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SGKent 
Samba Member
Joined: October 30, 2007
Posts: 41031
Location: Citrus Heights CA (Near Sacramento)
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 Posted: Fri Sep 15, 2023 11:26 am Post subject: Re: AFM Adjustment FAQ |
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there are many sources of information out there because this is a long time running issue. I solved it on my 1977 by putting in a NOS unit. I tried several of the rebuilt ones and they were not acceptable to me.
Example:
https://www.r3vlimited.com/board/forum/e30-classif...e?t=247831
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metahacker
Samba Member
Joined: May 26, 2010
Posts: 694
Location: san.diego
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SGKent
Samba Member
Joined: October 30, 2007
Posts: 41031
Location: Citrus Heights CA (Near Sacramento)
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| Posted: Sat Sep 16, 2023 4:33 pm Post subject: Re: AFM Adjustment FAQ |
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kills it all legally
Legal only for racing vehicles which may never be used upon a highway.
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busdaddy
Samba Member
Joined: February 12, 2004
Posts: 51172
Location: Surrey B.C. Canada, but thinking of Ukraine
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| Posted: Sat Sep 16, 2023 6:04 pm Post subject: Re: AFM Adjustment FAQ |
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| SGKent wrote: |
kills it all legally
Legal only for racing vehicles which may never be used upon a highway. |
Do they care about that in Sweden?
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SGKent
Samba Member
Joined: October 30, 2007
Posts: 41031
Location: Citrus Heights CA (Near Sacramento)
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| Posted: Sat Sep 16, 2023 8:57 pm Post subject: Re: AFM Adjustment FAQ |
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who knows. It is a kingdom I think. Meta is in San Diego. The idea of upgrading to a MAF has been around for sometime. Someone did it about 10 years ago and published a how they done it. It is a great idea. Probst talks about upgrading to hot wire systems in his book too. That said, I bought a NOS AFM and never looked back. So much easier than reinventing the wheel. These are 50 year old cars, which reminds me, I am 73 in a couple hours. No idea where the time went.
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Ozzieman
Samba Member
Joined: November 20, 2009
Posts: 7
Location: Gotland, Sweden
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| Posted: Sun Sep 17, 2023 6:42 am Post subject: Re: AFM Adjustment FAQ |
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Cool! I've been looking at a 123 distributor, but haven't thought about/seen the AFM to MAF conversion.
I think I'm still going to give the diy postions sensor a try, I think I can do it and keep the AFM revertable. Another idea would be to still use the AFM, but interfer withe the signal and retune it before sending it to the ECU.
| busdaddy wrote: |
| Do they care about that in Sweden? |
We have to have our vehicles checked every year (brakes, smog, lights, wheel bearings, etc), but for "veteran" cars over 30 years it's every other year (and they are tax exempt) and for cars over 50 years you never have to get it checked again. Of course you can always get fined if pulled over, and it's obvious that it's not really the original hp engine, but for small modifications on old cars, it's not really a problem.
| SGKent wrote: |
| That said, I bought a NOS AFM and never looked back. |
Yeah, that's prob the best route, I just want to play around some to see what is possible, since I got a Lambda sensor from Bylund Automotive. And I have an aftermarket cam that I suspect will need some more fuel (SCAT C25).
http://www.bylund-automotive.com/educative/lambda/
| SGKent wrote: |
| These are 50 year old cars, which reminds me, I am 73 in a couple hours. No idea where the time went. |
Congrats!
Tell me about it, I'm turning 50 in a couple of weeks  .
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Kleinbus -78, 2.0 |
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Ozzieman
Samba Member
Joined: November 20, 2009
Posts: 7
Location: Gotland, Sweden
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| Posted: Sun Sep 17, 2023 6:44 am Post subject: Re: AFM Adjustment FAQ |
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| SGKent wrote: |
| who knows. It is a kingdom I think. |
Yep and the king celebrated 50 years on the throne yesterday, though his powers are purely ceremonial. Nearly all polical parties are against the monarchy, but it's not a winning issue with constituents..
