Universal Air Filters

Are you building an open intake, or does the filter need to fit a custom-made intake pipe? Universal air filters are typically conical filters with a round flange, which you choose based on dimensions rather than car model. That makes them suitable for projects with your own piping and a modified intake.

How to choose the right universal filter

The product names typically state four dimensions, e.g. flange 6 in, base 7-1/4 in, top 5 in and height 9 in from Airaid. Check in particular:

• Flange diameter, so the filter seals tightly around your intake pipe.
• Height and base diameter, which determine whether the filter can sit clear of the radiator, chassis and hot components.
• Filter area relative to power output – a larger area can give lower pressure drop, but placement and access to cold air matter just as much.

Oiled or dry filter media

You can choose between oiled filters, e.g. Airaid Track Day Oiled, and dry synthetic media such as Airaid Synthamax, as well as dry filters with 4 or 5 in inlets. Oiled filters must be re-oiled after cleaning, and too much oil can build up on the mass airflow sensor. Dry filters do not need oiling, and whether they can be washed depends on the product. The category also includes brands such as K&N Engineering, BMC, aFe and Uni Filter.

Installation and protection

Secure the filter with a hose clamp around the flange, and position it so it does not draw hot air from the engine bay. An open filter can change the airflow reading, so the engine management may need adjusting in some cases. If you want to shield the filter from water and dirt, you will find filter wraps and pre-filters. If you simply need to replace an original filter, see replacement air filters or the full category of air filter elements and wraps.

Frequently asked questions

How do I find the right flange size?

Measure the outside diameter at the end of your intake or turbo pipe. The filter's flange size must match it so the clamp can seal tightly. Also measure the space around the pipe so the filter's height and base diameter will fit.

Can a universal air filter cause problems at vehicle inspection?

It depends on the product and the car. Changes to the intake can affect noise, among other things, so check the documentation for the specific part number and the rules that apply to your car before you fit the filter.

How often should the filter be cleaned?

It depends on the filter type and driving environment. On dusty roads or during track days, the filter can clog faster. Inspect it regularly and follow the manufacturer's instructions for cleaning and any re-oiling.