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Air filter mod?

floridawing

Well Known Member
Hello, I have a RV6 with a O-320 and MA4-spa carb. When I removed the air filter to clean it today I noticed a chunk of filter missing. It looked like the builder needed to do this to clear the accelerator pump on the carb. Is this a normal mod needed to Vans FAB kit? I hate to put it back like this. Thanks alot for your input!

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Same here

On my purchased RV-6A with O-320-E2D, carb, my air filter was similarly modified.

One data point.
 
more questions please

I have a friend with a -7 with an 0-320 also and his filter is modified like the pictures. Seems the airfilter is too small to fit around the base of the carb, and must be modified to intersect. Vans sells a FAB-320 with filter E-3260 and FAB-360/540 with filter E-3450. Couldn't you install the 360 airbox (that doesn't require moding the airfilter) on the 0-320 engine install?? Would it fit in the cowling? I know it would be a larger filter than the engine needs but would make future maintenance easier. I understand modifying the airfilter isn't that big a deal but it does keep you from being able to rotate the filter around to get a fresh area of media in the front with each cleaning/service. Does anyone have experiance with both the 320 and 360 airboxes to address this question? Thanks.
 
Trim Job!

Wow! I have never seen one trimmed that much! Mine has some rubber trimmed away but I've never got down that far into the filter element itself and it fits fine, lasts a long time!
 
Bumping for more info

"Vans sells a FAB-320 with filter E-3260 and FAB-360/540 with filter E-3450. Couldn't you install the 360 airbox (that doesn't require moding the airfilter) on the 0-320 engine install?? Would it fit in the cowling? I know it would be a larger filter than the engine needs but would make future maintenance easier. Does anyone have experiance with both the 320 and 360 airboxes to address this question? Thanks."

I'd still like to know if there is a size difference in the 0-320 and 0-360 airbox and if they both fit a standard cowling? Anybody?
 
Look for one of my old posts

I found an alternate K&N filter part no. that doesn't require butchering and posted the part number ~ 2years ago.

There didn't seem to be much interest then, perhaps not any now.

All I can say is that the alternative part has worked fine for me. I discussed the differences between the two filters with aK&N application engineer before I made the switch.

LarryT
Larry Tompkins
N544WB RV-6A purchased flying
W52 Battle Ground WA
 
Great Find!

I found an alternate K&N filter part no. that doesn't require butchering and posted the part number ~ 2years ago.

There didn't seem to be much interest then, perhaps not any now.

All I can say is that the alternative part has worked fine for me. I discussed the differences between the two filters with aK&N application engineer before I made the switch.

Larry - nice find - I plan to replace at annual and will be using your mod! Thanks!
 
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
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Thanks Larry, Good info..........reposting here to have info in another place, just spent 10 minutes searching old posts.....thanks for link Pete.

For future reference, my original question.......can the 360 airbox be installed on a 320 ??? will it fit in the cowling? I'm imagining the cowls are standard, I'm not a builder so I'm asking. seems like originally installing a 360 airbox would give a larger filter element and solve the problem at the source. Has anybody been down this road before???? again, Thanks Larry, good info!
 
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