question on the bolt on the left (US drvier side) of the cat converter.

rnln · 02-18-2008, 11:43 AM

I saw this bolt there on the left of the cat converter. Look like it doesn't hold anything in place, no purpose beside plugging up the hole. What is it for? Is the purpose to open the cat up, letting some of the air out, to gain performance? There is even a hole on the heat shield to access to this bolt.

ianc · 02-18-2008, 01:03 PM

Quote:

no purpose beside plugging up the hole. What is it for?

Plugging up the hole.

That's where the sniffer goes to measure the %CO. Upstream of the cat.

ianc

rnln · 02-19-2008, 12:25 PM

thanks ianc

x98boardwell · x98boardwell's Garage

I have a hole on my catalytic converter (now removed) which was for the air pump that injects fresh air into the cat (along with air into the exhaust outlets) to help with emissions.

I realize that is can be used for a sniffer, but those are mostly just put in the tail pipe at a smog shop.. Also, if your adjusting fuel mixture, you should use the O2 sensor hole as I was told, especially on a turbo car, not at the tail pipe due to fluctuations.

My .02 anyways.

Bryan

rnln · 02-19-2008, 08:37 PM

I can't sleep without trying it, and it's seem so easy unbolting the bolt, so I came out and give it a try. OMG, the RPM came up so much quicker. I have not pushed the car much yet, just little agressive driving for several miles. I don't know if this gain anything, I assume so since I am pushing air out before it comes to the cat, but the RPM moved a lot quicker. Yes, I can notice a little more basal noise back there. Came home, put the bolt back on. Now I can go to bed.
Thanks.

ianc · 02-19-2008, 09:11 PM

Quote:

I don't know if this gain anything, I assume so since I am pushing air out before it comes to the cat, but the RPM moved a lot quicker.

If that's the case, then your cat is probably plugged\marginal. X98 is correct that smog shops will put the sniffer in the tailpipe to measure emissions for smog, but for correctly measuring the %CO, you need the probe upstream of the cat with the O2 sensor disconnected.

Don't run it without the bolt; fix the problem. Or get a cat bypass and damn the smog cartel...

ianc

rnln · 10:16 PM

thanks guys. yeah, I already put it back. Just curiocity, what kind of damage(s) running without this bolt, beside the environmental problem?
And base on what you are saying, if my cat is good, there should NOT be any different running with or without this bolt? Meaning there should be no different open up the air flow in front of the cat?