Most of us don’t give our air filters much thought really. They’re a barrier between the outside atmosphere and your engine. That’s pretty much all there is to it, right?
Well yeah, but also, yeah nah. You see, that’s exactly what they are. But defining them in such simple terms is like calling Valentino Rossi an “okay motorbike rider” or the Large Hadron Collider a “big circle in Switzerland.” I mean, you wouldn’t be wrong exactly, but you’re not really getting the whole story across, either.
Air filters are an integral part of one of the three main components in keeping your engine running. You need air, fuel and a source of ignition (sparkplugs in petrol; compression in diesel) to make the crankshaft keep turning and your vehicle keep moving. If the air your engine is sucking in is full of bulldust or any other contaminant, not only is there a fair chance the whole show goes bang, but best case, you’ll be increasing wear and tear on the internal componentry by orders of magnitude.
So yeah, air filters are important.
The anatomy of an air filter
Air filters generally live in an air box or air filter housing (same thing). This box has an inlet and an outlet. The inlet is open to the engine bay or outside the vehicle via a snorkel while the outlet is connected to either the engine’s intake manifold (if it’s NA) or turbo inlet (if it’s turbocharged, duh). As a piston travels down in the cylinder, it sucks air in through the airbox inlet and through the filter, which catches any dust or contaminants. The now-clean air is sent down the intake (via the turbo and intercooler if fitted) and into the combustion chamber. Here, it is mixed with fuel, compressed, and set on fire, causing the piston to be sent downwards with a lot of force in order to turn the crankshaft and keep things working as they should.
Getting that clean air into the engine is paramount. The filters are sealed in the housing, usually via a rubber lip around the perimeter. Alternatively, they’re cylinder-shaped, so the air has to pass through the filter on its journey. They’re most commonly made from fibrous paper or synthetic material that is designed to allow air particles to travel through while capturing the nearly microscopic bits of dust and silica that are found throughout the country.
Performance filters vs regular filters
In some performance applications, air filters are bolted directly to the inlet, and the airbox is completely done away with. However, this is generally not a great idea for 4X4s for a couple of reasons. Namely, there’s a lot more dust, mud, and water to deal with in 4WD applications. Secondly, “performance” filters are good for racetracks, not for outback roads. They let way too much grit through to be useful to 4WDers, but that’s a whole other article. Let’s just say that if you’re going to drag race your fourby, by all means, bolt on a high-flow filter. If you’re heading bush, stick to the airbox and paper filters.
New tech
Air filters are being researched and updated on a near-constant basis. Most new “breakthroughs” are more marketing hype than anything else, and you’ll never go wrong sticking with quality paper-based filters (again, we’re talking 4X4 usage here, not squeezing an extra 5kW from your mang mang).
One product that we’re keen to try out, however, is Ryco’s new Nanocel High-Efficiency Air Filter. It uses a Supercar-based seal and a special pleating technique that allows them to fit over four times the material into the filter, which can reduce dust intake by up to 90% and filter down to 4 micron (vs. 8 micron for most OE filters). They also offer a degree of water resistance, so seem pretty much spot on for a 4WD. You can suss them out for yourself HERE.
Air filter maintenance
There’s no black art to air filter maintenance. If you’re mainly driving around the `burbs with the occasional weekend trip to your fav local spot then checking it every 10,000km as part of a service and changing out as needed should be sweet. If you’re on a longer trip somewhere dusty, which is pretty much everywhere in Australia, then you’ll need to lift the airbox lid as part of your everyday inspection before driving. Dusty conditions, particularly if you’re travelling in a convoy, can clog up a filter pretty quickly, so carrying a spare should be considered mandatory. This goes double for vehicles without a snorkel.
Pro tip: if you are driving in a convoy somewhere like the Simpson with its endless bulldust-covered roads, then leave a solid one kilometre between vehicles. Driving through your mates’ dust clouds is not only dumb but is also pretty bad for your vehicle.
Air filters are how your vehicle breathes. Keep them happy, replace them with quality filters and your 4X4, and your wallet, will thank you.