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MuzzcoVW
Samba Member
Joined: February 21, 2018
Posts: 1477
Location: Westfield, MA.
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| Posted: Mon Sep 18, 2023 4:35 am Post subject: |
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| SGKent wrote: |
If anyone tries this and they screw it up the damage is on them. DO NOT as some threads and forums suggest move the board or bend the wiper to get a better contact. Replace the AFM if the board is worn thru or the wiper bad. You can clean it with a high quality electronic cleaner designed to quiet potentiometers. Do not seal the door with regular RTV - it gives off acidic fumes that can damage electronic equipment. Use special alcohol based RTV if possible.
With the AFM out of the car make sure the door swings freely and smoothly. Set the door so it barely opens about the thickness of a piece of paper with a weight on the edge of between 59 and 61 grams. Then leave the spring adjustment alone. You will not reset it again.
Warm the engine to at least 180F oil temp. Make sure your timing is set per TheSamba specs to 30 degrees BTDC at 3500 RPM with the hoses disconnected. Put the hoses back on when done. Make sure you have no vacuum or exhaust leaks. Hook up your meter so that it cannot have any dilution from air outside the exhaust. Make sure the EGR is functional if you have one hooked up. The EGR tube in the plenum must be clean and not coked up. Your injectors must be clean and have good spray patterns.
Set the wiper so it gives you 14.7 to 15.0 with no load at 2000 - 2500 RPM.
Set the idle mixture to 13.9 - 14.1
Check the mixture at 2000 - 2500 again.
Do these steps several times until the numbers are stable.
Take it out on the freeway at 65 mph flat. The A/F mixture should be low thirteens like 13.1:1 13.3:1. Speed up to WOT and it should drop to around 12.5:1. If you are too rich or too lean from these numbers use the slider to adjust it until you get to them.
Drive down the street, flat and level in 2nd gear holding 25 MPH. The mixture should read about 14.7 - 15.0:1. Speed up to 35 mph in 3rd gear. The mixture should be about 14.7:1 - 14.8:1.
Please note - max power is about 13.5:1 to 14.5:1 however you will overheat the heads if you set the AFM to this at WOT.
It took me two years to figure these things out and numerous AFM's including rebuilt ones. Colin spent years perfecting it too. My suggestion is, and it stands that working on an AFM is the most dangerous thing one can do to their engine other than perhaps trying to time an engine by ear. I would suggest hiring Colin to do this for you rather than taking a risk with your bus engine. All other things must be correct or one is adjusting the AFM to hide other problems. |
Now the question is... would you happen to know the proper weight for a type 1 flap, or is it the same. I was just given 2 Beetle AFMs that appear to never have been apart so I will be measuring, just curious if you have any info on them. |
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SGKent
Samba Member
Joined: October 30, 2007
Posts: 41031
Location: Citrus Heights CA (Near Sacramento)
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| Posted: Mon Sep 18, 2023 11:10 am Post subject: Re: AFM Adjustment FAQ |
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no idea. Never measured one but if they are Bosch you might consider testing them against the measurement I made on the NOS bus one.
I might add, I had a used one that had been tampered with. When I set the flap at the weight above it ran perfectly and smog tested really clean and well. Lots of power. I am sure that the weight is a good starting point if an AFM has been tampered with, and performs poorly.
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metahacker
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Joined: May 26, 2010
Posts: 694
Location: san.diego
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mr matt
Samba Member
Joined: May 26, 2005
Posts: 819
Location: southeast Pa
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| Posted: Wed Mar 27, 2024 5:48 am Post subject: Re: AFM Adjustment FAQ |
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Just to add this site to contribute for adjusting. I cannot vouch for its accuracy
https://www.itinerant-air-cooled.com/viewtopic.php?f=50&t=7761
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1955 3-fold semaphore Oval beetle
1971 Convertible beetle
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Synergy Solutions
Samba Member
Joined: September 26, 2022
Posts: 89
Location: SoCal
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| Posted: Fri Apr 12, 2024 10:20 am Post subject: Re: AFM Adjustment FAQ |
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| busdaddy wrote: |
| There was another similar idea here on TS somewhere in the last year or two, but I can't remember where I saw it now, maybe Vanagon? |
https://www.thesamba.com/vw/forum/viewtopic.php?t=787821&highlight=afm+contactless
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Im a Mobile Aircooled VW mechanic, and work on old and new cars alike. Specialty in Camper busses/Vans, TDI, and FI diagnosis and repair.
