m30 AFM adjustment

[tonytony]

well i got mine and i'm not sure if the spring tension is correct or not, how would one go about adjusting it the proper way?

[browntown]

there was a recent thread to "never touch the spring" it's calibrated with lasers or some such.

[rwh11385]

dyno

[tonytony]

yeah......i guess i wont put it on until i ever decide to go on a dyno. but just to get me from my house to the dyno without blowing up, anyone know what it should be at, there's numbers on there so it must be for something dealing with adjustments

[regis101]

Try not to be intimidated and all will go well. You'll be able to get a middle of the road feel. If it is totally wacked you can start by loosening it up until the spring barely puts out enuff tension to keep the flapper closed. Consider this a zero mark and put some kind of mark on the wheel with a corresponding mark on the body. Then tighten it 20 clicks. It won't be one revolution of the cog. Fire it up. Let'er warm up a bit. Slowly stab the throttle/moderately bring up the revs. Look at the exhaust and listen to the sound of the engine. When the tension is loose, it'll be doggy and rich. Tighten it up 5 clicks at a time. stab it again. Look for the black at the exhaust to diminish. You'll be able to hear and feel it crispen up. Go another five. When you get too tight, you'll be able to watch the wiper arm sag to the right and the idle will drop. Just loosen it back up two. One can almost equate this method as you would adjust the idle mixture screws on a carb. Don't worry about the CO mixture screw on the AFM. No importance at this time. I'm gonna think that somewhere around 30 clicks, maybe 35 will get you safely down the street. Be careful cause it can get addicting when you get used to it. Now.. a second thing is that if it runs decent but you don't know for sure if the setting is right, scribe the witness mark first. Then you can back it off to zero tension and count the clicks as you go. Subtract that number from the middle ofthe road, 30 clicks, and you'll be dialed. Shit, where are ya? I'll do it. The three white numbers on the black toothed wheel are the part number that Bosch designates for the application. There are many different spring tensions available if you want to go custom. Too bad my 325is is in the shop, cause I'd count my clicks for ya. At least it would be something to go by. In the end, the real answer is to send it off to be calibrated. I have the glory of having an FI rebuild shop down the street. Prolly had five AFM's go through there. Watched them do three of them. Even after a bench calibration, you may still have to tweak it one or two clicks either way to suit your cars state of tune. This is my story and I'm sticking to it.

[tonytony]

hey thanks for the help, i'm from Oregon, probably no where near you though :(

[regis101]

www.fuelinjectioncorp.com Two offices. Northern and southern Cal. I am in the northern part; Livermore . Prolly have rebuilt units on the shelf.

[tonytony]

care for a trade with some cash?

[regis101]

I don't work there. Can't get deals. My name is John Q. Public. Just know that I get treated well. My German mechanic uses them exclusivley. Nice to know there are alternatives to the parts houses when you can go to the source. Peace

[CGDoig]

wow, seems confusing. I don't know if we have a dyno around here so it would be hard for me to tune my engine right.

[digger]

there is no point adjusting the tension until you know the voltage output is smooth and increases with flap angle the whole way. The output should be 4.5V at fully open. Then you can theoretically tune you car with the tension (as long as you mark it to allow you to put it back to original) but only on a dyno, as its impossible to tell any other way besides a gas analyser and you need to do it different engine loads.

[rwh11385]

but only on a dyno, as its impossible to tell any other way besides a gas analyser and you need to do it different engine loads.

this is r3v. no one wants to do it the right way

[AdamF 88iS]

If you want to just rig it so it'll run decently, try to get the output reading at about 1.2 volts at idle. This, of course, assumes your idle is at the proper speed and you dont have a bunch of vacuum leaks. If you can get that 1.2 at idle, it'll be ballpark in range and should hit 4.5v at wide open.

[tonytony]

thanks

[regis101]

I like the idea of measuring for voltage. Where and what terminals on the AFM would I put the VOM to measure? IIRC, one of the four is stricly for the air temp sensor backto the ECU. I can check a schematic i guess. * Just checked a wiring diagram for an 89 325is. It shows terminal One as the air temp input. Term Four is ground. Term Two appears to be a hot to the AFM. Term Three is at the full load part of the carbon board. These four conductors from the AFM go tothe ECU. My first thought is that a meter on term two and three will give you the full voltage spectrum across the resistive carbon board. You'd have to have the leads clipped on while you slide the wiper arm to get the varying voltage readings. My 325 is in the shop but I can try this on the 78 Westy for now. I can't scan else I'd post the drawing. Thanks for the voltage reading tip.