The 1998-2001 Subaru Imprezas (as well as Foresters), had an optional cabin air filter that could be installed. It works like this... The blower box that resides underneath the passenger footwell area has a pre-marked plastic area that can be cut/snapped out. Then the cabin air filter slides up into the opening and a metal/rubber cover screws on to hold it in place. This will filter all the outside air coming into your vents. It helps keep your car dust free. Unfortunately this cover has long been discontinued. I had alerts setup on eBay for over a year before I was able to find one. To my luck it was actually an overseas dealer liquidating their inventory and I ended up with 3 of them! Below are the oem part#'s:
The OEM filter is still available but it's $40+. I'm sure Subaru uses this filter in other cars that don't need the cover kit. It's also the filter I currently have installed in my car. An aftermarket version is also available for much cheaper. The Pentius PHBT6045 filter is about $16 shipped off Amazon.
I tried to get a few different people to design a 3d replacement of this item to help other Subaru owners. I even took measurements for someone, and shipped them one of my covers. It didn't work out (I did get my cover back). So I decided to try it myself. I knew nothing about CAD or 3d printing. I tried several CAD programs which I was not very good at. Finally I discovered OpenSCAD which is more of a programatical way of designing something. Once I had that piece tackled I spent about a week researching 3d printers. I decided to go with the Creality CR10S model. I set it up and did some test prints of simple items before messing with the cover.
This is what I ended up with:
It wasn't perfect my first try. The first one I had to hack up to make it fit better. Version 2 was almost perfect but one of my holes was still off by about 1.5mm. Version 3 was just right. Here is a look of my progress compared to OEM. The print quality is in draft mode as well (0.2mm Z height). I could potetentially make it smoother (0.1mm Z height), but I don't think it's needed with a part that is not visible. As is, it takes 4 hours to print.
It fits really well too. I had envisioned putting some kind of foam tape around the edges, but I do not think it is needed. The part fits so snug that I can lift the entire air box up by the cover without it even screwed on. I'm going to do a test with the fan on high just to make sure it doesn't leak and I don't get any strange wistles. I already tried shaking the box violently and it nothing rattled around.
Edit: Also printed one in black
Before I begin, here is what the oem instructions look like in black and white.
Step 1: Order an air filter. I would recommend the Pentius PHBT6045 air filter. It's an aftermarket version of the oem filter and about 1/3rd the price. You can get it off Amazon for ~ $16 shipped. It's what I test fit everything with.
Step 2: Cut out the underside of the air box. Subaru has the opening marked. Take a sheet rock knife and lightly score the left/right side edges 4-5 times. Eventually the blade should break through. Afterwards just push the center plastic in/out several times and it should break out leaving an opening. it's a good idea to take a vaccuum and air compressor to blow out any debris that may be in there. When I put the filter in my car I also pulled the blower motor just to clean out the area really well.
Step 3: Install the filter. The filter will slide up in the opening. There is a long ear on one corner of the filter. That ear goes on the bottom towards the back of the car. It's meant to fit in the slot of the filter cover as shown in the picture.
Step 4: Install the cover. Now the OEM cover would have 2 metal brackets that screw into the air box, and then the cover would screw to the brackets. My 3d printed bracket eliminates the brackets and just uses the screw holes that the brackets normally attached to. When you install the plastic cover it is going to fit snug. It should also hold the filter up without any screws. Get it installed where it needs to be before adding the screws. Put the bent end in first, then push the back side up into place. Don't overtighten the screws and don't try to use the screws to pull the cover in. It's also an awkward angle to hold a screwdriver. It would help if you prethreaded the screws first and maybe put a dab of grease on them.
EDIT: STILL A WORK IN PROGRESS - So fitment is great, but someone recently commented about the PLA material I am using. I know it starts to melt around 160C, and cars can get to around 80C in the sun. However it turns out PLA starts to deform well below that. I did a test in my oven and sure enough that is the case. There are other options such as trying to anneal the PLA plastic or using ABS. I refunded the few payments I had received and I'm going to try to work out this problem. Sorry about all of this, I am definitely new to plastics.
If you would like a cover please contact me. You can send me a PM on RS25.com (Fastfalcon94), or you can email me at firstname.lastname@example.org The going rate will be $45 shipped in the US. That includes the cover and screws and you can decide on grey or black. You'll also need to purchase the PHBT6045 filter off Amazon for $16.24.
The covers do take a while to print. I can print out 1 each night M-F and potentially 5-6 per weekend. I've had about 10 people express interest so far so I expect a mini-surge initially. To avoid driving to the post office everyday I'll probably do bulk shipments one day a week.
Short answer, No. I spent a lot of time and money to get this thing printed. I knew nothing about 3d printers, or CAD when I started and there was a big learning curve. I spent a lot of time getting everything dialed in. Then I spent a lot of time designing and re-designing the cover so it fit perfect. Not to mention the printer costs, the spare airbox costs, and tracking down an oem cover. I went through all the hoops to make this work (which I didn't need to do since I already had an oem cover for myself) and I'm hoping to recoup some of my costs by selling a few. Maybe eventually I will release the file if I ever get sick of printing them:P
I have not tested it. I do have an oem filter installed on my car. If it's a dealbreaker for someone I could possibly remove it and find out. The aftermarket filter looks just as good to me and is 1/3rd the price so I'd recommend going that route.
Yes I will include some screws. The oem Mitsubishi 3000gt interior screws seem to fit well and I have a lot of them from stripping/scrapping a few cars.
Sure, just send me an email and I'll figure out what the extra shipping will be.
Sure, I can combine shipping. Just send me an email.