The history of the car air filter is geekily interesting

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It cleans, it can help increase power and it’s a true lifeline for the longevity of your car. The air filter has been around pretty much as long as the motorcar, shielding the internal combustion engine from all manner of nasty contaminants for more than 100 years.

These days, we barely give a thought to the high-tech, high-flow filters that come in all shapes and sizes, making even the weakest of engines sound like they’ve had a serious tune-up.

I feel it’s time we gave the car air filter a bit of a tribute, an ode that will make up for all the times we’ve taken the paper, foam or cotton devices for granted. Cue the music.

So where did it all start?

Almost as soon as the internal combustion engine was invented, it was discovered that keeping airborne foreign bodies out of the combustion chamber was a good thing. Everything from tractors to lorries to early passenger cars were all powered by internal combustion, and cleaner air made for more efficient combustion and therefore more power.

Enter the air filter.

In the beginning, everyone went for a ‘bath’ filter

Up until the 1920s, the water bath filter was the usual kind of air filter. These work by using an air inlet pipe that feeds down into a bath of water. The constriction of the inlet pipe causes the air to speed up, meaning that by the time the air reaches the bath, the heavy, nasty particles keep travelling downwards through momentum and are caught up in the liquid.

The U-turn results in a reasonably effective filtration of the incoming air

The water method was soon replaced by an oil bath filter, because the oil allowed for much more effective filtration. Despite this newfound filtration greatness, the labour-intensive and messy servicing of these filters meant that by the time the 1960s swung around, the door opened up for…

Paper filters

Still used to this day in most vehicles, paper filters are cheap, convenient and perfectly capable of keeping the nasties out of your engine. The pleated filtration material can take the shape of a panel, a cone or even an old-school flat cylinder if your engine happens to be running on carburetors.

One of the main reasons that the paper filter took over in the second half of the 20th Century is that the surface area of the filter is massive. Due to the corrugated assembly of the ‘paper’, the surface area can be up to 50 times larger than the front face of the filter, perfect for catching all the dust and grime that gets thrown into your car or motorbike’s airbox.

However, petrolheads soon determined that they could eke more power out of their cars by experimenting with different filter materials, with the paper method feeling slightly too restrictive over time for their high-horsepower activities.

Along came K&N, who back in the 1960s invented something that would become the go-to first modification for passionate car people the world over…

Reusable cotton filters

Nevermind having to throw away your paper filter every 15,000-30,000 miles – a cotton filter will gather particles of dirt but has the ability to be cleaned, re-oiled and then put right back into action.

The layers of meshed cotton gauze will last the lifetime of a vehicle and are laced with a light film of oil, perfect for grabbing muck. Using a very similar method to a paper filter, the cotton and aluminium frame combination is pleated to greatly increase its surface area.

The oily aspect of a cotton filter helps as it soaks into the cotton fibres, attracting the dirt to them, snapping it up as it passes by. Next, the dirt is then soaked by the oil and becomes a further part of the filtering mechanism. This helps clear the air pathways of the filter as the dirt clings to the cotton, allowing air to travel through it smoothly. And more air means more power!

Cotton filters were once only used by hardcore petrolheads but it wasn’t long before anyone with a screwdriver and some time on their hands at the weekend was applying such a filter to their car. Some manufacturers will now supply their cars with reusable cotton filters as standard due to how simple and effective this modification can be.

Over the years we’ve also seen foam filters and even stainless steel mesh as a way of keeping engines healthy, but it’s fair to say that paper and cotton units are currently dominating the industry. And they’ll probably keep doing so while the internal combustion engine is still the primary source of powering a car.

Have you put an aftermarket air filter on your car? Or does the thought of getting under the bonnet seem a little intimidating? Tell us where you’re at through the poll below!

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Thanks to K&N for helping us out with this piece and making this type of cool engineering content possible.

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