Sean

Do you have a K&N air filter in your car? If so, do you believe it makes any noticeable improvement in performance? In sound?

Is K&N really significantly better than a paper filter? If so, do you have any dyno evidence or are you relying on the old fashioned 'butt dyno'?

944Play

[quote]Originally posted by Sean:
Do you have a K&N air filter in your car? <hr></blockquote>

Suffice it to say: When I bought my 944, it had a K&N; it no longer does.

Rich Sandor

When cleaned, it lets dirt in. (not a dangerous amount, tho)

When Dirty, it is as effective as a regular paper filter. (Unless you use a conical one)

If you convert to a conical filter, it needs to receive cold/ram air from somewhere.

I just bought an extra long K&N Conical, and will duct air up to it. I'm forced to do so, because the previous owner ditched the factory airbox. <img src="graemlins/cussing.gif" border="0" alt="[grrrrrrr]" />

Also, if you get a K&N conical, you need to make absolutley sure that it doesn't rub against the timing belt casing. (I attached a thin strip of aluminium to the filter, so that the filter's mesh doesn't rest on the timing belt case)


Lastly, more air, equals more power. The KN definately adds a tiny bit of umph, if done correctly, but it is SO minimal.

Raceit

Even all performance aspects aside it's a bonus it you have one in a S2. Just for shear conveince of not having to take the nose panel off to simply change the air filter.

Brian McCoy

I've seen this thread (and started it occasionally) on a variety of different lists/forums. To the person who doesn't really think about it much (just the average Joe on the street) - most would probably have the impression that a K&N does help. For those who've looked into it, the camp is split (at least from what I've seen previously) between those who vigorously stand up and fight for K&N and those who say it's a scam on an order slightly less than Duralube. It doesn't seem that either camp has much ground to stand on (single vehicle tests for both improved airflow and wear) if you accept that K&N is going to use statistics in its favor (every company does - it's called 'marketing'). The few people that I think would have a good input are those in control of a large fleet of vehicles (UPS/FedEx, USPS, and the like) and it's one of those people that I was friends with that swayed my decision.

My friend (Dave) was the lead Maintenance ME for a strip-mining company - Lee Ranch Coal Company, out of Grants NM - (dirt roads, LOTS of dust... more than the average car will see for sure). Their vehicles needed replacement paper filters on average about once every 7~10 working days. Dave decided to test out K&N filters on a new set of 6 work trucks with the 7th running paper. All the vehicles were identical, purchased in a group order and presumably built the same day at the factory. The K&N's were properly cleaned and reoiled about as often as the paper filament was replaced (not quite, K&N's actually work better when slightly dirty and properly oiled). At 100k miles, all the vehicles were brought in for a through inspection and the 6 running K&N were due for an overbore due to cylinder scarring from dirt intake. The 7th was still within limits and was sent back out to resume its tasks. More money was spent on the 7th vehicle leading up to the 100k miles with the replacement filters - but it was well in the lead cost wise after the engine rebuilds not to mention the time that those vehicles were down and out of commission. They went back to paper filters shortly there after and never looked back.

So, in a Very harsh environment, there was definite increase in wear due to particles making it past the filter. Does this relate to the average Joe on the street who's looking to improve performance? Maybe - I'm not sure that anyone would notice before the engine needed to be torn down for other reasons (better than 300k miles). This sure as heck doesn't answer the question of more performance - but some people are unwilling to take the increased wear in return for possible performance gains.

I've seen a few studies that show a clean, freshly oiled K&N against a stock paper filter where the paper filter flows more initially (while filtering better) - but the flow decreases a bit faster than the K&N once particles are introduced. So the K&N gives a more consistent airflow over the term of the filter... but never claims peak airflow performance.

Draw from this what you will - personally, I still replace paper with K&N and just accept that I'm increasing engine wear. I also don't keep vehicles for more than 100k miles, so it's not an issue in my book. When I do end up with my garage of nice classics that I spent time rebuilding the engine and restoring - they'll most likely have paper OEM style air filters.


<img src="graemlins/yltype.gif" border="0" alt="[typing]" /> whew.. to much of this...

Manning

I don't get why K&N type filters are allowed by the FAA (you see them on experimental or home builts) if they a supposedly such shyte.

Rich Sandor

They're not shyte. The point is that they let MORE particles into the engine than a paper filter.

And unless you take off from dirt strips regularly, (who the hell does that???) then there's no reason why a K&N would be unsuitable for aviation, where 99% of the time, teh running engine is in the air, with no worries of dirt particles.

