The Hated EGR Valve Discussion......

-
D

Dragonbat13

Well-Known Member
Joined
Jan 18, 2012
Messages
379
Reaction score
18
Location
lake charles Louisiana
OK,

Everybody hates the EGR valve and I cant understand why. I plan on utilizing one in my street build if possible.

Here is what I have always understood was the two reasons behind having it in the first place,

1. Gas Milage. When your cruising at part throttle, the EGR is open. It allows inert burnt exhaust gas back into the intake under the carb. This inert gas is used in the combustion process to make up for the lack of airflow at part throttle. This in turn raises the cylinder pressures and makes more mid throttle power.

2. Prevents Detonation. Even though its exhaust gas, its still alot cooler than the combustion chamber at part throttle. It lowers the combustion chamber tempatures and avoids detonation. (This actually proved itself to me when I built a performance toyota 22r engine. The engine would detonate at part throttle cruise speeds if the EGR was dissabled.)

Now those two reasons seem like pretty darn good reasons to keep it if you ask me. Not only that, but under WOT the EGR should be shut off, same as if it were dissabled/blocked off. So why does it always seem to get blocked off all together with plates and plugs?

Is there something I am missing?
 
It is hated only because it is a emissions piece. Nothing more, nothing less. It is perhaps one of the most misunderstood item on a engine except the Voo-Doo sci of a cam. And I get'em both.

Since the EGR valve is closed on a hard acceleration and if the car needs it for inspection, well it won't hurt to have it. Though it has proven itself to me at least to be less dramatic than yours was.

I have has this discussion many times here with all but deaf ears. Your going to fight a battle destin to be lost. Just like Stage VI & W5 heads suck due to cracking, big foot is alive with Elvis in the alien ship, etc......
 
Basic "operated by vacuum" wasn't everything it could be so first a ported vacuum switch and later electronic egr controllers were added.
Everyone has there own needs and don't needs going down the road whether its a egr valve, a radio, heated leather seats, 600 horsepower, girl under each arm, whatever. By all means preach on, you may convince a few to reistall the egr valve.
Good luck
 
I'm a big fan of it and I say do it. The main reason people toss it is that it costs money and adds complication.

However, I noticed that my '01 Neon had a factory EGR block-off, and my '96 Neon used EGR. Beats me...
 
Dragonbat13 said:
1. Gas Milage. When your cruising at part throttle, the EGR is open. It allows inert burnt exhaust gas back into the intake under the carb. This inert gas is used in the combustion process to make up for the lack of airflow at part throttle. This in turn raises the cylinder pressures and makes more mid throttle power.
Click to expand...

Not one chance in hell is this true
 
THe biggest reason fot it is to reduce combustion chamber tempertures. PERIOD. You can break it down into the individual things that accomplishes, but that's it in a nutshell. It's really a good thing.
 
actually low end performance can be gained..I plan to add one on my direct drive airboat...on a heavy truck or camper the egr valve is one of the most important parts of the engine....Just Sayin
 
waggin said:
actually low end performance can be gained..I plan to add one on my direct drive airboat...on a heavy truck or camper the egr valve is one of the most important parts of the engine....Just Sayin
Click to expand...

Puzackly.
 
EGR reduces cylinder temperature by diluting the oxygen intake and therefore causing the combustion process to be cooler so the thermal NOx formation is retarded. (think of a air bellows in a blacksmiths furnace, more oxygen, more heat, more Nox) It only forms at temps above 2500F so if you can keep the process under 2500 by reducing the O2 in the air/fuel intake, then you reduce NOx formation. Wanna make your NOx go through the roof? Remove the EGR, plug it, or add O2 (lean it out). My truck passed with almost failing NOx levels. I cleaned the EGR and more importantly, the tube that feeds it from the exhaust. It was very restricted with carbon. as for more midrange power, Im from Missouri, show me. EGR in a camper or motorhome probably just keeps the motor cooler.
 
Interested in more sequential information to the process and its results.

Seems that introduction of exhaust gases would dilute the charge in the combustion chamber. What is the advantage of this? Heating the charge? Cooling the charge? Creating more evenly distributed charge? Increasing the total mass of the charge effectively increasing the cylinder pressure during combustion at low rpm?

Interesting discussion..
 
E.G.R. valve will help cool combustion gasses. When using fuel injection, your a/f ratio is as lean as possible for fuel economy (from factory), this will help eliminate pre ignition (ping) at cruise speed and at tip in accel. Many other factors due to technology and year of design.
 
67Dart273 said:
Not one chance in hell is this true
Click to expand...

Why not?

It was explained to me that there is less volume of air going into the cylinder when the throttle plate is halfway closed. The exhaust gasses make up for this loss. If you have more of a fuel/air/inert gas mixture to compress before ignition, wouldnt you have more effecient use of the fuel, IOW more power?
 
