K&N filters are probably a good example of life cycle extension of a legacy product. They were probably an advance over the early paper filters and the oil baths in carburettored cars. Offering better intake airflow to a carurettor that had been adjusted to the greater airflow. Otherwise a lean condition?
Injected engines automatically adjust to their available airflow via the MAF sensor. In all but open throttle, max power conditions the increased airflow does not result in greater hp.
Perhaps we should test paper filters. I bet the good ones are no restrictive than an oiled up K&N.

 

I think GOOD ONES is the operative word!

 

Gus -

If you define efficiency as filtration (which is what a filter is supposed to provide), then the K&N is not as efficient as a paper filter, which definitely does block more particles while still allowing the engine to operate. I did not make up the facts abouth what's in the oil analysis - there is more silica (i.e., sand) when using the K&N versus paper.

While the K&N is more free flowing and therefore **in a modified engine** may provide a small horsepower gain, it is not a more efficient filter. A race engine has many factors, big and small, built into it that results in more hp, but simply adding one of these small factors (a K&N filter) to an otherwise stock engine will make no appreciable difference to the average poster here.

If one really wants to spend 70 bucks or more on a filter to only adds more sand to the oil, hey go for it. In the end I suppose neither the sand nor the 1hp gain will be noticed by the time the car goes ****-up.

 

My understanding based on a combination of following similar threads on other boards, looking at dyno charts that some folks on other boards have posted every time they did some mod comparing against stock, hearsay, and my own common sense, I think a newly installed K&N type filter and a newly installed stock paper filter will flow about the same (maybe a slight edge to the K&N). However, as time goes by the K&N will retain its free-flowing characteristics while the paper filter will not. In any case, I am not deluding myself into thinking that even if there were a 10-20hp gain from the K&N that you could feel or notice the effects in the type of everyday driving that most of us probably do.

Doug

 

well I went with a NORMAL filter. I know the last filter has been on the car for 13k miles, how long before that I don't know. But when I first fired up the car with the new filter it threw some smoke, not oil, but from rich/lean or lean state for the first time ever. The car has never smoked ANYTHING. Ha ha ha
I am assumign with the new filter that the car forgot what FRESH better flow of air was. It cleared up in a about 15 seconds.
I too got a off brand, MARTIN or something I think. Looked JUST like my factory JAG filter, same numbers, same germany on it, just no JAGUAR on it, for 20 bucks.

 

Slightly off the specific topic but it is probably good practice to have a look inside the filter box every so often. I opened up the box the other day and found a few pieces of that popcorn-type of styrofoam in the filter box. I guess this got suck into the intake (I am still not certain where the actual intake tube goes once it passes through into the fender from the engine compartment). Of course the piece did not get past the filter but it seems good practice to check the box occasionally.

Doug

 

@Stevetech,

Another way you could test the difference is if you have a good OBDII reader where you can also record the MAF reading. However you need to be absolutely sure the conditions of the test drive are the same, especially the intake temperature. So first do a test drive, make 2 or 3 samples of the stock filter, exchange the filter to a K&N, drive a while so the heat soak will go away (double check the IAT sensor value is about the same as the runs before) and then do the same 2 or 3 samples.

I would only check the IAT quickly, and then only select engine RPM and MAF sensor for the readings, as the more sensors you select the less values per second will be received.

You could then extrapolate the difference in HP and get some idea.

 

I've taken sage advice from one of the wiser posters here and have decided to drop out of the rest of this conversation. I wasn't able to pull off the test I wanted to on Friday. Got busy.

In making changes to your own car, at the end of the day, you have to be comfortable with your decisions. Not much else matters.

 

Wise move Steve. The K&N filter silliness gets thrashed to death on every car and bike discussion board ad nauseum.

This is another great example of a product invented for one purpose that gets spun off in another direction by the marketeers. The 'warning signs' of snake oilitis is no hard proof of it being effective in it's new found role.

 

Good discussion guys, but I feel we've covered practically ever angle and approach to the advantages and disadvantages.