No one mentions DOWN??????????
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Lead Lap
Joined: Aug 2012
Posts: 458
Likes: 7
From: KY
I can definitely understand the confusion.
Almost all aftermarket air filters have an arrow that says "air flow" with an arrow and aren't marked in a way that means "this side up". Some air filters are mounted vertically, so a "this side up" wouldn't work. It looks like the OEM filters, the arrow means "this side up."
For residential air filters, the filters indicate air flow and usually that means the air flows "up" towards the evaporator.
On a car, the air is usually flowing "down", that's why debris is usually on the top of the filter when it's removed.
I personally think a better way would be "this side down" and an air flow arrow pointing down, but the aftermarket makes so many different filters for different applications, it probably makes sense just to stamp it for the airflow direction and let the installer figure it out.
I'd be willing to bet there's almost zero difference though either way.
Almost all aftermarket air filters have an arrow that says "air flow" with an arrow and aren't marked in a way that means "this side up". Some air filters are mounted vertically, so a "this side up" wouldn't work. It looks like the OEM filters, the arrow means "this side up."
For residential air filters, the filters indicate air flow and usually that means the air flows "up" towards the evaporator.
On a car, the air is usually flowing "down", that's why debris is usually on the top of the filter when it's removed.
I personally think a better way would be "this side down" and an air flow arrow pointing down, but the aftermarket makes so many different filters for different applications, it probably makes sense just to stamp it for the airflow direction and let the installer figure it out.
I'd be willing to bet there's almost zero difference though either way.
Racer
Joined: Jan 2011
Posts: 1,760
Likes: 246
From: AZ
The downside to a filter being the "wrong" way would be airflow would be slightly less as the smaller "pores" would fill sooner than bigger holes on the filter.
The way the filter is supposed to work is the larger dust debris gets caught first and it gets finer on the other side to catch the smaller particles as they flow through.
Again though, this is a small effect, I doubt if you did back to back tests anyone would be able to tell the difference in the real world.
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