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tommu
Samba Member
Joined: November 15, 2011
Posts: 618
Location: L.A.
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| Posted: Fri Apr 12, 2024 6:54 pm Post subject: Re: AFM Adjustment FAQ |
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Works for me.
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airschooled
Air-Schooled
Joined: April 04, 2012
Posts: 12729
Location: on a bike ride somewhere
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| Posted: Sat Apr 13, 2024 10:46 pm Post subject: Re: AFM Adjustment FAQ |
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| tommu wrote: |
Works for me. |
It's a great start. My current "remanufactured" AFM ran 10:1 to 11:1 AFR out of the box. 12 mpg. I used the IAC method to get it in the ballpark for acceptable driving and milage. It got me to 13.5:1 at mid throttle, and acceptable richening under load.
Nothing beats an O2 sensor for confidently avoiding dropped valve seats… I'm currently running the smog AFM myself, netting 20mpg fully loaded up the Rockies.
Robbie
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BDorsey
Samba Member
Joined: April 29, 2015
Posts: 85
Location: SoCal
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| Posted: Sun Apr 14, 2024 8:56 am Post subject: Re: AFM Adjustment FAQ |
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| Quote: |
| My current "remanufactured" AFM ran 10:1 to 11:1 AFR out of the box. 12 mpg. |
This caught my attention because I have a remanufactured AFM on a newly rebuilt 2.0L CA Vanagon engine and I am getting terrible gas mileage - around 12 mpg. All usual suspects have been addressed: Tire pressure, brake adjustment, light foot, etc. I've been through the entire FI system and all components are within specs. Timing is 5* ATDC at idle (per Bentley) and 36* BTDC @3k rpm, hoses off the DVDA distributor (rebuilt by Sparkwerks). O2 sensor is new. Passed smog, no problem. Fuel pressure is 36 psi engine off and 32 psi at idle (1 psi higher than spec) per AFC manual.
The other "symptom" is that it sometimes doesn't return to idle immediately after running under load (e.g., at a stop light). It can take several seconds. Other than that it runs great.
I have run Colin's method previously (before AFM reman.) and I think I did ok, but am very reluctant to mess with the AFM after getting it rebuilt. I was hoping it would be 'dialed in'. I don't have a wide band O2 sensor.
If you please:
1. How likely is it that an AFM "rebuilt" in Tracy, CA needs adjusting? Robbie apparently had to do it, but have others found this necessary?
2. Is there anything I've not addressed that could help with MPG other than the AFM?
Thanks!
Brian
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airschooled
Air-Schooled
Joined: April 04, 2012
Posts: 12729
Location: on a bike ride somewhere
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| Posted: Sun Apr 14, 2024 12:33 pm Post subject: Re: AFM Adjustment FAQ |
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The Van (and 79 ca bus) have a special decel valve that takes longer to return to idle. This is normal, and I think it makes first gear parking lot driving smoother too. This decel valve on a SVDA setup will cause the idle to spike constantly, yours sounds like it's correct for your car.
The O2 sensor can help get the mixture right, but the AFM and ECU need to be able to get the mixture close for the oxygen sensor to be useful.
The reality is, I've had to adjust every "rebuilt" AFM I've come across. Spring tension doesn't mean anything if your engine isn't factory compression with stock camshafts and exhaust. Good news, is that if you are getting good drivability, the fix is just moving the wiper a little. My method is different from IAC, because I run more advanced timing and prefer fuel economy over CHT measurements.
