Dr F
Post missing.
Guys this is my understanding, i would be very happy to be corrected here.
Just to re-cap:-
SAS, as per the manual, is for improved light up speed of the catalyst, i.e. at start up, it also bleeds in air on engine over-run into the exhaust to burn excess fuel....i.e. at closed throttle.
lambda sensors detect air fuel ratio in the exhaust prior to the catalyst.
In closed loop operation (i.e. part throttle) the lambda sensors will adjust the fuel delivery slightly to improve the a/f ratio and prepare the exhaust gas mix to burn more completely in the cylinder and exhaust prior to the catalyst.
The ECU doesn't operate the SAS in conjunction with the altered fuel delivery to alter the mix prior ro the catalyst in closed loop operation. i.e. it only operate in light up and over run situations.
Imagine a bike engine without SAS, it solely adjusts the fuel delivery to control the mix rather than fuel and air.
So in removing the SAS system it you are only making the bike dirtier at start up for a short period of time and in overun situations.
Note that overly rich fuel can damage the catalyst over prolonged periods, hence its normal to remove the catalayst and SAS together... therefore no catalyst to damage with the overrun fuel burning off....
It is also prudent to use a matched fuel map to eliminate the overfuelling on overrun, and to ensure the mix is not excessively leaned off at higher rpm. (increases charge temp and can burn out exhaust valves etc).
So in summary SAS disconnected / removed is better without catalysts in the long term. However in removing the catalayst and SAS will leave a fuel map unsuitable for thenew condition hence a custon / adjusted map should also be employed.
Hoe this is of some use to some folk. pls feel free to slag off any inaccuracies in the above...
Cheers