Challenger Air Filter Performance

[MV Aviation]

Hi!

I've just upgraded my M20E from the filthy sponge-type air filter to a challenger (STC) one. They do advertise an increase in HP on their website. This is accomplished by a smaller pressure drop across the filter. Since my E has the power boost feature, which bypasses the air filter, I was able to precisely measure the pressure drop of the old filter by opening and closing the power boost and observing the MP. I've measured it a couple of times at different altitudes an always landed around dp=1" MP. With the challenger filter installed, I repeated the test and got roughly the same dp, hence, not performance increase with the new filter. I think I remember (not sure where I read it) that the pressure drop of the challenger should only be in the area of 0.3”. Has anyone of you done the same conversion and measurement and can confirm or refute my values?

Best regards,

Marco

[GeeBee]

When it comes to air filters, there is no free lunch. Better filtration, more pressure drop. Less filtration, less pressure drop. The Challenger filter is basically K&N's filter material. In fact their service kit is just re-labled K&N product. Now I'm not a fan of K&N in certain applications, like turbo cars and trucks because they don't filter good enough to prevent blade erosion on the turbo (aka dusted turbo). On an airplane, they are good enough because the air filter is really only needed on or near the ground. So I have a Challenger on my R. It does what it needs to do good enough. The idea that K&N puts out that you get "better filtration" and a "power increase" is marketing hype. Unless the new filter is dramatically larger to compensate for tighter material you cannot get both and trust me, K&N is not "tighter material", its oil saturation method not withstanding.

[A64Pilot]

I’ve done a LOT of work with K&N on Aircraft, the ENCU (airconditioner on the A model Apache) Barrier filtration system for the Blackhawk engines, and the engine filter for the Thrush Ag plane, attached picture is the Ag plane filter.

K&N is simply cotton gauze held in place by screen wire, the “magic” is the oil. it’s what stops the dirt, not the gauze. As it’s cotton one blast with shop air and the filter is trash, also don’t leave it out in the sun after washing to dry as it being cotton, it will shrink.

Only clean with detergent and low pressure water, I recommend the K&N filter cleaning kit and follow instructions, then re-oil it only with K&N oil and let it soak in throughly, it’s normal for a new filter to bleed oil, the attached photo is a new in the bag filter and all that excess oil is normal. Without the oil  the filter is pretty much completely ineffective, so don’t be stingy with the oil.

As part of the Army test we measured filter efficiency as it loaded up with dirt, the dirtier it got, the better it filtered until the dirt sucked up all of the oil. Best filtration is to add oil to a dirty filter, of course the better it filtered the more restriction there was, only way to keep good filtration and decrease restriction is to increase surface area, in theory the K&N does this by being folded.

The increased HP claim is bogus, if there were an increase in HP the FAA would have required new flight tests.

My personal opinion is the Brackett is a better filter and a lot less hassle (no cleaning)

 

Edited February 15, 2022 by A64Pilot

[MV Aviation]

1 hour ago, A64Pilot said:

 

The increased HP claim is bogus, if there were an increase in HP the FAA would have required new flight tests.

My personal opinion is the Brackett is a better filter and a lot less hassle (no cleaning)

 

Thanks for your feedback.

Regarding the increased HP: the engine will not produce more HP than it is rated for. The more dp the filter "produces", the less the engine will be able to freely breath and the less HP the engine will produce in a given environment. Since the filter can be bypassed altogether in my Mooney, there's no need for flight tests. A little "better" filter would lie somewhere between the "worse" filter and "no" filter in terms of pressure loss and engine performance.

The Brackett filter is messy. The sticky stuff runs out during flight and messes up the lower cowling and gear (especially when flying in rain). Also (in Europe at least) it's relatively expensive. As long as the Challenger filter survives its 2000h, it will be cheaper in the long run. Okey, there is some added labor for cleaning and re-oiling, but cleaning the mess of the Brackett filter is equally annoying.

