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A.I.R (smog pump) Valve Routing

610 views 2 replies 2 participants last post by  blown81 
#1 ·
Hello all. It's been several years and several hotrods ago since I've posted, but I've run up against a problem that I need someone smarter than me to figure out.

Let me start with the latest car. 86 Corvette convertible that I have stroked to a 383. I retained the cars TPI intake that I hogged out to accept a 58 mm BBK throttle body. Cam, headers, etc.... you get the picture.

My problem lies with the emissions system which I (against ALL of my hotrodder buddies advice) elected to retain in tact. Specifically, understanding how the A.I.R. injection to the headers and rear cat work. I can find a hundred posts on methods to eliminate the AIR and EGR systems, but not much posted on the Google machine to explain what triggers the valves and when.

I don't have pictures so I'll try to explain what I'm seeing. First, there are two valves directly down stream from the discharge of the smog pump. The first one in line appears to be a three way valve that can direct the smog pump air either to the second valve or to what looks to be a dump tube that discharges at the bottom of the engine. The second valve in line appears to be another three way valve that directs air to either the header injection tubes, or the larger tube feeding the rear Cat.

I'm sure I have the tube routing correct. My question has more to do with what triggers the valves to direct flow to the different directions. The are both electronically switched, I assume by the ECM, but what is the ECM looking for to make the switches (i.e. intake air temp, timing, EGT's). The way it stands now, the valves appear to be dead-heading the smog pump and not allowing to flow in any direction.

Any help in explaining how this thing works will be greatly appreciated. A schematic of the tube and electrical would be great. Thanks everyone!
 
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#2 ·
You probably have 4 cats. The font 2 are "Light off" or warmup cats.They are efficient when the exhaust is cold or warming but when fully warmed are not efficient. Their job is cleaning up rich exhaust during cold start enrichment .
Then they also aid in warming up the downstream cats, making them start to work earlier.By the time the Light offs are non functioning the downstreams are hot and working
The air injection, switches between the upstream, the downstream or dump to atmosphere.
Usually the deceleration mode dumps to the atmosphere to keep backfires from occurring in the exhaust.
That is determined by throttle position (abrupt close, or closed ) .The vacuum solenoid for the bypass (the first one) valve controls the valve so it can dump the AIR to the atmosphere or send it to the diverter valve ,which chooses upstream or downstream.
The diverter chooses which cat to feed air, upstream cat(light off) or downstream cat (Main cat) depending if engine is in warmup enrichment mode or close loop and on or off the throttle.
The air adds to combustion and also conversion of gasses from HC and C0 to H20 and CO2 .
The solenoids (2) switch the bypass and diverter valves, and is dependant on throttle position, engine temp,engine load,EGR position and engine RPM
 
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