camarosource

HOW important is the recirculation tube for the catalytic converters and emission passing??

My car, a 1992 Camaro Z28 with custom chip, mild cam, headers and flow master exhaust (with 2 brand new catalytic converters which are welded with flanges for quick replacements when emission testing occurs... It will NO LONGER PASS AIRCARE (BC Emissions testing).

I left the car with the dealer and they have had it for 3 WEEKS and have no idea why it won't pass. They re-installed the cats, and it failed. They have replaced the EGR valve, O2 sensor, checked gas cap, compression, air/fuel, and no matter what they do, they just CANNOT get it to pass. In fact they have been working with aircare (the mechanic of 20+ years who also owns a custom Camaro has been working with aircare and aircare isn't having any luck getting it to pass). They have given me a CONDITIONAL PASS (3-month) and even so aircare is CLOSING DOWN in December, you still MUST pass aircare within the 3 month period (just means you can renew your car insurance for the time being but if you don't pass within 3 months you cannot renew next time).

Last time they just had to RETARD the timing down so the car ran like CRAP and it passed with FLYING COLORS.. This time THAT is just not enough.

The ONLY thing *I* can think that is different THIS time and LAST TIME (2 years ago which was the last test) was that the car comes with 2 catalytic converters with AIR TUBES on the headers, and recirculation tubes under the car that connect to each catalytic converter. LAST TIME 1 was connected and the other BROKE OFF. So only one was working however with the timing RETARDED it passed.. Immediately after passing, I REMOVE the cats and replace the straight extensions however that leaves the recirculation tube "PIPE" dangling as was vibrating against the frame of the underside of the car. It eventually BROKE off so there are NO TUBES anymore (Both broke off right at the coupling from 1 pipe to 2 pipes (1 to each cat).

I didn't think it was all that important and at the time I was unable to find a replacement anywhere online.

HOWEVER according to Wikipedia, articles online, aircares website, and exhaust websites, emissions WILL FAIL if the "PIPE" is not connected to the cats otherwise the cats don't work to their full potential.

I've found that I can buy the "PIPE" online but what are the chances that is NOT the fix because this pipe will easily be $300+ by the time it arrives, not including install.. Likely $500-600 by the end if not more just to pass aircare (fully) and then never deal with it again..

Recirculation tube "PIPE" which is NUMBER #16

Injuneer

What were the emissions test results? What did it fail for (CO, HC, NOx)?

You need the tube. The tube supplies air to the cats, so they can oxidize the CO and HC to CO2 and H2O. You have cats that have two separate "beds", one for reduction of NOx and one for oxidation of CO and HC. The air is injected in between the beds. They are not like the newer cats that have a single, homogeneous bed that carries out reduction and oxidation as the ECM toggles the A/F ratio back and forth from slightly rich to slightly lean. OR, have they substituted new cats without the air pipe connection?

Surely a mechanic with 20 years of experience and the "aircare" people know this.

camarosource

I'll be going there first thing in the morning so I'll get copies of the tests and find out.

Right now they would be running the car with 2 cats that are equipped for recirculating connections but since the two pipes broke off under the car, they would be unconnected.

Injuneer

The pipe does not "recirculate". The AIR pump runs all the time, since you have a belt driven system (unlike the electric pump used in the 4th Gens). On startup, the AIR pump flow is directed into the exhaust manifolds. When the rich, cold-start A/F mixture, plus the injected air hits the cat, it burns and releases heat, causing the cat to heat up and become active. As the engine warms up, a valve diverts the air flow to the pipes on the cats, and the air is injected in front of the oxidation portion of the cat.

Don't confuse air injection with EGR. EGR is a recirculation process. Air injection is not.