"Cold-air intakes" and "high-flow air filter" FAQ
 

By popular demand, here's an FAQ thread for USEFUL information on cold-air intakes and high-flow air filters. Useless posts will be removed.

Go nuts.

Edit: know what would be cool? Maybe someone can make a nifty, tastefully funny but small and useful button picture that links to this thread for future threads discussing this subject. This would be a useful thing to do for other FAQs as well. For your convenience and a start, you can copy and paste this hyperlinked thing to offending threads:

Read the "Cold-air intakes" and "high-flow air filter" FAQ!

Reposted from here by request of TDIMeister.

In response to the statement, 'because they [K&N filters] are a proven way to make power on nearly every other car.'

No they aren't.

http://www.honda-tech.com/showthread.php?t=1768602
No gain in HP or torque (tiny bit more torque with stock system)

http://forum.e46fanatics.com/archive.../t-378208.html
'The Porsche Club of America dyno-tested K&N filters in a variety of new Porsches in 2001 and found no power increase whatsoever.'

http://www.apriliaforum.com/forums/s...postcount=3562
'On my old 1999 Mille I did a dyno test with full EGA on the stock filter, EVO, K&N, a Foam one I made and none at all. The dyno graphs all directly overlaid one another as did the mixture trace lines.'

http://www.gadgetonline.com/Dyno.htm
' It looks like TRD is right about this one, or close anyway. They told me that they have seen a slight reduction in power, to no improvement with the installation of the K&N FIPK.'

http://tl.acurazine.com/forums/showthread.php?t=601091
'The reality is 4.6 RWHP and ZERO gain in torque is PEAK number. The 4.6 additional horsepower did not increase the entire length of the curve...only a small peak at the high rpm.
...
Notice the red and blue line pulls are identical to each other with the difference of 4.6 RWHP [at one point, approximately 5400 RPM]. This peak number would not be felt on the street or shown in the 1/4 mile.
...
Then you have to consider how the K&N works in the first place. It allows more air to travel through it so no matter how many ways you look at it, the K&N filters less particles. It has been proven that an engine equipped with a K&N filter will show more silicate in it's oil than an engine with a "paper" element. Don't believe me? Analyze you own oil before and after a K&N install. I did.'

http://webspace.webring.com/people/m...nisign/kn.html
' I know of at least one Si/SiR owner who dynoed their car before and after installing a K&N drop-in like yours and mine, and saw horsepower losses.'

I could go on, but the claim of these oiled MAF-ruining bugcatchers making power 'on nearly every other car' doesn't hold water. Even if you don't believe the HP gains, the lack of filtration is my biggest concern. Price out a replacement MAF & turbo for S&G, or a valve job.

K&N filter media, notice the sunlight passing thru the filter! :eek:
http://pics.tdiclub.com/data/3340/KN_filter_media.jpg

dieseldorf's K&N "lie detector" test:
http://pics.tdiclub.com/data/3340/30..._KN_filter.jpg
From what I can tell from the dyno plots:
- 1st run: Baseline with NO FILTER installed. EMPTY airbox! :eek:
- 2nd run: Stock OEM paper air filter.
- 3rd run: K&N air filter.

ZERO performance improvement observed with K&N compared stock OEM paper filter or even NO FILTER at all! We've seen this all the time in the numberous K&N threads..."It (K&N) just HAS to be better!" OK, based on what? :confused:

As I've said in other K&N filter threads:

K&N filter = MAF eater + engine sander + ZERO performance benefits = BAD! :eek:

Stick to using only OEM filters:
http://pics.tdiclub.com/data/3340/DBW_OEM_filters.jpg

I use the cold climate version OEM filter, shown in the above pic. Here is an end-shot view:
http://pics.tdiclub.com/data/3340/30...otCWfilter.jpg

I use the cold climate version year round in my 02 Golf because I removed the snowscreen in the intake snorkel due to it regularly getting clogged with bugs and other debris.

Cold Climate version part number: 1J0 129 620 A
Standard version filter part number: 1J0 129 620

Note the "A" on the end of the part number is for the cold climate version.