I would NOT, EVER run a K&N in ANY car that traverses dirt roads often.

That's why K&N would be stupid to sponser rallys.

J Berk

My N/A had a K&N when I got the car...my father's early 85 N/A which has about 10,000 fewer miles then my car ( 70k vs 80k ) has the stock filter....both are maintained by the same mechanic and my car feels like it has twice the grunt.....only other difference is that mine has a round throttle cam and dad's is stock....but what we both feel is more than just throttle response!

Maybe it's related to the filter...and maybe not!

IanM

the reason you never see any dyno plots, is because the results would be impossible to interpret. Any gains would be negligable, unless you're removing a restrictive airbox and replacing it with a big conical filter. The normal variance in dyno results would probably be greater than any real hp gains.

MadMax

This topic is particularly interesting to me because I just spent ~$45 on a K&N for my S2. When installing it under the front nose panel I also drilled 3/4" holes along the lenth of the short and wide factory air box. I also removed some baffling from inside the airbox that used to redirect the incoming airflow. In the stock S2 the factory airbox forces two 90 degree bends to the intake airflow before it even gets to the filter.

What have I noticed?
Well, my car had a stumbling idle that I thought was due to a miriad of other things but it seems to be gone and may have been due to a dirty airfilter. Also, my engine does appear to rev more freely, especially in the higher rpm range (3500-6000) where before it would seem to hesitate a little. Again, this could be attributed to a clean airfilter not specifically a K&N and of course the reduced resistance to flow from the holes and removed baffling. Additionally, I do hear a lot more intake sound at 3/4 to full throttle (which I kind of like).

As for the semi-scientific filter analysis done by the mining company...Unless you are drivning through a dirt saturated atmosphere cleaning the K&N every 7-10 days is probably what allowed the increased particulate damage to the cylinder walls. K&N filters work a similar premiss to oil bath airfilters (remember those). Oil saturated cotton batting will trap more dirt once it is dirty than it does when it is clean. K&N recommends cleaning the filter every 50K so cleaning it every week and a half had to negatively affect its filtering ability.

If you want the best air filter...Oil bath filters are the best type of filters...better than paper, K&N, mesh screens, electro-static, whatever. Unfortunately they are very restrictive and not very convenient.

Anyway, I like the K&N and so far I am happy with it.

Regards, Max

BartW

if you don't mind the crap from the filter oil clogging up your intake and allowing more dirt into your engine use a K&N for the non noticable difference in flow, but understand that with time the damage it causes will certainly offset any gains and by over time I mean a matter of months. Look up the thread about cleaning your K&N in this forum and you will see why engine builders recommend to NOT use K&N

User 462021

This reminds me, I have a K&N knockoff that I was going to put on my car. I was going to concoct an adapter but I'm not going to put any more money into the car so if someone wants this, start the bidding now.

I'll make a new topic so I don't ruin this one.

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Olli Snellman

i have a K&N installed into my 951 (original box).I suppose it does not give noticeable difference comparing to original paper filter

Sean

This topic interests me for a number of reasons.

It seems that the K&N filter is one of those 'performance upgrades' that is widely accepted. But OTOH no one appears to believe with any conviction that the performance gain is significant! It's something we all do, but we're not sure if it even works. It's the automotive equivalent of ginseng extract.

I have a BMC filter in my Boxster S - in that case, it has changed the air intake sound to produce more of a growl. It sounds a little better (or at least a little different) than stock.

I know that my 944 once had a K&N (sticker is on engine) but a previous owner replaced it with paper.

Some people have told me that with "chip, filter, & exhaust" the NA performance can be increased. Perhaps these elements work in concert, so that the sum is greater than the individual parts?

Brian's post makes some great points, like considering engine wear & tear along with performance. It sounds like those who plan to keep your car for a long time should view the K&N with extra suspicion.

Thanks for your replies. <img src="graemlins/beerchug.gif" border="0" alt="[cheers]" />

alpenweissisnice

The debate rages on. I went with the K&N when I purchased the car as the paper filter was shot. I was amazed the turbo could suck up as much s*** as it did/does into the stock 951 airbox. Did I notice a difference? Not really, though the car sounded a little "racier" (not "ricier") at WOT. I don't drive my car in dusty/dirty conditions, and I over-service it, so I'm not concerned about the possible diminshed filtering characteristics. In the end, if you attend to your car like most of us do, it probably doesn't make a difference. It was worth (to me) the extra 20 bones for the "performance" upgrade. Then again, I'm a geek.