EGR how does it work?

[french dave]

how is the EGr supposed to work?
Inside I have found the piston, which I asumes should move?
However pushing it or pulling it, and the piston is rock soild. i should say that the EGR was quite clean as if the last owner had it cleaned.
PS had the car a week!

[philjudo]

By pass is the answer. http://www.ebay.co.uk/itm/FULL-STAINLESS-STEEL-EGR-BLANKING-REMOVAL-BYPASS-KIT-ROVER-75-MG-ZT-/161053482807?pt=UK_CarsParts_Vehicles_CarParts_SM&hash=item257f891f37

[VMax1000]

how is the EGr supposed to work?
Inside I have found the piston, which I asumes should move?
However pushing it or pulling it, and the piston is rock soild. i should say that the EGR was quite clean as if the last owner had it cleaned.
PS had the car a week!

http://www.youtube.com/watch?v=lL_ElXQVJo8

[french dave]

So do I understand if the piston is soild, its faulty?
If so will a bypass work?
Also the small vacum pipe is perished.
Will go for a bypass if the EGR is faulty.
i have a juddder at certain revs, like fuel starvation, and was going to go for injector cleaner on Sturday.
Thoughts?
thanks

[Mike Noc]

http://www.youtube.com/watch?v=lL_ElXQVJo8

Great find VMax; a good explanation of how the system works. :bowdown:

Only thing to add is the EGR on our cars is vacuum operated.

[VMax1000]

So do I understand if the piston is soild, its faulty?
If so will a bypass work?
Also the small vacum pipe is perished.
Will go for a bypass if the EGR is faulty.
i have a juddder at certain revs, like fuel starvation, and was going to go for injector cleaner on Sturday.
Thoughts?
thanks

EGR valve is operated by vacuum. Not sure if you can move it by hand :shrug:
If the vacuum pipe is gone there is a good chance it's stuck closed.

Get the vacuum pipe repaired, clean the valve/piston with carb cleaner and see how you go.
I used a big syringe to apply the vacuum to see if it opened and let the carb cleaner do its work behind the valve as well although that was on the V8 and not a diesel but assume principle is the same

[french dave]

So Is the bottom line.
if i think it might not be working, the easist thing is to buy a blanking kit for £40 and remove it completely.

would that be fair assumption?

[chrissyboy]

How the EGR Valve works:

The EGR valve is designed specifically to recirculate the exhaust gas into the air/fuel mixture, thereby diluting the air/fuel mixture enough to keep the NOx compounds within breathable limits. This is done by allowing a specific amount of inert gas to pass from the exhaust manifold into the intake manifold through the EGR valve.
It was discovered that short peak combustion temperatures create NOx. By blending an inert gas with the air/fuel mixture, scientists discovered that the rate of combustion slowed down, the high temperatures were reduced and the NOx compounds were kept within limits.

Modern engines are equipped with oxidation/reduction catalysts and fuel injection systems that keep the NOx compounds to a minimum. But even with these newer, more efficient systems, the EGR system is still necessary to reduce the excess emissions.

Early EGR systems are made up of a vacuum-operated valve( EGR valve ) that admits exhaust gas into the intake manifold, a hose that is connected to a carburator port above the throttle plate and a thermostatic vacuum switch ( TVS ) spliced into a pipe that is threaded into the coolant passage near the thermostat. The TVS detects the operating temperature of the engine.
At idle, the throttle plate blocks the cacuum port so no vacuum reaches the EGR valve and it remains closed. As you accelerate, the throttle uncovers the port in the carburator or the throttle body, the vacuum signal reaches the EGR valve and slowly opens it, allowing exhaust gases to circulate into the intake manifold.
Since the exhaust gas causes a rough idle and stalling when the engine is cold, the TVS only allows vacuum to the EGR valve when the engine is at normal operating temperature.
Also, when the pedal is pushed all the way to the floor under acceleration, ther is very little vacuum available, resulting in very little mixture dilution that would interfere with power output.

The EGR valve on early carburated engines without computer controls acts solely in response to the temperature and venturi vacuum characteristics of the engine.

The EGR valve on engines with electronic fuel injection systems is controlled by the engine control computer ( ECM ) . EGR valves on computarized vehicles normally have a computer controlled solenoid in line between the valve and the vacuum source. They also often have an EGR position sensor that informs the computer what position the EGR valve is in.

There are 2 common types of EGR valves: Ported vacuum EGR valves and backpressure EGR valves.
The valve we described earlier is the ported EGR valve, besides this type, there are basically 2 types of backpressure EGR valves; The most common type is the positive backpressure valve, the other one is the negative backpressure valve.
It is important to know the difference between positive and negative backpressure valves because they work differently and they are tested differently also.

Positive backpressure EGR valve:
This type o valve is used largely on domestic models. It uses exhaust pressure to regulate the EGR flow through a vacuum control valve. The stem of the EGR valve is hollow and allows backpressure to enter at the bottom of the diaphragm. When sufficient exhaist backpressure is present, the diaphragm moves up and closes off the control valve, allowing the full vacumm signal to be applied to the upper portion of the EGR diaphragm. This opens the valve and allows recirculation to occur during heavy loads.
Be careful not to incorrectly diagnose this type of EGR valve. Because backpressure must be present to close the bleed hole, it is not possible to operate the EGR valve with a vacuum pump at idle or with the engine off. The valve is acting correctly when it refuses to move when vacuum is applied or it refuses to hold vacuum. Remember that anything that changes the pressure in the exhaust stream will disturb the calibration of the backpressure system including aftaermarket exhaust systems, headers and even clogged catalytic converters.
To distinguish this valve, turn it upside down and note the pattern of the diaphragm plate. Positive backpressure valves have slightly raised X-shaped rib. Negative backpressure EGR valves are raised considerably higher. On some GM EGR valves, the only way to distinguish each type is by a letter next to the date code and part number. N means negative and P means positive.

