Performance Air Filter - The BIGGER the better - Why the biggest performance air filter is the best
Saturday, August 23rd, 2008What performance air filters are we talking about here? Where talking about cone filters here like those found on induction kits such as K&N 57i
OK, so why is the biggest performance filter the best, surely as long as it flows enough air for the engine its connected to its the best it can be? Well yes and no. A new filter of the correct size will make the maximum power possible. Off the shelf kits from the likes of K&N, Green and Raid hp are designed for standard or lightly modified vehicles, for cars with big power upgrades, a custom air filter system will more than likely be required.
OK assuming my car is standard, why would I want to fit the largest cone filter possible? Three reasons. 1. Increased service intervals, the larger the air filter the greater capacity it will have to hold dirt, therefore it will need cleaning less often.
2. Increased filtration, the larger the area of the air filter surface, the slower the air will move through the filter medium. The slower the air moves the easier it becomes for the filter to hold the dust particles as the particles have less momentum when they hit the filter. (Special car should be taken when cleaning an oversized filter as the dirt will fall off the filter much easier that it would with a small filter as the small filter would have sucked the dirt into the filter medium with much more force and therefore the dust will be more strongly attached to the filter). 3. Power. Although an appropriately sized performance air filter, when new, will provide all the air standard engine needs, over time, as it holds more and more dust, the less air the filter can flow. This restriction will hurt horsepower gradually over time and so slowly you may not even notice until you clean or replace the filter. The same effect will happen on a large performance air filter but as the filter can flow so much more air than is needed it will take much much longer for the dust to have even the smallest effect on flow and when it does start to restrict flow, the reduction in power will take much much longer. Filters designed to flow just the right amount of air will start restricting flow from day one as there is no spare air flow capacity built into the filter, whereas with a large filter there is plenty of spare capacity.
OK if oversized air filters are so great why don’t the performance air filter companies supply them as standard? It simply comes down to price; the aftermarket performance air filter industry is incredibly competitive. It may be hard for a manufacturer to justify a substantially greater price than a competitor, especially when the power benefits are hard to notice, especially when the filter is new and it is even harder to quantify the extra filtration capacity.
In conclusion, like with most things in life, bigger is better. If you are looking for a filter that will flow all the air you need, have superior filtration of dust and have a longer service life, bordering on fit and forget, the biggest performance filter you can physically fit to your car will always be the best. As we highlighted in a separate test, performance cone filters should, if possible, be shielded from the heat of the engine and exhaust manifold. Click here for the StrikeEngine performance filter heat shield test which details the temperature reductions heat shields can have on intake air temperatures and therefore power.
