I swap my exhaust system once a year for the test and was wondering if just the stock cat is good enough to pass. My buddy who helps me out with the test only uses one tail pipe, so that helps alot. I know the air pump saves the life of the cat but I only need it to work for one hour a year. So; what's the deal here?

 

Nope...I've tried it. Not even CLOSE.

 

Damn!

 

I'm pretty sure its was my hydrocarbons that were outRAGEOUSLY high. I'll look in my car at lunch for the test tesults papers.

 

The acv does supply fresh air to the cat thru the split air pipe, but the acv does more than that. At idle the *switching diaphram* inside the acv has a vacuum on it. With a vacuum on it , fresh air is sent to the *port* air passage of the acv. That leads into the housings where it exits a half inch hole next to the rear exaust port and mixes with the exaust air for emissions purposes. Theres also the AAV inside the acv that opens , I believe , during high vacuum in the intake manifold, and when it opens lets fresh air into the intake(best I can tell by the diagram which is flaky) to prevent backfire. Some say the split air is used to cool the catalytic converter. Thats an explanation I have serious doubts about. Coulda left that last sentence off, but I thought I could provoke a better answer out of someone. And by the way, if you own a turbo with the original acv on it, I'll bet money that its a crispy critter and does not work. The turbo heat seems to eat those things alive.

 

Put your air pump on and run a rubber hose directly to the split air pipe that runs to your cat.
I bet it will pass that way!

 

the cat runs hoter with the air pump, that's it's job. the hoter the cat the lower the emissions, the air is not cooling the cat, it's mixing with the unburnt fuel and burning, burning causes heat.

yes running the air pump straight to the cat will work great as it will make the cat even hotter, but don't leave it for very long, the cat will get way to hot and melt. like stick it on before you go test, and remove it as soon as you get home.

 

Hey Hailers you are dead right about the ACV,it's the switching valve diaphragm which usually fries first.There is a cheap solution--it is possible to make the switching valve and diaphragm from the N/A motor fit the turbo--about 10 mins worth of metal shaping.
As far as split air versus port air is concerned,according to Mazda,port air is supplied up to 3600rpm with middling throttle opening,with a heavier throttle opening air is switched to split air.Here in Ontario they use the ASM2525 emission test(25% load 2000-2500rpm)which means you have to make it on port air.As you say at idle it is all port air.
I haven't tried it but I would think hooking the air pump to the cat would be a recipe for disaster--kind of loke a cutting torch in there!

 

SixRotors....thanks for the tip on the switching diaphram. I've been more or less working on doing what you said except I've got a couple of acv off 82-83????? . There is a ear that I had to cut off on the first one I tried so it would fit. Unfortualtly that one has a minor leak in the diaphram so it didn't quite work out and I dropped that project right now. I'll be a little more motivated next Sept when emissions are due on the turbo.
And also thanks for the info on the purpose of the split air going to the catalytic converter. So its to aid in the catalyst in doing its job by adding some oxygen to the burning process. Sounds good to me.

 

One other note since your from the burgh also, under PA emmission laws, before the tail pipe test can be perfomed it must be visually inspected for all the components being there, to sum up no air pump = failed emissions inspection before the tail pipe test is performed.

 

jhjc52......better late than never. (humor)