FILTER COMPARISON: FOAM Vs. COTTON GAUZE

Filter Comparison

Weapon*R High Density FoamVs.Brand X Cotton Gauze

The most common aftermarket modification is the intake system. The available kits are mostly the similar; they include an aluminum pipe and a cone filter to replace the factory air box and tubing. But as we have shown in our Secret Weapon Test, not all intake pipes are created equal. The Secret Weapon pipes and filters outflow the competition hands down, but a common question is “How well does it filter?” In this article we’ll show you the differences between our Foam Filters, and the popular Cotton Gauze Filter used by many of our competitors. Our contenders for this filter test are:

Secret Weapon High Density Foam filter (SW filter)

• 3”inlet4.75” x 6”4 ply

Cotton Gauze filter (Brand X)

• 3” inlet 10” x 6”

These are the same two filters used in our Secret Weapon flow test. Our first test is to simply show the density of the two filtering media using light. We simply hold the filters up to a bright light source (e.g. sunlight, halogen light), and look for any sign of light showing through. As you can see, the Brand X filter allows light to shine right through, while the SW filter completely blocks out all light from coming through the foam. Any consumer can do this and see all the large pores in the Brand X filter.In the next comparison, we disassemble the two filters to measure thickness of the media. Using a micrometer we measure the media in their uncompressed form.

The Brand X filter measures about 2.36mm, while the SW filter is nearly 7-times thicker at 14.07mm! The Brand X filter only has once chance to catch dirt, and that’s in this 2mm of oil soaked fabric. The SW filter has numerous tiny pores and pathways in which to catch dirt, and uses a light oil to make sure the dirt sticks and never makes its way into the engine. We will have an independent dirt flow test conducted in a future installment.

The final comparison is in the base of the filter. The Secret Weapon Filter uses a full velocity stack to route air into the intake tract, while the Brand X filter uses a molded base with a curved inlet as a velocity stack. The Brand X version has a flat edge all around the velocity stack, while the Secret Weapon velocity stack is raised off the base of the filter to route air from all angles within the filter, and a fully rounded inlet lip to ensure the smoothest pathway for air to flow. This velocity stack is the same design used by many race teams and is proven to increase airflow into the engine.

In addition to all the advantageous features listed above, all of our filters utilize a mesh cage surrounding the foam to keep it being deformed under the heavy vacuum when the engine is revved.This is just a quick look at the advantages of using a foam filter over the common cotton gauze replacement filter. It has been shown that not only does foam flow better, it filters better as well.

Still not convinced? Well consider one of the dirtiest motorsports around, motorcross. These motorcycles are built to play in the dirt, and when their industries choose a performance filter, what do they choose? That’s right, a foam filter. Take a good look around, you’ll see that the claims of foam being inferior to cotton gauze are a very large misconception.