Secondary Air Injection System

[ughkane614h]

This is a very "psychedelic" video. =p

[ADPTraining]

@ughkane614h Yeah, accompanied by a bottle of wine and a few beers makes for a great weekend pass time.

[jwsmith1488]

The O2 sensors arent paid attention to until the ECT raises to operating temperature which then sets it into closed loop and adjusts long term and short term fuel trim accordingly based upon calculated load and O2 sensor switching among other things.

[jwsmith1488]

Actually this is not correct. During cold operation the system is in open loop and doesnt pay attention to the oxygen sensors. Cold temperatures put it in fuel enrichment mode which it is running extra fuel. Rich systems actually cool off the cat. The blast of oxygen into the cat does what is called "light off the cat". Basically reacts with the platinum palladium and serium inside the cat causing a sort of detonation which in turn super heats the cat bringing it to operating temperature.

[spelunkerd]

Thank you for this clear explanation, though one has to listen a second time because of the strange 'voice'.

It seems an expensive solution to trick the O2 sensors into thinking it's too lean on startup by adding an extra motor. Couldn't this be designed electronically for cold startup, by using an algorithm within the PCM? Why the extra motor?

[ADPTraining]

@spelunkerd It's a good logic, but the other and most important reason for the extra motor is to supply the converter with Oxygen or extra Oxygen for the burn off of fuel. The converter is like furnace. Thanks for posting.....Keep posting....

[spelunkerd]

@ADPTraining Thanks again for the quick response, and for a logical explanation. I knew it had to be more complicated than the common explanation that it is there to pass an arbitrary test.

[ADPTraining]

@spelunkerd It all boils down to this: At startup time the mixture has to be richer, depending on outside temperature (colder climates need longer startup times). So for this rich mixture to be burned completely more O2 is needed. During startup a lot of this combustion happens outside the engine, on the exhaust manifold and the converter. This systems is purely an emissions system to protect the environment.

[THOLIM90]

@THOLIM90 air is entering into the exhaust not the inlet manifold like wat it says in the description

[gardnerbm]

Im trying to figure out why the pump is needed when the ECM knows that the converter is cold based on the coolant temp sensor?

[ADPTraining]

@gardnerbm No, the ECT or coolant sensor has nothing to do with converter temperature. The air pump is needed for extra Oxygen during start up and warm up. The ECM increases fuel pulse for extra fuel, which makes for a quick converter light on.