Digifant AFM - Differences between Vanagon and Jetta units?

Dave.Arthur

Looking through my parts bin, I found an AFM from a Jetta. Similar in appearance to the Vanagon unit (2.1l).

Of course there must be some differences with the setting, electronics or both. Has anyone investigated what those differences would be?

xoo00oox · Posted: Sun Jul 15, 2012 5:26 pm Post subject:

Some things that are the same-
Temp sensor
Hall sensor (not complete Dist, sensor only)
Coil
Cap + rotor
Idle stabilizer
Oxygen sensor can interchange

Some things that are not the same-
Idle control is built into jetta ECM
Knock sensor used on jetta
ECM

This is just a quick list off the top of my head. I know I tried swapping a jetta air flow sensor into a van, I don't think it worked.

Vanagon Nut · Posted: Sun Jul 15, 2012 8:07 pm Post subject:

I've wondered too. I"m sure it's been discussed no?

Search here for Tencentlife video of measuring voltage range of Vanagon AVM, (edit: AFM) ignition on.

If it were me, I would:

- supply 12V, test and compare voltage range of Jetta AFM to Vanagon AFM. (IIRC Vanagon AFM is like ~ 0.25v "closed" to 4.5v wide open)

- no power supplied, measure resistances on each as shown in Bentley.

- measure air intake temp sensors, compare. (does Jetta AFM have this part?)

If all is the same, or even close, can't see why it wouldn't work. Think

I mean, the O2 system + ECU might compensate for any subtle differences?

Edit: and compare wiring to be sure they're the same!

Neil.
_________________
1981 Westy DIY 15º ABA
(VW Gas I4)

1988 Westy DIY 50º ABA

VE7TBN

Dave.Arthur · Posted: Mon Jul 16, 2012 4:32 am Post subject:

I wasn't able to find much in the archives. The unit is plug compatible, sensors (TEMP 1) have the same slope. The only differences I can see are the part numbers (both BOSCH and VW).

Since the unit measures the amount of air coming into the engine and yields a signal proportional to it, since the target AF mixture would be the same on any normal engine and that they are inputting to a similar ECU, I'm guessing that it will work.

However working and working well may be different issues Smile

Surely someone has tried...

MidwestDrifter · Posted: Mon Jul 16, 2012 6:34 am Post subject:

There is a chance that the spring tension maybe be set differently. If that is the case, it would yield different output voltages for the same flow rate. Regardless, I see no reason why it wouldn't at least run, though maybe very poorly.
_________________
2004 Dodge/Mercedes Sprinter (Custom Camper)
2000 Jetta TDI
1982 Diesel Westy W/ ABA I4 hybrid (Sold)
Epic Road Tripping since 08/05/12 | http://VagariesAbound.blogspot.com/
My Current Build | http://sprinter-source.com/forum/showthread.php?t=41215

Captain Pike · Posted: Mon Jul 16, 2012 8:33 am Post subject:

'Fant 2 has no spark. Nuff said
_________________
LEARN TO SELF RESCUE
59 Panel bus, 1966 Single cab. 73' 181. 73 Westy. 91' H6 Vanagon 3.3L.
....Bad Sneakers....

Dave.Arthur · Posted: Mon Jul 16, 2012 1:32 pm Post subject:

I rebuilt the Jetta AFM. Moved the pot wiper to a new track and cleaned the unit.

I confirmed my 2.1 timing, idle, TPS etc. and then swapped in the Jetta AFM. Other than setting the idle bypass mixture, it was a direct install.

Van works fine, as expected. My conclusion is that there is little difference, if any between the AFM units. Closed loop operation depends upon the lambda sensor for mixture... All theory, I will be doing a good road trip in a few days and will report back.

MidwestDrifter · Posted: Mon Jul 16, 2012 1:49 pm Post subject:

Good to know. I have a digi2 I4 setup in my van, would be a real resource to be able to use vanagon parts on the road.

Also, I can look up if someone is interested, but several models of BMWs from the 80s use the same AFM as the I4 digifant setup. Some have a slightly larger sized one which can be made to work by adjusting the spring tension.
_________________
2004 Dodge/Mercedes Sprinter (Custom Camper)
2000 Jetta TDI
1982 Diesel Westy W/ ABA I4 hybrid (Sold)
Epic Road Tripping since 08/05/12 | http://VagariesAbound.blogspot.com/
My Current Build | http://sprinter-source.com/forum/showthread.php?t=41215

nemobuscaptain · Samba Member Joined: March 07, 2002 Posts: 3874

Dave.Arthur · Posted: Tue Jul 17, 2012 3:51 pm Post subject:

I put a few Km's on the van today. The AFM worked well, I felt it had a bit more oomph in the upper RPM range (3-4K). I did readjust the idle mixture and TB idle bypass. I was getting a little hesitation between the idle and operation.

I'm attributing the better performance to the fact that I readjusted the pot in the AFM.

For my money they are interchangeable.

dave-1982 · Posted: Mon Jul 29, 2013 9:06 am Post subject:

Wow ! Glad to hear it worked, can you post the Bosch # of the Jetta AFM part?

Dave

denwood · Posted: Mon Jul 29, 2013 10:34 am Post subject:

Using a Digifant II AFM in my conversion. I could not discern a difference between the 1990 Vanagon AFM and Jetta Digi II ...and from this post I can see they are indeed interchangeable.
_________________
Cheers,
Dennis Wood
The Grape

Vanagon Nut

Has anyone tried a Jetta/Golf AFM on a 1.9 WBX?

Lucky me, found a spare AFM from a diesel Vanagon parts + I4 RV code set up I bought. Was able to move the PCB so wiper has new real estate.

Image may have been reduced in size. Click image to view fullscreen.

_________________
1981 Westy DIY 15º ABA
(VW Gas I4)

1988 Westy DIY 50º ABA

VE7TBN

16CVs

So the thoughts a that a Digifant Jetta coil will work with no issues on a Digifant Vanagon ?

Stacy
_________________
1987 Syncro Westfalia Triple knob (bastard)
1989 Syncro Tristar Triple knob "Swedish"
2013 Jetta Hybrid a true "Zwitter"
Samba member # 14980
Call anytime number 650 722 4914 .
Keep Your van running and upkept tastefully for the love of the hobby.
Don't let your van end up in an "abortions" thread.

kamzcab86

16CVs

Kam

Thank you !
_________________
1987 Syncro Westfalia Triple knob (bastard)
1989 Syncro Tristar Triple knob "Swedish"
2013 Jetta Hybrid a true "Zwitter"
Samba member # 14980
Call anytime number 650 722 4914 .
Keep Your van running and upkept tastefully for the love of the hobby.
Don't let your van end up in an "abortions" thread.

ALIKA T3

Just check the spark wire connection for the coil is identical to your distributor cap.
_________________
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Syncro transmission upgrade parts in the Classifieds.
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http://www.thesamba.com/vw/forum/viewtopic.php?t=416343
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Robw_z · Samba Member Joined: April 28, 2007 Posts: 993


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