AFM Factory settings

[Theo205 0]

Hello,

I am currently having some issues with my 1.9 and after running some tests It all comes down to a possible AFM problem.

I have  a spare 1.9 AFM but before swapping , I will open up  for cleaning  and re-tracking the wiper, and carry  all the tests for wiper resistance readings and temp sensor.

 

Now I know these AFMs  have been subject to fiddling in the past so what I want to know is whether  anybody can  tell me what is the factory preset on the preload spring so I know whether its running standard fueling or not. 
Is there a test method for the flap spring load with the AFM out of the engine?

Any AFM adjusting advice welcome. No need to point me to the AFM articles of the forum  I have already gone through them. 

 

Thanks 

 

Theo

[DamirGTI 342]

1 hour ago, Theo205 said:

anybody can  tell me what is the factory preset on the preload spring so I know whether its running standard fueling or not. 

Is there a test method for the flap spring load with the AFM out of the engine?

 

 

Nope ... it's not as simple as that .

 

You're best bet is - beg/borrow/buy wideband lambda sensor along with the gauge , and tune/adjust the AFM spring tension whilst driving it (drive around some back roads with low traffic and monitor air-fuel-ratio , stop and tweak the AFM spring a bit , drive on further and see what happened with the adjustments you've made , if still no good stop and weak some more , drive further and recheck etc. repeat process until you get it to in spec. air fuel ratio) ..

 

That or exhaust gas analyzer (myself i prefer adjusting it via wideband sensor , can adjust it really precise and change settings afterwards if needed/wanted or simply make a few marks on the AFM cog wheel for say two or three different AFR variations say standard spec. , then little bit one the rich side and little bit one the lean but without much deviation from standard spec) .

 

D

 

 

 

 

[wicked 103 3 Cars]

I think there are reference values for what the flap reading should be at idle (in V) and for the inlet temperature and that can be calculated back to reference resistance values.  

But if resistance track is dirty/dodgy, it can still give strange readings and crap running engine. 

 

Which AFM do you have? ...202 or an early one?

[welshpug 1,661]

2 hours ago, wicked said:

 

 

Which AFM do you have? ...202 or an early one?

 

 

Guess you mean Jetronic  Vs Motronic,  most of the world got both at the same  time depending  on emissions regulations, in the uk it was optional as early as 89 to have a cat, only became mandatory in 93

[DamirGTI 342]

There's one mod for AFM which apparently works based on experiences , includes digital TPS instead of OE film type resistor potentiometer .

 

People who tried this said it works really well (on various other car makes/models) .. and as a bonus eliminates completely common "kangarooing" sensation on/off throttle on Bosch vane AFM's  (slightly better fuel economy was reported also ..)

 

Prepared one of my spare AFM's , but haven't tried it yet :

 

 

[pugdamo 111 2 Cars]

@DamirGTI I'd be interested in any more information you have on this setup, ideally after you have trialled it and can give some feedback on it.

[DamirGTI 342]

Will see , maybe this winter time i'll try it on and see what happens ... i've not much time to "play with" stuff like so as 205 is my daily and only transport

and also i need garage space for doing other work inside .

 

TBH i completely forgotten about this one until recently ! it's been around 2 or 3 years since i piled up all the info , parts , and modified one spare AFM to be tested .. and got nowhere with it ie. it got lost and forgotten in my pile of parts .

 

Anyhow , it's digital TPS from/for Daewoo Lanos .. all the "usual" aftermarket TPS sensors are carbon film type , but this one specifically is digital made by some firm in Russia ..

I've somewhere on my PC database about all that , it's easy to wire it in instead OE potentiometer plate .. only fixing the TPS on the AFM shaft is a bit fiddly (some adapters need to be made) .. and , i remember , there's some slight adjustments/tuning that needs to be done once fitted on the car .

 

That or if you happen to have good OE potentiometer plate from Bosch AFM , can take it out and fit it inside Nippondenso AFM from 80's/90's Toyota 2.0/2.2l or Mazda 1.8/2.0l . (top tip ! - heat up the potentiometer plate phillips screws with soldering iron prior attempt to unscrew them to soften the thread lock .. otherwise you'll round them off and will need to drill them out as they're really tight)

 

That will also eliminate snappy/shaky sensation on/off throttle characteristically for early Bosch AFM's (Jetronic AFM's mainly) .

 

Nippondenso AFM's fitted on 80's/90's Toyota/Mazda are simply copy of the Bosch AFM's , but made better thus they operate smoothly on/off throttle .. from memory , retrofitting Bosch Jetronic AFM internals into Nippondenso unit is pretty much direct , only some minor tweaking/filing is needed . 

 

D

[SRDT 182]

The Jetronic AFM signal isn't flap angle like the Motronic one (not sure for Nippondenso), do you have a way to do the angle to airflow conversion like the original?

Also I think the Jetronic has a 12v signal when most modern TPS have a 5v signal.

[Thijs_Rallye 87 4 Cars]

19 hours ago, SRDT said:

The Jetronic AFM signal isn't flap angle like the Motronic one

The Motronic also doesn't measure a flap angle, or well, maybe it depends on how you look at it. Afaik it works similar to the Jetronic one with the exception of a +5V reference Voltage vs a +12V reference Voltage on the Jetronic unit. If my memory serves me right in the group A build manual there is a description of how to reset the AFM for the Jetronic ones when using the PTS engine and ram air intake with a weight on the flap. This looks to me how the mass flow vs Up/Uv is "set" for the changed engine conditions.

The transfer function is defined as Up/Uv vs air flow in m³/h

[SRDT 182]

The very early Motronic AFM worked just like the Jetronic ones but they quickly moved the transfer function inside the ECU to have less AFM models.

That's why the XU9JAZ AFM is shared with the XU9J4 and you can also find it on some unrelated Opel and Alfa Romeo engines.

It seems that spring rate and preload can be identical as long as you get the transfer function right.

[DamirGTI 342]

Well , i'm far from being expert in electronics thus don't expect much from me with regards to that specifically ! 

I know how to work my way with the wrings and electronics to a degree , most of what is usually needed for fixing stuff but everything else beyond that , i simply do not have knowledge nor training "how to" .

 

Thus i'll share info about this , so you can discuss and analyze further . 

 

Unfortunately all the data i've collected about this years ago seems to be lost , on one of my burnt HD drive as it seems .. tried searching but found none thus it must've been on that HD which went bust .

 

Anyhow , majority of the info about this you can find on Russian car forums (Russian , Ukrainian , Belorussian etc.) .

 

The digital TPS in question with specs. is :

 

https://www.vtnauto.com/en/3102.html

 

Some of the forum talks and "how to" for start :

 

https://www.drive2.ru/l/6633095/

 

.. simply google "3102.3855" and you'll find a lot of info both written on the forums and also videos on YouTube with cars actually running and driving with such TPS modified AFM's . 

 

They seem to measure OE AFM flap opening resistance in steps of 1000rmp. and then adjust the TPS modified one to suit the OE resistance readings .

You'll notice that the values are pretty much bang on with that digital TPS , with very little difference/deviation (mostly around 3000/3500rpm range) .

 

They've been doing it on both the Jetronic and Motronic AFM's on Audi's , VW , Opel etc. .. thus , it must've work on a 205 too .

 

D