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

blackened

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Aug 30, 2009
Location
Port Jeff Sta, NY
TDI
2010 black/black dsg moonroof jetta sedan tinted with r8 headlights
Ok. I guess based on previous experience with ram air set up from gm such as the ws6 trans am with a ram air hood feeding into the ram air box. I know that traditional ram air doesn't do anything special until highway speeds, with its benefit directly related to vehicle speed. Seeing as how tdi's are popular with people driving many highway miles it seemed like a reasonable intake solution. Would the intercooler negate the positive affects of a "ram air" style set up?
 

Ben Dur

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Mar 8, 2010
Location
Pensacola FL
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2000 VW golf tdi
Ok. I guess based on previous experience with ram air set up from gm such as the ws6 trans am with a ram air hood feeding into the ram air box. I know that traditional ram air doesn't do anything special until highway speeds, with its benefit directly related to vehicle speed. Seeing as how tdi's are popular with people driving many highway miles it seemed like a reasonable intake solution. Would the intercooler negate the positive affects of a "ram air" style set up?
a turbo negates it almost entirely

that being said, vw's setup is essentially a ram...
not the most efficient one ive seen, but still
 

T_D_I_POWER

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Jun 7, 2007
Location
Savannah. GA. USA - Toronto. ON. CANADA
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'04 VW PASSAT GLS TDI '06 Audi A4 q Avant 6-Spd Sport Pkg
Ben Dur said:
today the skis cleared up just enough for me to pull my little green TDI up to the garage to swap my crap cone filter with my stock air box......






finally i installed the stock air box
:)
By leaving big opening as shown, the engine will breathe warm-hot air generated from the surrounding engine compartment.

The solutions are:
-Close the opening
-Close off the surrounding AFB area to block warm-hot air
-Route a round duct which directs cold air to the opening
 
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Jtroy

Member
Joined
Aug 7, 2010
Location
Northern NJ
TDI
1998 Jetta


That's the dirt let thru after just 501 miles of driving on a NEW FACTORY OILED K&N
For a more fair and complete comparison from "Bob Is the Oil Guy" site see the following link:
http://www.bobistheoilguy.com/airfilter/airtest3.htm.

Why not let the members read Bob's actual report and make their own decisions? Though Bob's tests show that filters can differ in their ability to stop particles, it's not as extreme as comparing a completely clean after-filter patch to an unused filter patch.

I've been researching to determine if I should purchase a K&N filter (for my gas-drinker, not my TDI) and, after reading Bob's original article and looking at his photos, I found this particular photo to be misleading.
 
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Plus 3 Golfer

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Oct 29, 2008
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ARIZONA
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Und tschüss! 2009 Jetta 12/23/2012
For a more fair and complete comparison from "Bob Is the Oil Guy" site see the following link:
http://www.bobistheoilguy.com/airfilter/airtest3.htm.

Why not let the members read Bob's actual report and make their own decisions? Though Bob's tests show that filters can differ in their ability to stop particles, it's not as extreme as comparing a completely clean after-filter patch to an unused filter patch.

I've been researching to determine if I should purchase a K&N filter and, after reading Bob's original article and looking at his photos, I found this particular photo to be misleading.
Actually, why not read this report which does a little more than capture dirt on some gauze.
 

Drivbiwire

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Oct 13, 1998
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Boise, Idaho
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2013 Passat TDI, Newmar Ventana 8.3L ISC 3945, 2016 E250 BT, 2000 Jetta TDI

ChippedNotBroken

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Joined
Dec 29, 2004
Location
Pocono\'s, NYC
TDI
Jetta A4 1999.5 Green
Look at the specs, the TDI filter has lower restriction at 300 CFM than the Donaldson at 176 cfm....Not sure if thats an upgrade.
My understanding is that the filter is designed for moderate dusty driving and that removing the dust collector (a major restriction at the entrance to the filter) you will no longer be at 176 cfm. If you look at the consctruction of the filter it can absorb a lot of junk before you see any restriction from a dirty filter.
 

