BMW AFM

[Doug Gould]

I thought I'd get a 3 inch AFM for the 3 litre engine that is threatening to go into my GTV6. There seem to be about 10 variants in the L-Jetronic series. Bosch part numbers 0 280 203 001 to 0 280 203 114 (from memmory) numbers higher than 14 are Motronic AFM's with a different connector. The 0 280 seems to be a generic AFM number. 203 seems to indicate 3 inch (as opposed to 202 as fitted to the GTV6 standard). The final 3 numbers refer to some sort of vehicle specific code, but I cannot find any information on the difference between (say) a 0 280 203 001 and 0 280 203 002 AFM. There would be about 6 different 3 inch AFM's available on ebay. Does anyone know?

[four90s]

FWIW, when I put a 3.0 litre in my GTV6, I just swapped the board and the wiper under the plastic cover and it started and idled fine, but wouldn't operate under load.

I'm currently running a standard AFM and it goes like a cut cat with that. Still working on the 3" one.

The engine is a converted 164 one, running the original L-Jet. Seemed to be the path of least resistance at the time as there was one induction runner missing off the 164 engine!

Steve
Adelaide

[Doug Gould]

The 164 uses the Bosch Motronic system, which includes timing and a Lambda probe and a different cold start system (ie no cold start injector). The GTV6 uses L-Jetronic, which is an open loop fuel only analogue system. The 3.0 litre 75 uses a 2 inch AFM P/No. 0 280 202 010. From memory the 2.5 litre is 0 280 202 002. Auto Delta used the 3 inch 0 280 203 002 AFM for their 2.5 litre setup.

Still confused about the P/no differences.

[Duk]

My understanding is that the L-Jetronic used an AFM signal that was greater than the now more normal 0-5 volts.
Years ago I played with a larger AFM body and existing circuit board in my supercharged MR2.
While I could get the car to idle by setting the flap spring tension low enough so the AFM gave the correct voltage, to get that whole shooting match to work properly, I used the  http://www.jaycar.com.au/productView.asp?ID=KC5385&form=CAT2&SUBCATID=965#11.
Autospeed has some decent articles on the device and its application to early Bosch injecton http://autospeed.com/cms/title_The-Digital-Fuel-Adjuster-Part-1/A_2418/article.html and http://autospeed.com/cms/title_The-Digital-Fuel-Adjuster-Part-2/A_2420/article.html.
Note that unlike MOST voltage interceptors, the DFA can be configured to work with voltages higher than the normal 5 volts.