omilu

About a year ago a reputable porsche mechanic told me that K&N filters can do two negative things,
1. Lead to hot wire failure
2. not filter as well, leading to premature ring/cylnder wear.
So I took the K&N off, and put the paper filter on(slower!).

Last week another very reputable porsche mechanic told me the K&N filters were fine, as long as you used the K&N oil(non silicone based). I am considering putting it back on.
Anyone have thoughts?
Thanks
Omilu

Porscheologist

According to Bruce Anderson in Excellence Feb 06 the 3.6 liter engines can use more air flow. He recommends usings the drilled or Cup Car air cleaner covers and aftermarket air cleaners to help supply more air. He makes no mention of the issues you describe. I use the K&N and have never heard of a Porsche having the issues your mechanic mentioned. I also use them on my Jeep and know many people that use them with no ill effects. I have heard of Volkswagen and BMWs having some of these issues however. The key appears to be to use the K&N oil and don't over oil it. I have read that If the oil gets on the air mass wire it can cause damage long term. Just my 2cents.

graham_mitchell

There have been some issues with K&N, which you can find in the archives. At the same time people have noted no power gains and i believe one person even dyno'ed before and after the installation and lost power. It's all in the archives.

My advice: find other ways to increase power.

Bull

As mentioned, the key is to use the correct cleaning solution (K&N) and oil (K&N), then make absolutely sure that you don't over oil the filter. Follow the directions provided.....very lightly oil with the spray applicator, then let it sit overnight so the oil is completely absorbed. The filter should be grayish-white when fully cleaned, then a very light pink-red when oiled properly. The one case where I have seen the MAF damaged was due to a mechanic who thought "if some is good, more is better". The filter was almost dripping with oil when we removed it!

No single change is likely to give a meaningful power increase. Getting more air in is only useful if the engine can do something with it and get more gases out the other end. Changing the air-box and the filter will give a nicer sound, IMHO.

FlyYellow

i tried the k&n on the dyno with and without. You get a different power curve with a little gain in peak power but at a loss of low end power. Not sure if it is worth it or not.... i guess a bit depends on your driving.

omilu

what type of airbox did you use? Seemed to me when I modified my airbox cover with large holes, that the K&N made a differance over the stock filter.

24FPS

isn't the k&n supposed to last for something like a 100k? before it needs a cleaning.

STLPCA

This issue has been discussed here for years w/many threads. The clear consensus was if you want extra intake sound & aren't concerned about engine life, use a K&N which just does not filter as well as the oem paper.
I used a K&N in another car & noticed a regular accumulation of sediment on the fltered air side of the airbox not experienced w/the paper filter. I stopped using the K&N. Since then I have not & will not use a free flow filter to protect any engine I care to preserve. BTW, other than better sound it added nothing to performance as tested w/my G-Tech.
As mentioned, a Rennlister posted before/after dyno results here showing a slight loss in power w/the K&N.
A few years ago K&N discontinued the 993 filter due to disintegrating rubber getting sucked into engines. It was then returned to the market w/supposedly a better seal.
YMMV.

Bull

True, if the goal is to "preserve" the engine, allowing the least amount of air, or anything, to enter the engine is the way to go. Of course, how much longer an engine will last with one filter vs. another is the fodder of the forums!

Steve Weiner-Rennsport Systems

Hi Bob:

There are several variables that affect the success or failure of filter media:

1) Fitment. In many cases, K&N's don't fit as perfectly as OEM filters do and one must be VERY careful to make sure its installed correctly. I've seen some that air went right around the cotton element due to installation error.

2) Maintenance. Aftermarket, serviceable filters MUST be cleaned and re-oiled right by the book with the manufacturer's products.

3) Environmental variables. Anyone in a dusty climate is better off with the OEM filter, but it must be changed regularly to maintain peak performance.


Honestly, long-term oil analysis is recommended to track the effectiveness of ANY filter you use.

FWIW, I've not seen any HP improvements on the dyno between a new OEM paper element and a K&N or other oiled gauze filters. The K&N's merely pass a lot more air after they appear to be dirty.

When it comes to power, the air cleaner housing is a much bigger influence. As an example, installing a cone-type filter reduces HP,.....

zoomzoom

Perhaps I'm missing something here, but isn't an oiled filter supposed to accumulate sediment as the sediment/particles get stuck to the oil? If a paper filter does not have the sediment, doesn't it suggest that the sediment has simply passed INTO the engine - something which isn't desirable?

STLPCA

You are missing something. To clarify: the sediment had NOT been captured by the K&N, but had gotten through it & accumulated on the bottom of the airbox which was configured differently than the 993 - the filter was horizontal. I presumed what I saw was just a portion of the passed grit, the rest of which had gone into my engine. I've no question in my mind a K&N passes more air (which stands to reason since it passes more dirt). What I've never seen is any objective testing that shows a K&N yields more power in an otherwise stock 993. Indeed, what I've seen posted here concludes just the opposite. So, if there's no benefit and just the possibility of detriment, my decision was clear.

Some filtration testing from a cursory Google search:
http://www.bobistheoilguy.com/airfilter/airtest1.htm
http://home.usadatanet.net/~jbplock/ISO5011/SPICER.htm

zoomzoom

Thanks Dan for clarifying my understanding. I've been tempted by one of these as an easy way to "improve" the sound. I suppose Steve's advice on correct fitment as his first point is key...

Cheers -

STLPCA

Have you drilled your airbox? If not, that's a whole lot less expensive (& IMHO better) than a K&N.

Bull

Hi Steve,

Your findings are very similar to mine. As I stated in my earlier post, the correct cleaning and oiling of the K&N filter is very important, both for filtration and in order to not foul the MAF. I also mentioned that I wouldn't expect any meaningful power changes (unrelated to different dyno runs) from simply changing the air filter. If done as part of a complete package of changes, improvement can be seen.

The fitment issue is a good point. I didn't mention it because all of the 993 K&N filters I have seen/used in the past few years have been an excellent fit. I assumed he would be using a new K&N with the better fit.

My most recent post was simply to agree that if "preservation" of the engine is the goal, I wouldn't change anything. If extracting more power from the engine was the goal, I would change many things.

Happy New Year!