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AFM Tweek
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kurt vonnagon
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PostPosted: Sat Jul 28, 2012 7:09 am    Post subject: AFM Tweek Reply with quote

I ran across this and wondered how many people do this . what were your results . I have mine apart if someone could tell me how its done exactly thanks Kurt...

tencentlife wrote:

Instead of a chip, take the top off your AFM and back off the return spring preload by 3 gear notches. You'll get a nice power gain under acceleration with a negligible drop in fuel mileage. Try it. Totally free, and reversible if you don't like the results.

I was skeptical, but went ahead and tried it on my 2.2 wbx and picked up substantial acceleration and hill-climbing torque. I marked the old and new brush positions at idle, 3000rpm, and WOT. At steady-state rpm's, the brush only advanced a tiny bit from the stock setting, but WOT it jumps way higher. I had tried this in the past on other L-jet systems, but only did one notch, afraid to go too far, and there was no noticeable power gain. 3 notches, though, and you can really feel it.

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kurt vonnagon
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PostPosted: Sat Jul 28, 2012 7:47 pm    Post subject: Reply with quote

Judging from the great response I gather its bull shit . Oh well just trying to get motor to its max performance.

Edit: maybe bull shit isn't the right word.


Last edited by kurt vonnagon on Sat Jul 28, 2012 9:39 pm; edited 1 time in total
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peaceful warrior
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PostPosted: Sat Jul 28, 2012 7:55 pm    Post subject: Reply with quote

kurt vonnagon wrote:
Judging from the great response I gather its bull shit . Oh well just trying to get motor to its max performance.


If Chris said it works, it will work. Not having tried it, I have no response.
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PostPosted: Sat Jul 28, 2012 7:57 pm    Post subject: Reply with quote

I wouldn't dismiss it out of hand. The tuners in the VW inline 4 world talk about fine adjusting low end response by tweaking the spring tension on the AFM.

From what I understand you move the black toothed ring to change the spring tension. If you already have the AFM cap off, it wouldn't hurt to do a little experiment for the rest of us Very Happy Just make sure to mark your starting point.
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kurt vonnagon
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PostPosted: Sat Jul 28, 2012 8:15 pm    Post subject: Reply with quote

I will try it. Im not sure if its the top clicker thing or the bottom. Im just looking to fine tune response. Was hoping others had tried this and could explain how to do it in laymen terms. I would hate to break it works fine.
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PostPosted: Sat Jul 28, 2012 8:24 pm    Post subject: Reply with quote

Here is some info from the web on adjusting the AFM. Hope it helps some.

http://www.vanagonauts.com/Adjusting-Wiper-Spring159.htm
Quote:
Hi Larry,
Your van should run near normal with the o2 sensor pulled. Possibly your
afm (air flow meter) main spring has relaxed a bit and is causing your too
rich mixture. I have seen afm off enough that the oxygen sensor / ecu could
not compensate enough and the vans ran very rich all the time. I would
suggest you attach a lcd meter to the black wire on the o2 sensor and check
the voltage after running a couple of minutes. Have the o2 disconnected.
Below 0.5 is lean , above 0.5 volts is rich. This may seem stupid as you
already see black exhaust but it will let you know the o2 sensor is
working.

Now if you pop the black plastic top on your afm you will see a wiper
with a contact on it. If you move the wiper to the right is leaner to the
left is richer. See if you can get a reading on the o2 to go rich and lean
by moving the wiper left and right. If you determine the afm is set up too
rich or lean you can adjust the tension on the main spring you see in the
afm. Mark where the black plastic gear is situated before you move it . To
adjust the tension pull the detent, loosen the detent screw is easier, out
of the gear teeth and increase spring tension to run leaner and decrease
tension to run richer. One other little detail, the afm should be adjusted
around 3k rpm and I like slightly to the rich side of the perfect 0.5 volt
reading, about 0.6-0.7 volts. With the voltage adjusted at 3k using the afm
main spring tension now adjust the idle mixture using the idle bypass screw
on the afm box. Double back and recheck at 3 k and idle again, tweak them a
bit if necessary.
Good luck with your quest. One little word of caution it is necessary
that your tune up items be in good shape no bad wires etc. If you have a
leaky injector this will not be good either. So please mark the gear so
you can return it to the original position.

