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EGR recirculates exhaust back into the engine to help control NOx (oxides of nitrogen). These occur at extremely high combustion temperatures(above 2500 degrees if I'm not mistaken). NOx (It is an X because the amount can vary, NO, NO2, ect.) NOx are harmful to the atmosphere. Not only does EGR control NOx, it also CONTROLS knock by diluting the air/fuel mixture with inert exhaust gas (exhaust gas will not burn, thus lowering exhaust gas temperatures). EGR has a "leaning" effect when it is purged into the cylinder, which is why it is only purged on mild acceleration and coasting, not at idle or WOT. Keep your EGR, it does nothing but help your gas mileage, keep your engine knock counts lower and mother earth happy.
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Originally posted by el aguila:

EGR recirculates exhaust back into the engine to help control NOx (oxides of nitrogen). These occur at extremely high combustion temperatures(above 2500 degrees if I'm not mistaken). NOx (It is an X because the amount can vary, NO, NO2, ect.) NOx are harmful to the atmosphere. Not only does EGR control NOx, it also CONTROLS knock by diluting the air/fuel mixture with inert exhaust gas (exhaust gas will not burn, thus lowering exhaust gas temperatures). EGR has a "leaning" effect when it is purged into the cylinder, which is why it is only purged on mild acceleration and coasting, not at idle or WOT. Keep your EGR, it does nothing but help your gas mileage, keep your engine knock counts lower and mother earth happy.

Are you referring to Knock as emissions N0x, or Knock knock, like from timing advance or a lean mixture?
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Originally posted by w00t:

Are you referring to Knock as emissions N0x, or Knock knock, like from timing advance or a lean mixture?

I'm referring to both actually. From the emissions standpoint it is used to control NOx, and from the "knock" standpoint, it controls this also. When the ECU "hears" "knock" (from the knock sensor), it can do one of three things:

 

1. retard timing

2. add more fuel (to cool)

3. Open EGR

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Originally posted by el aguila:

I'm referring to both actually. From the emissions standpoint it is used to control NOx, and from the "knock" standpoint, it controls this also. When the ECU "hears" "knock" (from the knock sensor), it can do one of three things:

 

1. retard timing

2. add more fuel (to cool)

3. Open EGR

Thats kinda interesting. That seems a bit backwards if a car was detonating at WOT that the EGR would open making the mixture leaner. In retrospect though, It would seem like it would create some sort of blanket with inert gases in the cylinders.

 

Innnnnnnnnnnteresting

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Originally posted by n8:

Thats kinda interesting. That seems a bit backwards if a car was detonating at WOT that the EGR would open making the mixture leaner. In retrospect though, It would seem like it would create some sort of blanket with inert gases in the cylinders.

 

Innnnnnnnnnnteresting

Read my first post. I said it doesn't open at WOT ;)
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Originally posted by n8:

Oh, the only knock I have ever seen is WOT knock..

 

Does part throttle knock exisit?

Oh yes, it may not be as pronounced but it does happen. On a car that is suppost to have EGR and it has been disabled or is simply not working you can get a VERY pronounced spark knock at part throttle. Reason is that the motor can be run LEANER with EGR, and eht fuel maps take into account the EGR and expect it to be there. If it is disabled and the computer leans out the motor and advances the timeing, which is exactly what a part throttle sensing computer WILL do, it can bang REALLY hard. (Read that clatter like a diesel).

 

The guys that are saying that their EGR either doen'st work or makes no difference, unless you are remapping your fuel with an FMU, it's most likely working. If it wasn't, you would hear it rather well.

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Typically you will notice a improved performance with removing the EGR, not saying it is a good idea to run right out and do it:) Not so much on the 4.6L's, but on the 5.0's. It will trigger the CE light, unless you have the PCM recaled.

 

The inert gas will actually slow the burn rate down...the EGR actually has a spark adder in the PCM this is the reason for the knock. The EGR is not injecting inert gas to slow the burn, but you are still getting the timing...so your not running leaner your just running to much advance....as a loose term explanation:)

 

Regards,

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IS that proven performance, on a dyno, or it feels different because I was screwing around under the hood performance?

