GREGGPENN

I understand the AIR pump shoots air into the manifolds during startup. Then, it diverts it to the main cat during closed loop.

I think the purpose of the air to the CAT is to help oxyginate the unburnt fumes to aid in "cleansing" exhaust. What's the reason for air into the manifolds during warm up?

I've heard to help the O2 warm up. Is that because the extra air helps get the exhaust manifolds hotter faster?

If I took the AIR stuff off, what would be the real effect? (I have new cats -- pre and main. They are hi-po).

btw: I like removal because the crap is simply in the way. Also, my AIR pump has been whining -- probably louder than it should. I might be able to kill the whine by following the tech tip regarding modification to the "tabs" inside. Still the darn thing is a pain to work around. The pump itself blocks the upper driver's side and the diverter blocks even more on the other side. I'm not thrillin over the possibility of paying good money to redo it.

I guess the question becomes "How much good does it do really". If alot, I'm in. If not....

gp

williammackean

The AIR system only injects air into the manifolds & cat during open loop. Then it diverts all air thru a dump at the front of the engine.

Completely worthless system Never did what they said it would. Remove it all. Leave the check valves on the cat & manifold tubes. Tape the connectors out of the way. No codes or computer data involved.

GREGGPENN

That "dump" at the front of the engine is a tube leading to the cat. You're not quite right.

Aggravated4life

Theres another tube that goes down where the water pump is.I think this is what he is talking about.
The tube leading to the cat goes down on the passenger side to the cat converter.

I removed the entire system off my former 86 and if yours is like mine,there is a pipe/tube with a filter looking bottom on it attached to the water pump.You have to look real close to see it.I put 2 washers in place of where that pipe went,since it may have added some thickness to the accessories bolting up correctly.

yoitsmatt

Alot of states dont allow removal of the A.I.R. system for state inspection. The A.I.R. system is stictly for cleaning up tailpipe emissions, and it works pretty well if you look at the gasses coming out of the tailpipe when its running or at the front 02 sensors when testing the system. In the old days we used to rip all that crap off and throw it in the trash, but that was before we could actually see the system work and it became an inspection nightmare.

Strick

So, on my 92, LT1, I have no tubes going to the cats. Can I assume that the only function of the AIR system on my Vette is in the open loop? Also, I don't think I have a "dump" valve. Is that right?

AGENT 86

http://members.shaw.ca/corvette86/Ai...n%20System.pdf

c4cruiser

The basic function of the AIR system is to provide extra air to the exhaust gas so that the catalyic converter heats up faster and reduce emissions. The L98 system uses a pipe running to the main cat only.

The electric AIR pump on the LTx motors is controlled by the ECM and the pump only runs as needed. So there is no real need to have a specific dump valve like the L98 system. With the cats being so close to the exhaust manifolds on the LTx motors, there is no need for a separate air tube.

On the 92 LT1, the AIR pump operates after start-up any time coolant is above 59 degrees F. It runs for a maximium of 150 seconds or until the system enters closed loop. It also runs for 25 seconds if coolant temp is above 149 degrees F at startup or until Closed Loop starts. The ECM will shut the pump off once the system enters Closed Loop.

williammackean

Correct. It is the 'j' shaped piece on the bottom of this pic.



The AIR system is the most worthless 30# of metal on an L98, IMO.

BTW: If you're thinking of removing it, buy the 2-pulley 'underdrive kit' from MAM or similar along with the AIR removal pulley kit. This way, you can buy a new belt size once. I wish I did that...

Strick

Thanks for the explaination. Any idea where to get the replacement foam filter that covers the intake to the AIR pump? I would guess that the "check engine soon" would come on if the AIR system were pulled out as the ECM would sense no electrical flow to the pump, correct?

williammackean

The ECM on my '85 does not notice it. IIRC, no L98 ECMs do. Those connectors are just to send a time-based signal to actuate. There is no return signal port/line.

c4cruiser

The ECM sends a ground signal to the AIR pump relay for operation so I don't think it would check for current flow.

