Hi all. I have an early 'small bore' MAF on my 93 80Q 2.8 (UK Car), so I need a later (471A) type so it can get the Mance treatment.

I can get one in the UK from a breakers for around £75 ($110 ??).

What do you guys in the states expect to pay from a breakers for these ?

Cheers
DA

and there are several, if not many in the $70-$100 range. Just sign on to their site, list your car as 96/97 A4 2.8, then in the "part" drop down box select "air flow meter."

If you order in the states you'll save additional "BPS" by only paying trans-oceanic shipping once. I'm happy to accept direct shipping from a salvage yard if you make sure they put a little note inside with your name and email address so I can determine ownership and contact you.

I'm not as up-to-speed on this small-to-big bore MAF conversion as I should be. Has it become a simple conversion, who's done it and what's involved? I've been a little outta the loop keeping up with 30V orders but I should know whats happening on the 12V side.

I began to dig into that issue and quickly found that (at least from the one angle I was looking at) it would be VERY difficult, if not impossible to swap a 4-pin for a 3-pin. It's primarily the way that each MAF determines the fuel measurement (I think.)

I poured over the Bentley wiring diagrams to each MAF for quite a few hours. Here's what I found:

Both MAF's have an "extra" wire. That is to say that the 3-pin (471A) actually has four wires associated with it, and the 4-pin has 5 wires. The primary inhibitor is that the 4-pin MAF has 3+1 wires which feed the ECM. The 471A has only 2+1. So from that standpoint, I figure you'd have to swap ECM's in order for the engine to accept a 471A swap. The second inhibitor (although possibly solved by re-wiring) is that the "4-pin MAF" has 4 pins for a specific reason. The #3 pin collects additional information from each of the ignition coils in order to determine the fuel/air ratio (??) Why...I have no clue! Bentley calls this function the "CO Fuel Trim (ft) potentiometer". Now the 471A MAF has a similar regulatory monitor, however it's #3 pin is wired to a Heated O2 sensor, and does not carry that extensive title....it's just "MAF". This is all from Bentley BTW, so you can reference the info yourself if what I've said doesn't make sense or you'd like to investigate yourself.

So, that was the re-wiring I was talking about. But even if you splice into the O2 sensor, there's still the issue of having that "extra" pathway into the ECM (engine control module). And I'm sure in operating conditions the ECM looks to that pathway for information, and probably gets "pissed off" if there's nothing there.

Now, that was only one angle from which I approached. I just recently thought of another.

O.K., a MAF is just a sensor correct? It has inputs (heated wire) and outputs (pins). Does anyone know if you can remove the housing on the MAF where the pins & plug connect? If you can, my idea was to simply swap these parts between a 4-pin & a 471A. There may be some soldering involved (I don't know) but this is the MAF brain and where the information from the various inputs (ign coil, O2's etc..) is delivered to the ECM. If these two parts are removeable and swapable, then you could SIMPLY upgrade the aluminum shell of the MAF inlet housing, install the 4-pin brain which the ECM is familiar with, and potentially fool the system.

I haven't actually looked into this, like I said I just thought it up a few days ago. I have my doubts about this, and don't really expect it to be possible, but it's worth a try. It's about all there is left, short of major changes.

So yea, that's what I've found. I'll keep investigating and attempt to have you all up to date. If anyone (UrS4) is willing to donate a 4-pin MAF for teardown -or even do this themselves- that would save me sourcing one because I AM NOT wrecking my one and only OE MAF.

Anyhow, sorry for the length. I hope this was informative. Questions, Comments, Thoughts??? thanks again,

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92 100. gPilot, I willing to participate at this project and share the cost of it. Please let me know how can I assist you.

all in the name of research!!

However this is probably the last possibility we "4-pinners" have at an upgrade. If this doesn't work I'm plum outta ideas (until I figure out how to mod a small-bore), and we'll just haveta put up with the 1.??" crappy-MAF =( It's sad, but every once in a while we need to come back to reality and reassess what is and isn't possible. But I won't give up until then.

