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THIS DISCUSSION / SOURCE-DERIVED OVERVIEW
Discussion summary
YOUR RESEARCHK&N air filter
Leading reported evidence
Run ipd competition plenum w/gt3 tb
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However, I run the IPD Competition plenum w/GT3 TB which includes the elbow and cap.
Leading evidence: 'Run ipd competition plenum w/gt3 tb' (no explicit attributable resolution; this is a reported action or suggestion). Across 1 matching discussions, The most frequently discussed action is 'Clean bmc or kn filter or not' (1 discussions). For that action, 0 discussions report a resolution and 0 report an unsuccessful attempt. No action has an explicit, attributable resolution report under the current rules. These are forum reports and suggestions, not a confirmed diagnosis.
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I have run the K&N, BMC and OEM since 2002 on the street and track.
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In addition they have been tested by tuners and shown to do nothing, or even to reduce power.
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In the many decades I've used K&N filters on dozens and dozens of race vehicles/bikes/atv/SxS/cars/trucks/etc, never had a oil fouled MAF sensor.
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Suggestion
Yeah, it comes down to whether you want to go thru the exercise of cleaning your BMC or KN filter or not.
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Outcome without a verified action link
I noticed no difference between BMC, KN or OEM on my car.
Is it worth it to replace factory air filter on a 2004 40th AE with X51 with a K&N air filter? If so what is the power gain? I plan on keeping all the original for next owner. Thanks
I doubt you'll get any power gains, those engines are know to be pretty optimized from the factory.
You may get a bit more induction noise, but that's about it. Also, oiled filters may cause harm to your MAF sensor, and the 996 units are $700 from Porsche (though there are cheaper alternatives).
You won't gain any power. You will not have to replace it, so over time you will save some money. The filter eventually will have to be cleaned and there are multiple reports of the cleaning and re-oiling process resulting in excess oil being pulled through the filter and fouling the MAF. I installed one on my 996 but have not reached the point where I have had to clean and re-oil.
I have put in K&N filters in my daily drivers for the last 30 years. Gas mileage went up on all these cars by 1 or 2%. Essentially, I would get 5 to 10 miles additional mileage per gas tank. I would clean them every couple of years. Never had any problems. I have NOT used in on the 996 - mileage is irrelevant. My current daily is forced induction so I will not use it either. I do know that the K&N's don't filter as good as paper until they are somewhat dirty.
I'll start with the admission that I'm a K&N skeptic. Specifically for the 996, I'm a big skeptic. They're not even the best option for people who insist on changing the intake. In addition they have been tested by tuners and shown to do nothing, or even to reduce power. They may add noise, but there are other ways to do that as well.
Better airbox options IMESHO:
FSI/LN carbon fiber ($$$$)
Rennline carbon fiber ($$$)
997 3.8 airbox
EVOMS
IMHO, I wouldn't waste your money. I have run the K&N, BMC and OEM since 2002 on the street and track. No benefit what-so-ever on the track, which is really where it counts. Stick with OEM and replace it every couple of years.
There are plenty of other things you can do with your money to the 996.
Just want to make sure we're talking about the same thing. Do you mean changing out the air box for a K&N filter set up..?
Or just a replacement K&N filter element in oem air box..?
The K&N filter box replacement, exchanging the oem airbox, is not a good idea imo. The K&N filter element replacement in oem air box if fine and might show
miniscule
gains in power and slightly more in mpg. Especially if you have a partially plugged oem style filter.
You will get more intake sound, I like a good throaty intake howl at redline so thats fine with me.
When cleaning the K&N filter one must follow the instructions and not use high pressure water stream that could tear the filter media. I wash/spray/soak with K&N filter cleaner, and rinse with a low pressure stream of water from the inside out to let dirt come out the same direction it came into the filter. I clean mine when ever they look a little dirty and don't go for the long clean intervals as prefer always having a clean filter. And the K&N if cleaned properly can take many many proper cleanings.
After washing i like to shake out any water and then set in sun to dry for a little while before oiling the element. And only use enough oil to properly coat filter evenly. Then let filter set on clean shop rag in sun to drain any excess oil that the filter didn't absorb. I wipe off any excess oil from the filter before installing. This will prevent the MAF sensor from the possibility of getting oil fouled....
This is also a great time to clean the MAF sensor with a good MAF cleaner when K&N filter is drying/absorbing oil evenly/draining off....
In the many decades I've used K&N filters on dozens and dozens of race vehicles/bikes/atv/SxS/cars/trucks/etc, never had a oil fouled MAF sensor. Or cylinder scoring from ingested dirt/debis.
Just Don't go in thinking you'll get a big boost in power, as you won't. You will always have a clean filter to maximize mpg/hp, and save money in the long run on replacement filters vs buying new filters. And you'll have a nice throaty intake howl' at load.
jmho
Yeah, it comes down to whether you want to go thru the exercise of cleaning your BMC or KN filter or not.
My logic to moving back to OEM air filters was pretty straight forward after messing with all of them over the past 22 years.
1. I didn't want to have to keep cleaning them
2. Didn't want the headaches of oil screwing up the MAF
3. The OEM air filters were pretty inexpensive so to change them all the time was no big deal
4. I wasn't giving up any performance by going back to the OEM air filter.
5. It was pretty easy to look at the OEM air filter and see when it needed to be changed.
But it all comes down to the owners personal preference. Our job is to provide our feedback when someone asks.
Regarding enhanced intake sound. I noticed no difference between BMC, KN or OEM on my car. However, I run the IPD Competition plenum w/GT3 TB which includes the elbow and cap. It's the elbow with cap that gets you more intake sound. They can be bought for $120.
Here is a picture of my dirty engine with the elbow, cap, and UAOS. They were ripping up the roads locally and dust was everywhere. It was time for an air filter change.
From my research, I learned that while the K&N filter (and other oiled filters) improves the airflow which theoretically improves power by a nominal amount, the improved airflow comes at a cost. The increased airflow is because the K&N filter does not filter as well, allowing more dirt into the intake, which ultimately contaminates the intake and the oil. As mentioned by others, K&N and other oiled filters require cleaning and re-oiling and can cause MAF contamination.
I prefer a clean engine, so I chose to replace the K&N with the OEM filter.
This is a source reference. Confirm exact model applicability in the original material.
