those of us you live in states like mine which don't check emissions have no problems with free mods and I have done them all with no problems here. Sorry for you.

It's original intention was to compensate for preignition from the inability to retard timing. That's it. in the 70's when it came out, there was before the fuel shortage etc. Now it might be an emissions device moreso.

drivemusicnow said:

Oh, and as far as "dirtying" things up... PCV VALVE!!!!!! seriously, nothing like spraying oil, blow bye, and hot air into the intake tract to REALLY get things messy.

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That's exactly why people run catch cans.

Honestly, who really cares what the original intention was? We now have ECU's that can correctly control timing to prevent knock and EFI that keeps the mixture where it should be to prevent knock. That leaves the EGR as an intake poluting emissions device.

America has an obesity epidemic correct? Good ole Uncle Sam desides he's going to help everyone out. Its now federal law that everyone eats 5 cotton balls with each meal to make them full faster. Does that solve the fat problem? Yes. Will the cotton balls kill you? No. Are they good for you? No. Could they be replaced with real food that will give you more energy to burn? Absolutely.

Dumb example but its the same principle. As someone else mentioned before, just because its a federal mandate doesn't mean its the best solution to the problem or even good for the system.

I've never understood the logic of contaminating something to make it work less effciently in order to prevent heat. That's like telling your employees to do a half a$$ job because they'll be less tired that way. That's the standpoint I'm coming from.

Keep in mind the EGR isn't even opened under light cruise situations (or at least it shouldn't be because my electronic unit on the saturn wasn't). Its used MOSTLY under high load/light throttle. This is when combustion temps will be able to climb to the nox creating point during light throttle. So think about this. Why do we have this intake tract polluting decive that only reduces emissions under <5% of driving situations? Uncle Sam. Why do newer cars have close coupled cats that are severely restrictive and substantially reduce power and create excessive combustion temps and back pressure? Because the EPA needs to kill power and knock resitance all the time in order to get a 10 second quicker cat light off which will reduce warm up emissions for the first 0.1% of your typical drive to work. Federal efficency at its best. So now we can add more EGR to compensate for that close coupled cat raising cylinder temps and creating knock. Then your dealer can sell you a $150 fuel injection service every 2 years to clean the deposits left by that EGR that's compensating for the cat that's cleaning air for an extra 5 minutes on the year. All the while your new car is making 20hp less than it should because of reduced timing and excessive restriction. Just to save a miniscuile (sp?) amount of air that will later be grossly polluted by the factories making all this stuff to save the air (as mentioned by someone else).

So as far as saving the earth, I think people need get off their high horses and stop listening to the government and the EPA, two of the world's most inefficent and illogical organizations.

If you want to know just how badly emissions tuning in new cars effects power. I was told by the regional Toyota rep that the new Avalon's 3.5L V6 which is rated around 280hp in the Avalon, will make 340hp without breaking a sweat. Simply be changing the tune to one that doesn't take emissions into consideration.

how much do you gain from removing the egr anyway?

dsmracer2005 said:

how much do you gain from removing the egr anyway?

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Not enough to EVER notice. Probably a fraction of a horse and only at partial throttle. It mostly opens at deceleration when you aren't using any power.

well if that's the case sounds kind of stupid making your car illegal for half a horsepower

because you get to say in the back of your mind you get to say F the government. HAHA Its good for eliminating boost leaks and cleaning up the engine bay. Whatelse is there to discuss..
When was the last time you saw a aftermarket manifold with an egr hole?????

99gst_racer said:

For example, this second sentence of the first paragraph, "Way back in 1972 GM used them in an attempt to reduce emissions of oxides of nitrogen (NOx) which were a major cause of air pollution."

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Entirely accurate. And, early STP EGR kits had a propensity for incinerating cars, especially air-cooled VWs. You have no idea how much we hated them.

That clearly states what their original intentions were with the EGR.

And then further down: "The automotive engineers figured that they needed to do something to lower the peak combustion temperatures....... So they invented a way to allow some very inert gas to get back into the combustion chamber only when needed."
And now it states that it is for reducing combustion temp and knock.

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Which they now are. That they also reduce part-throttle/load NOx emissions are another benefit. It's not a "knock control" device.

The EGR valve. I'm going to say one last time. It was invented for the sole purpose of knock. GM made it cause they had a lot of drivability problems because of no way to retard timing on the older cars. Period. It doesn't open at idle, or any throttle position except light cruise. It runs off ported vacuum.

