A/F ratio adjust

[mrjezza]

I just installed an A/F ratio meter today and it seems that the mix really leans out above 4000 rpm on WOT (note: I have the ProFormance chip)

Obviously, when its running closed loop and the O2 sensor reading is being used, the mix is okay, bouncing back and forth between rich and lean so thats okay but its got me a bit worried that its running lean (pretty much as lean as the meter will show).

Will adjusting the screw on the AFM make it run richer at WOT?

[e9nine]

If your a/f meter is hooked to a narrow band 02 sensor...don't tweak the AFM.
Don't tweak the AFM even with your chip. For comparisons sake, I'd swap in the stock chip and see what readings you get.

AFM tweaks aren't all they are made to be and highly frowned upon on basically stock cars. If you don't have any vaccum leaks and the likes, you should be ok. Our cars are know to run lean @ WOT

[mrjezza]

I wasn't going to be attempting to tune it with a narrowband sensor, just adjust it slightly because I don't like the idea of running lean.

Curiousity got the better of me and I turned the screw just under 45 degrees inwards; now its running a tad on the rich side which was the desired effect.  I know the stock position so I can always set it back.

From all the reading I've done regarding A/F tuning, don't you always want it to be a tad rich (or at least stoich) when you're under power?  All good to run it lean when you're cruising because you're not developing much power or heat, but in terms of engine life running it a little rich will keep the cylinder temperature down too; less heat stress to the engine doesn't sound like a bad thing to me either.

e9nine, as you can see I'm a bit of a theorist but also I rarely follow advice unless the reasoning behind said advice is explained to me . Why would I want the car to run lean at WOT, as far as I understand lean = bad for everything but the environment.

[jonboy318is]

on the side of my air flow meter, there is a plastic cap that can be pried off. beneath this cap , there is some sort of potentiometer , that can be viewed if you take the cover off, so as to adjust the spring inside the meter.
 does anyone know what  this little screw/potentiometer is and what it does?

[mrjezza]

thats the on eim talking about.  what it does is adjust the amount of air that bypasses the flap, therefore adjusting your rich/lean mixture - if you have less air bypassing it, more air moves the flap and therefore ecu gets signal to run richer.  however, on closed loop the setting doesnt matter (as long as its not way off tune) because the mix get re-adjusted according to the O2 sensor.

on idle and wot is when the tuning of the AFM is important.

i was running lean at wot so i removed the little circular cap and there was a brass screw. turned it 40ish degrees clockwise (turning the screw in makes it richer)  and now the wot a/f reads a touch on the rich side, as opposed to way on the lean side.

[jonboy318is]

no , i know what youre talking about , the air bypass screw, i have that on my 325 E's air flow meter. what im talking about isnt a screw for that , this is attached to a small electronic potentiometer, if youre standing on the intake side of the engine, and you take the cover off the meter , like you were going to adjust the spring, in the far right corner closest to you , there is a  small blue rectangular piece of plastic about an inch long , and it has a flat head screw type knob on the  end of it. to get to this screw , there is a small black round plastic cover on the side of the meter that you must remove , also facing towards you, towards the left side of the car . thats what im talking about
 i dont have an air bypass screw on my air flow meter..........