K&N Air Filter [Archive]

mvw2

12-20-2004, 02:09 AM

I've always thrown a K&N air filter in all my vehicles. It's partially for performance, but also a maintainance thing too. Only touching it once every year or two is nice. A quick clean and it's like new again.

Other than the convenience factor, what gain you will get from the filter varies by car. Some are quite restrictive stock and some aren't. For example, my old GMs with the 3800 series engines. The air filter isn't that big and the engine likes to break a little as it's a 3.8L. From a Fram to a K&N, there's a noticable difference, not much but noticable. Throttle response increases as well as a touch of spunkiness. You even get a little more intake noise if you like that sort of thing.

On the other hand, my Forester didn't change one bit going from the factory paper filter to a K&N. Then again the Forester is a 2.5L AND has double the filter area as the 3800 series in my old Lesabre. Most people say, the Subaru intakes on those engines are really good to start, so changing them doesn't do much at all.

So,
will you see any performance gain?

Well, probably. How much? I can't say. I don't (yet) own a tC and don't know the size of the filter. It's a 2.4L and is of a decent size. Oddly, it uses the same size as the much smaller engined Corolla as zoltiz stated. If it is pretty small in area, you may in fact see a noticable gain. What you may notice will be quicker throttle response, a little more throaty sound, and a touch more power through the higher rpms.

Loss of power?
Well, it's possible. Everything I've seen about loss of low end torque comes from larger exaust and loss of back pressure. The intake should have a far less influence on that type of thing. However, there IS an optimum temperature and velocity of the intake gases to best atomize the fuel/air mixture. The velocity is a factor of intake cross-sectional area(how big of a hole you have), not ease of flow. The intake should be as free flowing and least turbulent as possible to produce the most horsepower. A better flowing air filter will help this.

If you're really worried about low end torque, just don't get big 3" diameter exaust, lol. HotRod magazine did a little study of this. They ran through several diameters of exaust as well as downpipe lengths to determine the optimum size for a v8 engine, don't remember what but I'll guess a 350 for this example. Oddly, a 3" exaust, even on a v8 caused LOWER power. It goes to show, sometimes bigger isn't aways better. They found a 2.5" exaust and a medium lengthed downpipe to work best, on a v8. On our little 2.4L, a 2" would probably work better than anything else unless it's Turboed and you really need the flow.