Aircraft is RV-6A w/ O-320 engine and MA-4SPA 10 - 5217 carburetor.
I installed an E-3322 Air Filter instead of the E-3260 sold by Vans because I did not like the idea of taking a divet out of the air filter and patching it up with RTV.
A calculation of the perimeter of the E-3260 round filter showed that its ID is 0.2" too short in the intended oval application. A calculation of the E-3322 showed that it was 0.39" too long for a perfectly oval application. I reasoned that this might be just enough extra to stretch around the mixture enrichment casting boss on the aft side of the carb and the accelerator pump bottom cover on the pilot's side of the carb. After purchasing a E-3322 from the local speed shop, Baxter Auto Parts, I tried installing the E-3322 on the carburetor. It fit without modification.
E-3260 has a 300 cfm rating
E-3322 has a 295 CFM rating. The OD of this filter is 1/8" less than the 3260, which is what makes the packaging w/o modification possible.
For future reference, I have talked to K&N tech support and learned:
Air flow ratings are based on 6cfm/ sq. in of perimeter surface area.
Because the 3322 is a thinner ring (less pleat depth) the filter might have to be cleaned more than the the 3260.
HOwever, the filter cleaning interval for cars is 50K miles operating in a dirtier environment than our planes. 50K is 250+ hours, most of us probably don't fly that far between annuals.
Because I am a mechanical engineer I am very aware of the Law of Unintended Consequences. I hesitate to pronounce this a success since I haven't accumulated any hours in service. I guess I will just describe it as a "packaging success" that avoids cobbling up a filter.
Larry Tompkins
I installed an E-3322 Air Filter instead of the E-3260 sold by Vans because I did not like the idea of taking a divet out of the air filter and patching it up with RTV.
A calculation of the perimeter of the E-3260 round filter showed that its ID is 0.2" too short in the intended oval application. A calculation of the E-3322 showed that it was 0.39" too long for a perfectly oval application. I reasoned that this might be just enough extra to stretch around the mixture enrichment casting boss on the aft side of the carb and the accelerator pump bottom cover on the pilot's side of the carb. After purchasing a E-3322 from the local speed shop, Baxter Auto Parts, I tried installing the E-3322 on the carburetor. It fit without modification.
E-3260 has a 300 cfm rating
E-3322 has a 295 CFM rating. The OD of this filter is 1/8" less than the 3260, which is what makes the packaging w/o modification possible.
For future reference, I have talked to K&N tech support and learned:
Air flow ratings are based on 6cfm/ sq. in of perimeter surface area.
Because the 3322 is a thinner ring (less pleat depth) the filter might have to be cleaned more than the the 3260.
HOwever, the filter cleaning interval for cars is 50K miles operating in a dirtier environment than our planes. 50K is 250+ hours, most of us probably don't fly that far between annuals.
Because I am a mechanical engineer I am very aware of the Law of Unintended Consequences. I hesitate to pronounce this a success since I haven't accumulated any hours in service. I guess I will just describe it as a "packaging success" that avoids cobbling up a filter.
Larry Tompkins
