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Has anyone found a K&N airfilter for the AeroInjector that will fit in the Onex cowl without having to modify the cowl?

petep wrote:Has anyone found a K&N airfilter for the AeroInjector that will fit in the Onex cowl without having to modify the cowl?

Nope. I did modify the bottom of my cowl. Doesn't look that bad.

I have a K&N 3120 on my AeroVee engine, it fit right on. I did not have to do anything to the cowling although it IS close. There are no marks on the inside of the cowl that would indicate it has ever touched it.

Happy Landings
John
N50NX

K an N makes a small round filter that fits the injector and the cowling. I don't know the number but it shouldn't be hard to find,
Onex 107

Edit: The original numbers were quite wrong! The correct numbers are now below.

I researched several K&N filters when I was selecting my Jabiru 3300 filter. According to K&N's calculator, the Jabiru 3300 needs 32 sq inches of filter area for 200 cu in displacement at 3300 rpm. I use the RU-0630, and it just fits between the AeroInjector and the engine mount tubing (tail dragger). It's oversized, but it has been working great!

My full results are below.

All these filters will clamp right onto the 2.25" diameter bell mouth of an Aerocarb or AeroInjector using the included hose clamp.

Filter # / Dia (in) / Height (in) / Effective Area (sq in) / Notes
RC-1950 / 4.5 / 2 / 24 / Chrome top
RC-0650 / 5.5 / 2.5 / 37 / Large and round; chrome top
RU-0650 / 5.5 / 2.5 / 37 / Large and round; 3/4" Off-center Flange
RU-0660 / 5.5 / 3 / 45 / Large and round; taller than 0650; 3/4" Off-center Flange
RU-0630 / 4.5 / 4 / 47 / Tall and skinny; centered opening
RB-0600 / 3.5 / 4 / 35 / Tall and skinny; 5 Deg Offset Flange Angle
RU-1710 / 3.5 / 5 / 43 / Tall and skinny; 20 Deg Offset Flange Angle
E-3120 / 4 /2 / 20 / Direct size replacement for the Sonex paper filter element

Jeff

Jeff,
How did you calculate square inches considering the height of the filter is not necessarily the height of the available filter material? The RC-1950 looks like a good match for the Aerovee - 23 sq in required per the K&N equations assuming 3600 RPM vs 24 sq in in your table.

I don't think a filter taller than 2" will work in my cowl.

Hi,
I fitted A K&N RC1980 filter onto my AeroInjector and this fitted into the cowl without modification. Also added a strap around it so it couldn"t come loose as it is only held by a collar. See pic.

Thank you Dirk! I had also been considering an RC1980 and had shortened the rubber coupling and intake for clearance. I was concerned about the inlet being slightly larger than the aerocarb and also about the proximity to the exhaust pipes. It looks like you are not having problems with either of those two concerns, though I do see you wrapped your pipe near the filter.
Pic below.

Edit: mine is a Waiex, my cowl room may be different. This picture was taken before I shortened things.

Bryan,

K&N published a formula on their website to calculate the effective area of their filters. It subtracts 3/4” off of the height to account for flow losses near the ends. The resulting height is them multiplied by 3.14 ("Pi") and then by the diameter to yield the effective area.

It’s their formula (and the above is from memory alone so it may be slightly off). I just ran the numbers and reported back. However, I think it’s a conservative approach that will yield good results.

Jeff

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-edit-

Here are the equations K&N uses, and the link to their website for those that want to know more.

Equations:
Area (sq in) Required = CID x RPM / 20,839
Effective Filtering Area (sq in) = Dia x Pi x (Height - 0.75 in)

https://www.knfilters.com/filter_facts.htm