Posted by Mike W. on April 29, 2005 at 22:25:32 from 205.188.116.134
In Reply to: 3.5L Fuel System Calibration (Long) posted by Chris Richards on April 29, 2005 at 15:52:28:
There are other variables also, but to simplify it, the ECU sends a signal to the injectors based on what it receives from the AFM. It doesn't care if it's a 2.8 or a 3.5 or what, the system delivers fuel based on how much air is flowing. On 80-81 cars, 633/733 cars used the same FI parts (AFM, ECU, etc) as E12 528i's. It is possible to run out of capacity (starvation or lean at high RPN) but calibration will be correct (or very close) until then. An AFM from a euro 3.5 won't prevent you from running out of capacity, that is a injector/fuel pressure issue. You could keep things in calibration tightening the AFM spring only if you also increased the fuel pressure. But before you do that, hook up a meter and see if it is going lean at high revs or not. If it isn't going lean, you don't have a problem.
So far as swapping AFM's and it still seeming in calibration, I bet the numbers wouldn't be the same in an EPA lab, which is what they were originally set up to do, or to pass. A properly functioning O2 system will mask a variety of faults but without it things would have to be pretty damn close to even think about passing smog, let alone at original levels and conditions. So, just because driveability is fine it doens't mean it is the same.
Mike