. The website is basing it's calculations on a 4 cycle. A 2-cycle takes a gulp of air on every crankshaft revolution, a 4-cycle on every other crankshaft revolution, but it isn't a whole 121.6 cc gulp of air on a 2-cycle like it would be on a 4-cycle due to a 2-cycle's inherent inefficiencies.