[A64Pilot]

Actually the engine can and most in fact do produce more than rated HP, The rating is a min that the engine must meet, as all engines aren’t identical in order for them to all meet rating, most will exceed it by some amount, usually not by enough to be significant.

I guess Mooney convinced the FAA that ram air increase is minimal, so no need for a second set of charts, but that’s just a guess, or went with it’s better when open and closed charts are conservative.

Either way any increase in HP from an air filter likely isn’t measurable.

Buy the K&N filter cleaning kit, available at many car parts stores and Amazon, save some money on cleaning. it comes two ways, one squeeze bottle of oil, the other a spray bottle of oil. I like the squeeze bottle, apply it to the edges and it soaks in.

I have cleaned and re-oiled many, the pic of my Daughter spraying cleaner on a filter was for a class on how to clean them I put together years ago.

She’s in her early 20’s now and getting married this year.

 

 

 

Edited February 15, 2022 by A64Pilot

[DXB]

I've been using the Donaldson filter over the Brackett for the last few years - supposedly it provides comparable filtration but less flow restriction than the Brackett (no clue if that claim is true).  Maintenance is a snap though relative to the Challenger/K&N though - just blow it out with shop air once a year, replace at 500 hours. The Bracket filter elements are dirt cheap to replace annually ($10); the Donaldson is considerably more (~120 if I recall) even if you account for lack of need for annual replacement.

[cferr59]

I don't know if I get better performance from my Challenger filter, but I was not happy when I flew in moderate rain for 2 hours and it started looking ratty and I could see light through it.  It was about 5 years old and I replaced it.

[philiplane]

https://www.donaldsonaerospace-defense.com/library/files/documents/pdfs/007217.pdf

My experience with Donaldson filters in extremely dusty & abrasive mining environments is the same as this study above. 

Brackett filters let dirt through, cost you some horsepower, and make a mess. K&N (Challenger) filters can't take rain, and pinholes develop quickly. And who has the time to wash, dry. and re-oil a filter?

Edited February 15, 2022 by philiplane

[Guest]

The best place for a Challenger K&N filter is in a box on a shelf, not on an airplane.  

Clarence

 

[jaylw314]

Do watch out for the challenger air filter, the STC actually specifies to check and/or reoil the filter after flying through rain.  The J protects the air filter fairly well behind the cowl so I've never had to reoil it, but the older cowls might not.

Also, the STC specifies that it can only be cleaned and reoiled 25 times before needing to be replaced.

I'd also point out the pink oil does spray into the intake box, so it's pretty sticky in there.  One day I'll rinse out the inside with mineral spirits or something, but it doesn't sound much cleaner than the other style filters.

I bought my J with a challenger air filter installed, so I've flown it with the stock filter.  

[PT20J]

If you look at the power charts in the Lycoming Owner's Manual you will see higher HP for a given MAP/RPM combination than the charts in the Mooney POH. This is because the installed engine will put out less power due to the induction (including the filter) and exhaust systems.

[EricJ]

I recently bought a Donaldson paper filter to replace the oiled-foam Brackett after dealing with some of the goo that comes out of the Brackett filter.   I don't use K&Ns in cars, or race cars, because they don't filter well and foul MAF sensors.   A while back I saw something from Don Maxwell alluding that the goo from Brackett filters may foul fuel servos via the ram tubes, and since I've had an in-flight fuel servo failure (due to gritty contamination, probably not related to the filter), I finally figured I should make that change.   The Brackett is staying in until annual inspection in May and then the Donaldson will go in.  The Brackett has been in since I bought the airplane, so maybe I'll be able to tell a difference or not. 

[Guest]

Long ago there was a service document from Brackett which suggested squeezing the filter between some clean shop towels to get rid of the excess oil.  I don’t know if it’s on their website?

Clarence

[EricJ]

5 minutes ago, M20Doc said:

Long ago there was a service document from Brackett which suggested squeezing the filter between some clean shop towels to get rid of the excess oil.  I don’t know if it’s on their website?

