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EGR: Purpose and Misconceptions

M

Mustangcwo

Guest
EGR Theory. EGR serves one purpose and one purpose only. That purpose is to reduce Oxides of Nitrogen (NOx). Under normal combustion, Nitrogen(N2)
Oxygen (O2) in the air and Hydrocarbons (HC) in the fuel combind into water
(H2O) Carbon dioxide (CO2) and the Nitrogen remains unchanged. Under very hot combustion temperatures, the Nitrogen reacts with the other two byproducts and forms Nitrogen oxide (NO). After being released into the atmosphere, it picks up another Oxygen and becomes Nitrogen dioxide (NO2). In the presence of sunlight, it combines with other compounds like Hydrocarbons and forms Smog. (Liberals dont like smog).

Since exhaust gas is inert (very stable) it doesn’t burn again. So by being introduced into the combustion chamber, it will lower combustion chamber temps enough so that the Nitrogen doesn’t react with the other compounds and is passed unchanged out the tailpipe thus not contributing to smog. Now, since exhaust gas doesn’t burn, it doesn’t exactly help with combustion. At higher RPM’s, this really isn’t noticable, but at idle, the reintroduction of exhaust gas will cause a very rough idle and can cause stalling if to much is introduced into the combustion chamber.

EGR Operation. Like mentioned before, EGR flow is good at higher RPMs, but not good at idle, so some sort of control needs to be place on the EGR system. Earlier systems used ported vacuum straight to the EGR valve. At idle, the throttle blades are closed, so there isn’t any ported vacuum. When the throttle is opened, ported vacuum starts to build. The more throttle, the more ported vacuum. This is how vacuum advance distributers work (and why we dont use them any longer). As throttle is increased, the EGR valve opened further. Once the throttle is closed, ported vacuum is lost and the valve closed.

WHY did I post this, to correct those that the car is better off with the EGR in place and functioning.

If you believe that the EGR is better: Hook your exhaust pipe to your air intake and lets go racing.

SOME believe that the timing is better with a cooler cylinder....I agree, but inserting non-combustible gases from the HOT exhaust is not the best cooling medium. I say "add more/cooler air into the intake to cool the cylinder....WORKS BETTER.

YES!!!! I blanked the EGR on the race car TODAY!!!

NO EGR flow should occur where it inhibits operation of the vehicle....such as WOT
 

wickedstangs

Chula Vista, CA
Staff member
Administrator
EGR Theory. EGR serves one purpose and one purpose only. That purpose is to reduce Oxides of Nitrogen (NOx). Under normal combustion, Nitrogen(N2)
Oxygen (O2) in the air and Hydrocarbons (HC) in the fuel combind into water
(H2O) Carbon dioxide (CO2) and the Nitrogen remains unchanged. Under very hot combustion temperatures, the Nitrogen reacts with the other two byproducts and forms Nitrogen oxide (NO). After being released into the atmosphere, it picks up another Oxygen and becomes Nitrogen dioxide (NO2). In the presence of sunlight, it combines with other compounds like Hydrocarbons and forms Smog. (Liberals dont like smog).

Since exhaust gas is inert (very stable) it doesn’t burn again. So by being introduced into the combustion chamber, it will lower combustion chamber temps enough so that the Nitrogen doesn’t react with the other compounds and is passed unchanged out the tailpipe thus not contributing to smog. Now, since exhaust gas doesn’t burn, it doesn’t exactly help with combustion. At higher RPM’s, this really isn’t noticable, but at idle, the reintroduction of exhaust gas will cause a very rough idle and can cause stalling if to much is introduced into the combustion chamber.

EGR Operation. Like mentioned before, EGR flow is good at higher RPMs, but not good at idle, so some sort of control needs to be place on the EGR system. Earlier systems used ported vacuum straight to the EGR valve. At idle, the throttle blades are closed, so there isn’t any ported vacuum. When the throttle is opened, ported vacuum starts to build. The more throttle, the more ported vacuum. This is how vacuum advance distributers work (and why we dont use them any longer). As throttle is increased, the EGR valve opened further. Once the throttle is closed, ported vacuum is lost and the valve closed.

WHY did I post this, to correct those that the car is better off with the EGR in place and functioning.

If you believe that the EGR is better: Hook your exhaust pipe to your air intake and lets go racing.

SOME believe that the timing is better with a cooler cylinder....I agree, but inserting non-combustible gases from the HOT exhaust is not the best cooling medium. I say "add more/cooler air into the intake to cool the cylinder....WORKS BETTER.

YES!!!! I blanked the EGR on the race car TODAY!!!

NO EGR flow should occur where it inhibits operation of the vehicle....such as WOT

Good Job blanking the EGR Plate. But, if you weren't as stubborn as you are at buying parts for your car you would be racing with us right now:) Last night, all, I was mearly telling you was that it was removed by DMP in the computer and pinched off at the exhaust tube and putting the plate is not going to do much since the computer commands the EGR to open at freeway cruise speeds. The parts that make it open like the solenoid make the EGR valve open. Now exhaust gas is rerouted from the exhaust back into the intake manifold via the EGR ports. Now you have a difference in intake pressure compared to before when the EGR valve opens. This is what the computer sees. If the pressure remains the same then the computer codes for a P0401. But, its all been removed.
 
M

Mustangcwo

Guest
Good Job blanking the EGR Plate. But, if you weren't as stubborn as you are at buying parts for your car you would be racing with us right now:) Last night, all, I was mearly telling you was that it was removed by DMP in the computer and pinched off at the exhaust tube and putting the plate is not going to do much since the computer commands the EGR to open at freeway cruise speeds. The parts that make it open like the solenoid make the EGR valve open. Now exhaust gas is rerouted from the exhaust back into the intake manifold via the EGR ports. Now you have a difference in intake pressure compared to before when the EGR valve opens. This is what the computer sees. If the pressure remains the same then the computer codes for a P0401. But, its all been removed.

Since we wont be cruising at freeway speeds, the tuner can eliminate all the EGR tables by putting the settings out of range. Then the computer will not see anything and wont throw the code. Besides it has a 2 next to the EGR code.

PS: If I would have went elsewhere to get my tune I'd be racing too!!!! No more advice from YOU!!!
 
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