Gil

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May 16, 2004
Location
Wallingford CT
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2002 auto wagon and 2004 stick
Too bad this thread doesn't deal with the PDs system which is quite different.

The air box has 2 chambers.
The bypass valve is located on the engine side of the air box drawing hot clean air into the air cleaners smaller chamber.
The PD has no snow screen (a few may have one).
The filter element has the now popular winter filter acting as a snow screen.

The main difference in the systems is the bypass valve. The PDs main chamber may plug up and then air is sucked into the smaller chamber. This is a better design than earlier TDIs IMHO.
.
 

Gil

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May 16, 2004
Location
Wallingford CT
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2002 auto wagon and 2004 stick
The only problem that I have with the newer design is that the engine will only draw air through one side of the air filter element.
Now IF the main side of the filter gets restricted, that means that the bypass valve may open and let hot air into the system defeating the cold air intake from the front of the car.

I have modified my 04s airbox by punching a few large holes in the divider making full use of the element ( did this a number of years ago ). Then a few weeks ago I got the idea to plug that bypass valve to make sure that no hot air will ever find its way into the engine. Now the system is about the same as my 02 TDI.

After this new change the car seems to be quicker and run better under all driving conditions.
.
 

Drivbiwire

Zehntes Jahr der Veteran
Joined
Oct 13, 1998
Location
Boise, Idaho
TDI
2013 Passat TDI, Newmar Ventana 8.3L ISC 3945, 2016 E250 BT, 2000 Jetta TDI
I have been installing CAT restriction meters on all my customers cars, the new generation air box with dual chambers pulls about 7" WC at full power, the limit is 25"WC at full power. I am sure that you can still get 80,000 miles or four years from the new style elements and boxes from the accrual of restriction I have seen.
 
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ChippedNotBroken

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Joined
Dec 29, 2004
Location
Pocono\'s, NYC
TDI
Jetta A4 1999.5 Green
Look at the specs, the TDI filter has lower restriction at 300 CFM than the Donaldson at 176 cfm....Not sure if thats an upgrade.
While pulling about 40# of boost at 5000 RPM the vacuum gauge on my air filter did not budge. I took a video while it was on the rollers, I will try to figure out how to post it when I have time after my dad goes back to florida.
 

emantman

New member
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Dec 15, 2010
Location
Colorado
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2009 Jetta TDI Sedan
2009 TDI Sedan at Altitude

I was posting on another thread, but this seems like a more appropriate place.

I have a 2009 Jetta TDI Sedan in Colorado. I live at ~6000ft altitude. I have been told (and I absolutely believe) that engines (diesel, gas,etc..) lose ~10% power for every 4000ft of altitude. This is because the air is much less dense, and there's much less oxygen. That means I'm running at ~86% actual power than the engine should actually be producing.

I drove my TDI to La Bufadora, near Ensenada in Baja Mexico for the whole week of labor day 2009, and I know my TDI had WAY more power at sea level. I come back to Colorado and it's just not as powerful.

I want to install the new AFE power air intake system (one of the first aftermarket products for the 2009 TDI) to increase the air flow (which supposedly increases horsepower, etc...), but another post (by a veteran tdiclub member) recommended that:

"Don't do it. The factory intake already draws cold air, flows more than adequately, and will actually do more harm than good in the long run."

So I want to know how it would hurt my car if I increase the air flow (and hence oxygen) when I'm always at a high altitude (99.9% of the time)?

Please any suggestions, comments, thoughts, etc... would be much appreciated! I love my TDI!
 

GoFaster

Moderator at Large
Joined
Jun 16, 1999
Location
Brampton, Ontario, Canada
TDI
2006 Jetta TDI
The aftermarket air intake system will make 0 difference to your car. Zip, zero, zilch.

