Hi all,

There are many trade offs when assessing expected increased power gains versus issues that arise from non-OEM components/enhancements. For background, I have a BMW 740i and a 997 4S.

In my case, after reading many posts and talking directly with manufacturers of air filters and my Porsche service manager about aftermarket air filters for my car, I decided to hold off permanently on replacing my stock air filter with an aftermarket one. This holds true for me as well on aftermarket headers and high flow cats. In some cases, gains were not documented, or where there's documentation, always a caveat or method of disproving (like statistics). Too confusing to know who's accurate and truthful. Also, spending thousands of $ for minimal horsepower gains and the risks of CEL lights and dealer hassles, etc. wasn't worth it to me. "Discussions" with the service department for warranty repairs (especially if they're adverse to non-OEM parts), is not what I want to do with my time.

In addition, in discussing with the Porsche service manager, once the MAS is clogged, it has to be replaced. Don't know if this is caused by an oiled air filter. From my discussion with aftermarket manufacturers, it sounded like a great deal of testing proved this wrong. Also, when I spoke with the Porsche service manager about this issue, his reply was "I've had to replace the MAS at times, but this didn't seem to have anything to do with the filter." Again, accuracy and truthfulness is hard to gauge, given the motivation for each party and what they've been told or are told to say.

Since I have a K&N filter on my BMW 740 (for over 3 months and 5K miles), it doesn't run lean or have any MAS issues. In matter of fact, if BMW hadn't recommended that I use this filter rather than the stock filter, I wouldn't have done so. When I replaced the stock air filter, my gas mileage increased by almost 5 MPG. Go figure.

Hopefully, those who have installed these after market components are trouble free.

Question: I wonder what % of those who did install aftermarket headers, hf cats and/or air filters or cold air intakes don't have problems? I only hear and read about the ones with problems.

 

zero problems with my evo intake and headers

 

Smart decision.
I believe the Porsche engineers know a little more about what they use in their cars than some aftermarket guru.

 

its not a matter of who knows more.....biased assumptions about qualifications aside...its more about the goals of each party. Porsche engineers have specific parameters within which they must work. Many are set by marketing execs and compliance departments, etc... at a reputable tuner, performance and quality are usually the only parameters. So you get different results. For those of us who like to squeeze ever drop of performance from our cars, it is neceassary to remove some stock parts and replace them with parts designed for max perfaormance. I have never had any issue with any car I have modded, porsche or otherwise. Doing it right with the right parts is the key.

As for the example offered, MAF sensors can be cleaned...but the failure problem is almost always resulting from an improperly oiled filter, not the filter itself. Its user error, not the modification that is the problem. Same is mostly true for many other mods...poor instalation or missues causes the majority of issues.

don't be affraid...just be smart.

dw

 

don't be affraid...just be smart.

dw[/quote]




A wise man once said: " Only fools are not afraid "

There have been numerous threads regarding the K&N air intake if you are interested.

 

A MPG increase from a filter tells me one thing....your cars probably running leaner. More air = more dirt. More dirt = shorter engine life. Its all about how much 3-4hp is worth to you when it comes to filters. Stock paper filters from MAHLE etc. filter very well and flow plenty vs. cheaper generic brand of paper filters which K&N etc. love to compare to.

I have seen MAF problems with stock K&N's (factory oiled). K&N's do make power when the supporting mods are there. Practically all race cars use a form of cotton / oil filter if they run them but there engines dont come with warranties and are expected to last a race or season...not measure in years.

 

Not sure if more air = more dirt, could be stock paper filter was constraining air input. Its not an HP gain that I saw, it was an MPG gain.

Wanted to try paper filters like you suggest. I agree on your perspective as to why K&N are in racing engines, given life expectation.

Thanks for your input.

 

There has been numberous tests performed on K&N vs. a few paper filters. The filtration was terrible vs. paper with more dirt particles being allowed through. Now for those leasing the car or dumping it within 5 years this is not that big of a deal. But with those with 'keepers' I'd avoid them.

At the very least if you run a K&N send your oil out for analysis every once in a while (blackstone labs) and make sure nothing nasty is residing in there.

 

Some links:

http://home.comcast.net/~nhparrot/ts...FilterTest.htm

http://mymiata.paladinmicro.com/K&NComments.htm

http://www.mkiv.com/techarticles/filters_test/2/

 

In a normally aspirated engine, you can't get "more air" into the engine.
All you can ever get is the volume of the combustion chamber at atmospheric pressure.
If you want more air , you need to compress it first ( via Kompressor, turbo , supercharger or whatever else you want to call it ) But the engine does not need as much energy to suck the air thru a less restrictive filter in the intake ,therefore there is a little more power available at the driven wheel.

As you said, less restrictive also means that the filter does not clean well and lets a lot of dirt pass into the engine.
OK for a few laps on the track, but not for a daily driver .

 

thats actually only partially true/accurate. An important point to consider is that motors have both a static and dynamic volumetric efficiency. the later being very much dependent on the timing of valve events and piston movement. but altering restriction in the i/o path can also have a significant impact on the total volume of gasses being combusted and ignighted in the chamber. the result being that a less restricive element can increase acual airflow within the window of the dymanic event.

dave w

 

my experience w drop in KN and a CAI is that you'll get more sound than HP gain, if any. on cars with large filter element surface such as 996/997, i really don't think there is much restriction of air flow. cars with small filter panel can probably benefit from a drop in or CAI.