Smog pump vs. CO%

[tiorio]

So I get to be one of the lucky 2% of Californians who get a random smog check this year even though I'm not due. Which I'm ticked about but regardless...

I've got the 930 running sweet, CO% set to factory specs but this got me wondering.

I don't have the smog pump belt connnected. So everything is there but it's not pumping.

Would this affect my CO% when hooked back up? Am I running too lean now as the smog pump would reduce CO% if hooked up (and so I would have lower CO% readings and would therefore richen the mixture to bring it back to factory specs)?

I'll have to hook up the Gunson this weekend and do some tests but I'd love to have some free time to spend with my daughter rather than battling the smog-nazi for 2 days in a friends borrowed garage!

Thanks!

[Jdub]

My understanding is that the smog pump simply puts o2 into the exhaust after the fact, at the (is it?) post-header point. That would mean it would not effect the CO2 at all. Of course, I am talking from an SC perspective here, so unsure if your 89 is like this at all...

Those who know should chime in. You could always put the belt on and do a before and after CO at a local garage. Do be sure to replace the filter in the smog pump so you get all the air you'll need.

John

[Tyson Schmidt]

The smog pump pumps oxygen into the exhaust after combustion. It reintroduces oxygen into the exhaust so the unburned HC can be reburned in the exhaust.

It won't affect the mixture at all, but will lower the emissions. You won't need to readjust the mixture.

[tiorio]

Well, this is a little harder to describe than I thought...

If I set the CO% with the smog pump disconnected, will the reading change once I hook the smog pump up (the mixture will stay the same, but will the reading change).

That gets to the crux I think...

[Tyson Schmidt]

Yes, the reading will change. You always set CO with it not functioning, or it gives a falsely lean reading.

[tiorio]

So I should set CO with the smog pump DIS-abled? I thought I was supposed to set it with the pump operating?

What is the standard procedure to temporarily turn it off to set CO if that's the case?

Or maybe it's in the shelf full of expensive 3-ring binders I have sitting around here somewhere...

[TerryH]

Remove the belt?

[Tyson Schmidt]

Crimp off the inlet hose.

[tiorio]

Well Tyson, you've saved me a lot of worrying then. I set my CO with the pump disconnected...

Sometimes you get lucky! For fun, I'll post CO numbers (although only Gunson accurate) before and after. Wonder how many folks here don't disable the smog pump before setting CO and end with a too-rich mixture as the readings would be artifically lean...

Thanks again!