ARC1 is a MAF calibrator. It is designed to allow the user to modify the MAF values +-20% to achieve proper a/f ratio.

<img src="http://tomasz.data2net.org/gallery-albums/Audi/Picture_003_Large_001.jpg">

Got the ARC1 connected and working. Well, eventually anyways. The first attempt I hooked it up to the existing ground wire and apparently the connector didn't quite go through the shielding. As a result when I turned the ignition on I got "MAF values too high" error code. Redoing the ground connection fixed that.

The MAF signal is a bright green wire in the longer of the two connector on the ECU. It is the only bright green wire with no stripes on that wire loom. I used a inline fuse connector to separate the wire and provide a place for the ARC1 to plug in. This works very well and also allows me to bypass the ARC1 at any time by using a regular fuse in place of the connectors.

<img src="http://tomasz.data2net.org/gallery-albums/Audi/Picture_001_Large.jpg">

The power comes from a blue/black wire in the brown connector in front of the ECU. It is the middle connector of 3 in that location. Unlike regular accessory switches power, this stays hot during cranking, which is very important for the ECU not to throw codes.

I didn't mess with the WOT a/f ratio yet. I'll either need a good a/f gauge or a dyno/wideband O2 to do this, however I was able to improve my idle substentialy. The best setting seems to be +4%. Looking at the VAG O2 readings, it's a setting where they seem to hover closest to 0. This also smooths out the idle and gets rid of jerkiness at low speeds. Since +4% is showing ECU more air then the MAF reads, this means that I'm actually enriching the mixture, right? I always thought it was rich to begin with, so I was quite surprised to find out that apparently it was actually somewhat lean. Is it possible that due to trying to compensate for lean idle the ECU was over-riching at part-throttle and/or WOT? This just shows how little I actually know about how the ECU/MAF/O2 sensors operate. I know I'm running rich at least part of the time, I can tell this by the soot on the exhaust tips. Apparently idle is not one of those times, go figure. I'm glad I didn't decide to buy a larger MAF, that would've made the problem worse instead of better.

 

I do not know the answer..just wondering.

 

If your ECU a/f mappings are correct then this would be of little use, however my G1 chip was never optimal, and with addition of the intercooler what the ECU thinks I need and what I really need are two different things. This fools the ECU into providing correct a/f ratio. Unlike changing the fuel pressure or changing injectors, this will not result in an error code or a CEL. The other way to change the MAF readings is to go to a larger/smaller MAF. However if you do that you have no way of adjusting, it's a one time change and you better be sure it's the right one. The ARC1 let's me fine-tune mixture at both idle as well as WOT.

 

I was having problems with my stage 3 MAF from Mance (UrS4) and his fix was to put an o-ring infront of the MAF sensor element. It fixed the entire problem and make the car run/pull smoother through the entire rev range. I'd be more confident in what you are doing, though for a long term application.

 

With this I can switch to a very large MAF and adjust the signal to work right.

 

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I started with crimps on my SAFC, and noticed a smoother operation when I soldered all the connections.