Originally Posted by DoubleWasp
https://www.impalassforum.com/tech/engine/air_pump/air_pump.htm
Typed too fast. EPA legal and approved is more like it.
My understanding is the smog pump doesn't even operate but for short periods upon startup. Once the engine is going, they're just paperweights.
The one in my Roadmaster I could hear. Came on for maybe a minute, then nothing.
Unless one towed their car to an emissions testing station and started the engine cold for an immediate emissions test, they would be outside the range of the smog pump's operation anyway.
Good reason to dodge them besides the water contamination issue. I had a check valve go, and smoke came billowing out from under the hood after exhaust went past the check valve burning the entirety of my air injection system (all plastic and rubber upstream of the check valves).
What I've learned about air injection systems is that many do not have the power to push air into the exhaust much beyond idle either. The mechanical system in my 92 has a bypass valve that opens and renders the pump useless pretty much under the same circumstances as my electric pump in the 96 shuts off.
I can also tell you from experience that the Pierberg pumps used in a lot of Euro cars aren't even constant duty pumps. Even with constant 12V applied, they encounter thermal shutdown within minutes.
Smog pumps have a real and true effective purpose on some engines. A company back in the early 2000s got a 450rwhp RX7 to pass California emissions using an industrial catalyst and a LOT of air injection at several points in the exhaust. A GM rag got a high-build 70s Camaro to pass using a similar strategy.
But for tame, low compression, broomstick cammed V8 engines? They had very little work to do, and apparently nothing relevant at all.
Thanks for the link, I was working as a GM dealer tech when LT1 B&D bodies were new. I don't remember doing any modifications outlined in the TSB.....Doesn't mean I didn't though!
The theory of operation you outlined is correct for most applications & just about ALL iterations of Secordary Air Injection used in the last 25 years.
However.....Some of the old Batch-Fire PFI systems (A lot of Carbureted vehicles as well) had to have air injection at the catalyst/s after engine & catalyst warm-up to control CO.
The Air Pump would pump air into the manifolds during open loop operation.....After warm-up & catalyst light-off, The Air Control Valve would close & air would be pumped into the middle of the 2 catalyst substrates. The only time the Air Diverter/Bypass Valve in this system would open & dump to atmosphere is during deceleration.
I believe the zone between the 2 Subtrates in the Converter is low pressure & the Air Pump can deliver a good amount of O2.
I guess if the OP deletes the AIR system.....We'll see if CO can be controlled without it (If he reports back?) It may be wise just to remove the Smog Pump belt & see if it will pass CO??