The wiper affects high speed running mixture, because no matter the spring setting, full throttle high speed puts the air vane flap in roughly the same spot. The ECU senses "change" in wiper position more than it really senses a stationary wiper. Set your wiper for around 13:1 or so under high speed moderate load. (Don't worry about full throttle, the ECU/switch take care of that.) For me, this is about 18mpg in a bus and 16mpg in a Vanagon. Don't touch the needle anymore. This will be a safe place if your O2 sensor goes out and the ECU/AFM have to take over mixture without feedback.
Adjust the clock spring for smooth driving, any hiccups or flutteryness at light throttle or hard acceleration is a little too lean. Just like adjusting carbs, I'll usually keep leaning out a few clicks at a time until I notice a drop in performance. The coil spring is much more sensitive at low RPM and changing speeds; the airflow is at a right angle to the flap vane at low speeds, and much more parallel with the flap at high speeds. On buses without O2 sensors that need smog testing, I go for 17-19mpg at steady 55mph and three clicks richer on the coil spring from where it starts to flutter under gentle loads. (Those flutters are misfires and will spike your hydrocarbons and ruin your cat.)
The adjusting can be done with any AFM, not just rebuilt units. If you mark where you started so you can return, I'd recommend a slight leaning on the wiper only.
Robbie
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mr matt
Samba Member
Joined: May 26, 2005
Posts: 819
Location: southeast Pa
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| Posted: Mon Apr 15, 2024 5:26 am Post subject: Re: AFM Adjustment FAQ |
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I would love to see a video on how to do what was just said....
anyone interested in making YouTube instruction video?
The AFM is a scary thing to mess around with...
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1955 3-fold semaphore Oval beetle
1971 Convertible beetle
1977 Westfalia, FI, Berlin interior |
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Synergy Solutions
Samba Member
Joined: September 26, 2022
Posts: 89
Location: SoCal
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| Posted: Mon Apr 15, 2024 6:28 am Post subject: Re: AFM Adjustment FAQ |
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| mr matt wrote: |
I would love to see a video on how to do what was just said....
anyone interested in making YouTube instruction video?
The AFM is a scary thing to mess around with... |
Or pay airschooled to teach you one on one. Better then any youtube video could ever be is Robbies personal one on one experience. Hire a teacher instead of guessing
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Im a Mobile Aircooled VW mechanic, and work on old and new cars alike. Specialty in Camper busses/Vans, TDI, and FI diagnosis and repair.
(206) 841 7324 |
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airschooled
Air-Schooled
Joined: April 04, 2012
Posts: 12729
Location: on a bike ride somewhere
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| Posted: Mon Apr 15, 2024 7:38 am Post subject: Re: AFM Adjustment FAQ |
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| mr matt wrote: |
I would love to see a video on how to do what was just said....
anyone interested in making YouTube instruction video?
The AFM is a scary thing to mess around with... |
The people who REALLY know what they're doing don't have time to make videos. 
I don't usually do video consultation on AFM adjustment unless I've personally worked on your car and inspected everything else. Otherwise we'd need a four hour consult just to get to the point where every other potential problem is eliminated first.
The AFM really is the last thing to adjust, once you've perfected everything else.
Robbie
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mr matt
Samba Member
Joined: May 26, 2005
Posts: 819
Location: southeast Pa
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| Posted: Tue Apr 16, 2024 5:26 am Post subject: Re: AFM Adjustment FAQ |
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For someone who is slightly in the boonies, and knows other VW people who are not familiar with AFM, are lost.
THe VW mechanics around me are gone, but fortunately I can do most of the work that I need to do, but AFM is not one of them.
As more a more people who age and ....depart... a great amount of knowledge is permantantly gone in one fell swoop.
2 years ago, great friend of mine and VW mechanic who taught me a lot passed due to cancer, so that knowledge for me is gone.
Just saying it would be good to keep knowledge out there for the record, for other VW people who have zero access to other VW people, and for those who love VW's in the future.. I just cannot see anything wrong with that.
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1971 Convertible beetle
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