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  #71  
Old 05-02-2020, 02:05 PM
Pilot135pd's Avatar
Pilot135pd Pilot135pd is offline
 
Join Date: Jan 2019
Location: Vaca Moo Airport - TA37 in East TEXAS
Posts: 1,505
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Quote:
Originally Posted by hgerhardt View Post
K&N's work better with some dirt on them.
K&N addressed that rumor.
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Sadly sold my RV-8 however still trying to enjoy life by living on my airport with FREE campsites for pilots to enjoy www.facebook.com/VacaMooAirport/ & flying my OnSpeed equipped C-177 while waiting for the RV15 !

Exempt by 3 out of the 10 ways but I still donated.
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  #72  
Old 05-03-2020, 07:41 AM
vic syracuse vic syracuse is offline
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Join Date: May 2005
Location: Locust Grove, GA
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Just addressing a couple of comments/questions:

I haven't seen any shrinkage on the square filters used in the snorkel inlets. I think it is due to the fact that they are installed in a position more like that in an automobile---in the cooler area of the engine, and not subjected to leaking avgas and other fluids.

Second, I don't know about the comments that the air filter is not the correct size. I vaguely remember doing some analysis a few years back and that size of filter does support the airflow needed for the engines in our RV's.

A quick test is to open the alternate air door during full throttle. If the engine surges, then the air filter is a likely constraint, but I have only seen that on some of the earlier Rod Bower ram air systems, where the filter was remotely located.

I believe the primary cause of the shrinking is the exposure to the higher temps , especially after shutdown, and the avgas that drips down on them, from carburetors when pumping the throttle prior to engine start, leakdown from injection units after shutdown, and from overpriming prior to engine starts.

I do think a aluminum sheet in the bottom half of the FAB is a good idea, as we replair quite a few FAB's where the air filter has eaten away at the bottom of the fab from movement.

Vic
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Vic Syracuse

Built RV-4, RV-6, 2-RV-10's, RV-7A, RV-8, Prescott Pusher, Kitfox Model II, Kitfox Speedster, Kitfox 7 Super Sport, Just Superstol, DAR, A&P/IA, EAA Tech Counselor/Flight Advisor, CFII-ASMEL/ASES/RW
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  #73  
Old 05-03-2020, 08:25 AM
Kyle Boatright Kyle Boatright is offline
 
Join Date: Aug 2005
Location: Atlanta, GA
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I tripped over this issue yesterday. I'd removed the airbox/filter a few days ago for a carb replacement, and when I went to reinstall the filter, it was too small to easily reinstall. I'm sure I could have cussed it into place, but it just wasn't worth it - a new filter will make cleaning/reinstallation easy for the next several years.

A point of minor frustration was that the local auto supply stores used to carry the right replacement filter. They don't anymore, so I had to order one instead.
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2001 RV-6 N46KB
2019(?) RV-10
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  #74  
Old 05-03-2020, 09:09 AM
506DC 506DC is offline
 
Join Date: Jun 2010
Location: Fresno, CA
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Quote:
Originally Posted by vic syracuse View Post
Just addressing a couple of comments/questions:



I believe the primary cause of the shrinking is the exposure to the higher temps , especially after shutdown, and the avgas that drips down on them, from carburetors when pumping the throttle prior to engine start, leakdown from injection units after shutdown, and from overpriming prior to engine starts.


Vic
I agree with the above. I have been flying my RV-4 for 20 years and have struggled with shrinking air filter and cracking air bracket. I solved both problems as follows:

I redesigned the air bracket by remolding with fiberglass. I have no metal in the bracket other than nutplates and filter retainers. The input opening to the air induction is round not oval. The opening is only about 2" diameter and I mathematically calculated the inlet flow far in excess of the air requirements.

Nothing on the bracket touches anything on the cowling and does not require any support brackets. A fabricated gasket was made from wet suit material of which I recently replaced. I have flown it for several years and several hundred hours and never have had a single problem. Dave Anders helped me with the design of the inlet taper degree which gives me about 1/2" more manifold pressure than the original bracket. It is a lot stronger and lighter than the original Vans designed bracket.

I am careful about over priming so I don't get any fuel in the air-filter assembly. I drilled a small hole in the bottom aft part of the air filter bracket that drains fuel or any liquid that may get into the filter box area. I don't clean the filter unless I can not see light through it. It stays pretty clean most of the time. I do knock out debris like bugs etc. It does shrink a bit but I simply stretch it back out by grabbing the sides opposite of each other and it returns to the normal dimension.

On inspection, I check the inlet to the engine on the fuel servo and it is always sparkly clean so I figure I must be doing the correct thing as far as filtering the air is concerned.

Hope this helps someone
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  #75  
Old 05-03-2020, 09:38 AM
Kyle Boatright Kyle Boatright is offline
 
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Location: Atlanta, GA
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Quote:
Originally Posted by vic syracuse View Post
I believe the primary cause of the shrinking is the exposure to the higher temps , especially after shutdown...
Vic
K&N's own literature mentions shrinking due to excess heat.
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2001 RV-6 N46KB
2019(?) RV-10
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  #76  
Old 05-03-2020, 10:36 AM
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Snowflake Snowflake is offline
 
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Without searching back through the thread... Will K&N still replace a shrunken filter? They used to at one point, although you couldn't tell them you were using it on an airplane...
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1996 RV-6 "Tweety" C-FRBP (formerly N196RV)
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  #77  
Old 05-03-2020, 11:10 AM
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AlexPeterson AlexPeterson is offline
 
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Location: Ottertail, MN
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Quote:
Originally Posted by Snowflake View Post
Without searching back through the thread... Will K&N still replace a shrunken filter? They used to at one point, although you couldn't tell them you were using it on an airplane...
We all have our comfort levels in terms of ethics...

Perhaps at some point, K&N will simply stop making the sizes that we use on our planes if they are replacing enough of them for use against their indications. I guess it depends on how many other applications those sizes are used for.

For me - I replace mine every 3 to 5 years - by purchasing one.
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RV6A N66AP 1750+ hours
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  #78  
Old 05-03-2020, 02:34 PM
JDeanda JDeanda is offline
 
Join Date: Apr 2013
Location: Ventura, CA
Posts: 274
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I just ordered one and paid for it. My ethics have a certain comfort level, too. It would be nice if K&N detailed their warranty info on the box, but I already know what those requirements are. Besides, I got something over 6 years and 600 hours or so from the last one. In the airplane world, that?s a howling bargain for a $46 air cleaner. No regrets.
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  #79  
Old 05-03-2020, 04:04 PM
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Carl Froehlich Carl Froehlich is offline
 
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Location: Dogwood Airpark (VA42)
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For you RV-10 guys wanting a bigger filter, one option is to replace the standard filter with a taller one, the K&N E-1000. It is taller but same outside diameter.

You take the standard filter box and invert the top. Note the aluminum plate on the bottom of the box with the brackets. This was done to help prevent the filter from going conical.

This was for an RV-10 with a James Cowl and it worked very well. I assume it will work for a stock cowl but don?t know.

Carl


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  #80  
Old 05-14-2020, 09:13 PM
echostar7 echostar7 is offline
 
Join Date: Aug 2019
Location: Savannah
Posts: 40
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2nd owner, first time filter is getting replaced after 7 or 8 years I think.
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RV-6
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