DIY In Cabin Air Filter *solved with instructions* cost: $10

[stevieray122854]

I am seriously considering fabricating/manufacturing an "oem fit" drop-in cabin air filter with better CFM flow characteristics and then sell em at/near cost to whoever wants them.

Had a long conversation earlier today with a custom manufacturer of HEPA and other type of filters (he makes the HEPA filters used in some commercial aircraft)

He said that the great majority of in-cabin filters are made in China and India, and that the large percentage of them are not actually HEPA filters.

He said they are usually made from the same kind of material as furnace filters with electrostatic polypropolene fibers and sometimes an active carbon layer to block odors. Said that 3M Filtrete would be a good candidate fabric to use.

If you guys wanna pursue a perfect fit drop-in option, we need get some raw non-filtered CFM numbers on the factory heater blower at standstill and also at various driving speeds.

Its gotta be good for at least 5 horsepower ; )

I'm definitely in if you do this. In looking at the Kenmore 86889, it appears to be constructed exactly as your filter man described and it is a close fit but not exact as evidenced by the trimming I had to do on this one to get it to go in the vent:

If you're wondering why, the corners on the intake vent are rounded which is why I had to trim the Kenmore filter. Also, there is really no means of support to keep the filter from getting pulled into the blower motor so I ended up using 1/8" thick adhesive felt strips (with the help of some Super Glue as well) to build a ledge for the filter to rest on.

So far, it looks like it will work OK but I have concerns as to what will happen, if for some reason, the filter gets sucked into the blower cage. I have absolutely no desire to pull that blower motor out because of a $4 filter and would very much rather have a purpose-made HEPA filter with a rubber or plastic seal that would just fit right over the top of the vent without being actually down inside of it. I like the concept of the DF/SOS HEPA filter but for me, the cost is prohibitive and I really think the size of that thing is overkill.

BTW, a replacement Eureka HF2 absolutely will not fit. Much nicer filter but way too big.

Discuss.

 

[Hrant]

What is the size of the opening, how much depth you have to work with and what is the size of the opening when flush at surface level? I am going to assume all model years are the same.

Those parameters help figure out the options.

 

[AdvansCPAP]

Just run some bolts, screws or metal rods (coat hanger material) through the marked areas at the bottom in the blower intake to support the filter. Problem solved.

Or Shish kebab a metal rod or two through the filter to prevent it from falling in.

 

[stevieray122854]

Well, after further examination, it looks like even if the filter does manage to work it's way loose and drop down, there's really not much way it would manage to reach the squirrel cage on the blower motor. From what I can see & feel, there's a plastic brace that would block the filter from dropping too far.

AdvansCPAP's suggestion above would most definitely work but it appears to me that it would involve removing the blower motor housing. Not that it would be a major problem to do so but after checking the stability of the felt "ridge" that I made, those pieces feel to be solidly attached, to the point of the plastic of the intake vent flexing when I push on them. Guess the combination of cyanoacrylate and the felt's adhesive backing on the plastic makes for a pretty damn strong bond.

At this point, I'm going to give this a whirl and see how it does. However, I'll have to keep an eye on this adhesive combination to see how it holds up to temperature variances. Still open to a purpose-made filter, though.:biggrin:

 

[RedWings]

I am going to assume all model years are the same.

Yup, I checked every year and the plastic blower shroud part number is the same so we only need to make one cabin air filter to rule them all.

The shroud is about $52, and I'm assuming that there is at least one lurking on a shelf somewhere in dealer-land, so I'll grab one as the base mold for design, etc

Can someone with an anemometer or air flow meter get some speed and pressure numbers with the blower on full to establish an unrestricted baseline on maximum "suction" air flow at the intake. If there is a way to get measurements at each vent inside the car, that would be handy info to have on hand.

Should be an interesting winter project for anyone that wants to help out and obsess about air flow, CFM, filter material specs, scented or un-scented, etc

 

[stevieray122854]

Yup, I checked every year and the plastic blower shroud part number is the same so we only need to make one cabin air filter to rule them all.

