K&N A039A4 is what I have installed on my Aerovee with AeroCarb. The original PN is no longer available, but K&N E-3120 is still sold and may work though it will be tight based on my measurements. I did a search for other filters with similar specs online but I didn’t find any reputable options.
Note: based on another discussion thread, the E-3120 is a little bit short (only 2” high vs. the old E-4310 at 2.75” high). So the 3120 may not provide sufficient airflow.
2 Likes
I wonder if they increased the size of the filter on AeroInjector models. The filter on my AeroCarb measured approximately 3.5 inches in diameter and 2 inches tall. The through bolts that hold the filter and the base in place are only about a quarter inch away from the exterior moldings.
There is a discussion of the Baldwin PA4557 disposable paper element, it’s nearly twice as long, with the same diameter, longer AN3 bolts will be required.
Another option, might be able to use the stock bolts, Speedway Motors paper element, their part number 91011004, only two inches high though.
http://www.speedwaymotors.com/Speedway-3-7-8-Inch-Paper-Air-Filter-Element,4262.html
This seems to be a common size for two barrel hot rod carbs. Speedway also has a washable element version like the K&N E-3120.
http://www.speedwaymotors.com/Speedway-3-7-8-Inch-Washable-Reuseable-Air-Filter-Element,4264.html
I recently installed a K&N RU-1900, went right over the intake bell of the AeroCarb and clamped down tight
2 Likes
Thanks to all who posted other alternatives. My original filter is 20 years old but it does seem to be in decent condition. I run K&N filters in most of my cars and motorcycles so I was able to clean and reoil it. I’ll see how it goes and I’ll investigate other options people have listed if needed.
1 Like
Hi Guys,
I’m in the process of switching from a Zenith Carb to an AeroInjector. That requires me to totally redo my induction system (Outside Air). The clearance between the cowl bottom and the air filter seems to always be a problem. In my search for the “perfect” filter for the AeroInjector, I ran across the K&N RU-045V. The filter does not hang as low as the standard Sonex air filter assembly, it provides more filter area, and it requires no extra plumbing. The input flange is a tight fit but after forcing the bell of the AeroInjector into the opening the filter sucks up on the beveled portion of the input bell and sits there tightly. The input flange of the filter is offset which means it sits no further forward than the Sonex filter. It does have a vent in the top that I will have to seal.
I obviously haven’t flown it yet, but this will solve some fitment issues I’m having. If tuning goes well with this filter, I’ll be a happy camper.
Next, how-to fab a housing for the filter.
20260527 154909 1
Wes
3 Likes
That looks like a good solution. I’d definitely switch filters for my VeeCU installation. I’m thinking I’d want ram air if the AeroInjector mixture was in cutoff, else it should be open in back.
2 Likes
I will have NACA on the front of the cowl. I still don’t fully understand why ram rise would cause a problem if I have a forward-facing fuel vent line.
Wes
I would also like to have ram air but I’m planning to leave my aerocarb in the original configuration since aero conversions doesn’t advise it.
I’ve often considered that. I think well-designed ram air could give you a higher static pressure than a pitot-tube type thing.
1 Like
I don’t necessarily want ram rise. However, I had it with the Zenith and I have to either use or patch the hole in the front of my cowl. The problem with ram rise is that there is a possibility of adding back pressure to the fuel inlet which would lean out the mixture. However, if I have the same ram rise being forced into the fuel tank, it seems they would cancel.
If I have problems, maybe I’ll vent to that vent hole in the top of the filter. That should fix it.
Ram rise only helps at full throttle. That is climb or race mode. In climb, at 100 MPH (86 Knots), you only get about 0.35 IN.HG. rise. That’s about 1 HP. In race mode you could see more like 3 H.P. The big win is feeding the engine cooler air.
Wes
1 Like
Now I do like this filter! It would ‘fix’ the same problem I had with cowl..filter interfacing, while, maybe, increasing the overal area of the filter. I will look into getting one! Thanks!
1 Like
We spend a lot of time in climb, and some of us do the race mode thing. Assuming the AVC people get through the info I submitted! There is also the high altitude cruise case. I think over 7500’ or so you need WOT in most normally aspirated aircraft just to get 75% power.
2 Likes
Yea, always an interesting discussion, especially while flying a fixed pitch prop. I guess what I was trying to point out is that, at the speeds we fly, you have to be right at the end of the throttle before you can see an increase due to ram rise.
With the props we use with our lower powered engines, it is my experience that full throttle, regardless of altitude, produces an unacceptably high RPM for cruise flight. So, I never cruise at full throttle.
Earlier you said that you had changed props after some performance increasing mods you made. I’m interested in what prop you are flying now.
Wes
Interestingly, both props are Prince 54x44. The original was definitely built differently as I was seeing 3300-3400 in climb and it would go to over 3600 RPM at WOT. Never found out the endpoint as it was too scary, and I was only getting about 120 kts. This prop I’m currently seeing about 3070 in climb. I’m not sure if it is the density altitude of the warmer temps, or maybe the head porting I did was harmful, but on my last WOT run to 02C and back I was only seeing 3360 RPM. I used to get a little under 3600.
That is interesting. I’m flying a Prince 54x50. Early on, before I had to dial back the carb due to the highest EGT busting 1400, I was seeing 3400 in climb and 1000 FPM. I’ve never been able to make sense of that.
I do remember that when Sonex quit offering Prince propellers they stated that there were inconsistencies between “identical” propellers.
Lonnie is a nice guy. I’ll discuss it with him after I get the engine running the way I want and fix my horrible out of rig condition 
Wes
Now I understand what drives the mad scientist.
Edit: here’s a fix.
1 Like