You should not see a SES light as the only function of the pump is to push air into the exhaust manifolds. The ECM controls when the pump runs. There are no other sensors in the 92 and later LTx systems.

I would think that the foam dust filter is not available from GM. Some electronic components are shipped in a soft foam sheet that is warpped around them. That stuff is soft enough to bend and it's not so dense as to restrict air flow. Try a computer store to see if they will give you a chunk from shipping boxes they receive. It's usually a gray color.

GREGGPENN

There are also hoses running to the manifold. The router diverts air from the manifolds to the cat. And, I'm thinking that happens at closed loop.

No one has touched on why the manifolds are filled during warm-up. Does that get it hot faster and let the O2 sensor start leaning and "tuning" the mixture faster?

Thanks Agent86 for the pdf!

gp

SunCr

The pump gets it to closed loop sooner and on these earlier Years cleans up what the CAT can't handle (except doing decel when it can ignite an overly rich mixture so the air goes overboard). The faster your CAT heats up, the quicker your exhaust stops smelling like an air cooled Beetle, so if you wonder why some of the other Vettes aren't waving, maybe that's one of the reasons. There are no codes through '89. Later technologies can sense when the circuit is grounded and when it should and shouldn't be, using the same principles that all ECM driver circuits use to do their thing - voltage/no voltage. As far as I know, there are no serviceable parts but rebuilts are no more than 50 to 60 Bucks.

yoitsmatt

The earlier system with a single wire 02 sensor arent monitored the way later model systems are. 4 wire 02 systems(all obd2 possibly some obd1) run the air pump and watch the pre cat 02 sensors drop to the double digits while the pump is running and can throw codes for either bank A.I.R. system failure if the heated 02's dont respond quick enough.

steven mack

The air to the cat also helps prevent unburnt fuel in the exhaust from backfiring on deceleration.

yoitsmatt

when the engine is cold the fuel mixture is excessively rich and the convertor is easily overloaded. So the air pump runs causing an overlean exaust mixture that "lights off" easier in the converter as it gets up to temp.

GREGGPENN

Thanks. I can confirm the overboard part as mine has been popping alot during decel/shifts. I had wondered if the AIR was part of the "issue". I think the faulty injectors are more of the problem.

The overall design of the system can try to compensate for a lean mixture which can make it overly rich (like when an injector starts leaning out). This would presumably cause more pollution -- so GM wasn't perfect.

Since my cats are all new, the exhaust is new, the plugs are new, the coil/dist are new, and the injectors are about to become new, I bet the car will be cleaner w/o the AIR than it was with it before. All of this w/o throwing any codes.

The $21,000 question though is how much benefit does it do? 10% cleanup, 5%?. I think I remember Vader saying there is no benefit after warmup. And, how much/long would that be w/o it? Are we splitting hairs?

gp

yoitsmatt

The vast majority of polution from cars is from cold engine operation, after the engine is warm and the convertor is up to 1800 deg. the emissions are often in the double digits parts per million, where as cold engine I've seen as high as 1800 ppm of hc. The backfire situation is a symptom of a bad diverter valve on the older system, the diverter actually blocks the air system on decel so the rich mixture that enters the exaust with closed throttle(no air and injectores still firing) does not re-ignite in the convertor, bad check valves and diverter valves are usually the backfire cause, also exaust leaks can do it, so when your engine is cold it will put out more hc than it used to , and colder thermostats also cause more hc , but whe its warm your right you should be cleaner.

The % of cleanup is dependant on the type of driving you do if the car is a daily commuter and it warms for 5 minutes and drives for 15 total then the amount of cleaning is quite alot, if its a weekend car of used for trips and it warms up and stays warm all day then its very little, but the factory has to engineer for worst case because thats what the feds base thier numbers on.

jsup

Especially about the 30 pounds of usless crap.

Do you have a link to the 2 pulley "underdrive kit"? I can't find it.