AFM reostat board recoating

[micbrody]

The initial conductive paint I used dryed in a non-hard, non-durable finish .
I plan on trying again with one that is acrylic based; and is rated as hard and abrasive resistant.

I ordered 838AR
http://www.mgchemicals.com/downloads/co ... 0Chart.pdf

I chose this paint because it did have some residual resistance that is above the fixed, segmented green printed resistors.

[micbrody]

I just finished recoating with the new paint.

It was very easy to remove older paint that I first used. It had a consistency of hard, crumbly caulk, which validated my opinion it was the wrong type of paint for durability.

I used fine sandpaper to remove the the original black coating to just the point that the fully conductive silver "fingers" were exposed.


I taped off board:


Then I applied two coatings with a tiny nylon arts and craft brush (30 minutes apart). I let it cure over the holiday weekend.
(the consistency of dry paint seems much more durable than first paint.)

I reassembled and tested AFM on bench with 9 volt battery; and it worked perfectly.

I then put on my vehicle. Drove a few miles; it was great; however, I did have to adjust bypass screw and then throttle idle. I had engine running about 20 minutes during this procedure; I repeated a couple of miles drive. Everything seems perfect!

I will give updates as I add miles to car.

[RRoller123]

If this is reliable over time, this is what we would call in New England, "Absolutely Wickhud Pissah!"

[micbrody]

Lol!
Even if it reliable for just a few thousand miles, the process is easy; maybe just repaint the board every 3-5k miles, like an oil change!

[micbrody]

Update on newly painted AFM:
So far so good. I’ve driven the car at least 30 miles. Probably started and stopped engine 10 times.
Temperature outside has been as cold as low 50’s to low 90’s. Some drives have been 3-5 minutes; some 10-20 minutes long. Engine revs evenly with great power (no lagging or studdering when accelerating). Idle is rock steady and temperature appropriate.
In conclusion: definitely working better than first paint; very optimistic this will last a significant amount of time

[launieg]

Please keep us posted. I have a spare AFM that could use this treatment. I'm thinking I'll order the paint anyway. Thanks for the effort to resolve this problem.

[micbrody]

Paint is only $15 on Amazon . Try it out so we have more AFMs “treated”; that way we can access if it is the cure

[micbrody]

Another option:
If people want to mail me their board, I can repaint them. That one $15 bottle probably would paint 500 boards!
The only caveat: I won’t be held responsible if it doesn’t work!

[micbrody]

Update: another 120 miles (so about 150 miles total). Everything working great

[micbrody]

Over 300 miles, still seems to be running flawlessly. After last gas fill up: 28 mpg (probably 75% highway speeds/25% city).

[micbrody]

Over 500 total miles. Zero issues

[micbrody]

Another 200 miles; 700 total no problems

[QuebecFiatSpider]

Honestly your work and attention to details is incredible. Reading your post is really educative.

Since I'm having weird symptoms with my FI car at the moment, I'll probably remove my AFM and do the voltage test like you did and see from there...

When you said that you adjusted the bypass screw on the AFM, how you done this without reading the %CO from exhaust?

[QuebecFiatSpider]

Since this is a highly interesting topic right now from my perspective, since I'm having weird behavior of my FI spider, I want to challenge the ideas a little bit

Everything that has been written about recoating the sliding electrical band inside the Vane Airflow Meter is an extraordinary solution for keeping those FI spider on the road for a long time....BUT...What if it was possible (and I'm convinced it is possible) to replace that Vane Airflow Meter by a modern Mass Air Flow system but keeping the OEM ECU...

I've done some research on the web and discovered those two website of interest:

https://www.millerperformancecars.com/s ... onversions

https://splitsec.com/product/psc1-009-p ... hv-output/

It seems like a kit has already been developed for old BMW's using Bosch L-Jetronic injection system...but found nothing for our Fiat Spider...

I'm throwing that here because restoring an AFM is a good idea...but the engineer in me thinks that it would be better to replace by a more reliable solution, more modern technology and also it seems it would had some HP and torque to the engine since the «flap» actuation restriction in the AFM would be gone...

What you FI owners think?

[micbrody]

Thanks for positive comments! As for adjusting bypass screw I used procedure suggested by another poster So Cal Mark:
“the most accurate way is to use a gas analyzer. You'll find the L-jet system fuel mixture isn't linear; idle CO will be different than cruise rpm CO. You can get it very close by disconnecting the O2 sensor, attach a voltmeter to the O2 wire, hold the rpm at 2000 and adjust the afm screw to achieve .450 on the voltmeter”
Mark Allison