What will bigger air intake K&N filters and sport mufler do to a car?

 

There has been debate on this forum as to whether or not K & N filters do that much for a car by themselves. Any power gain would be minimal.

A muffler that provides for reduced resistance will also gain you a few horsepower. After all, the engine doesn't have to work as hard to push out the exhaust gases.

Perhaps the both items together might give you enough for a small but noticable gain in power. I'll defer to the opinions of the experts.

 

From modern cars, there are a lot of things that can limit horsepower. For example maximum rpm and pressure (reduce load on mechanical parts), mixture adjusted to minimum fuel consumption and emission laws or whatever. I am pretty sure that for most of the cars the air intake is not the most restricting part of the engine (when it comes to gaining a few hp). It is known that most of the cars can gain a few hp by making the mixture a bit richer at max load (example: Mercedes former V12 engine, M120, first came out with 408hp. Later emission laws have changed and Mercedes needed to make mixture leaner, then it had 398hp). So, if you really want to have more hp, maybe you can start with modifiying the engine ECU (or putting another in it).
I have already seen air filter tests with a test case with test dust that went trough it. Vacuum pressure measurements showed how long it takes before the filter needed to be replaced (and how good they were when new), and the amount of test dust showed how good the air was filtered. The results were that there is a lot of difference between the different brands. Good were filters used by Mercedes for first mount (example: Knecht).
The type of filters that K&N are do not filter as good as the original paper-like filters mounted in the factory. They will also produce a lot more intake noise. I would not recommend to use them for normal traffic use and I also doubt that you will really gain power.
Another muffler will maybe gain an neglectable amount of hp's, but not without making more noise. It is the complete exhaust system (and valve timing,...) that makes the exhaust gases pass quicker or not.
My opinion is that it is the one or the other, either you have an ordinary car for everyday use, or you have a car for rallyes or whatsoever that you tune to the max. For me there is no way in between.
(The difference between a Mercedes SL500 and a SL55AMG is also just not those "air filter/muffler/...-things", but a serious amount of engine modifications).
I do not like half-hearted solutions.
Patrick

 

THank you and I will keep it untouched. I wanted more then just "a few" horses.