Removing Air Screen in MAF increases Air Flow

Another good reason to descreen the MAF!

Both our TDIs have been descreened for over two years now with excellent results, increased throttle response, more power, and less smoke

http://www.racer-x.f2s.com/proc/mafmod.htm

http://www.dougrippie.com/drm/inductioncomp/c4_mass_airflow.htm

The BOSCH MAF in the TDI outputs a 5.0 volt max signal to the 10 bit A/D convertor in the ECU where the signal is digitized and compared to the fuel map alogrithims.

The signal is most accurate at higher flow rates above 50% and up to WOT when more air is moving across the hot-film sensor, greater variability is induced at lower air flows. The signal is not linear and that is another reason why it is compared to standardized fuel maps in the ECU.

One of the easiest and worst ways how the MAF gets out of sync in its operation is if the reference voltage signal (against which the output is compared). This can be due to a dying battery, bad ground, or some electrical noise or interference.

These are the screens I removed:

This is how the output graph of airflow vs. MAF output voltage looks like on the TDI, except that on the TDIs 5.0 volts maxxes out at 340-360 cfm.

Still I thought it was bad thing to remove the MAF screens and only do the snowscreen.?

i could have sworn I heard it was bad to remove the snow screens

1)leave snow screens intact for Florida operations.

2)remove snow screens for Virginia operations.

right, the "snow screens" are there primarily to keep rats and mice from crawling up the intake tract and devouring the tasty OEM paper air filter. They leave droppings, shreds of paper, and dead feti in the air intake box and this gets sucked into the MAF screens. Generally, though, you are in luck since rat snakes are hot on their trail and will enter the air box for a meal and a nap. Sometimes, however, your screens are already totally blocked up with leaves, dead insects, and other debris leading to the failure of your Turbocharger due to overspeeding and attempting to maintain boost pressure. If your turbo blows, be sure to clean the "snow screen" when you install the new replacement turbo, or it too will blow shortly.

If you have severe problems with insects, rats, mice, snakes, prairie dogs, chipmunks or other vermin clogging up your intake tract, or you have nightmares about rodents and insects in your sleep and are paranoid about them crawling around in your TDI, please do not remove any of your screens.

If you want more air flow and performance, toss all them right now.

[ June 14, 2001: Message edited by: SkyPup ]

the only bad from removing the MAF screen is this;

1- you could damage your MAF if not carefull($300+ to replace)

2- the screen would stop large objects from entering your turbo/damage the MAF if they where to get thourhg your EOM paper filter (no need to worry if you have a foam after market such as the piper cross which has metal webing on it )

3- as the story goes, the screens are there to "smooth" out the air flow for the MAF. (although my screens have been off for about 45,000 miles and everything works just fine )

now if you have a cone type filter, i would leave them on for sure. if ever plan to get a cone filter, leave them on. if you go with an after market flat panel filter, sure take them off but is it worth it? i don't know as you first take a chance of damaging the MAF with handling.

if you are going to remove all the screens and run a cone filter like I've been doing on both our TDIs for years, be sure to run right out and do it immediately. I have heard that thinking about doing it can lead to instant MAF failure, the less you think about it, the less worry, and the less chance of ever experiencing any MAF problems.

Since I operate two TDIs, I would be statistically more likely by 100% to have MAF problems since I have twice as many TDIs as normal owners, however I actually have never had any kind of problem of any kind with anything, that makes me just the direct opposite of what you would normally think.

Indeed, I am a statistical abberation and to tell you the truth, I like it better that way, it keeps the TDIs running stronger and the MAFs more reliable.

BAH! Humbug. Remove all the screens.

-mickey

SkyPup:

....But isn't removing the MAF Screens a Snow (Screen) job?

Doing so would allow the rats to eat away at the delicate film of the MAF Sensor and I just can't picture you allowing that to happen.

aw rats

I'd like to remove the snow screen, but gee--the designers must have had some good purpose in mind when they put it there. Not that my faith in the designers is complete. They may have been the same ones who did the glovebox door.

Still, it would be good to get an official explanation of what its usefullness was supposed to be (in view of its apparent uselessness) before I remove it.

My screen was full of dirt particles and a flying insect. After removing it there is noticeable HP gain and my turbo sounds louder. I just unscrewed the sno screen off the end of the lower intake pipe. I'll be keeping an eye on the filter.

One cannot help but be paranoid that removing the maf ones will subject me to that 1 in a 1000 chance of totally pooching something. How well does the stock filter stop particles? Cone filters?

It's possible that these screens were put in play as a safety mechanism for idiots, but perhaps they do serve a practical purpose. It's to the gurus to explain!!

Coop

N.B. Do mice really like air filters??

[ June 14, 2001: Message edited by: fincoop ]

SkyPup,
you are, indeed, a statistical aberration: you tell the truth.

your erudite humour is greatly appreciated, too.

perhaps, most of us could "make do" with cleaning the MAF screen, and descreening further upstream.

[ June 15, 2001: Message edited by: gardentender ]

Screens?
We don't need no steenkin' screens.

Pup, where did you get the graph? It tops out at ~930 kg/hr, which is pretty close to 475 cfm.

Does anyone know more about the MAF sensor? There are two openings, one goes straight through, the other makes a 180, then exits out the side. My guess is that the straight through one is to allow airflow to bring the sensor substrate to temperature equalibrium with the airflow, and the bendy path has the actual sensor.

You get alot less smoke with NO SCREENS and MORE AIRFLOW.

Here is a link to how the MAF works 707K PDF:


http://www.kolbenschmidt.de/KSWebGate/KSPG_WG_51.nsf/vwFiles/MassAirFlowSensor/$FILE/Lms_e.pdf


Read and learn!