Tech Article Title Author Date
Air Filter Upgrade Options Steve Sherwood 1998

INTRODUCTION

To help you understand what types of air filters are available for your Audi A4, you will find a brief description of the main types of "panel" air filters that will fit into your existing air filter compartment as well as a step by step guide on how to remove and re-install a new aftermarket air filter.



DIFFERENT AIR FILTERS

Stock OEM (Paper Filter) - This filter is ok to stop large and small particles from entering into your throttle body and eventually your engine. As it gets dirty with dust and the like its ability to allow air to properly flow through it diminishes. These are usually changed, depending upon the level of dust in your area, about every 30,000 miles. Stock Filter
The basic stock paper (OEM) filter


K&N Panel - The panel filter uses a special reusable cotton fabric sandwiched between pleated layers of aluminum screen wires. Conventional filters use paper or foam material in tiny irregular passages to trap incoming particles. The passages eventually become clogged and the filter is discarded. K&N Engineering developed their panel filter first for its performance capability and second as an economical and environmentally sound alternative to the traditional paper filter. K&N Filter
This is the K&N panel air filter

Performance is significantly improved with the K&N panel filter. The sandwiched layers of cotton gauze, specially treated with K&N air filter oil, provides five times more filtering surface over the element circumference. This serves to smooth incoming air flow while reducing intake restriction. The increased intake of non-turbulent air allows the engine to receive a larger, smoother gulp of air. The result is "free horsepower" and improved engine performance. Among racing professionals, the K&N Filtercharger is mentioned as one of their top choices for air filters.

For continued high performance, service is recommended every 30,000 to 50,000 miles. To service, simply remove the filter, clean it with K&N biodegradable detergent, apply fresh K&N oil and reinstall.

The K&N is very similar in size to your existing stock paper filter. It is easy to install even by people who are realitively unfamiliar with auto maintenance techniques.

The only issue with the K&N filter for the A4 is that K&N officially states they do not make a filter for the A4. Therefore, several aftermarket shops sell different sizes. I originally had the #33-2550 on my A4. Other people have the #33-2675. I now understand that the #33-2675 may be a better fit to the A4. Until K&N officially comes out with a fitment for the A4, I would probably hold off on buying theirs until it is officially in their catalog. This is just my opinion.


Jamex (foam) filter - This is a filter similar in shape to the K&N and stock filter. It has foam and several layers of porous material that block out particles. It is made in Holland. This is the filter I currently have in my A4. It fits very well. The only problem with this filter is the availability of cleaning solution made specifically for the Jamex filter. This stuff is not found in your local auto parts retailer. Jamex Filter
This is the Jamex foam panel air filter


RamAir filter This filter is just hitting the mainstream market. It has been used in altered form in Super Touring Auto Racing. Several race teams have converted over to this type of filter recently. This filter seems to be covered or dipped in some type of sticky substance, allowing it to capture and retain small particles and dust. Some A4 owners have complained that this filter leaks out this sticky substance into the air filter assembly. Stock Filter
This is the RamAir panel air filter

RamAir multi-stage filter collects 'real world' airborne contaminates progressively throughout its entire volume. It is made of a unique reticulated Aeriform material.

The Aeriform, in porosities of 10 to 100 pores per linear inch, is flame laminated typically into a three-stage filter. The primary filter captures the larger particles and the two secondary stages trap the smaller particles. The progressive filtering action eliminates surface dirt loading which results in longer filter life. Aeriform though, is only half the equation for the filter. Each filter is also impregnated during manufacture with a Dirt Retention Polymer (DRP). For safety, flame retardants are included in the DRP formulation.


K&N Cone Filter - This is a filter that like the name says, is cone shaped. It is sometimes called a Filtercharger. It is used in car racing to some extent. This fitment requires moderate alteration to your A4. There is also an issue that using a cone filter without proper ventilation will draw warm or hot air into your throttle body. This is not good, especially for turbo-charged autos. Your car wants and needs cool air to work at maximum efficiency. K&N Cone Filter
K&N cone filters are the ones shaped like cones


INSTALLATION OF THE AIR FILTER

Now, regarding installation. Yes, the installation of a K&N or Jamex filter is very easy. If you know what you are doing (and the engine is cooled down - very important), it may take only about 4 - 10 minutes to do this change. Please note that these are instructions for the removal and re-installation of an air filter on a 2.8 12V engine. However, the procedures are identical or very similar in both the 2.8 30V and 1.8T engines.

The difference for the 1.8T engine is that you will need to loosen the hose clamp that attaches to the front of the airbox in order to push the hose off and towards the radiator. Also, there are additional hoses attached to the top of the airbox that limit the vertical travel of the airbox cover. Filter on a 1.8T
The 1.8T engine bay with different air filter assembly

Finally, it is very helpful to remove the four screws that attach the heat shield to the right side of the airbox. This procedure allows easier access to right side snaps but it also helps you avoid the need for profanity should your fingers slide along the very sharp edges of the heat shield.
And now, on to the installation of the 2.8 12V air filter... Filter on a 2.8
Air filter cover assembly is the plastic piece with the K&N sticker

1) Remove cover to air cleaner assembly (detach at passenger side of engine bay). Be careful this thing breaks easily (how do I know? I broke it). It pulls straight up. Exposed filter assembly
Air filter assembly exposed - after cover is removed

2) Remove the piece that starts at the grill and ends at the top of the air cleaner assembly. You need to move this back and forth to get it off. Removing hose
Remove flexible connector hose

3) Notice the three chrome plated snaps (it is hard to see the 4th snap - but there are actually four). Undo these. The one closest to the engine itself, way in the back, is very close to a manifold. This manifold can get very hot, be careful.

4) After the snaps are undone, reach inside and gradually move out the OEM stock air filter. Inspect it, see how much dirt and debris it had been able to catch, then discard it. Removing filter
Undo 4 snaps, pull up top of unit, remove filter

5) Take a clean towel or rag and wipe out any large debris still found in the air cleaner assembly.

6) Insert the replacement filter (whatever type). Make sure it is right side up. You will be able to tell by how well it fits. If it doesn't fit well, its probably upside down.

7) After the filter is in put the top of the assembly back on, and redo the snaps. Then put back on the air connector hose that goes from the grill to the air filter assembly.

8) Lastly, put back on the cover to the whole thing. And voila, you are done.


that goes from the grill to the air filter assembly.

8) Lastly, put back on the cover to the whole thing. And voila, you are done.