Does Changing the Air Filter Affect Engine Performance?

One area of interest in the eternal quest for more engine power is the air filter.

The equation is easy: One can mix in more fuel when there is more air. The increased airflow increases the volume of oxygen which allows the fuel to burn more completely, therefore releasing more energy from the fuel.

But there is a sense of contradiction in the case of the air filter. On one hand, it has to keep impurities such as dust, water, insects and everything else in between out of the engine. Yet, it has to provide a smooth flow of air to satiate the demands of the engine. A filter that’s too restrictive will keep out all impurities but not provide enough air. On the other hand, a “loose” filter will provide more than enough air but allows impurities into the engine as well.

Bear in mind that impurities will destroy many parts of the engine if allowed in. This includes the throttle bodies, valves, pistons, piston rings, cylinder walls. Furthermore, the dirt will get picked up by the oil and circulated around the engine, damaging even more parts in the long run. So never, ever ride without an air filter!

The conclusion is: A good air filter will allow the right amount of air through in a smooth manner whenever needed, while keeping other objects that have no business in an engine out.

But does changing the air filter provide more engine power?

As a general rule of thumb, changing the air filter doesn’t necessarily equate an increase in engine power. That’s because the ECU controls the corresponding amount of fuel to the amount of air that goes into the engine.

However, the fuel injection system does measure the amount of air entering the airbox and its pressure. If more air could be allowed in, then the ECU will compensate with the amount of fuel being injected, thereby increasing power. You may also retune the ECU to gain the maximum amount of engine power. Check out the graphs below.

Also, an air filter with good flow characteristics provides a much smoother throttle response. In some cases, the lethargic or slow throttle response could be cured somewhat by replacing the stock air filter to an aftermarket one. The same could be said about cruising or accelerating in the engine’s midrange, plus when you go off the throttle.

We’ll give you an example. This writer found his 2011 Kawasaki ER-6f’s throttle lacks acceleration in the initial opening, before “kicking” hard a little while later. The engine had too much engine braking, too, when he went off the throttle. These traits make for stressful cornering, as it makes the bike shift its weight to the two wheels like a seesaw.

Acting on trusted advice, he replaced the stock foam air filter with the DNA filter. The change was immediate, and the bike behaves much better since then. Besides that, he also noticed a bigger fuel saving. Whereas he could get an average of 190 km to one tank of gas, he could now safely hit 210 km per tank.

All with just one air filter change.

NOTE: DO clean your air filter at regular intervals, regardless of brand of type you use, to ensure smooth engine operation and good fuel mileage.