These products are consumed by those praying for miracles. Just say no, and save your pennies for something with a tangible payback!

http://pics.tdiclub.com/data/500/med...the_filter.jpg

http://pics.tdiclub.com/data/503/med...NONAME016s.jpg

http://pics.tdiclub.com/data/503/1366NONAME022s.jpg

http://pics.tdiclub.com/data/500/med...F_elements.jpg

http://pics.tdiclub.com/data/503/1366NONAME018s.jpg

http://pics.tdiclub.com/data/500/med...icture_2_1.jpg

http://pics.tdiclub.com/data/500/med...6_072009AA.JPG

http://pics.tdiclub.com/data/500/med..._TDI_Turbo.jpg

http://pics.tdiclub.com/data/500/KKK_Compressor.jpg

http://pics.tdiclub.com/data/500/med..._110124AAb.jpg

http://pics.tdiclub.com/data/500/med..._110936AAa.jpg

http://pics.tdiclub.com/data/500/med...pressor_1s.jpg

http://pics.tdiclub.com/data/500/medium/kn1.jpg

That's the dirt let thru after just 501 miles of driving on a NEW FACTORY OILED K&N

Best bang for the buck
 

http://pics.tdiclub.com/data/500/041922.jpg

Plus

http://pics.tdiclub.com/data/500/medium/8N2694.jpg

http://pics.tdiclub.com/data/500/med...er_how_too.jpg

Or if you have a Mercedes it's already built into the MAF sensor (a "Delta-P" or Differential pressure sensor monitored by the ECU)

http://pics.tdiclub.com/data/500/med..._Manometer.jpg


General rule of thumb:

Replace the filter when:
-25-30" of H2o restriction
-4 years
-100,000 miles
-Whichever occurs first.

If you have a Snow Screen installed, clean it every 10K by removing ONLY the base retaining bolts, NEVER EVER open a filter to take
a Look, if you want to inspect the filter, it can be viewed on both sides when removing the UNOPENED BOX from the car.

-Remove the two 10mm bolts DO NOT REMOVE THE TWO philips screws securiung the top of the box to the lower portion!!!
-On the MAF sensor, remove the two philip screws holding the MAF sensor to the box.
-Once the MAF is removed you can inspect the upper and lower sides of the filter. The filter MUST look dirty, as long as there are no tears in the pleats, press on and don't mess with it.

To clean the screen just just some shop air and blow out the debris. The more you stop in the screen the longer the life of your air filter!
Thanks to Compu85 for these pictures...Exactly the way it should be inspected and cleaned.

http://pics.tdiclub.com/data/3210/medium/Step1.jpg

http://pics.tdiclub.com/data/3210/medium/step2.jpghttp://pics.tdiclub.com/data/3210/medium/step3.jpg
http://pics.tdiclub.com/data/3429/me...now_screen.jpg

A Blocked screen may indicate approx 10-15" H2O, so be prepaired to clean the screen rather than replace the filter. If you see 25-30" suddenly you may have had water or snow ingestion, inspect the filter and determine a course of action. Either way start with inspecting your snow screen.

so please point me to a good cone filter as I have no room for stock airbox in my car..

I shall post some pics from Apexi filter too =)

http://pics.tdiclub.com/data/500/thumbs/DSCN6498.JPG

http://pics.tdiclub.com/data/500/thumbs/Image378.jpg

I now run an airbox from a mitsubischi carisma turbodiesel, it has a paper filter but it's quite restrictive, I measured over .1bar of pressure drop at high rpm, + I think it lets some very fine dust true as the inside of the pipe from airbox to compressor is always dusty, altough the dust if fine enough to not damage the impeller directly ..

There are several synthetic media cone filters from Amsoil, AEM and AFE.

I believe the air restriction on our cars is the exhaust, it would be surprising to hear that increasing the air intake capability would result in a material increase in performance. That said, I don't see the harm in lowering air intake resistance so long as filtration is not impaired. I read somewhere here on the forum about moving the battery to the trunk in order to make room for an air filter meeting that description.

For those running much larger turbos and chipped to run up to 6000 RPM I could see where the stock intake might start to become a limitation.