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kurt vonnagon
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PostPosted: Sat Jul 28, 2012 9:33 pm    Post subject: Reply with quote

Thanks for the reply and the link .
My motor runs perfect their is no problem. Maybe I should not mess with it.
My other thought was to install a Euro ECU.
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dustibus
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PostPosted: Sat Jul 28, 2012 10:15 pm    Post subject: Reply with quote

That black gear looking thing is what youll be moving, when you move it(either ''clicks/teeth'' tighter or looser) it changes the spring tension and either makes the air-fuel mixture richer or leaner. Looking at your picture you have, right next to the 8?mm bolt or the square black hole is a spring/lock, pull that down off the ''gear'' and rotate it counterclockwise however many teeth you want (they were saying 3) and that will make the spring tension weaker and the tracer will go further down the tracks and make the mixture richer. Technically everywhere ''richer'' but more-so at the top end, and thats what makes your gas mileage suffer but you can find the sweet spot for yourself not too much all out power and not too bad gas mileage, its a trial and error thing just got to figure it out. Just mark your original spot and go testing!!
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Wildthings
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PostPosted: Sun Jul 29, 2012 8:31 am    Post subject: Reply with quote

The O2 sensor is going to try and keep the mixture the same regardless of where the cog wheel is set, the exception being at full throttle. Of course if you are running with a bad or disconnected O2 sensor then changing the wheel with make a difference over the entire range.
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kurt vonnagon
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PostPosted: Sun Jul 29, 2012 8:39 am    Post subject: Reply with quote

The cat has bin bashed out . O2 is still in should I unplug it ?

Thanks:
88vanagain
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PostPosted: Sun Jul 29, 2012 8:57 am    Post subject: Reply with quote

10c said the power gain is when you are under acceleration not when you are cruising. I guess the backing off of the tension is to give a slightly richer mixture to the engine for a little power gain. Once you are up to speed, the ecu will adjust to the correct mixture based on the O2 input.

http://en.wikipedia.org/wiki/File:Ideal-stoichiometry.jpg
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PostPosted: Sun Jul 29, 2012 10:59 am    Post subject: Reply with quote

Steve thanks for link:

So I went three notch. Seems like off the line it suffers but once rolling It's got good kick down. I will tweak a little this week and report back

Thanks Kurt
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PostPosted: Sun Jul 29, 2012 11:37 am    Post subject: Reply with quote

kurt vonnagon wrote:
Steve thanks for link:

So I went three notch. Seems like off the line it suffers but once rolling It's got good kick down. I will tweak a little this week and report back

Thanks Kurt


When you say off the line, do you mean the instant you put your foot down ? But once it is starting to accelerate, it pulls better ?

I suggest try 3( or 2 ) notches both way to see the results.
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PostPosted: Sun Jul 29, 2012 12:00 pm    Post subject: Reply with quote

To find out for sure. Get a helper to drive while you manuliplate the pointer. Yea the hatch will be off so don't fall in. You will feel it when you find a sweet spot. Rememember the position. Ajust the spring tension as needed to set. Done.
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PostPosted: Sun Jul 29, 2012 12:50 pm    Post subject: Reply with quote

If I tromp it off the line it seems to bog down. Have to feather the pedal. If I pull out normal it's ok then at normal cruise say 40mph in 3rd it will kick down and zoom. Crap I don't think i had said it's an auto.

As for sitting In the back I guess I could put the bed down .