On a Heavy truck or motorhome the engine has more work to do as with a direct drive airboat, the propeller is a constant load that increases with engine rpm, the egr in place allows for more timing and at low rpm there is a chance of preignition when the engine has been run hard, when it is time to shut the engine down after a long run it is customary to let the engine idle for a few minutes before shut down so that is doesn't "run on" although I have the Mallory hyfire IV and programmed it to reduce timing below 1000 rpms and the idle speed is set at 50 rpm's the weight of the spinning propeller will allow for engine run on at shut down...so the addition of the egr may be the hot ticket....
pishta said:
EGR reduces cylinder temperature by diluting the oxygen intake and therefore causing the combustion process to be cooler so the thermal NOx formation is retarded. (think of a air bellows in a blacksmiths furnace, more oxygen, more heat, more Nox) It only forms at temps above 2500F so if you can keep the process under 2500 by reducing the O2 in the air/fuel intake, then you reduce NOx formation. Wanna make your NOx go through the roof? Remove the EGR, plug it, or add O2 (lean it out). My truck passed with almost failing NOx levels. I cleaned the EGR and more importantly, the tube that feeds it from the exhaust. It was very restricted with carbon. as for more midrange power, Im from Missouri, show me. EGR in a camper or motorhome probably just keeps the motor cooler.
Click to expand...
 
All I can say it the EGR is used heavily in the class 7 and 8 truck industry in the 2007 to 2010 model years, mainly to reduce NOx. Mileage and power were both robbed by using it! Now with the use of UREA to clean up NOx the engine manufacturers are backing off on the amount of EGR used and fuel mileage and power are much better.
 
Dragonbat13 said:
Why not?

It was explained to me that there is less volume of air going into the cylinder when the throttle plate is halfway closed. The exhaust gasses make up for this loss.
Click to expand...

Yes you are correct, when the butterflies are closed down you DO get less volume of air flowing, that is how engine speed is regulated! The exhaust gasses do not make up for that, the exhaust gasses are added to reduce the NOx.
 
rumblefish360 said:
Are they still in use on todays cars?
Click to expand...
Not much anymore. They are becoming more obsolete now with the advent of variable valve timing.

EGR valves were on engines to do 1 thing. Reduce NOx gases in the exhaust. PERIOD! There is no performance gained by introducing non combustables into the engine. It was purely an emissions device.
 
Dragonbat13 said:
Why not?

It was explained to me that there is less volume of air going into the cylinder when the throttle plate is halfway closed. The exhaust gasses make up for this loss. If you have more of a fuel/air/inert gas mixture to compress before ignition, wouldnt you have more effecient use of the fuel, IOW more power?
Click to expand...
Boy did they feed you some bunk! Think about it for a minute. If the throttle is 1/2 closed its supposed to feed less air(& therefore fuel) into the motor to keep the speed controlled. Exhaust gases are non combustables(assuming for a moment the engine is tuned & operating properly) so therefore wouldn't add anything to help support combustion- to make up for the lost air. In fact that's is the priciple on how EGR works. By introducing spent exhaust gas into the intake to dilute the A/F mixture & reduce combustion energy(heat/ temperature). That's why you cant have it running EGR at idle & why it isn't added in WOT because it hurts performance. It's used during cruising speed to reduce emissions. Period.
 
I understand what you are saying, but in order to compress the air fuel mix you have to have volume to get maximum compression. If you only have half the amount of gasses to compress, your not going to get maximum compression. If you make up for the loss of volume due to the carb being closed with the EGR, then you should be able to make a higher amount of cylinder pressure during combustion with the lesser amount of fuel. In other words, you would make the combustion more effecient, because the air/fuel mix that is in the chamber would not have to make up as much volume and start pushing down on the piston if the compressed inert gasses were not there.
 
I found this article, and it does shine some light on my confusion. The EGR does make up for the lost volume, but it is that same makeup that also cools the combustion.

"Basic EGR operation
As we mentioned earlier, NOx forms under high pressures and
temperatures commonly found in the combustion chamber, so we can
control its formation by either reducing the compression or the
temperature in the combustion chamber. Emission control engineers
chose the latter. How is temperature controlled? By introducing a
metered amount of inert gas into the cylinder to partially quench the
fire, much like misting your barbecue when it flares. It doesn't put
out the fire, but it slows things down a bit. The result is that the
fire in the combustion chamber is less intense. EGR exhaust gas
occupies space that would otherwise contain air. With EGR, the fire is
more like a smoldering pile of leaves than a blast furnace. Exhaust
gas was chosen because it is free and plentiful. EGR reduces the
formation of NOx up to 60 percent. The cat usually cleans up much of
the rest."

Here is a link, pretty good read if you are a weirdo like me.

[ame]http://www.aces.edu/~parmega/efi/egr.txt[/ame]

Oh yea, Im still sticking an EGR on my next engine build.
 
You must log in or register to reply here.
-

Back
Top