So I had been in the constant struggle of wanting a cabin filter, not because I necessarily can't withstand some dust and need pleasant filtered air; more so the issue of the condenser filling up with debris and burning up (real issue, google it people find birds nests in there). As well its nice to not feel dirt in my teeth whilst following someone on a dusty road.
So I came up with this: I would put it over that intake!
Note: If your vehicle has a spot for a cabin filter; this instructable may only be good for saving money as the pre made ones to fit in the intended slot are expensive ($20+). If you do not have a slot for a cabin filter (common with pre 1996 vehicles) you will need to do this.
Step 1: Find Where to Place It
So if you do not have a factory intended spot for a cabin filter this is where you get creative.
There are many different openings for air where a cabin filter can be retrofitted in your search just make sure to find a spot that:
1. Is on an early stage of the intake so it doesnt permitte debre into areas befor the intake, partially defeating the purpose of the filter
2. Is befor any splits in the air system, you wouldnt want to have only half your cabin filters
There are ways to modify the condensory to fit a cabin filter (where they are commonly placed in newer vehicles)
In this instructable I do it on the air intake under windsheild cowl.
For reference this was done on a 1994 nissan pathfinder
Step 2: Fitting Your Filter
Once you access your air intake, in my case it involved removing the wiper blades, measure the air intake you intend on covering and cut and trim a suitable filter.
I regret cheeping out, I bought the smallest and cheapest air filter I could, it was perfect width so I only needed to really trim on one angle, however since its for the engine it was rather thick. I fear It may have slightly dropped the pressure of my blower. I would recomment useing one meant for cabin air (although they are thin and may get destroyed by the elements) or getting creative and use a furnace filter
Step 3: Strap It In!
Then strap it in with duct tape, I only needed to do so on one side because of how snug it was.
This is a link to my origional post doing it, some of the comments may help