It's easy so Ill just play with it.
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denwood
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PostPosted: Mon Jul 30, 2012 6:58 pm    Post subject: Reply with quote

Yes, the o2 sensor and computer will try to modulate mixture between lean and rich to ensure your catalytic converter is working well. However, there is a limit to the ability of the system to operate when conditions are outside of the air/fuel map. If your cat is cored, strongly suggest you replace it. HC emissions are in the order of a 100x greater without a cat, not to mention CO and the other nasty stuff coming out of your tailpipe.

Suggest you not disconnect 02 sensor as once the system is warmed up and the digifant coolant sensor (blue) signals to the ECM the engine is warm, it will attempt to keep the engine at 14.7:1 air/fuel. Actually it will oscillate the system between rich/lean to put the cat into an oxidative/reductive mode for proper operation. So if you're watching open loop operation with a volt meter connected to the o2 sensor output, you'll see rapid fluctuations above and below .5 volts. If your voltmeter has an averaging function (just bought a Fluke that is great for min/max avg) then it should average at .5 at constant rpm if your AFM is set "perfectly".

This post is excellent in terms of describing what you are doing: http://www.thesamba.com/vw/forum/viewtopic.php?t=356377

Your van runs in open loop until the coolant sensor, and 02 sensor are up to temperature. It also runs open loop at full throttle while the WOT switch is engaged. Adjusting your AFM spring will have a direct effect on these modes, as well as dramatically change your CO at idle. Incorrect adjustment will damage/destroy the CAT, waste fuel and/or increase nasty stuff out your pipe. Adjusting according to the link above will work...assuming you have no vacuum leaks etc. at idle. There is no need to adjust it with a dude hanging over the engine bay!!..although you'll want to do a few test drives. Connecting a voltmeter to the 02 sensor lead (leave it connected to the ECM) and running wires up to the console so you can observe the voltages works very well too. You'll want to see the ECM signal bouncing equally above and below .5 volts while at cruise. At full throttle, you'll want to see .8 at least. At cruise if the voltage is biased below .5, the ECM is trying to lean a rich mixture. If biased above .5 at crusie, it's trying to add fuel ..therefore you're too lean on the AFM wheel. At 900 rpm, you should disconnect the 02 sensor, connect the voltmeter to it (+ to 02 sensor, - to ground) and adjust CO screw so you see .5 volts steady. You must adjust idle speed every time you adjust CO and check again. With the digifant II jetta AFM I'm using you need to rev beyond 3000 rpm 3 times to reset unit's idle memory each time...I think vanagon ECM requires same. That process should give you the best running van.

Cheers,
Dennis.
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PostPosted: Wed Mar 24, 2021 1:55 pm    Post subject: Re: AFM Tweek Reply with quote

digging this up. Kurt, you're still around? Any news on your tests?
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PostPosted: Wed Mar 24, 2021 5:42 pm    Post subject: Re: AFM Tweek Reply with quote

Kurt hasn't been here since 2012:

https://www.thesamba.com/vw/forum/profile.php?mode=viewprofile&u=259945
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PostPosted: Wed Mar 24, 2021 6:03 pm    Post subject: Re: AFM Tweek Reply with quote

The flap inside the AFM moves the wiper arm across the carbon track and gives the ECU a reading which tells it how much air is coming into the engine.

When you move the spring, you are making the flap resistance to the air flow either harder or easier. It will change the behavior for sure but it will not give you more power IMO.

You get most power when you floor the pedal because that also closes the TPS signaling to the ECU you want full power.
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PostPosted: Wed Mar 24, 2021 6:36 pm    Post subject: Re: AFM Tweek Reply with quote

There was someone on eBay a few years ago selling a performance 'chip' for the WBX.

As I recall the 'chip' was just a resistor that made the ECU think the intake air (Temp 1 sensor) was cooler than it actually was inducing a slightly richer mixture.

If the engine is running well with the original set-up I would be reluctant to mess with it -- at least anything in the vein of fooling the ECU.
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