School me on the smog system

[dstang01]

Could someone school me (or send me a link) about the smog system on the 94-95 gt? What does it consist of, whats the point of it (whats the theory behind it), what are the benefits of removing it, and what (if any) are the drawbacks of removing it? Whats the EGR, AIR, etc...

 

[HGFireHazard]

I can give ya some info, but not all of it.

One of the purposes of the air pump is to supply fresh air to the cats. When using stock cats this prevents them from prematurely going bad. The smog system also supplies fresh air to the back of the heads via the thermactor tube.

It would benefit you to remove the air pump and connecting lines if you have an off-road mid-pipe/no cats. Another advantage is less parasitic loss on the engine, but I don't assume it to be a lot.

I don't know as much about the use of the EGR and the pros/cons to keeping/removing it, but I know others can help.

 

[HISSIN50]

To add a little to Donavan's excellent info:

For the most part, I'd only remove the A.I.R. system if, as Donavan noted, you have no cats and no sniffer test.

EGR introduces inert (spent) gasses at cruise. This helps to lower emissions and increases engine efficiency. The inert gasses (think of it like 'filler') allow more timing and less fuel to be introduced. Performance goes down as a result but you're just cruising, right. And because performance goes down, you step deeper into the throttle to maintain speed (you generally wont even notice this happening). This opens the throttle a little more than it would be otherwise, which improves efficiency.
I'd only remove the EGR if it was broken or for aesthetics. Others will disagree with me.

There are other items like the EVAP system, which does nothing but richen the mixture slightly when the purge solenoid dumps stored vapors (or raw fuel if your name is Paul ). It's nice to have the EVAP system closed, especially if you park your car in a garage or someplace near an appliance with a pilot light. I'm not real big on having fuel fumes vented near pilot lights.

I think those are the biggies you might be considering.

Good luck.

 

[dstang01]

Sorry to bring this back, but Im still a little in the dark. So basically, AIR (smog pump) and EGR (exhaust gas recurculation) are the two emissions systems the cars came with? I hear the whole air pump system can be removed straight up, and the holes can simply be plugged. For EGR, I hear you either have to tune it out of the EEC, use a simulator, or rig up your stock plunger to sit halfway open to make the computer happy. My main concern is, will removing these systems hurt my engine or its performance in any way? Also, is there any other emissions systems on the vehicle that Im not aware of? Thanks, Ill try to do more research once I get the basics down

 

[Dino Dino Bambino]

Sorry to bring this back, but Im still a little in the dark. So basically, AIR (smog pump) and EGR (exhaust gas recurculation) are the two emissions systems the cars came with? I hear the whole air pump system can be removed straight up, and the holes can simply be plugged. For EGR, I hear you either have to tune it out of the EEC, use a simulator, or rig up your stock plunger to sit halfway open to make the computer happy. My main concern is, will removing these systems hurt my engine or its performance in any way?

I removed both the EGR and AIR systems from my Stang and I think this was one of my best mods so far. No problems at all, and I used c182pilot's ebay EGR eliminator simulator so that kept the "check engine" light off. It's nice to also be able to change the passenger side plugs and plug wires without twisting my fingers around all the crap that was there.

 

[chuck943]

To add a little to Donavan's excellent info:

For the most part, I'd only remove the A.I.R. system if, as Donavan noted, you have no cats and no sniffer test.

EGR introduces inert (spent) gasses at cruise. This helps to lower emissions and increases engine efficiency. The inert gasses (think of it like 'filler') allow more timing and less fuel to be introduced. Performance goes down as a result but you're just cruising, right. And because performance goes down, you step deeper into the throttle to maintain speed (you generally wont even notice this happening). This opens the throttle a little more than it would be otherwise, which improves efficiency.
I'd only remove the EGR if it was broken or for aesthetics. Others will disagree with me.

There are other items like the EVAP system, which does nothing but richen the mixture slightly when the purge solenoid dumps stored vapors (or raw fuel if your name is Paul ). It's nice to have the EVAP system closed, especially if you park your car in a garage or someplace near an appliance with a pilot light. I'm not real big on having fuel fumes vented near pilot lights.

I think those are the biggies you might be considering.

Good luck.

To add a little more to this, EGR is used to lower combustion chamber temps, the idea is to use exhaust gases to displace the air fuel mixture to keep combustion temps below 1400 deg to reduce nox gas or smog.

 

[dstang01]

Thanks guys, so is the general consensus that EGR and AIR can be removed without hurting the engine? Will fuel economy or power be affected at all? The last thing I want is to go thru all this work and end up making the car run crappy.

Also, what is the canister purge and what exactly does it do? Is it related to the emissions control?

 

[HISSIN50]

Cannister purge is for the gas tank venting system. The purge solenoid opens to vent stored vapors from the cannister. A side effect from it's removal is a gas stench or possible fire risk if you park near open flames (like a pilot light in your garage).

Good luck.