Subject: RE: Bosch LE/2 AFM

[Roderick Warner]

Hey can someone tell me the overall effect of the AFM on the mixture?

      I was of the opinion tha the AFM was only good for low speed running,
      i.e. under about 3000 RPM with light throttle, Maybe higher revs with
      lighter throttle etc.

      Some people have been telling me that if you richen the mixture by the
      spring tention in the AFM it will get a richer OVERALL mixture.
      According to what I thought this cannot be true.

      Does the final resistance of the AFM when it's fully open effect the ECU

      opperation? (If it does then I see how it works) or does it move to
      another set of sensors/vaiables and disregard the AFM when the flap is
      wide open?

      Steve

Rod Warner:-

      You are correct  when you say that the flap is fully open by  X,000 revs-
      that will depend upon the AFM , the engine and the spring tension. I
      gather on a standard set up its usually about 4K revs . Once the fully
      open point  is reached then there is no more mixture per  inlector pulse
      due to the AFM . The theory being that max volumetric efficiency ( max
      torque ) and hence max fuel charge per plulse  occurs below these revs at
      higher revs you dont need so much fuel per pulse , just more pulses.
      However  the ECU  does have additional mapping that is rev related, but if
      its anthing like the Lucas equivalent its pretty weak at higher revs- just
      what you don't want !.  Overall the AFM is the predominant mixture
      controller.

                    Rod



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