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  #21  
Old 08-23-2017, 04:31 PM
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Originally Posted by DanH View Post
As compared to pulling air from inside the lower cowl, through the plastic flap valves. The rise is large because it's so badly choked with the butterfly closed. It is definitely not an optimized filter system.
rod has a new case that resolved that issue. With the butterfly closed, I now get the same MP as the factory air filter. There definitely were issues with the earlier cases.
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  #22  
Old 08-23-2017, 04:33 PM
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The enticing feature of the K&N filter is that it has screen on both sides of the pleats so there's no possibility of any paper coming loose and lodging in the carburetor. The rubber cap at the small end seems to be really well secured.

OTOH, I have had high silicon readings on my oil analysis since day one. Some say the K&N filters aren't as efficient as paper filtersl. That could well be true, but I doubt my high silicon readings are from dirt passing through that filter. I recently re-plumbed my oil separator to drain to a small cannister rather than back into the crankcase. My crankcase vent hoses are all silicon rubber so that could be the source. I'll know in a few months.
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  #23  
Old 08-23-2017, 04:36 PM
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Originally Posted by 1001001 View Post
Glad you posted this. I was getting close to sending a message about it! I remember when I came out to look at your airplane and we talked about it, but I was drinking from a firehose and forgot so many things you told me, including who made the ram air for your bird.

Are you still satisfied with it? I remember looking at your build log and not seeing too much in the way of plan modifications to install it. Is that really the case, or did it require a lot of fiddling with the cowl and such?
I probably wouldn't do it again. It does what it advertises, it it hasn't been without its issues. You have to install it correctly. Just ask Vic Syracuse about the ones he found installed improperly.

I went through three or four upgrades. I feel like I was doing beta testing for a rod. I had to upgrade the reed materials until I found a thickness that work well with a io-540.

But it does work. It allows me to reduce MP and save a little fuel when doing a cross country.
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  #24  
Old 08-23-2017, 05:50 PM
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Originally Posted by JonJay View Post
Russ McCutcheon's RV4, horizontal induction, no filter. He has flown it that way for many years. I do not know how many hours but a bunch. Perhaps he will chime in.
My '42 Aeronca L3 didn't even have provisions for a filter. It had 1000 hours on it when I got it and I put 600 more in the ten years I owned it. It ate a lot of bugs and never seemed to mind.

So, plenty of examples running without filters but I don't think you will find any real data on engine life comparisons filter vs not.

I agree with DH. There is no reason not too given the small, perhaps insignificant, gain going naked.
Hi Jon, 1600+ hours on the current engine since 2006 with no filter, the old engine had 900 hours with the same setup and had no problems related to being unfiltered. I don't really have any preference, I'm just not going to do a bunch of work to add a filter when it has proven not necessary.
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  #25  
Old 08-23-2017, 06:08 PM
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Originally Posted by SJordan View Post
Hey gusy don't forget Air Flow Preformance makes a alternate air "Y" with nice filter. It's honestly a pice of art work it's so nicely made. Much cheaper than than Rods system and much simpler. I agree ram air is probubly more work than it's worth and filtered air is best but if your like me and have to have ram air check out the Y from Don at Air Flow Preformance.
I checked the Air Flow Performance site, and it appears what I have is their FM-100 "Y" and the filter they suggest. I didn't see any pics of the FM-100 Y with filter attached, but on the FM-200 they show a tapered filter attached directly to the Y. I'm assuming there wasn't room to do that will the supplied filter for the FM-100, so it got remotely located with scat tubing, which I'd be willing to bet is horrible for intake airflow. Next time I have the cowl off, I'll do some measuring and browsing of the K&N site to see if there's a direct fit option available that will fit without the scat tubing. that would at least make me feel a little better.

Cheers,
Rusty
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  #26  
Old 08-23-2017, 08:37 PM
AviatorJ AviatorJ is offline
 
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Originally Posted by rleffler View Post
I probably wouldn't do it again. It does what it advertises, it it hasn't been without its issues. You have to install it correctly. Just ask Vic Syracuse about the ones he found installed improperly.
I bought one, it's sitting in my garage right now. Waiting on my engine to do anything with it. My question is how do you install it wrong? To me it looks like only one way to install it.
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  #27  
Old 08-23-2017, 09:14 PM
Bicyclops Bicyclops is offline
 
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Default Conical K&N

Not all the conical filters have shallow pleats.

https://www.knfilters.com/images/l/E-0995.jpg

https://www.knfilters.com/search/pro...&mp_mt=b&pdv=c

This is the one I used. I has about 7/8" deep pleats for a bunch of surface area. I don't have the calcs at hand, but I remember the area being substantially larger than the flat filter Van's uses for the snorkel setup. The pleats on that one are pretty shallow, maybe 3/8", if I remember correctly. I built a glass box for it and can tap alternate air off the back of that if needed. I made a custom scoop on the front of my cowl to accommodate it. Superior sump. At 11,500' and 74 degrees OAT, I was making 20.5" MAP. Density altitude had to be about 15K. That same day at 8500' and 83 degrees, 22.9" MAP.



