learn me about ERG Valves

[juanbenae]

i know its a part of the emmissions system, but how does it work? what is it for, and what does the its operation consist of? when they go bad how will that affect emmision testing?

i am to do a swap out of exhaust and i believe the pipe that ties into the cross over on the stock exhaust originates from the ERG. is this correct? what have others done when doing an exhaust swap on a 02 pump equiped car. i have heard plug the line into the exhaust and leave in place. cal emmissions testing required here so i will be having to reattach ever couple years and hopfully have it continue to function.

yes i did do a search and struck out.

tia

[Superman]

EGR stands for Exhaust Gas Recirculation. It involves taking exhaust gasses and running them back through the combustion chambers. My personal perspective is that these gasses have gone through the engine once already, and the engine has rejected them. I respect the engine's decision.

[project935]

EGR - Exhuast Gas Recirculation valve

Vacuum or solenoid operated by detecting exhaust gas temperatures. Controls the amount of exhaust gases and intake charge temperature re-introduced into the intake airflow to reduce or increase emission quality via air/fuel ratio monitoring (via other vacuum circuits or ECM (DME in Porsche-speak)).

Removing/plugging the EGR circuit will cut down on intake carbon build-up, but your optimum air/fuel ratio will suffer unless controlled by other means (O2 sensor, electronic injectors, etc).

Usually go bad when the thermal sensor or actuation mechanism is clogged up by carbon deposits since it directly sees exhaust gasses.

When bad, they are either stuck open or closed allowing too much or too little exhaust gas into the intake airflow.

Usually doesn't have anything directly to do with the O2 pump - which supplies clean/fresh air into the exhaust gasses ... again for emissions quality and proper air/fuel ratio performance.

[RAM]

Superman wrote - "My personal perspective is that these gasses have gone through the engine once already, and the engine has rejected them. I respect the engine's decision."

Excellent way of explaining this. I like it!

[juanbenae]

Originally posted by Superman
My personal perspective is that these gasses have gone through the engine once already, and the engine has rejected them. I respect the engine's decision.

that is the funniest thing ive heard all day! it is still early though.

very good explaination 935, thank you. how do you feel about follow up questions?

so if i disconnect it at the (stock) exhaust cross over pipe, plug it there how will it affect my air fuel mixture when the SSI's are installed? will it be at low or high rpm where it is no longer efficent? can this be addressed by changes in the air/fuel mixture? there is no oxy sensor on my 78 sc, it has the pump so what can i do to minimize the affect?

[asphaltgambler]

EGR valves are an afterthought add-on that introduces spent exhaust (for the most part inert gas)back into the lower intake to dilute the combustion explosion thereby reducing combustion chamber temperature and eliminating or greatly reducing 'ping' or 'detonation'.

It is a very crude but effective solution to poor fuel quality, poor flame travel in the combustion chamber due to outdated piston dome/ chamber/ cam profile design.

[Bill Verburg]

The recirculated gas does reduce combustion temperature and a side effect may be to reduce pinging but the main intent is to lower combustion temperatures to reduce the production of NO_x

Another side effect is reduced power and efficiency, the engine made a good choice in trying to get rid of those gases in the first place.

[juanbenae]

bill i was hoping you might chime in. so i should not concern myself with it not being hooked back up except for smog test days?