I use Hengst filters -Air/Fuel/Oil- for both of our Passats, and my other cars. This one is for the 04 TDI.


http://pics.tdiclub.com/data/4385/medium/IMG_1858.JPG


http://pics.tdiclub.com/data/4385/medium/IMG_1860.JPG

Here are the actual dimensions:
L X W X H = 9.500 X 7.875 X 1.875
A = 74.813 in2
V = 140.273 in3
No. of pleats: 87
L (calculated)= 163.125 in = 13.594 ft.
As (calculated)= 1284.609 in2 = 8.91 ft2

VS

Direct drop in K&N flat panel filter P/N 33-2125

http://www.knfilters.com/images/l/33-2125.jpg

Overall dimensions taken from the website:
L X W X H: 9.875 X 8.25 X 0.75
Actual (-.75/side for sealing): 8.375 X 6.75 X 0.75
A = 56.531 in2
V = 42.398 in3
No. of pleats:29 (from website)
L (calculated)= 21.75 in = 1.813 ft
As (calculated)= 179.438 in2= 1.246 ft2

As you can see from the calculations above, the OEM Hengst has greater filter media area, volume, and no. of pleats over the K&N. The greater the surface area of a given air filter, the better an engine will breathe and perform.

Thats the point of using a manometer in my post above, there is NO restriction with the OEM filters even with performace tunes.

The OEM filter for a TDI has MORE flow capability (read larger area) than the filter on the Twin Turbo Audi S6 that can push north of 350hp and turn 8000 rpm.

The TDI already has a filter that is overkill in terms of flow, no amount of modifications can exceed its ability to flow unless you start adding cylinders to the motor, even then it can meet the demands of a V6-V8 turbo charged engine.

Also FWIW, the VW TDI filter has more area than my I6 and V6 CDI/Bluetec diesels pushing 220hp in stock form. I have the restriction data of those filters and at max power the total restriction at the turbo inlet at Maximum boost and full load is 3hPa!

All of that is very interesting but I think there is an easier way to prove to everyone what works and what doesn't: Get a VCDS unit or OBD-II scanner, and take some mass airflow readings with the stock filter, K&N filter, and finally the cold air intakes(any brand). Intake air temp. should be measured as well.

By testing these filters and intakes in this manner, anyone and everyone can see whether or not these products work on their own car. I think
that some people continue to believe in this nonsense simply because it is nice to get something for nothing.

But in defense of cold air intakes, if one of these units really did increase the flow of cooler air to the engine, then someone who had smoke with, say, T4's might be able to use those same injectors with little or no smoke.

All TDI's already have a "Cold Air Filter"....whats the point?

Another aspect that is overlooked is the OEM intake point is drawn from a region of high pressure, if you defeat this you just lost 3-5 hPa of air pressure driving down the road.

Most after market filters are hardly "Cold Air Filters" in fact the majority suck in hot engine air from inside the engine compartment. They try to disguise the poor designs with vertical blocks and try to draw air from around a headlights but you are still drawing in from a lower pressure region of air.

Using a manometer inside the air box is the best way to monitor restriction. sure you could place a port at the turbo inlet but the difference in pressure would be minimal if any at all since they are both being measured in the same duct with the same pressure.

MAF readings will not tell you anything, MAF readings are not limited by the filter but by what is being commanded by the ECU. The MAF sensor only reads what the ECU is telling the turbo to pump into the engine...Don't confuse naturally aspirated concepts with forced induction...you will confuse yourself and the data that you are trying to interpret.

Again this takes us back to a pressure that is not dependent on any engine component, but is shows the net affect of the filtration and induction system, system being the operative word.

The bottom line is that a filtration systme is measured on two fronts:

-Whats the total pressure drop of the system as measured at the turbo inlet.
-Does the filtration system provide 10-15 micron filtration with 98% efficiency and still permit 60,000 miles between changes without any meaningful increase in restriction at the end of its service life?

I understand what you are saying. I completely agree with you about filtration efficiency as well. There simply can't be any compromise. But is the pressure drop in the system pre-turbo the only definitive measurement that we can use to ascertain whether or not these aftermarket intakes actually work? In my opinion, the most important aspect to the induction system(pre-turbo) is the intake air temperature (as far as performance is concerned). And in this area, no intake system out there is as effective as the stock intake. It is the only intake I have ever seen that draws in air outside of the engine bay.

That is exactly what makes K&N, Carbonio, aFe, Spectre, etc. complete rubbish. And it makes me think about the turbocharger pressurizing the incoming air to 15 psi, at which point, it heats up. Then the efficiency of the intercooler is really what matters at that point.

So, in conclusion, it basically comes down to filtration efficiency with minimal restrictions coupled with a cool, positive-pressure air source that constitutes a good intake, right?