The stock air intake is already a low-restriction cold-air intake. Open the hood ... see that little grid of openings in the plastic next to the latch? That's the engine air intake. It leads to a large-diameter duct into the air filter housing, and that leads to a generously-sized duct to the turbo inlet which is about as straight as they can make it. You can't eliminate restriction that is not there to begin with. You can't lower the temperature below the temperature of the air coming in the front of the car. The engine doesn't care whether the intake ducts are the original parts, or have a fancy brand name on them. A lot of those aftermarket air intakes use aftermarket-style air filters, which in many cases don't filter as well as stock-style air filters. All of this, and considerable other supporting information, has already been posted or linked to in this thread.

Leave well enough alone.
 

nicklockard

Torque Dorque
Joined
Aug 15, 2004
Location
Arizona
TDI
2010 Touareg Tdi w/factory Tow PCKG
Amen. The ONLY way an aftermarket "cai" will make your car faster is if you've been saving up the money for one in pennies and carrying them around in your car. Thus when you go to purchase said "cai" your car is 50 lbs lighter.

And faster.


Leave well enough alone unless you just like to burn money pointlessly.
 

JSWTDI09

Top Post Dawg
Joined
Jan 31, 2009
Location
Las Vegas, Nevada
TDI
2009 JSW TDI (gone but not forgotten)
So I want to know how it would hurt my car if I increase the air flow (and hence oxygen) when I'm always at a high altitude (99.9% of the time)?

Please any suggestions, comments, thoughts, etc... would be much appreciated! I love my TDI!
One additional comment. The primary reason why aftermarket intakes can flow more air is because they filter it less. They flow more air because they cause less restriction, they cause less restriction because they don't filter the air as well. Less filtration equals more dirt getting through the intake and into the engine. Can you think of any advantage in sucking more dirt into your engine? Flowing more air is ONLY an advantage if the stock system can't flow enough for the engines needs. Also a dynamically controlled turbocharger does a pretty good job of making up for differences in ambient air pressure (altitude).

Read this entire thread - it's full of data and graphs showing poorer filtration with increased airflow. If you really need to spend money - buy whatever you want, just don't expect much in the way of provable positive results.

Have Fun!

Don
 

Got Bearings?

Veteran Member
Joined
May 5, 2007
Location
SoCal
TDI
2001 Golf GLS
The best cure for your lack of high altitude power is more boost. It's common to turn up the boost in high altitude areas as long as the turbo can handle it. I have no idea if your turbo can handle it. Other than that, a tune will help.

You lose approximately 1% of power output for every increase in 1000 feet of Density Altitude. Depending on the atmospheric conditions, your static altitude of 6,000' may actually feel like 8,000 or 4,000 depending on the atmospheric conditions (barometer, temp, dew point, humidity).

Here's a good calc
http://wahiduddin.net/calc/calc_hp_dp.htm
 

Curtis328

Well-known member
Joined
Dec 16, 2010
Location
Manitoba, Canada
TDI
2001 Golf TDI - Manual
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.
Just wondering why you stress to never open the airbox to check the condition of the filter. I've never thought there was a problem with opening an airbox...
 

Bob_Fout

Oil Wanker
Joined
Sep 5, 2004
Location
Indiana
TDI
2003 Jetta - Alaska Green (sold) / 2015 GTI 2.0T
Just wondering why you stress to never open the airbox to check the condition of the filter. I've never thought there was a problem with opening an airbox...
The seal (the foam/rubber) may not conform correctly again, allowing unfiltered air past.
 

Jack Frost

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Nov 30, 2007
Location
Rural Manitoba
TDI
2009 Clean Diesel
I think what was meant is that if you open the air filter box, you should replace the air filter. The old gasket may have lost its resilience and not form a proper seal if it is reassembled with the air box.
 

ChippedNotBroken

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Dec 29, 2004
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Pocono\'s, NYC
TDI
Jetta A4 1999.5 Green

KERMA

Vendor , w/Business number
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Location
here
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99 beetle and 04 jetta
I don't into a cone filter benefiting any otherwise stock car, and here's why: (BEW for example)

Diesel operates on a fuel throttle, not air. More fuel= more power, period. More fuel is the only way to make more power. The lambda (a/f ratio) varies widely, from 0.8 to 10 (these are factory ecu calibration limits, anyway). Diesel does not require a fixed (stoichiometric) air/fuel ratio, so adding more airflow without fuel won't add power, especially when you are already running "lean" in gasser terms. Yes, it has a lambda sensor, but it doesn't serve the same function in the same way as a gasser. At full load, the lambda map(s) is/are a fuel limiter, not a fuel/air ratio regulator.