Puller said:

The EGR valve. I'm going to say one last time. It was invented for the sole purpose of knock. GM made it cause they had a lot of drivability problems because of no way to retard timing on the older cars. Period. It doesn't open at idle, or any throttle position except light cruise. It runs off ported vacuum.

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Maybe GM did invent it for knock (still haven't seen proof).

But either way, it was put on the 4G63 motor for emissions only. That was it's purpose for our cars.

With that said, I don't recommend removing it unless you have a good reason to do so (and many people here don't).

Maybe they did it because Federal mandate requires an egr. Isn't there a federal law requiring all pasenger, truck, public, etc. vehicles to be built with an egr from the factory?

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No. Not all cars and trucks have a EGR valve from the factory,all the way to the current model year.

Puller said:

under light cruise, you're car is concerned with fuel economy and emissions since this is what most sane people drive daily. you are running as lean as possible in order to extend fuel economy. as we know, lean conditions are hotter, which in turn creates preignition, which we know is bad. adding inert gases from the exhaust cools and combats knock. instead of dumping more fuel in and hurting economy, these inert gases are added.

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if your so damn worried about being economical..you should NEVER have bought a DSM.

I never said I was worried. I explained its purpose.

I have a somehwat related question. Would running H2O injection be a decent substitute for en EGR? I understand all the usual benefits, but it would be adding inert gas/liquid into the combustion chamber. Would the final emissions result be lower nox?

Here's some insight:
As for vehicles "Not Having EGR's", Camshaft's have been designed to create more lift and a slight overlap at the end of the combustion cycle eliminating the need for EGR's
After reading this article written by a couple of Engineers at NMSU I would say it's pretty clear why the EGR was implemented on passenger vehicles.

In 1970, as stated earlier, Congress adopted the first major "Clean Air Act" (And EPA) The EPA sent forth standards on auto emissions requiring new cars to meet .41 grams of Hydrocarbons (HC), 3.4 grams of Carbon Monoxide (CO) and .4 grams of Nitrogen Oxide (NOx), per mile. To put this into perspective, the typical car in 1960 emitted nearly 13 grams of HC, 87 grams of CO, and 3.6 grams of NOx per mile. The first step in attempting to meet these requirements was the addition of the air injection pump and Exhaust Gas Re-circulation (EGR) valve. Air injection is a system that introduces fresh air to the exhaust manifold. This helps raise the exhaust temperatures which promotes continued combustion of the exhaust gases. The hot (partially unburned) gases leaving the exhaust valves receive a fresh shot of air, causing them to 're- burn' as they leave the manifold. The air injection also helps promote the chemical reaction which takes place inside the catalytic converter. The catalyst system, located in the exhaust flow, needs to reach an operating temperature of approximately 300 deg. F before it is effective.
The EGR system was designed to reduce the NOx emissions. The valve routes unburned gases from the exhaust manifold back to the intake manifold where they could be reintroduced into the combustion chamber. NOx emissions are a direct result of extremely high temperatures (2500 deg. F) which occur during the combustion process. Exhaust gases are considered to be relatively inert and cannot support the combustion process. Therefore, introducing exhaust gases back into the air intake system will dilute the air/fuel mixture and, in turn, reduce the temperatures achieved during combustion. The problem with this theory is that it can also have a very negative effect on the performance of the engine if the gases are introduced at the wrong time.
The first EGR valves were controlled by a relatively simple process which utilized manifold vacuum to open and close the valve. Basically, the valve would open when manifold vacuum was at its peak, under load, and close during reduced manifold vacuum. There were no electronic or mechanical devices to determine the valves position. This resulted in performance problems due to valves not functioning in a timely manner. For instance, if they were to stick open during low rpms, the engine would operate extremely rough. This condition resulted in the research and design of a better valve that would have to be able to "sense" when it should be opened or closed.
Today’s EGR valves have evolved into electronic control systems which utilize solenoids and position sensors in order to function properly. During the evolution, the valves were hybrid which consisted of part mechanical and part electronic. The vacuum portion would control the opening and closing and the electronic position sensor would report it’s position to the vacuum controlling device. The vacuum controlling device could then adjust the amount of vacuum applied to the valve which resulted in a much more efficient system.
The latest EGR valves, General Motors in particular, are completely electronically controlled devices with no vacuum input required. The valves have three built-in solenoids that are connected to three different size openings for gases to flow. The valve can open any one, all three or any combination of the openings to control exhaust gas flow depending on the engine load. To determine engine load, the valve uses inputs from the Mass Air Flow (MAF) sensor, the throttle position sensor and engine RPM. Also, in order to prevent exhaust gas flow on a cold engine, the coolant temperature is monitored. Through the use of sensor controlled EGR valves, NOx emissions have been reduced dramatically.

