An above post states in part:
"Any HP or MPG gain is minimal if at all.
If the product produced more HP and MPG's the vehicle manufacturers would buy it.
Manufacturers would raise their CAFE numbers.
MPG and HP gains would be beneficial for manufacturers."
This contains two common misconceptions. I'm not going to address mpg gains as to either misconception, because I've never seen reliable evidence of mpg gains from using a K&N.
The first misconception is that a K&N will only minimally, if at all, increase HP. This is true for some engines. It is not true for others. The dyno tests that I've seen range from a miniscule increase of 1/2 HP or less to an increase of up to 6-8 HP, depending on the engine and/or the existing air intake system. In addition, if you combine a K&N with an air intake system modification or kit, the HP increase is greater than when just switching to a K&N. But again, it all depends on the engine and the existing air intake system. Dyno tests of some engines show that an air intake system modification or kit plus a K&N results in only a 1-2 HP increase. Other engines dyno out an increase of 8-10 HP or more, tho not much more from what I've seen.
You can often increase HP by giving the engine more air to breath, but not all engines. That is, for example, the whole point of a turbocharger or supercharger, each of which forces a large amount of air into the combustion chamber, thereby increasing HP. Some engines can, and will, breath in more air if you install a K&N, and will breath in even more air if you also either modify the air intake system or install an aftermarket or home made air intake kit. On the other hand, some engines come stock from the factory breathing in as much air as they can use and a K&N plus an air intake modification or kit will make more air available, BUT the engine simply won't and doesn't take in more air. On a similar note, you can usually, but not always, increase HP by allowing the engine to exhale quicker and easier, which is why people install aftermarket exhaust kits with larger pipes and more freeflowing mufflers. Here again tho, it also depends on the engine, and dyno tests range from a miniscule 1 HP to 8 or more HP, depending on the engine. Some engines and exhaust systems already, stock from the factory, exhaust the gases as quickly as they possbily can, no matter how much you open up the tailpipe and muffler.
The second misconception is that vehicle manufacturers would install the K&N if it increased HP and since vehicle manufacturers don't install the K&N its evidence that the K&N doesn't increase HP. This is a misconception because in order to maximize the HP increase you also have to modify the air intake system or install an air intake kit to allow for even more of an increased air flow into the engine than if you just installed a K&N. The two together is what increases HP, ON SOME ENGINES. However, when you do this, whether or not the HP increase is minimal or respectable, you ALWAYS increase the noise level considerably, and THAT'S why manufacturers don't install a K&N. Most people don't want noisy engines. This HP vs. noise tradeoff also applies to exhaust systems. The more restrictive the air flow into the engine and the more restrictive the exhaust flow out of the engine, the less noisy the engine is. The less restrictive the inflow and outflow, the noisier the engine is. And the manufacturers know that most people don't want the noise. Of course most kids DO want the noise (and also a lot of people who are past the kid stage) and open up the intake and exhaust to get the noise, even if the resulting HP increase is negligible.
I thought this was going to be another "K&N-haters" thread. I'm glad I read it anyway. I've been using them (and S&B)for 11 years, and I don't plan to return to paper.