The shroud is about $52, and I'm assuming that there is at least one lurking on a shelf somewhere in dealer-land, so I'll grab one as the base mold for design, etc

Can someone with an anemometer or air flow meter get some speed and pressure numbers with the blower on full to establish an unrestricted baseline on maximum "suction" air flow at the intake. If there is a way to get measurements at each vent inside the car, that would be handy info to have on hand.

Should be an interesting winter project for anyone that wants to help out and obsess about air flow, CFM, filter material specs, scented or un-scented, etc

Excellent. Seems like I saw something in an old thread where there had actually been some CFM measurements at the intake, may have been the original GB thread about the DF/SOS HEPA filter cowl. Wait for it...found it:

http://nsxprime.com/forum/showpost.php?p=892141&postcount=120

I like the description of the filter media that's talked about in this post, activated carbon sounds like a winner.

 

[Russ]

I'm in. My ONLY reservation is the rain issue & what happens to the filter during a downpour? I mean, what if there's another NSXPO in the Northeast? :biggrin:

I am seriously considering fabricating/manufacturing an "oem fit" drop-in cabin air filter with better CFM flow characteristics and then sell em at/near cost to whoever wants them.

Had a long conversation earlier today with a custom manufacturer of HEPA and other type of filters (he makes the HEPA filters used in some commercial aircraft)

He said that the great majority of in-cabin filters are made in China and India, and that the large percentage of them are not actually HEPA filters.

He said they are usually made from the same kind of material as furnace filters with electrostatic polypropolene fibers and sometimes an active carbon layer to block odors. Said that 3M Filtrete would be a good candidate fabric to use.

If you guys wanna pursue a perfect fit drop-in option, we need get some raw non-filtered CFM numbers on the factory heater blower at standstill and also at various driving speeds.

Its gotta be good for at least 5 horsepower ; )

 

[stevieray122854]

As info, here are some pics of a intake filter that I was able to source off of Yahoo! Japan. It has a reinforced pleated filter that is supported by 2 plastic "U" shaped brackets and the air intake is sealed with an adhesive foam strip:

Seems to work quite well but as with most JDM items, it wasn't cheap. What it does allow me to do is adapt the Kenmore filter to work with these brackets which is WAY cheaper.

 

[BATMANs]

Why not go to Walmart and use the Filtrete media?

 

[donwells]

Using what I learned from the previous postings, here is my approach:

Buy a Kenmore 86889 HEPA filter:



Take a plastic container with straight sides



Cut it into "hangers"



Glue the Hangers to the filter



A close up, just for the heck of it



Cut the corners of the filter to match the opening and wrap with duct tape



Insert into air intake



I used a couple of small binder clips (tape would work) to keep it from popping out when the doors are closed.


A $3.00 filter, leftovers from yesterday's Ham sandwich, a penny of tape.......cleaner air

 

[anesthesia]

Very nice donwells, thanks for posting the picture

 

[stevieray122854]

Great idea, donwells. Did you consider leaving a lip down in the bottom edge of the "hangars" for the filter to rest on instead of gluing them? Just curious---

 

[etang789]

wow awesome idea! will look into it...seems like this design can be tweaked a little more

 

[Track Addict]

Using what I learned from the previous postings, here is my approach:
...
A $3.00 filter, leftovers from yesterday's Ham sandwich, a penny of tape.......cleaner air

Brilliant! Thanks for the extra 30 minute project.

 

[donwells]

Great idea, donwells. Did you consider leaving a lip down in the bottom edge of the "hangars" for the filter to rest on instead of gluing them? Just curious---

The depth of the container I cut up was too deep to do that. I have a hot glue gun so it took seconds to glue without clamps, etc.

You don't end up with a 100% seal around the outside, but it is tight. The inlet goes from a hole that a baseball could fall through to something slightly smaller.

 

[M Baker]

How much does the Kenmore 86889 HEPA filter restrict air flow?

 

[donwells]

I haven't sensed a difference in the airflow of my A/C, and my scientific test consisted of just blowing through it, where I didn't sense much of a resistance, if any.

