Looking at most of my GM documentation, it appears the 1227730 ECM w $8D code (and prolly ALL others) has 3 modes for the AIR PUMP.

1) Air pumps to manifolds during open loop / warm up
2) Air pumps to CAT during closed loop / engine hot
3) Divert mode - air pumps to neither cat nor exhaust, but straight
to atmosphere.

Any folks expert on when mode 3 is used??

At one point i ripped out all the emissions on my car. Its going back in now. I was thinking of using a 4th gen electric pump and running it direct to the kitty since my headers have NO AIR fittings.

I was thinking I could use the ECM leads for mode 1 + 2 to power the pump relay circuit for the electric pump, and run the AIR hose DIRECT to the cat.

Should I provide air to the cat during warm up?

Should I only provide air to the cat when in closed loop?

If I do NOT provide air to the cat during warm up, but I do not provide air to the headers (which I cannot do) will the new cat I'm buying quickly clog up?

I know this is not 100% prom, but in some ways it is. I really need to understand what the divert mode (3) is for.

-- Joe

 

From my understanding, there are only 2 modes. One is where the AIR is pumped into the manifolds (I understand the purpose being to aid the O2 in warmup) then it switches the AIR to the kitty. I always thought this was divert mode, and used the diverter valve to divert the AIR to te kitty. Someone correct me if I'm mistaken!

 

I stand corrected. I was answering another post and remebered what the 3rd mode is for. I believe it's for decel or conditions where the extra air would cause a backfire.

As for the CAT, I don't think you'd have any problems with it just running th AIR to it, and not to the headers. From what I understand, the AIR to the headers is more for helping to warm up the O2 faster than anything.

Someone chime in if I'm wayt off on this stuff.

 

You hit it on the head. The only thing not having air ported to the headers/manifolds would do is make it take a little longer to hit closed loop, unless you have a heated O2 sensor anyway.

 

Hey guys,

OK good deal.. What are your thoughts on using an electric pump vs a belt driven?

-- Joe

 

The down side of the electric pump is that I don't think it was designed for contiuous running. I'd have to verify, but I don't remember the AIR pump on an LT1 running constantly, I think it was primarily for warmup.

Are you putting the cat back on to pass emissions testing, or just to be "Nice"? I'm putting one on mine when I get the TPI installed, but I don't think I'm gonna run AIR. I'm not so sure it will be required other than if we had emissions testing (We don't! WooHoo!)

Just some thouhgts, and maybe again someone can offer their experience with no AIR, but with a cat?????