sstrickstein

I have a 1986 Porsche 944. It was my first taste of the insanity. I recently read a post online about making a home made Cabin air filter. You remove the two screens on either end of the plenum and cut home airconditioning filter material to match the size. Has anyone ever heard of a similar DIY for the 928. We are coming into Monsoon season here in the Desert and would like to find a way to keep the dirt out.

http://only944.com/upgrades/cabinfilter/

linderpat

nice fix!

MainePorsche

Nice job on the 944 filter.
I had considered, and attempted, to place filter material to our system. I was going to place a triple folded over shear filter material folded over the aperture of the evaporator. I was hoping to have it held in place by the rubber sleeve. I was considering how to reinforce the hold there, but it was moot anyway.
It was not possible for me to reach the bottom of the aperture to arrange things appropriately. I didn't want to go any further for any type of filter here must be easy on/easy off.

sstrickstein

It would have to be put on the intake of the blower. That might be tough

MainePorsche

I wouldn't make the effort on the intake of the blower -> it has to be an easy on/easy off filter. I was thinking where I attempted to place it, it would have still functioned as a media filter for air input to the cabin.

Gary Knox

I made one several years ago for the '88 S4 that I had at the time, after seeing how DIRTY the AC evaporator had become (cleaned it first). I took the boot off between the blower and the evaporator plenum, carefully bent a piece of stiff coat hanger wire so it would loosely fit within the plenum opening, cut a piece from a household HVAC filter to fit over the wire frame, put adhesive on the wire frame and put the filter on. Installed it, and trapped a good bit of dirt over the next year or so. I removed and cleaned (soap and water) the 'cabin' filter annually.

Alan

To do it right you need to emulate the factory approach I think - So it depends how bold you are:

This means cutting a slot out of the top of the air plenum just in front of the evaporator, it will need to be bigger than the filter so you have room to install a frame of sorts. Then you will need to relocate the blower resistor pack out of the air plenum and plug the hole (prob just with a dummy sawn off resistor pack).

You need to fabricate (mold) a new air plenum top with a removable screw on attachment mechanism, this probably requires a rubber (weatherstrip) air seal. Then use a suitable filter (maybe even the factory one).

This has the advantage that is quite easy to change the filter, has a large enough area to be effective at low flow drop and if you make a lexan/polycarbonate top - you will be able to see the filter condition without removal. Its safter because there is no risk of filter material contacting the hot resistor pack

Downside are its a lot of work and there is significant risk of damage to the evaporator - once you cut into the plenum its a one way trip - no going back... You'd need a '94-'95 resistor pack with just 3 resistors & you can't use the '94 factory mounting point if you have intensive washers...

I have considered this - but that's all so far..

Alan

MainePorsche

Alan,
Why wouldn't a decently secured media filter at the intake plenum to the evaporator be adequate ?
Craig

Alan

Technically this is in the intake plenum to the evaporator - but if you mean at the existing mouth:

The area is too small - it will clog too fast in dusty environments and will anyway restrict airflow more under all conditions - the area ratio is > 2:1

Alan

MainePorsche

Makes sense.
Thanks again.

Randy V

Using some relatively thin filter material it should be a simple matter to have it held in place by the rubber boot that connects the plenum to the evaporator housing..

Just fold it over the plastic housing and the rubber boot holds it in place. Easily replaced.

MainePorsche

Not that easy to do with a good seating of the material on the mouth of the plenum intake.

davek9

I have just taken a couple of old HVAC boxes apart to harvest the AC and Heater cores and other bits, one is from a early car wit Manual Mixing mech the other is out of an S4 w/ the Mixing motor.
Also I want to learn how difficult it would be to change the cores w/o removing the HVAC assembly by separating the halves in the car (dash completely out) and it not all that bad to do.

Wow I found a lot of crap all nested up inside both of them, I'm about to do my third (inside the car) as the heater core has a leak, I't always leaked from day one, so I plugged it and been using it for DE/Track events, however I have a fresh interior and its going in this winter

I'd like to build a retrofit that uses the stock GTS cabin filter, but never seen one, can someone please post up some pics of the top of the box, the lid and inside.
I'll measure it all up, post up the process w/ pics if I can make it work.

As far as I can tell the Box's and the AC evaporators are the same just improved, so this retrofit / mod should work for any model year.

Thank you,

Dave K

byrdman454

https://rennlist.com/forums/928-foru...en-filter.html

davek9

I did not see that one in my searching, thank you Mike!

Dave

Edit: Wow a much bigger hole than I would have imaged, a plastic lid could be 3D printed.