If you've read this far it means you might be interested enough to take a look at what the future holds when it comes to NOx reduction, why say EGR when you can say PLASMA


http://www.gm.com/company/careers/career_paths/rnd/prj_knocking_out_nox.html



Ciao,
Steve

This may seem a little off-track, with all the egr valve removal pro's and con's, but allow me to refer back to the original post if I may...

As far as the engineers are concerned with all their r&d work and millions of dollars poured into research, we aren't as smart as them, thats true to a point. However, you must realize they still have restrictions and boundaries to their work. They have to be compliant with so many things its unreal. The free-mods are little ways we help to make the cars more fun assuming we know what we are doing. There are no guarantee's, apologies, and the only people responsible are those that take matters into their own hands. True, most free-mods do little to help performance, but they are ways around what those highly paid engineers were forced to incorporate in their design.

Now, back to the egr debate at hand....Do I run one? Yes. On every single car I've owned. How many times have I been told I should take it off for more power? Several. Does it make a noticeable difference? No. Why don't you see them on race cars? You might on some, but for the most part they don't need them, so an egr valve is just that much more dead weight the car has to carry. If I were to live in an emissions free state and had to choose between and expensive egr and a cheap block off plate, I would be a tight ass and get the plate. If for some reason I started having drivability issues, a new egr would most definitely find its way under the hood.

Catalytic Converters! If you think you have a problem, replace it, don't gut it. Todays aftermarket cats flow like crazy, not like the old school bead filled units. You will lose more than you think you gain if you gut it.

The only free-mod I've had an issue with is bypassing the safety switch for the clutch. That is probably the most dangerous one on the list, and I can't say I've ever owned a car that had throwout bearings go out before the clutch did. Maybe that says something about my driving....


I guess it all comes down to this; Just because you CAN do something, doesn't mean you should. Think about what you are doing before you do it and see if its really something that is going to be worth your time and money, should it fail and make something go BOOM.

99gst_racer said:

That link contradicts itself.

For example, this second sentence of the first paragraph, "Way back in 1972 GM used them in an attempt to reduce emissions of oxides of nitrogen (NOx) which were a major cause of air pollution."
That clearly states what their original intentions were with the EGR.

And then further down: "The automotive engineers figured that they needed to do something to lower the peak combustion temperatures....... So they invented a way to allow some very inert gas to get back into the combustion chamber only when needed."
And now it states that it is for reducing combustion temp and knock.

So which is it?? I understand that Mitsu. wasn't the first to use the EGR valve, but I am curious to know if they chose to use it mainly for emissions or knock control.

Click to expand...

It was for Emissions.

HOw do I come by this startling conclusion? Becasue I have owned the same make and model of vehicle on both sides of "73 street". MY MGB had no EGR in 72, had it in 73+ and after 75 had a different distributor with vacuum retard instead of vaccum advance. (more emmisions bogusness) and a cat.

Everything on the car was the same electronics and fuel wise except the head had openings for the egr rail. I dumped it and noticed dramatically better performance. Beleive me, with a 90 hp vehicle you really notice 5 extra horses.
ON my talon it works, but if it ever quits I'll get rid of it. EGR is a stupid emissions idea, that no manufacturer would EVER use if they did not have to by law.
And yes true European cars that did not have it drove a WHOLE lot better than their American spec siblings

bestwestranger said:

The only free-mod I've had an issue with is bypassing the safety switch for the clutch. That is probably the most dangerous one on the list, and I can't say I've ever owned a car that had throwout bearings go out before the clutch did. Maybe that says something about my driving....

Click to expand...

As far as teh clutch safety switch.
It's liability, not safety. The same reason why pedals are spaced so far apart now, especially on automatics (audi idiots hitting the gas instead of the brake). My car is TT'd so it is sitting in neutral all the time, and even if it wasn't, I was driving cars that never had them, and that is what I am used to.
Having to sit in the car jsut to start it is one of those dumb ideas that started back in the 70's with in seat pressure switches (not clutch switches).
And it is not for the throwout bearing but for the THRUST bearing... ie C walk. PUSHING THE crank into a DRY bearing and then starting the car just seems dumb to me.

