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Square filter

cgoldy

cgoldy

Registered User
Moogerah Queensland Australia
I have an O - 375 from Bart. I want to change to a square filter. Word has it that these engines need plenty of air. Can anyone recommend a supplier of a square filter assembly I can order?
 
Javron makes a nice square carb air box if that is what you are referring to.
0-375 is the same as an 0-360 for your purposes.

Randy Ruppert also makes carb air boxes and is very well respected.

I believe Wag-Aero may also have one for sale.

Hope this helps

Bill
 
Highly recommend Randy Rubbert (that is RuBBert wth Bs as in Bill; Mr Rusk) excellent workmanship--best of any I have seen. Randy's # 701-847-3008
 
The round airfilters provide more air. But you have to modify the lower cowl.

john
 
Round filters do not provide more air they just have more filter area. The airbox is the exact same size. Make sure the airbox you buy has the cross hairs in the riser between the box and carb flange. The cross hairs straighten the airflow into the carb. Look at the Donaldson Air Filters. I no longer use bracket filters.

Jason
 
you are correct, the airbox is about the same size. The round filter has more filter area and the cowling configuration provides more ram air affect then the square filter. I also don't use Bracket filters. I use K&N filters.
John
 
I did some static thrust testing a long time ago. A round filter would out pull square every time . Id rather have out of the hole thrust then cruise speed ram air flow in a cub.
 
cubunltd said:
you are correct, the airbox is about the same size. The round filter has more filter area and the cowling configuration provides more ram air affect then the square filter. I also don't use Bracket filters. I use K&N filters.
John
Click to expand...

John, are you using K&N on the square or the round filter? If it´s the square, could you or someone provide which K&N part fits?

Thanks,
 
Round filter but I think they make one for square filter also. i'll see if i can find the info. may take a few days.

john
 
here are the pics of a round filter air box showing the inlet and the cross-hairs

IMG_0900.jpg
IMG_0901.jpg
IMG_0912.jpg


And here is info on the air filters I prefer to use. Much better filtration than a bracket with out restricting the flow and it's a cleanable 500hr filter. I like these better than anything else on the market.

http://www.donaldson.com/en/aircraft/ga/


Boz, any chance you ever did a pull test with no filter installed? What brand of filters were in the 2 diff airboxes you used when testing the difference between round and square? I have heard that removing the air filter will give you a few more static RPM.

I like the look of the round filter lower cowling but as a mechanic I prefer the square filter lower cowl and airbox.


Jason
 

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Challenger is the one that handles the K&N filters. Pretty sure they have the square one also. They can be cleaned and reused over and over again.

john
 
Hi
Would anyone have the donaldson # for the round PA-18 filter and can do you buy them from spruce??
Thanks, Aurele
 
Hi Aurele,

Here's a link to an old thread where Donaldson filters were discussed. Look at the last post on the tread. I doubt the filter Bob refers to is a listed aircraft filter but then neither is the NAPA version. Some time back I tried to contact Donaldson to see if there was a PMAd round Cub filter available and didn't get a quick answer. Their aircraft division staff was at a big conference somewhere and my attention span was short. http://www.supercub.org/forum/archive/index.php/t-40098.html?

SB
 
jgerard said:
Boz, any chance you ever did a pull test with no filter installed? What brand of filters were in the 2 diff airboxes you used when testing the difference between round and square? I have heard that removing the air filter will give you a few more static RPM.

I like the look of the round filter lower cowling but as a mechanic I prefer the square filter lower cowl and airbox.


Jason
Click to expand...

Yes, Filter removed on the square would pull the same as a round installed. That told me the square just didn't have enough area. These were stock 150 and 135 cub boxes on a 320. The round was the orange fram, don't remember on the square.

Maybe one of these fancy new (and I'm sure not cheap) square filters will get close to the performance of the round when new, but what happens when it gets some dirt or moisture on it. For me the cheap round filters I can pick up at napa are a no brainer.
 
the donaldson filter website reads good and sounds good and I'd be willing to try one however I can't seem to find a listing for the round filter. All they show is the square one. The round filters from NAPA work fine but are not approved. the K&N are more expensive but filter better and pass more air and are re-usable and approved.

john
 
Hey Col,
have you spoken to Randy Rubbert yet? i'll be interested to hear his take on all this?
cheers,
Phil
 
I'll call him tomorrow. There must be a square available with good flow.
 
Well,if you look at the round version,the inlet area is much bigger than the square style, which must be only 5-6" square. Or roughly 20-30 square".. But then they both swedge down to the inlet side of the carby. You need a supercharger or turbo????
 
Hi Ron, the short answer is slowly. But I feel that I'm gaining momentum! I am building in my hangar, about 20 minutes from home. So I go out for the day. I don't have power as yet, and still setting up benches and buying tools. I'll have a lot of packages to open when I get home at the end of the month, which will set me up for more progress. It's the Jamestown fly in next month. So we are heading over to that. Any thoughts of attending?
 
The PMA'd Donaldson square filter for a 150 hp Super Cub is the P10-7150 noted above. It is also the filter for the Cessna 150 (O-200 powered). The Donaldson filter for the Cessna 172 (O-320 powered) is the P10-7172 (from memory). It is a much larger filter. I wonder how that would compare with the round filter with respect to engine power output. Would be good not to have to put that big ugly round filter set up on these nice experimental Cubs.

Andrew.
 
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