The max power the factory setup can make, with the factory ecu calibration, is NOT airflow limited, it is limited by the 2d torque map at full throttle. (yes, I know it's really 3d, but let's pretend it acts like a 2d map for the sake of argument). Once you hit about 85% throttle position it's done, no more fuel (power) for you, in the factory calibration. At high altitude it's less throttle before you hit the limit. The smoke map(s) stops being limiting at full throttle, by design, about 2500 rpm. From then on up it's what's commonly referred to as the "torque" map that limits full power.

You can observe this by data logging vag-com measuring blocks group 8, which displays the torque request alongside the rpm/altitude limiter and the "smoke" limit.

Group 3 will show the airflow. EVEN IF the new filter did somehow increase the max airflow, it wouldn't matter for making more peak power, because airflow is not limiting above 2500 rpm IN A CAR WITH FACTORY ECU

THERE IS ABSOLUTELY NO BENEFIT TO AN OTHERWISE COMPLETELY STOCK CAR

There MIGHT be an argument to be made about better turbo spool at lower rpm, or maybe better torque at lower rpm, IF you can show a shift in the MAF-based fuel limiter to max out at a lower rpm, for example.

You could say there's less smoke in a stock car "before the turbo spools", which is immaterial with a properly operating VNT and maf sensor

You could even argue the benefits for turbo safety in a tuned car, (lower pressure ratio for the compressor due to "less restriction" -what a lovely catchall phrase that is), but if you don't improve the intake tract after the maf (OMI) then you still haven't fixed the problem.

You might could say smoke is reduced in a tuned car, but unless you are maf-limited it won't matter, any way.

If there is a dyno showing a benefit, I would tend to suspect the test car had a bad maf, or something similar. There have been numerous dynos of completely stock BEW at very close to the rated HP/TQ of 100 hp and 177 ft-lb. (VW rates these cars at the wheels) It looks like the second dyno is a healthy, stock car.

Boost pressure is ECU regulated, stock boost, stock airflow. Maybe the turbo doesn't require as much drive pressure to make the boost, resulting in a better delta and a reduced vnt angle, better overall efficiency? Maybe a little, but not 15% gain. Any gain will tend to get lost in the statistical noise.

There are benefits to be had for a modified car, but stock, no way will you see any appreciable magnitude of gains.
 

Jethro

Veteran Member
Joined
Jan 16, 2011
Location
Los Alamos, NM
TDI
2003 Jetta 1.9
I love this thread. Always thought it to be true. However, it falls under the same realm of an exhaust. I want it for the sound.

I am going to get a WIX catalog and find a good tractor filter, and replace the closed air box with an open element. I wanna hear that baby turbo SING!
(In the Diesel truck world, it's called the BHAF -Big Honkin Air Filter-)
We did one on my buddies '03 Stroke, just sounds AMAZING. Love it!

I'm not worried at all about intake air temperature, after the turbo pressurizes it, I can't see it making a tangible difference.
 

jcilforever

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Feb 17, 2010
Location
Southeast
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2004 Jetta (SOLD), 2004 Beetle, 2003 Jetta Wagon (parts car) all manuals all for sale
Sorry tried and failed on tdi cai

Please post this on the sticky at to why CAI's do not work on our cars!

Just want to tell everyone here that they were right about CAI's made to this day not working on a TDI engine. I know this will soon be closed but I wanted to let all of you out there now that while I had advertised the Injen CAI's for sale I did not end up selling any because of what I found out. I did post some information that was overlooked by Injen that was questionable and I am sorry.

The car that it was put on during testing I did not know it had issues because it was a loaner car out in California and I am in the Southeast. I vetted applicants and took the car with the best service history and least mileage. Then set up the testing at the Injen facility.

