One of the most popular choices for an aftermarket performance air filter is a cone or cylinder filter. The benefit of a cone over a flat panel is simply that a cone offers a greater surface area whilst still fitting within a small physical space, often narrower than that occupied by the panel filter. Think of it like this: rolling a panel filter into a cone doesn’t change the panel’s surface area, but it does allow the part to squeeze into a small space. Neat!
Installing a cone or cylinder filter often requires the removal of the car’s original air box. The new filter is then installed directly onto the end of the intake trunking. Alternatively, it can sit within a bespoke air box or behind a
custom heatshield. This setup is usually what people refer to as an induction kit. It eliminates the standard air box’s restrictions by drawing air in from all directions instead of relying on air being fed inward via a specific route dictated by uncompromising air box ducting.
The downside to all of this is that controlling where intake air is drawn from can prove to be a challenge, with some poorly designed filters pulling in hot air from around the engine bay. This is what’s referred to as ‘heat soak’ and is massively detrimental to performance. If you’re really unlucky, your car might be producing far less power than when its stock air filter was in place! Open air filters work well on naturally aspirated engines where improvements in airflow feel more pronounced than when playing with air filters linked to forced induction equipment (such as a turbocharger or supercharger). Moreover, tuned naturally aspirated engines need large volumes of air to be drawn from the atmosphere, but often feature air boxes which won’t allow air to flow beyond the manufacturer’s standard specification. Cone filters used in forced induction applications tend to be much larger than those fitted to naturally aspirated engines. This is simply because forced induction applications usually produce more power than those free of a ‘charger, dictating the need for vast quantities of intake air.