my truck is a 87 bronc and i was looking into cleaning up the wire and tubing mess under the hood. is the smog equipment really neccissary? i do not quite understand the purpose of its exsistance. could someone exsplain to me it perpose and if i could remove it? thanks in advance.

 

The only thing to really worry about harming if you remove the smog equipment (other than your pocket book if you live in a state with emmissions inspections), is the catalytic converter. Without the fresh air injection it will destroy itself because its designed to super heat itself so as to burn off pollutants that don't get burned off during the normal combustion cycle. While it might not seem like a big deal to have a cat eat itself alive, consider that when it dies the substrate inside will become brittle and crumble from the inside out. The pieces tend to break off and clog the exhaust pipe. Not certain what effect not having the air injection to the cylinders will have since the PCV is a closed loop system, there is no way for the blow-by gasses in the crankcase to really escape on their own. Again the smog pump pushes fresh air into this part of the engine to help move these gases up and out of the engine and back through the combustion chambers or into the vapor canister. While the system may look unnecessary and awkward in the enigne compartment, it does what its supposed to if this functioning properly. Removing it can cause 02 sensor difficulties, EGR problems, etc. Any component that relays information to the computer on the engine and how its performing, will be affected by these changes.

 

[updated:LAST EDITED ON 31-Dec-02 AT 07:01 PM (EST)]The smog pump is NOT part of the PCV system, but both are emissions systems.

The air pump (thermactor air system) provides air to the exhaust system (thru the head and thru a small pipe just upstream of the cat or 2nd cat in a 2-cat system) to burn otherwise unburned gasoline in the exhaust, reducing HC emissions. Other than the tiny drag of the pump, this system has no effect on how your engine runs or how much power it produces.

The PCV (Positive Crankcase Ventilation) system uses the vacuum in the intake system to pull air thru the foam filter in the side of the air cleaner, into the crankcase (valve cover & oil pan, picking up fumes), and then into the intake to be burned by the engine. A leak in this system will cause the engine to run lean, and suffer from low vacuum. If the engine is worn out, the pressure from the cylinders will leak into the crankcase & blow oil out of the filter in the air cleaner. Deleting this system will cause the engine to wear out faster because the gasoline that gets into the oil reduces its viscosity, but this system has no effect on how much power the engine produces.

The carbon canister (evaporative emissions) collects gasoline vapor from the fuel tank and stores it until the engine is hot & running @ a high RPM, when a trigger causes fresh air to be pulled thru it "purging" the stored vapors which are burned, much like the PCV fumes. A leak in this system is almost unnoticeable. Deleting this system may damage the fuel tank or allow contaminants into it.

The EGR (Exhaust Gas Recirculation) system reduces NOx emissions by lowering the combustion temperature at high RPMs, which is when most NOx is produced. When it's working properly, it has no effect on power, and it's so simple that repairs are cheap & easy. When it malfunctions, it can cause low power, low vacuum, sputtering & coughing, & poor driveability. Deleting or disabling this system will increase NOx emissions.

 

Steve,
If the smog pump and the PCV system are not in any way related, perhaps you could explain why there is any need for the air injection at the cylinders. My '69 Cadi had a smog pump and the ONLY thing it did was pump fresh air into the crankcase for the express purpose of forcing fresh air into the crankcase so as to aid in the expulsion of blow-by. 69 Cadi's have NO catalytic converters and the air injection is into the cylinder heads only! And it isn't for intake purposes not considering the volume of air consumed by the Q-jet carb on top.

 

[updated:LAST EDITED ON 31-Dec-02 AT 08:00 PM (EST)]The air is injected into the head, but the journal it goes into is connected to the exhaust ports, right at the valves. (That's why a GM has an external journal built into the air pipe and a separate fitting for each exhaust port.) This combines oxygen with exhaust that's hot enough to burn it without the aid of a catalyst. The exhaust then goes by the oxygen sensor, and more air may be pumped in just before the catalytic converter as needed.

If an automaker wanted to pump air into the crankcase, the pump would be connected to a valve cover or to the oil pan at a rubber grommet like the PCV valve is. But the purpose of the PCV is to keep the flow moving in one direction, AND to keep it small enough that the air/fuel ratio isn't disturbed. Pumping that much air in would kill the vacuum in the intake, or blow all the gaskets out of the crankcase.

 

>The PCV (Positive Crankcase Ventilation) system uses the
>vacuum in the intake system to pull air thru the foam filter
>in the side of the air cleaner, into the crankcase (valve
>cover & oil pan, picking up fumes), and then into the intake
>to be burned by the engine. A leak in this system will
>cause the engine to run lean, and suffer from low vacuum.

Steve, I don't understand this at all. The PCV system is not sealed at all. By it's very nature it is open to atmosphere because of the filter in the airbox. IOW this is not a sealed crankcase system.

On top of that the stock PCV is just a light press fit into the pass side valve cover, at least on the V8's, and the only thing holding it in is the fact that the IM won't let it come up far enough to fall out.

I simply run another crankcase filter in place of my PCV and have had no low vac or lean issues.

 

>>The PCV (Positive Crankcase Ventilation) system uses the
>>vacuum in the intake system to pull air thru the foam filter
>>in the side of the air cleaner, into the crankcase (valve
>>cover & oil pan, picking up fumes), and then into the intake
>>to be burned by the engine. A leak in this system will
>>cause the engine to run lean, and suffer from low vacuum.
>
>Steve, I don't understand this at all. The PCV system is
>not sealed at all. By it's very nature it is open to
>atmosphere because of the filter in the airbox. IOW this is
>not a sealed crankcase system.
>
>On top of that the stock PCV is just a light press fit into
>the pass side valve cover, at least on the V8's, and the
>only thing holding it in is the fact that the IM won't let
>it come up far enough to fall out.
>
>I simply run another crankcase filter in place of my PCV and
>have had no low vac or lean issues.

I was typing fast when I wrote that, but I'll clarify: The leak would have to be at the PCV, in its hose, or at the port in the IM, so that would be within a total of ~3". You're right that it's not sealed (as that quote says - it takes in air at the filter), but from the PCV to the IM, it IS sealed except for the METERED leak thru the PCV into the intake. If that leak becomes UNMETERED (by a stuck PCV or a crack/leak), then you'll have problems. Your filter where the PCV used to be has eliminated the "PCV" system, since there's no forced flow thru the crankcase now. You blocked the port on the IM, right? That's why you don't have a leak or low vacuum.

 

hey thanks guys, that clarafys alot. its kinnda a funny thing though. the recent owner of my truck had cut open the catilac converter and ripped the guts out, then welded it back up. but the cool part is that my truck has still passed emissions twice since then.