Clarence

I think many of them say that on the instructions to "squeeze or blot with clean dry cloth" or squeeze out the "excess wettant".   I'm not positive whether the Mooney ones say that or not, but who knows what the hangar fairies might do if they don't.  

 

[A64Pilot]

My C-140, and I believe my J model use the same brackett filter, BA-108 from memory so I’m not real sure it’s right.

For some reason I’ve not had the excess sticky oil issue, but they do remind me of a lawnmower or chainsaw etc filter. My old Husqvarna was nearly identical, just used two stroke oil in it.

My take is the Bracket works well, as defined as stops dirt, K&N not as well, I don’t have Donaldson experience.

But do change the Brackett every year even if it looks clean, because the foam deteriorates and falls apart over time. I had my 140 in storage for three years and it was crumbly after three years.

Edited February 16, 2022 by A64Pilot

[Tx_Aggie]

On 2/15/2022 at 12:06 PM, EricJ said:

I recently bought a Donaldson paper filter to replace the oiled-foam Brackett after dealing with some of the goo that comes out of the Brackett filter.   I don't use K&Ns in cars, or race cars, because they don't filter well and foul MAF sensors.   A while back I saw something from Don Maxwell alluding that the goo from Brackett filters may foul fuel servos via the ram tubes, and since I've had an in-flight fuel servo failure (due to gritty contamination, probably not related to the filter), I finally figured I should make that change.   The Brackett is staying in until annual inspection in May and then the Donaldson will go in.  The Brackett has been in since I bought the airplane, so maybe I'll be able to tell a difference or not. 

Hi Eric - so did you go with Donaldson and do you observe any difference? 

[jetdriven]

On 2/15/2022 at 6:58 PM, M20Doc said:

Long ago there was a service document from Brackett which suggested squeezing the filter between some clean shop towels to get rid of the excess oil.  I don’t know if it’s on their website?

Clarence

I think now the wrapper says do not squeeze the oil, just install. 

[EricJ]

10 hours ago, Tx_Aggie said:

Hi Eric - so did you go with Donaldson and do you observe any difference? 

I did and I like it a lot better.   I've since cleaned up a lot of the goop that was around the air box and it stays clean now. 

[Fly Boomer]

46 minutes ago, EricJ said:

 I've since cleaned up a lot of the goop that was around the air box and it stays clean now. 

I have not seen mine apart yet -- what should I be looking for?

[EricJ]

2 hours ago, Fly Boomer said:

I have not seen mine apart yet -- what should I be looking for?

The Brackett filters can leave a dark, goopy, sticky, oil residue.   On my airplane it was all over near the filter, inside the air box, and running down around the baffle and front of the air box.   Once I got to cleaning it there was a lot more than I had originally noticed.    I've no idea how long this airplane had a Brackett filter as that's what was in it when I got it.   It may be aggravated by our high AZ temps that might make it run out more than in other places, and the airplane was in southern NV before I got it.

[Tx_Aggie]

4 hours ago, EricJ said:

I did and I like it a lot better.   I've since cleaned up a lot of the goop that was around the air box and it stays clean now. 

Do you observe any performance difference?

[EricJ]

8 minutes ago, Tx_Aggie said:

Do you observe any performance difference?

Nothing noticeable.   There may have been some improvement, but if there is it's small.

[Fly Boomer]

4 hours ago, EricJ said:

The Brackett filters can leave a dark, goopy, sticky, oil residue.   On my airplane it was all over near the filter, inside the air box, and running down around the baffle and front of the air box.   Once I got to cleaning it there was a lot more than I had originally noticed.    I've no idea how long this airplane had a Brackett filter as that's what was in it when I got it.   It may be aggravated by our high AZ temps that might make it run out more than in other places, and the airplane was in southern NV before I got it.

Mine has had Brackett filters for many years, so I'll be interested to see it when it comes apart.  Thanks.