In Reply to: Re: Noise explained posted by Jon Caldito on October 06, 1999 at 11:49:04:
: Actually... the air injection system, as you explained, helps lower hydrocarbons and Carbon Monoxide. It does not lower Oxides of Nitrogen or Nitrogen Oxides(NOx).The EGR lowers NOx but our M3's do not have an EGR so cam timing takes the place of it or doesn't need one. The AIS is controlled by the DME. O2 sensors just see how effeicent combustion and CAT is. Plus the system mostly works during open loop so O2 sensors are dead unless brought up to operating temp. Can you imagine what would happen if the AIS was on all the time even on closed loop?