I'm sure it will become more resistive over time, but a vacuum cleaner filter and several turkey sandwiches is all that I will need to get it back to original.

 

[JW]

I have watched this thread since last year, and after seeing the dust that does accumulate, the cabin air filter is the way to go. Even as low tech as this is, it is amazing to see minds at work to overcome a problem. Great work! I will be heading to Sears to pick up a few of these filters and the grocery store to get some sandwhich containers. Thanks Don.

91 Red/Black
09 VW Jetta TDI White

 

[JW]

Well, I tried the hepa filter, for the cabin air filter, but I found that there was too much restriction in air flow, so I thought about it for a while and came up with this. Its simple, cheap and relatively easy to build. It won't catch everything like a hepa filter would, but it catches a good deal and has a low restriction. Materials used are 3/8" x 3/8" mesh, and a commercial air filter, which has a light coating of a very sticky oil on one side of it. I also made a template of the opening where the basket fits in by using a lead pencil to cover the top edges of the opening and then pressing a piece of cardboard on it firmly so that the imprint was transferred to the cardboard. The basket that is shown being made is for one layer of filter which is 3/4" thick, the one that I use, is for two layers of filter and the rough cut basket is 1 and 1/2 inches wider and 1 and 1/2 " longer (shown in pic # 2) to allow for the second layer of filter. In the pic with the the three white filters, the one on the left side is clean, the one in the middle is the bottom layer of the that was in the car and is slightly darker in color from dust and the one on the right hand side is the top layer in which you can see that it is darker from catching the biggest and most particles of dust. The basket itself, fits over the edges of the opening and has not moved in the three months that I have had it installed. I used a tool, which is a bar bender, which is used by tinsmiths, but as this mesh is pretty easy to bend, you can use a straight edge of some sort and the results should be about the same. In the ninth and tenth pics you will see the cover which holds the filters in. The straight cut off ends protrude through the sides of the basket and holds down very well.

91 NSX Red/Black
09 VW Jetta White TDI

 

[Rob4092xx]

You guys are nuts (just kidding of course!)!

Why not just keep your A/C on "recirculate" and your dust issues goes away!

 

[cosplayerkyo]

Gonna try redbirds technique

I found these filters really cheap on eBay if anyone else was also interested:

http://item.mobileweb.ebay.com/viewitem?itemId=220854494926

$6.94 with free shipping

 

[Hrant]

Reviving and old topic ....... curious as always, if the HEPA filters seem to be restrictive, what about lawn mower filters? I saw a generic one at Ace hardware store was 3.5"x5.75", here is one for Honda mowers; and this one is genuine Honda which is slightly larger at 3.7"x5.9"

So what is the size of the opening? I believe the 4"x6" is too big so perhaps the 3.5"x 5.75" might work?

Also for all those concerned about rain or raining, why not try wash the car and see if the filter gets wet?!

 

[nikey22]

Also for all those concerned about rain or raining, why not try wash the car and see if the filter gets wet?!

okay so let's see.... I'm concerned about my filter getting wet, yet if I didn't have one, the water from washing the car would penetrate directly into the blower motor and that somehow would be a better scenario?

seems to me filter=more protection.

 

[dablackgoku1234]

Personally, I've tried trimming a filter to fit the hole, but I've found the FRAM CA 9115 air filter is the *best*. Even with the extra fins, the whole thing fits snuggy into the hole. No trimming, no extra work. Just drop in and go. With it being snug, there is no chance of it moving about.

Where the filter/hole is situated, the chances of it getting wet is close to none. Obviously, if you pressure wash the front with the hood up, then you'll have backsplash water hitting the filter. In the rain or in a normal wash, the filter won't get wet.

 

[Hrant]

Can you clarify the measurements of your FRAM filter. The CA 9115 has the following dimensions:

Air Filter Overall Height (in): 10.02
Air Filter Overall Length (in): 4.89
Air Filter Overall Width (in): 2.25

What is the opening of the air duct? No one has responded to measurements! I guess I have to measure it myslef.