Cars Simplified: Everything Automotive Explained

Air Filters

Air filters keep unwanted material from entering and damaging the engine. All filters reduce air flow into the engine, which reduces power, but this loss is necessary for long-term use of the engine. The amount of power lost can be reduced with a performance air filter, by using a filter with more surface area, or (in a less practical way) by adding more openings to more filters (which is basically another way to increase the total surface area).

How to Air Filters Work?

Air filters keep debris from entering the engine by catching the debris with fiberous material and/or by being made of a material full of holes too small for the unwanted material to get through.

Performance Air Filters

Performance air filters can improve the engine's power output. The amound gained depends on how restrictive the original was, and how little air flow the performance filter restricts.

Some racing vehicles run without filters because their engines are cleaned out regularly, or are only run in controlled environments. Most drag race cars run without filters because they don't run for a long time, and get rebuilt after every race run.

Performance can be gained not just from better flowing filters, but by increasing the number of filters or making room for and installing a larger air filter that has more surface area to pass air through.

The Performance/Protection Trade-Off

Generally speaking, there is a trade-off between performance and protection (within a given amount of filter material) ability, because the filter's job is to trap undesired materials so they don't make it to the engine internals, but in order to do that, the filter has to be able to catch these materials via tiny restrictions. Those restrictions make it more difficult to get air through, so when the filter material has large openings to let more air through, protection from debris is reduced.

Because of this, performance filter manufacturers have to utilize other technology to make the filter flow better while still providing protection. An electrostatic charge or oil coating is sometimes used to attract dirt to the filter when it would otherwise pass through an opening. However, generally the safest way to provide additional airflow is by making a given size filter hold more filter media by including more and/or deeper folds.