Ed Holyoke

Quote:
Originally Posted by DanH View Post
John, the cone filters are relatively restrictive, as compared to the flat panel K&Ns. The pleats on the flat filters tend to be 7/8" to 1" deep, while the pleats on cone filters are quite shallow. Imagine cutting the media from the filter body and stretching it out flat. BIG difference.

Last edited by Bicyclops : 08-23-2017 at 09:22 PM. Reason: trying to insert image
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  #28  
Old 08-23-2017, 10:23 PM
Jetj01 Jetj01 is offline
 
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Default Unfiltered RV-4 O-360

I finished my RV-4 with an O-360 A1A and carbureted in 2009 and designed the intake on the Sam James cowl to be unfiltered. I have flown my -4 now 8+ years and over 500 hours with no problems and enjoy the 'ram effect' of additional MP for faster TAS! I carry an intake plug when I park my airplane and use the carb heat if worried about ground taxi in dusty conditions. There was a time when most RVs were unfiltered, as was my original purchased RV-4 with a carbureted O-320. That airplane currently has over 2,200 hours on the original engine. YMMV but there will be no air filter on my RV.
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  #29  
Old 08-24-2017, 06:52 AM
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Originally Posted by AviatorJ View Post
I bought one, it's sitting in my garage right now. Waiting on my engine to do anything with it. My question is how do you install it wrong? To me it looks like only one way to install it.
The problem/advantage of the Bower Ram Air is that Rod is a tinkerer. He's always improving the product. There were many early variations of the sump elbow and at least two variations of the canister that I'm aware of at the moment.. The new aluminum one is pretty nice. Some of the predecessors lacked some of the elegance of the new one on how they were fasten.

If my memory is correct, I believe that Vic Syracuse found a couple installs in which things weren't fastened in an acceptable manner while doing conditional inspections. I would defer to Vic if he wants to share the specifics. My suspicion is that the installer was a bit na?ve and didn't understand proper techniques.

If you have the aluminum elbow, it's hard to screw up the installation. For the IO-540, Rod upgraded the canister from four holes to six. This helped increase airflow when the butterfly is closed. In comparison to the standard airbox on a RV-10, I'm now generating comparable power with the ram air closed and still getting about a 1" MP above the plans airbox when open.
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  #30  
Old 08-24-2017, 07:35 AM
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DanH DanH is offline
 
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Quote:
Originally Posted by Bicyclops View Post
Not all the conical filters have shallow pleats.

https://www.knfilters.com/images/l/E-0995.jpg

I built a glass box for it and can tap alternate air off the back of that if needed. I made a custom scoop on the front of my cowl to accommodate it.
Ed, have any photos of your airbox and inlet?

Straight ram air obviously has no protection against airborne dirt. Ignore it if you wish, but it's there; filters get dirty, don't they? However, dirt isn't the only issue. A good filter system eliminates small rocks, flying insects, snow, ice, plastic bags, balloons, toilet paper, bird feathers, and all the other **** that we, sooner or later, hit with an airplane.

Balloons and bags and ice are pretty obvious. But a bug? Allow an example. A Bendix-style dual diaphragm fuel control balances dynamic (ram) and venturi pressure against a fuel pressure delta:



Plug the ram opening with a fat bug, or snow, or ice, and theory says mixture is going lean. (Nope, I do not know exactly how much.) A Bendix RSA (left) has four ram tubes. A single bug might not get them all, but snow or ice remain as possibilities. An AFP control has one ram opening.



A good intake system takes its alternate air from behind the filter, so the filter can stop the trash, and the engine can still get air. And the alternate air needs to work with 20+ inches of suction pulling on it (i.e. with the filter blocked); quite a few sliding or rotating alternate air doors are not going to move under those conditions.
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Last edited by DanH : 08-24-2017 at 08:23 AM.
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