They worked on the car for 3 days and were able to get a boost in performance but it had a weird dip in the dyno curve. That some of you pointed out.

Yes I did defend it out of blind faith in Injen and I am sorry (will not do that again for any company).

I then asked repeatedly why it was there and could not get a straight answer. They said they did not want to put any more money into the project without selling some but I refused until they would test another car.
I had to front the money in the beginning for 8 units and once I got them I tested it on my 2004 BEW stock car without EGR.

Yes I did offer them for sale before I tested them on my own car because I dealt with Injen in the past as a customer on gassers and was very pleased with quality and results. No CAIs are not the best improvement for the dollar but they improve aesthetics and did give some boost on performance on gassers.

Fast forward I had some people approach me about buying them but did not want to sell them before I tested them on my own car.

Yes I offered them at a GTG for sale but none were sold.

So dyno day came and I did a run with the stock filter and I pulled around 95 hp for a 2004 PD BEW best out of 4 pulls. Then I put the Injen CAI on and did best out of 4 pulls and the car actually went DOWN 5HP!!

So I contacted Injen and tried to get answers for a couple of weeks and could not get any, all that was given to me was well we did the best we could with the car we had, but there was a gain.

Well I knew my car was solid so I shipped all of the CAI's back and lost my shipping and testing investment but did not sell a single one to anyone even though I could have. If I would have I would have refunded their money one I tested them on my car and they failed.

Yes I did offer a product that was not tested by me first for sale but that will be the last time. I am truly sorry.

After that with my health getting worse and Forge not wanting to back the intercoolers on Mk4 diesels in US and me myself having to front the whole project and website for such a limited market just for mk4's ALH and PDs I packed it in and contacted the club here to remove myself as a vendor.

Sorry for the mistake, hope you can take an apology.
Right now I guess I will have to be content with working on them as a hobby and meeting nice people.

As of now I have had the Forge FMIC on my 04 BEW for a year and a half and love it one I worked the bugs out of the hose fittings.

Sorry I disappeared for a few months I was sick (personal illness due to an accident) and I wanted this to blow over and present the truth once things cooled down, got my money back, and could not salvage Forge downsizing involvement in MK4's Diesel's.

I will post the dyno result VCDS logs in my documents once I find them.

All it did was make car sound loader, slow it down by 5hp have dyno, and potentially set it up for hydro lock because of how low below the fender it mounted.

ended up using drop in AFE dry filter to save money because you can wash them overnight with soap and water, not spraying them with high pressure air or water, let them dry then put them in in the morning, saves money over time but now performance loss or gain.

I would appreciate all of those who can forgive me and accept me back into the TDI community. As said before no units were sold no customers were hurt.

Thank you for your understanding
 
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RDC98tdi

Veteran Member
Joined
Sep 14, 2009
Location
Louisville KY
TDI
'13 Jetta 6MT Prem / (RIP) '98 Jetta 5MT [280k+mi]
I really want to do the APR intake and the new turbo damper pipe for JUST the sound, because stock, the 2013 barely makes ANY turbo noise other than the initial spool, or on the highway in 6th gear if you mash it around 2k RPM. I want the turbo to sing, but it's not worth the hundreds of dollars for maybe 1 extra HP for the damper pipe and slightly more noise from the intake.
 

Bob_Fout

Oil Wanker
Joined
Sep 5, 2004
Location
Indiana
TDI
2003 Jetta - Alaska Green (sold) / 2015 GTI 2.0T
JCL,

Peak HP went down, but was the powerband wider? [more HP earlier and/or later]
 

loudspl

Veteran Member
Joined
Apr 22, 2005
Location
Osakis, Minnesota
TDI
02 ASV w/ 02J
I think Injen's testing would have been better suited on TDIs with significant mods.

Like Charlie said, there is potentially more to be gained on a highly modded setup vs. something that is close to OEM output..

As far as the hydrolock potential goes, there are several manufacturers that make a water resistant/breathable "sock" to go over the cone...although that might reduce max CFM who knows..
 
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