 

The computer is mapped to use the EGR, if the EGR is not working, the computer can't of course use it, and since it knows its been fucked with it will put the computer in limp mode and light the you shouldn't have been fucking with it/ it's broke get it fixed light.

 

I am curious to hear what your explanation is for why a car will run better without the EGR working properly.

It's obvious that it's there for a reason, car companies don't just add shit for the sake of having it. And if it makes it perform better to not have it, why do the Mustangs/Cobras/GTO's and the like have it? Those are purpose built hotrods, and the makers are in the middle of a horsepower war, so if the car performs better without it, why install it?

 

I hate to put you out on front street, but you are indicating something that makes little sence, if it was true the EGR circuit wouldn't be there to begin with, and we don't care for "loose term explanations" here, at least I don't. So spell it out.

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Originally posted by desperado:

Oh yes, it may not be as pronounced but it does happen. On a car that is suppost to have EGR and it has been disabled or is simply not working you can get a VERY pronounced spark knock at part throttle. Reason is that the motor can be run LEANER with EGR, and eht fuel maps take into account the EGR and expect it to be there. If it is disabled and the computer leans out the motor and advances the timeing, which is exactly what a part throttle sensing computer WILL do, it can bang REALLY hard. (Read that clatter like a diesel).

 

The guys that are saying that their EGR either doen'st work or makes no difference, unless you are remapping your fuel with an FMU, it's most likely working. If it wasn't, you would hear it rather well.

Your post now has me wondering. I was just thinking on a performance engine, BUT now that you mention it causing a knock, my truck has been knocking pretty bad lately (last 5k miles) BUT wont knock in 1-3 and in 4th it wont knock until ~70, in 5th it wont knock until I go up big hills at highway speeds (and give ~ 1/2 throttle to get up the hill), or go into a strong wind, or go above 65.

 

Originally thought it might be some water in the gas (as I has siphoned about 25 gallons out of the boat which had been sitting for a month). But 10 tankfuls later (all speedway gas, just like what I have run from day 1, not to bring up the gas debate, but call this a constant) it is still knocking.

 

Had the timing belt done (120k miles, didnt know if it had been done before, good idea either way), thought that was it, it wasnt. So how would you check if the EGR is sticking?

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No worries I like to be on front street:) When I say performance I am speaking of how the car drives of feels to the owner. You are correct that the manufacturer putt's it on for a reason, it is called emissions. If it is to be sold to the general public to drive on public roads the EPA will have the last say...and I don't think they care of type:)

 

Just as a rule of thumb for making better performance, don't put un-burnt, hot inert gas back into a clean, cool air charge...sort of defeats the purpose of the 'cool air is better' rule:) This is how it helps performance:)

 

I have never seen a car go into limp mode due to the EGR being disconnected, I have see alot of blower cars make 500+ rwhp with the EGR just caped.

 

I do apologize for the loose explanation there...I thought I gave enough explanation to fill in the blanks, again my bad:(

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Originally posted by desperado:

The computer is mapped to use the EGR, if the EGR is not working, the computer can't of course use it, and since it knows its been fucked with it will put the computer in limp mode and light the you shouldn't have been fucking with it/ it's broke get it fixed light.

My car ran a 13.4 with the EGR capped and the CEL on. Must be a bad-ass limp mode. http://rds.yahoo.com/S=96062883/K=dunno.gif/v=2/SID=e/l=IVI/SIG=11q9v6dcc/EXP=1108616598/*-http%3A//www.mrclam.com/smiles/dunno.gif
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Guest James C Hensler
Ford as well as every Manufacture has to comply with something called cafe! Corp,avg,fuel, ecom. The egr was a way to help out on emissions. I think on the 05 Ford did away with it all together.
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Originally posted by Assured Risk:

So how would you check if the EGR is sticking?
Depends on what kind of valve it is. If it's just a plain old diaphragm valve, apply vacuum to it and it should open slowly. If it's a positive backpressure valve, rev the engine at idle to around 2-3k RPM and apply vacuum to it and it should open. If it's a negative backpressure test with engine off and apply vacuum and it should open.

 

N or P is on the valve for negative or positive.

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