Foam pre-filters on paper filters?

[metroplex]

I've started to notice more OEM-equipped air filters or OEM replacement air filters that glue a foam pre-filter to the bottom (dirty side) of paper panel filters. 2 examples come to mind.

The panel filter used for the Malibu 2.0 LTG (at least on the 2013-2015 2.0 Turbo LTG) and the 2013-up Ford Fusion/Edge/Continental/MKZ 2.0/2.7/3.0 as well as the Ford GT (the supercar, uses a pair of the Fusion filters, one for each turbo). The factory filter for my Fusion Sport (2.7 Ecoboost V6) is just a paper panel filter, but the Motorcraft replacements have a foam pre-filter.

Any ideas on these? I understand turbochargers will draw as much air as they need, but the extra pressure drop on a tuned vehicle could mean less efficiency. On the Malibu's stock filter with the foam, I noticed dirt/leaves starting to collect around the foam at the pleats as if the foam was restricted. There's no easy way to tap out the dirt from the foam.

 

[BMWTurboDzl]

On a stock engine the stock intake does not starve the engine for air. Sure an aftermarket filter can give you perhaps 10 hp but 99 percent of the time that's at WOT which for all intensives purposes people do not drive at nor would they notice the 10 hp.

Many times the foam "pre-filter" contains embedded charcoal and it's there to capture vapors (blow-by, gas) leaving the engine through the intake.

 

[metroplex]

On my Fusion Sport 2.7 Ecoboost, there's an extra panel filter inside the upper airbox lid that looks to be embedded with charcoal. This is on the clean side of the filter. The foam pre-filter that I am talking about looks like a piece of foam glued to the dirty side of the filter, usually white or blue without any charcoal.

I understand the stock intake boxes are not restrictions, nor are the stock filters. But when they get dirty, the pressure drop can increase (even as small as say 0.5 psi to 1 psi) which can cause a tuned application to run the turbos less efficiently, but still flow the air demanded. Not a big deal on a stock turbo application as the OEM usually runs the stock turbos far from its limits.

 

[BMWTurboDzl]

Originally Posted by metroplex
On my Fusion Sport 2.7 Ecoboost, there's an extra panel filter inside the upper airbox lid that looks to be embedded with charcoal. This is on the clean side of the filter. The foam pre-filter that I am talking about looks like a piece of foam glued to the dirty side of the filter, usually white or blue without any charcoal.

I understand the stock intake boxes are not restrictions, nor are the stock filters. But when they get dirty, the pressure drop can increase (even as small as say 0.5 psi to 1 psi) which can cause a tuned application to run the turbos less efficiently, but still flow the air demanded. Not a big deal on a stock turbo application as the OEM usually runs the stock turbos far from its limits.



The filter for my vehicle has the carbon foam attached to the filter itself yet the base model for my vehicle does NOT have the foam. Perhaps it's noise reduction? Of course the design of the intake has an impact upon the flow rate actually reaching the engine. Only by specific vehicle testing would you truly know whether the presence of the foam is impacting performance because even with a "dirty" filter you could still be reaching boost targets. Some tunes obviously require a less restrictive filter and/or redesigned intake along with an upgraded intercooler. That's more of a systemic approach.

 

[Donald]

Mice really like the foam.

 

[rrounds]

If you have a cone or round filter you can buy the foam, I would use a filter restriction gauge to know when to clean the foam.
https://www.knfilters.com/airforcewraps.htm

Rod

 

[metroplex]

That's not the foam I'm talking about. Check out the FA-1912 Motorcraft filter, OE replacement for MKZ/Fusion/Continental and the Ford GT:

https://www.amazon.com/Motorcraft-F...;qid=1554281995&s=gateway&sr=8-1

Notice the blue/white foam.

 

[DoubleWasp]

That truly great that Ford parts bin engineers put their stamp on the Ford GT with the air filter setup. As exotic as the GT has become, it's nice to know there's still a little old school sense going on in there.

 

[UG_Passat]

On European vehicles, it's referred to as the "Cold Weather/Climate Filter", so that snow hits the foam without soaking into the paper filter.

 

[UG_Passat]

Originally Posted by rrounds
If you have a cone or round filter you can buy the foam, I would use a filter restriction gauge to know when to clean the foam.
https://www.knfilters.com/airforcewraps.htm

Rod


What's the point of buying the K&N gauze filter in the first place then? Might as well get a foam-based cone filter to start with.

 

[gonefishing]

My work car (2018 Chevy Equinox 1.5 turbo) has a piece of foam on the bottom of the filter. This is the first time I've seen one. My 2010 Tundra had one of those charcoal pre-filters but that was attached to the air box.

 

[K20FA5]

The air filter on our 4Runner has one too. The Wix I replaced the OE filter with also has one glued on.

 

[rrounds]

Originally Posted by UG_Passat
Originally Posted by rrounds
If you have a cone or round filter you can buy the foam, I would use a filter restriction gauge to know when to clean the foam.
https://www.knfilters.com/airforcewraps.htm

Rod


What's the point of buying the K&N gauze filter in the first place then? Might as well get a foam-based cone filter to start with.

Here is what K&N has to say
"is a specially designed foam air filter wrap made to extend the service interval of your K&N Filtercharger when used in very dusty conditions"

So if you drive in very dusty conditions it will keep the main filter cleaner and for a longer time before you have to clean/replace the main filter. What they don't tell you is how often/miles you have to clean the pre-filter. That is why I said to use a air filter restriction gauge so you know when to clean the pre filter or the main filter.

Rod

 

[metroplex]

When I did run a K&N conical filter, I used their drycharger wraps. They weren't restrictive at all according to my datalogging, and they kept the cone filters a LOT cleaner as the small dirt/dust particles never have a chance to collect in the pleats.

 

[DoubleWasp]

A cotton gauze filter wrapped in foam is the OEM design for many off road machines.

 

[va2001ss]

Originally Posted by UG_Passat
On European vehicles, it's referred to as the "Cold Weather/Climate Filter", so that snow hits the foam without soaking into the paper filter.

I think this is the best explanation for the foam pre filter.
Here is a picture of the Malibu 2.0T version

 

[purelux]

Some are woven cotton not gauze as well think of a shirt vs a gauze bandage wrap. At a quick glance though they will look quite similar and may be multiple layers of increasingly finer filtration, tighter fibers.