Lose Your Hot Air: A Guide to Aftermarket Air Filters

Panel FilterUpgrading an intake system is one of the first modifications typically made to a new performance car. By simply allowing your car to breathe easier, extra horsepower can be had cheaply and safely, particularly handy for warrantied cars. But before you drop $150-300 on an entirely new system, there may be an even better way to begin: high-flow air filters.

As we all know, the more air that enters the combustion chamber, the more powerful the explosion. The result is more horsepower and significantly more smiles per gallon. By adding a new, less restrictive performance air intake, more air will get to the throttle body. You’ve likely seen someone pop the hood at a car show and reveal a ‘cold’ air intake, like the one pictured below. Notice how the filter is located in the engine bay without a heat shield? That’s not-lovingly referred to as a hot air intake, and while there is more air getting in, it’s not necessarily effective.

Hot Air FilterA true cold air intake system should either completely enclose the filter or, preferably, relocate it away from heat sources. Interestingly, a number of modern performance cars have already taken care of this problem. The result: instead of investing hundreds in a cold air intake, similar results can be had by simply adding a high-flow air filter and smoother air inlet tube. For this post, we’ll focus on the former.

Generally, there are three types of air filters: paper, gauze and foam. Paper is generally what stock filters are made out of, and while it definitely does the job, sheer performance isn’t a high priority. Manufacturers like to save money, and dropping the same air filter in your performance car that is used in much slower vehicles is an easy way to do so. It’ll filter out dirt beautifully but leaves much to be desired in actual air flow.

Gauze is the next step forward. By using a less restrictive design and decreased surface area, air flows through more freely. To help catch some of the dirty particles that might pass through, some gauze filters come pre-oiled. The issue with gauze filters is that the material is inherently flimsy, requiring a ‘cage’ on both sides. Additionally, dirt can build up unevenly in the grooves of the filter, limiting airflow and requiring fairly regular cleaning. Even with these downsides, it is a solid improvement over a paper filter, helping more air get in without any unwanted particles.

If you’re comfortable spending a few dollars more, foam filters increase airflow even further but without a few of the gauze penalties. Since there is no cage or “V” shape in the fabric, a foam filter allows for even distribution of particles, smoother airflow and less turbulence. Oiling is required to compensate for the decreased surface area, and over-oiling can be bad news for the MAF sensor. It’s not a big issue but is something to be aware of when considering your filter options.

Our humble opinion? Foam filters offer a substantial improvement over stock filters and don’t carry the compromises that come with some gauze alternatives. You will need to purchase a cleaning kit, typically involving oil and degreaser, but top-grade options are available for less than $20. Plus, you only need to clean and re-oil when dirty, which, depending on your driving conditions, can extend to tens of thousand of miles.

Stay tuned, as we’ll go over the do’s, and more importantly do-not’s, of installing an aftermarket air filter in a later article.

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