Negative backpressure EGR valve:
In this system, the bleed hole is normally closed when exhaust backpressure drops, the bleed valve opens and reduces the vacuum above the diaphragm, cutting the vacuum to the EGR valve. The negative backpressure EGR valve is similar to the positive backpressure EGR valve but operates in the opposite way. This type of valve is tipically used on engines that have less than normal backpressure such as high performance vehicles with free flowing mufflers and large diameter exhaust systems.

[spyder]

MMMM OK.
That aside, if the vacuum pipe is perished and leaking it will affect all the other systems operated by vacuum. Block the pipe off, make sure your vacuum system is "air tight" and see how the car goes then.
Fit a bypass regardless and forget.

[VMax1000]

What is it with diesels and EGR bypass?

Would it work on a V8 as well or only on tractor engines:getmecoat:

vacuum leak needs to be sorted before any conclusion can be reached

[VMax1000]

How the EGR Valve works:

The EGR valve is designed specifically to recirculate the exhaust gas into the air/fuel mixture, thereby diluting the air/fuel mixture enough to keep the NOx compounds within breathable limits. This is done by allowing a specific amount of inert gas to pass from the exhaust manifold into the intake manifold through the EGR valve.
It was discovered that short peak combustion temperatures create NOx. By blending an inert gas with the air/fuel mixture, scientists discovered that the rate of combustion slowed down, the high temperatures were reduced and the NOx compounds were kept within limits.

Modern engines are equipped with oxidation/reduction catalysts and fuel injection systems that keep the NOx compounds to a minimum. But even with these newer, more efficient systems, the EGR system is still necessary to reduce the excess emissions.

Early EGR systems are made up of a vacuum-operated valve( EGR valve ) that admits exhaust gas into the intake manifold, a hose that is connected to a carburator port above the throttle plate and a thermostatic vacuum switch ( TVS ) spliced into a pipe that is threaded into the coolant passage near the thermostat. The TVS detects the operating temperature of the engine.
At idle, the throttle plate blocks the cacuum port so no vacuum reaches the EGR valve and it remains closed. As you accelerate, the throttle uncovers the port in the carburator or the throttle body, the vacuum signal reaches the EGR valve and slowly opens it, allowing exhaust gases to circulate into the intake manifold.
Since the exhaust gas causes a rough idle and stalling when the engine is cold, the TVS only allows vacuum to the EGR valve when the engine is at normal operating temperature.
Also, when the pedal is pushed all the way to the floor under acceleration, ther is very little vacuum available, resulting in very little mixture dilution that would interfere with power output.

The EGR valve on early carburated engines without computer controls acts solely in response to the temperature and venturi vacuum characteristics of the engine.

The EGR valve on engines with electronic fuel injection systems is controlled by the engine control computer ( ECM ) . EGR valves on computarized vehicles normally have a computer controlled solenoid in line between the valve and the vacuum source. They also often have an EGR position sensor that informs the computer what position the EGR valve is in.

There are 2 common types of EGR valves: Ported vacuum EGR valves and backpressure EGR valves.
The valve we described earlier is the ported EGR valve, besides this type, there are basically 2 types of backpressure EGR valves; The most common type is the positive backpressure valve, the other one is the negative backpressure valve.
It is important to know the difference between positive and negative backpressure valves because they work differently and they are tested differently also.

Positive backpressure EGR valve:
This type o valve is used largely on domestic models. It uses exhaust pressure to regulate the EGR flow through a vacuum control valve. The stem of the EGR valve is hollow and allows backpressure to enter at the bottom of the diaphragm. When sufficient exhaist backpressure is present, the diaphragm moves up and closes off the control valve, allowing the full vacumm signal to be applied to the upper portion of the EGR diaphragm. This opens the valve and allows recirculation to occur during heavy loads.
Be careful not to incorrectly diagnose this type of EGR valve. Because backpressure must be present to close the bleed hole, it is not possible to operate the EGR valve with a vacuum pump at idle or with the engine off. The valve is acting correctly when it refuses to move when vacuum is applied or it refuses to hold vacuum. Remember that anything that changes the pressure in the exhaust stream will disturb the calibration of the backpressure system including aftaermarket exhaust systems, headers and even clogged catalytic converters.
To distinguish this valve, turn it upside down and note the pattern of the diaphragm plate. Positive backpressure valves have slightly raised X-shaped rib. Negative backpressure EGR valves are raised considerably higher. On some GM EGR valves, the only way to distinguish each type is by a letter next to the date code and part number. N means negative and P means positive.

Negative backpressure EGR valve:
In this system, the bleed hole is normally closed when exhaust backpressure drops, the bleed valve opens and reduces the vacuum above the diaphragm, cutting the vacuum to the EGR valve. The negative backpressure EGR valve is similar to the positive backpressure EGR valve but operates in the opposite way. This type of valve is tipically used on engines that have less than normal backpressure such as high performance vehicles with free flowing mufflers and large diameter exhaust systems.

Wow, you wrote that yourself or did you infringe any copyrights ?

[spyder]

Wow, you wrote that yourself or did you infringe any copyrights ?

Thats not nice.:D

It also does not mention EU emission control, oh wait that has nothing to do with why it is fitted to our cars now does it.:getmecoat:

[VMax1000]

Thats not nice.:D

It also does not mention EU emission control, oh wait that has nothing to do with why it is fitted to our cars now does it.:getmecoat:

Sorry.....................:shrug: