The engine requires a relatively rich mixture for smooth operation on cold start. For this reason, the ECU operates in open loop mode with a fixed fuel map for the first 20 to 120 seconds of engine operation until the oxygen sensors have heated to operating temperature.
Because of this, exhaust gases contain high levels of carbon monoxide and hydrocarbons after cold starts. The unburned hydrocarbons could be further oxidized, except there is no oxygen left after combustion. By feeding air into the exhaust manifold (secondary air), CO and HC are oxidized through afterburning at temperatures over 600°C to form water and carbon dioxide. The exothermal reaction also increases the exhaust gas temperature, which warms the catalyist more quickly.
To achieve efficient warmup operation, a high secondary air flow rate must be achieved within the first few seconds of engine startup, and the air flow rate must be maintained until oxygen sensor control is in operation. Air flow is maintained by an electric air pump.
Once the oxygen sensors and catalytic converters have reached their operating temperatures, valves cut off the secondary air flow and ECM turns off pump.
By removing SAI you not only put out more CO than you need to during start up, but you also can run rich whichmay not be the best thing for your catalytic converter.
I figure my rover pollutes enough as it is, if leaving my SAI intact a)helps the environment even just a wee bit b)helps my cats last longer, I'm sure the engineers didnt add the SAI system just for shits and giggles.
No it wont affect your day to day performance and yes it may make access to the coil pack easier.
I'll be leaving mine on...