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Split Second sells MAF kits. Now, I'm sure if any of their kits will work but maybe they will have some insight into the small bore MAF. I am interested in your results because I was thinking about getting a Cabriolet sometime and I believe (correct me if I'm wrong) they have the small bore MAF, also. Do you have any better pics of the MAF sensor and where it is exposed inside the MAF? I looked at your pic poster already.<ul><li><a href="http://www.splitsec.com">Split Second</a></li></ul>

However since they are crappy pictures, I'll be taking better ones soon. For now, check this:

I am worried about this slit which is built into the small bore MAF. I don't seem to recall this being in a 471A type. I have a feeling it has to do with the "CO Fuel Trim potentiometer" thingy, although I'm not sure. If it is, we're SOL right from the word "go". Can anyone confirm this, or that a 471A has it?
<img src="http://pictureposter.audiworld.com/53503/maf3slit.jpg">

Here is what my new angle is. If it's possible we remove the section bordered in yellow. I have my doubts about this, but second step is to try and remove what's outlined in red. We NEED to keep the 4-pins circled in green. Ideas?
<img src="http://pictureposter.audiworld.com/53503/pinhousing.jpg">

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These are the pic I have of the 471A MAF:

<img src="http://pictureposter.audiworld.com/38881/mafcompare1.jpg">

<img src="http://pictureposter.audiworld.com/38881/mafcompare2.jpg">

<img src="http://pictureposter.audiworld.com/38881/mafcompare3.jpg">

Is that your MAF? Is that how it gets modded, the whole center pole &amp; directed sensor intake is removed? I would've liked to have seen what was behind the screw plate of that "pole". Oh well, it doesn't appear to have the "slit" eh? Hmmm, I really need a spare 4-pin MAF.

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an extra sensor that my MAF doesn't have. Hmmmmm.

You can try this place for a tester....<ul><li><a href="http://www.force5auto.com">http://www.force5auto.com</a</li></ul>

probably when I'm through with the tester 4pinner, I'll put it on the band-saw and slice it in half. At least then that'll show the internal pathways (if any) and perhaps lead to insight as to how to get around 'em.

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and like 90's &amp; A4's they're year-related MAF's. Late 95-97 has the 471A MAF and 94-early 95 has the 471 unit. I havent done an earlier unit nor do I Know when they first came to the US. Two of the cabriolet's I did had the correct MAF and one had to find a 471A upgrade MAF. I don't know if the cabriolet was available when the small bore MAF's were the order of the day.

<center><img src="http://pictureposter.audiworld.com/6922/hacked.jpg"></center><p>Appears to be just an outlet for the air after it passes the sensor.

but I've prettywell concluded that swapping a 471A into a 4pinner car is virtually impossible. All the electronics are set up to look for (and use information from) than damn Fuel Trim potentiometer. And since a 471A doesn't have that, I can go no further.

My dad and I figured it was a method of measuring suction (and therefor air pressure) in order to cross reference againt the heated wire.

Since the wire takes time (I don't know how long) to heat-cool-heat, there would be inacuracies in the fueling during those periods. We guestamated that the FT potentiometer function, since pressure measurement is instantanious, is used to counter the lag times in the heated wire. I suppose it's "numbers" could also be used by the MAF to compare against those from the heated wire, and then rendered into a nominal fuel/air mixture. So yea, I don't think there's anyway of getting around that damn thing. It has an output range of 1.0-7.5v, so perhaps you could install something which will provide the range of voltage WITH RESPECT to engine RPM. But even then there are so many variables surrouding how air pressure can change, that there's no way to simulate it without the actual instrument.

Is the 4pinner a better MAF because it has 2 measuring devices?...one slow and extremely accurate, the other instant and less accurate. I don't know....it's probably more expensive to manufacture because it is more complex as compared to a 471A, which is probably the reason for the change. As far as modification goes it's not as good a platform, unfortunately. But better, maybe....perhaps that's why I tend to get better mileage than people with even just a normal 471. I honestly have no clue. Oh well....

Maybe I'll get a 4pinner from Force5 &amp; just see if it can be bored even a little. Unless someone wants to provide me one (free or really cheap of course) for testing in the name of science...I'll leave it up to you. If I ever make progress I'll let ya'll know, but for now UrS4 is right. If you have a 4pinner there ain't nothing you can do!!

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