High flow cats w/o air pump
Tech Contributor
Joined: Aug 1999
Posts: 14,382
Likes: 6,401
From: At my Bar drinking and wrenching in Lafayette Colorado
Yes. In fact, on ECM-controlled cars, the A.I.R. pump only injects air into the exhaust manifolds when the engine is cold and in "open loop" operation. Once the engine goes closed loop, the diverter valve prevents the air from being injected into the manifolds because it would send a false signal to the Ox Sensor. The air injection helps get the cat hot quicker for reduced CO emissions during rich, cold engine operation. Once the cat is hot, it works fine without the injection.
Intermediate
Joined: Nov 2007
Posts: 40
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Your response to la80vette was of interest to me. I recenly purchased a "cherry" condition '81 corvette from an individual in California. Everything is original and it runs great. Its not the same performer as the '68 454 I'm used to, but it is a nice '81. I'd like to keep the engine as original as possible but I'd also like to eliminate the A.I.R pump. Can I just remove the belt that drives the air pump. If I do, will starting be a problem or do I have to make any other adjustments to the carburator? I'd greatly appreciate more information on this subject if you have the time and patience for a response.
Tech Contributor
Joined: Aug 1999
Posts: 14,382
Likes: 6,401
From: At my Bar drinking and wrenching in Lafayette Colorado
You have little, if anything, to gain by removing the A.I.R. pump drive belt. The pump only moves air, and is under load, while your ECM-controlled engine is in "open loop" operation (engine dead cold). Once the engine warms up and goes into "closed loop" operation, the ECM signals the diverter valve to close off the A.I.R flow to the manifolds. When this happens, the load on the pump is eliminated, and it basically free-wheels. There is no performance penalty in keeping the pump operational on an ECM-controlled car.
