i have dual cats with AIR, but i read alot of stuff about just taking it off, so what effect does that have on the exhaust and/or emmissions? my car is completely gutted right now, so this would be the time to leave it off, but... a new exhaust from front to back will be going back on...

KAM

 

Primary purpose is tp provide oxygen to the cats for the chemical reaction that goes on inside the cats.

 

Look into ur local emission standards and # requirments before u start yankin' #$@!# If u get it wrong it can b costly in the end!!! Keep in mind u must keep the ,o2 for the comp, 2 run right! if ur local inspector needs the emissions tag 2 pass b carefull!! and make sure it iz coverd!!!

 

i thought it was so it would heat the cats up qicker so it would work as soon as u turned the car on. but then once it was heated up anyway it didn't matter.....how wrong am I

i'm talking about the cats being heated up and working, just in case

 

You're right, the only purpose is to heat the cat up faster at start-up. After a certain length of time, the AIR pump shuts off for the rest of the time you're driving.

 

Are you sure about that?

If you have the AIR lines to the cat(s), doesn't the pump push air to the cats so that they can work better while in closed loop (all the time under cruise and accel once/while in closed loop)?

That was my understanding.... was I misinformed?

 

I heard that the air was also used to prevent backfire from a rich condition on deceleration. Maybe it only applies to my other TBI vehicle.

 

That may be the case for the 3rd gen engines, I realized as I read your post I was thinking about the LT1's, as the topic came up the other day. I know for a fact what I posted is how the LT1 AIR system works. I didn't have AIR on my car when I got it so I can't say for sure. My bad.

 

ok its easy to see why air gets pumped to the cats, then why are the air tubes connected to the headers? that just seems crazy

 

A.I.R. was in use before catalytic converters, so you can assume that your assumptions about A.I.R. are incorrect if you assume it is only there for the cat.

The extra air is added to provide oxygen for two things: Complete the combustion of any unburnt hydrocarbons in the exhaust; and conversion of CO to CO2. The A.I.R. is routed to the manifolds in open loop (and certain closed loop conditions on some models) for the former, and to the cat for the latter.

 

why would you ever route o2 to the headers in closed loop? thats absurd.

 

I've only heard it being done on TPI systems. Apparently, the factory found some conditions where routing some to the manifolds was beneficial.

See the sticky at the top of the forum.