<center><img src="http://pictureposter.audiworld.com/711/mafscreen.jpg"></center><p>More than one way to skin a cat! First off this is very prototypical. Hasn't been tested but it's the next thing going into my car. The screen is stainless steel and just a smidge more restrictive than the stock screen. But due to it's location at the front of the hot wire sampling tube this deficiency should be somewhat compensated for. I also have several ways to increase it's flow if it were to lean out at high RPM's. And thats no illusion... it is a domed screen which should also help compensate for it's slightly more restrictive passages, ie; 12% less flow but 50% more surface area than the sampling tube.
Dunno if it'll work at this point but it looks great! I'll get it on and fiddle with it over the next few days, see what happens. It just could turn out to be a way to fine-tune the MAF without an electronic calibration or piggy-back system by streamlining and speeding up/slowing down the air across the hot wires samplers... within limits.
Besides if it doesn't work I'm no worse off than I was before I thought of this. I can always take it back to stock. But at least its innovation rather than imitation.
One thing worries me, though. Since the goal of the MAF screen is to even out the airflow, it might not work well if the screen is too close to the sensor wire. I guess testing it will be the only way to find out. And testing is half the fun!
04-13-2003, 02:44 PM
Did you make the screen from a faucet's airator?
04-13-2003, 02:47 PM
mounting this screen to a short extension tube that put it out front of the sampling tube a distance equal to the stock screen. Then I decided to give this a whirl first, see if it works. I can always make it more expensive and complex later but I would I feel awfully silly if I did that then one of you guys found it works just as well/better attached directly to the sampling tube. Gotta at least try cheap/easy before guilding the lily.
04-13-2003, 02:52 PM
I bought 3 ea in 6 different mesh sizes in whatever diameters it took to get the different (smaller/larger) mesh sizes. And who knows... I may have to go smaller/larger mesh but I'm sure the right one is in there somewhere or with a small extension tube.
04-13-2003, 03:10 PM
04-13-2003, 03:13 PM
04-13-2003, 03:26 PM
what do you think could get through the filter and not get through that?
they say they're working on VW but they've said that for over a year. They also claim they will make one if I send them my airbox, filter and MAF for 2-3 weeks and further that if I'm not happy they'll refund the purchase price... but not any consequential damage that they admit "can occur."
Love the idea and it sounds promising but also potentially lethal at most and risky at least. I'll go second;-)
04-13-2003, 04:46 PM
04-13-2003, 04:48 PM
04-13-2003, 04:52 PM
If you've established that the OEM screen was a restriction and that with your alterations it is not needed,why do this ?
04-13-2003, 05:07 PM
if you count the wires (112) and multiply it by the wire diameter .008" its a surprisingly huge restriction. But I still believe the sensor wires like smooth clean air going across them and further that the MAF functions better and is more accurate/efficient with some streamlining of the sampling air.
To wit; Keep the diffuser while allowing all other air flow to pass, undiffused and unrestricted.
04-13-2003, 05:24 PM
Been running center post removed MAF on my 93 90.
Probably why I dont get a CEL?
Initially, I cut the center post from my MAF. Car ran funny. Sent the MAF off for recalibration, car runs fine. Havent had a single problem since.
Maybe the MAFS need recalibration after removing the screen?
How much turbulance, to the incoming air, does the lip where the screen goes, cause?
Just offering up some "food for thought" as to options available for MAF mods.
04-13-2003, 05:37 PM
say they haven't done any Audis before but that if I send them my stuff they will.
Entirely possiible the screen groove sans screen contributes to or causes a CEL. Who knows? And I'm sure a re-calibration post screen removal would help gobs.
I'd really love a 73MM MAF body too but again the people at that link say they've never done an Audi tho they have been working on VW for over a year.
Willing to say whose MAF and calibration you're using, specifically? Then that way I and everyone else who wishes can stop fumbling around in the dark.
What I'm doing is a lot of hit & miss. Only thing I have going is "time"... plenty of time.
But specific info would help alot.
04-13-2003, 08:30 PM
and sends accordingly info for so much fuel, but you are actually having more air going through...wouldn't be too lean??
