Afm co screw

[france320isco]

Hi

I was wondering if the CO screw on the AFM of a non cat M3 version (often protected bvy a plastic cap) is of any use and what is the CO range attainable by operating it.

What's the position of the screw in a brand new AFM, is it fully open or close? And what CO reading do i get in the stock position?

Thanks

[kiko]

There's anumber stamped right next to the screw hole (sounds awful...I know) that number is the distance that particular unit had from the top of the screw to AFM surface when set at the factory. Mine was 27.1mm

[france320isco]

There's anumber stamped right next to the screw hole (sounds awful...I know) that number is the distance that particular unit had from the top of the screw to AFM surface when set at the factory. Mine was 27.1mm

Thanks, i noticed that number always wondering what did it stand for...
And these distances are the same on all the non cat BOSCH M3 2.3 AFMs or not?
What is the CO reading with an all stock engine with the correct screw surface distance?

I'm asking this cause i have a % CO spec on a manual but i dont understand if the system foresee a CO adjustment by the screw if it is screwed up :yup:

[kiko]

No, that number is different for all AFM's that's its stamped one each and everyone otherwise it would just be part of the factory manual.

The CO should be around 1% some say the idle is smoother with 1.5%.

[france320isco]

No, that number is different for all AFM's that's its stamped one each and everyone otherwise it would just be part of the factory manual.

The CO should be around 1% some say the idle is smoother with 1.5%.

Well i've set the screw in the stock position (it is said 27.6 on my brand new AFM), drove around, my narrow band lambda sensor (which i installed just to check CO) reads 0.8 volts.

The car runs ok, injectors have been recently cleaned, bosch super 3 spark plugs with approximately 10.000 km on them, 15-16 bar compression in each cylinder.

Pushing down slow at low rpm the engine is way lean but goes ok, then, passed the half of the pedal run and increasing the pushing rate, it enriches the mixture to 0.7-0.8V output of my lambda sensor (that unfortunately is narrow band ) and stays there at wot.

[kiko]

What a mess! First, CO is measured in % not volts! Then to adjust CO on a Lambda equipped car you have to disconnect the LAmbda sensor! And then again if your car is running lean when driving it's most certainly not related to the CO adjustment on the AFM has this is for idling.

Pls see the factory manual here and do it has they say:

http://m3guru.bmwe30m3.net/bmw-e30-m...ice-manual-s14

[france320isco]

What a mess! First, CO is measured in % not volts! Then to adjust CO on a Lambda equipped car you have to disconnect the LAmbda sensor! And then again if your car is running lean when driving it's most certainly not related to the CO adjustment on the AFM has this is for idling.

Pls see the factory manual here and do it has they say:

http://m3guru.bmwe30m3.net/bmw-e30-m...ice-manual-s14

Thanks for the link.

My lamdba sensor is NOT in anyway linked to the ECU and that's why its signal CAN'T absolutely be taken into account by the EMS and so modify the injection.
This is why it hadn't to be disconnected.
The lambda sensor is just connected to an A/F ratio meter.
But, again, not to EMS/ECU.

Even if the lambda sensor is an OXYGEN sensor, the CO content of exhaust gas is proportional (but not linear) to the output voltage of the lambda sensor (which usually is in the range 0.01 - 1V:
(see emission curves, maybe google it).

~0.45-0.5V => AFR = ~14.7 => CO% =~0.6-0.7% (that is never 0)
~0.6V => AFR = ~14 => CO% =~1.4-1.5%
~0.75V=> AFR = ~13 => CO% > 5%

Thanks again for the link...

[hardtailer]

Well i've set the screw in the stock position (it is said 27.6 on my brand new AFM), drove around, my narrow band lambda sensor (which i installed just to check CO) reads 0.8 volts.

The car runs ok, injectors have been recently cleaned, bosch super 3 spark plugs with approximately 10.000 km on them, 15-16 bar compression in each cylinder.

Pushing down slow at low rpm the engine is way lean but goes ok, then, passed the half of the pedal run and increasing the pushing rate, it enriches the mixture to 0.7-0.8V output of my lambda sensor (that unfortunately is narrow band ) and stays there at wot.

hi francesco,

between half and 3/4 of pedal travel the WOT switch closes and the mixture richens. It seems from your description that it's exactly this you're seeing. The rate of pedal travel shouldn't make much of a difference but give it a try again and keep the rates equal and see if anything changes.
I used to see lean running at every load and rpm with the original AFM. With a refurbished one all is fine and my 320is (without lambda control) runs at AFR of 15.5 at idle, slightly leaner at 16 at low load and low rpm and again at 15.5-16 at revs >2000 rpm. As soon as the WOT contact is closed I see AFR of 13.5-13. These numbers are valid at engine operating temp.

[france320isco]

hi francesco,

between half and 3/4 of pedal travel the WOT switch closes and the mixture richens. It seems from your description that it's exactly this you're seeing. The rate of pedal travel shouldn't make much of a difference but give it a try again and keep the rates equal and see if anything changes.
I used to see lean running at every load and rpm with the original AFM. With a refurbished one all is fine and my 320is (without lambda control) runs at AFR of 15.5 at idle, slightly leaner at 16 at low load and low rpm and again at 15.5-16 at revs >2000 rpm. As soon as the WOT contact is closed I see AFR of 13.5-13. These numbers are valid at engine operating temp.

Hi Hardtailer it's good to read you again.
I was under the impression that the richer mixture increasing the pushing rate was due to the acceleration enrichment maps.
In point of fact i've done the pushing rate experiment you suggest and i noticed that the lean range last all the more while pushing at a lower rate, till you reach wot where the values are the same you pointed out.
On the contrary it enrichens istantaneously if you increase the rate in all RPMs conditions from a lean state (acceleration enrichments).

How it begins...

I had a problem of engine hesitating during the warm up phase (also new Coolant Temp Sensor and intake gaskets).
Two refurbished AFMs purchased recently via ebay in the US from two different professionals didn't solve the problem, i felt Jakelove i mean engine not revving correctly, etc so i won't buy a refurbished AFM once again.
So i bought this stock BOSCH AFM with a 60% off from the price that i've found really new in the electronics (ceramic strip without a single scratch, never used), but it is one of those parts that were "returned items".
In this case the reason of "return" was simply the detachment of the plastic cover due to a fall or maybe a lack of sealant.

Anyway this AFM solved the warm up problem perfectly, but i got maybe a 2-3% CO reading at idle.
The spark plugs are well coloured.
I tryed to get it down with the CO screw, but then KIKKO here told me the meaning of that number next to the CO screw hole so i'd like to stay on the stock settings.

[kiko]

Francesco,

The measurement at the factory was a base setting and should be looked like that! You can start from there and adjust the CO to your particular car set-up (injectors, fuel pressure variations, etc) that's why the adjuster is there in the first place!

[france320isco]

Francesco,

The measurement at the factory was a base setting and should be looked like that! You can start from there and adjust the CO to your particular car set-up (injectors, fuel pressure variations, etc) that's why the adjuster is there in the first place!

thanks kiko for all the help, i'll do like you say