04-14-2003, 01:34 AM
Here's some good reading! ;O)<ul><li><a href="http://forums.audiworld.com/vag/msgs/456.phtml">http://forums.audiworld.com/vag/msgs/456.phtml</a</li></ul>
04-14-2003, 01:45 AM
"Initially, I cut the center post from my MAF. Car ran funny. Sent the MAF off for recalibration, car runs fine. Havent had a single problem since"
Sounds like your under the impression I'm running a C&L MAF, which I am not.
My MAF is an OEM with the center post cut, and has been recalibrated for the mod.
I posted the above picture & link to show a center post removed MAF & for the proceedures of MAF recalibration.
04-14-2003, 03:14 AM
Since whoever you sent yours off to must have some basic Audi parameters I'd like to send a spare MAF off to them be recalibrated. It's no prob cutting the center-post out for me. Just put me in touch with who did yours and I'll find out what they need from me and comply.
04-14-2003, 03:42 AM
smaller mesh I can match the mesh openings to the flow by virtue of a precision tapered awl. If I sense by the fuel/air gauge I'm lean at high RPM's due to increased flow I can insert the awl to a marked depth therby increasing the mesh diameters in alternating openings a precise and consistent amount. That would then allow more diffused air past the sensor element and tell the heated sensing elements to increase the fuel taper and the screen would still operate as a laminar diffuser so long as mesh openings are consistantly sized, even if alternating mesh openings are larger/smaller. Long as the openings are consistent and balanced the screen will still operate as a laminar diffuser.
Not as good as an electronic re-calibration to be sure but certainly within the MAFs stock range when running without a screen. However if I cut the sampling tube post out ala MikTip I'll run out of mechanically compensatable margins LONG before it would flow sufficient or appropriate fuel at high and/or possibly even low RPM's. That would then require a full scale electronic MAF re-calibration.
But the screen does offer some mechanical adjustment just by varying screen mesh openings if done consistently across the screen surface while retaining it's primary function as a diffuser.
Another way to move more air thru the sampling tube or even the same "x" amount of air past the sensing elements faster without modifying the screen is to drill a hole (bleed/vent orifice) in the rear sampling tube cover centered directly behind the sensor wires and aligned with the sampling bore. Starting with maybe a .040" drill bit and going incrementally larger if necessary. Doing this will allow more air or the same amount of air faster thru the unmodified screen by giving a small amount of the sampled air a faster escape route. More air out=more air in. More air in=richer MAF compensation at high RPM.
It's important to remember none of these things will recalibrate the MAF to do anything more than than the inherent parameters they are programmed with from the factory. Only a re-calibration will accomplish that. But this should allow them to compensate to a greater/lesser degree to running without a MAF screen by activating their inherent + or - 10% safety margins. All electronic MAF calibrations make allowances for "margins" rather than a precise "carved-in-stone" "xx.x" setting and I'm sure there's at least a 10% margin here which can be achieved by one, the other or both methods I mentioned above.
04-14-2003, 12:53 PM
Had it done over 18 months ago!
I was dealing with both C&L & Pro-M at the time.
Cant remember exactly who? ;O)
I'll see if I can find the paperwork?<ul><li><a href="http://forums.audiworld.com/9080/msgs/3747.phtml">http://forums.audiworld.com/9080/msgs/3747.phtml</a</li></ul>
04-14-2003, 02:42 PM
They're about 10 minutes away from my house.
I'm having a Univer Plus made for my car:
Saturday we'll be flowing my meter. It's a bosch type though, doesn't look anything like yours.
The reason they need to have the airbox, is because it affects the transfer function of the meter. In my case, however, the chip I have was created for a 3" housing and a cone filter, so there's no need to flow mine with an airbox.
04-14-2003, 04:38 PM
04-14-2003, 06:52 PM
Get the hell outa here. ;-)
04-15-2003, 09:05 AM
21890 Meyers Rd
Oak Park, MI 48237
Just south of 9 mile, and east of coolidge
I'll be there saturday, starting around 8:00am or so.