Puller said:

The EGR valve. I'm going to say one last time. It was invented for the sole purpose of knock. GM made it cause they had a lot of drivability problems because of no way to retard timing on the older cars. Period. It doesn't open at idle, or any throttle position except light cruise. It runs off ported vacuum.

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Say it however many times you want.

Doesn't make it true. it Is emissions... No one even MONITORED "knock" back in the 70's
It was calling pinging back then., and if you read the above facutal statement it was "invented" to reduce NOx by reducing combustion temps, and first started being used about the same time as the AIR injection pump. Why because the pump and cat wouldn't do anything for that one item. Yes it has gotten better in functioning, and less problematic, but it still is only incidentally realated to "knock" by virtue of reducing temps. Kind of like adding a bigger turbo may sometimes help improve gas mileage vs the quick spooling t25. You don't add one for GAS MILEAGE, that is a possible incidental improvement.

The sky is falling...

The Sky is falling...

The sky is falling.

Still not true no matter how many times I read the story.

Attack Eagle said:

It was for Emissions. It still is only incidentally realated to "knock" by virtue of reducing temps.

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That, I do agree with.

Puller said:

It's original intention was to compensate for preignition from the inability to retard timing. That's it. in the 70's when it came out, there was before the fuel shortage etc. Now it might be an emissions device moreso.

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For the most part you are correct, but let me clear these things up:

1) EPA mandated a 3.0 gram/mile NOx standard starting in 1973. This is what forced the manufacturers to add EGR. This is why DODGE started with EGR in 1971 (California models) and Most of their light duty passenger car lineup in 1972 (and light duty trucks with the 3.7L 6 banger). Buick was the only GM division with EGR in 1972.....All the rest came in 1973.

2) The reason NOx became an issue is that the manufacturers were using leaner mixtures and later timing to be in compliance with the HC and CO regulations.

3) Vehicles non-computerized vehicles use both ported vacuum and venturi vacuum to control EGR operation, with Venturi vacuum being a better indication of load, but with less vacuum available to work the diagram, usually requiring a amplifier or reseviour.

4) EGR flow is more directly controlled by backpressure (positive or negative), not the vacuum source, since EGR is controlled up to 6-10% total cylinder volume depending upon cylinder loading. It is also usually controlled through a temperature switch to prevent it from applying when the vehicle is cold as well.

5) EGR does increase fuel economy slightly when used in a light cruise mode, it's benefits are reduced as load (and loud pedal) are increased. This was a side effect, but now is incorporated with ultra lean mixtures to meet CAFE standards.

6) EGR does allow for more advanced timing since it does cool the combustion process and reduces the amount of heat absorbed into the combustion chamber, spark plug and valves, but this was not any of the manufacturers goals, it was benefitial side effect as well.


I run my EGR valve. Need more acceleration? Give it more pedal, when the vacuum drops and boost rises the EGR is turned off.

In the end its a personal decision, but remember: Everyone who drives contributes to air pollution and the losses imposed by running these emission devices is pretty small. I personally try to have a little better air quality for my kids sake.

Tweaker_911 said:

The first step in attempting to meet these requirements was the addition of the air injection pump and Exhaust Gas Re-circulation (EGR) valve. Air injection is a system that introduces fresh air to the exhaust manifold. This helps raise the exhaust temperatures which promotes continued combustion of the exhaust gases. The hot (partially unburned) gases leaving the exhaust valves receive a fresh shot of air, causing them to 're- burn' as they leave the manifold. The air injection also helps promote the chemical reaction which takes place inside the catalytic converter.

Ciao,
Steve

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I didn't read the rest of what you wrote because I had to clarify this statement you made. Which is slightly wrong.

When they first started use catalytic converters they were only 2 way cats as opposed to the 3 way cats used now. So in order to reduce the 3 main emission components from a SI engine, NOx HC's and CO's, the engines were ran rich which reduces NOx however this resulted in lots of HC's and CO's being emitted from the engine. This is where the air pump and catalytic converter come into play. Keep in mind that NOx is already reduced. The excess HC's and CO's in the exhaust stream need excess air to burn inside the 2 way cat. So the air pump pumps excess air into the exhaust system to provide the extra O2 so that the excess HC's and CO's can combine into (CO2 and H2O) chemicals that are found everywhere. It takes the 2 way cat to achieve this along with running the engine rich and introducing excess air into the exhaust. It doesn't just start happening in the exhaust.

The new cats are 3-way cats so they don't need the air pump, however they do require the engine to run at as close to stoicheometric as possible(14.7:1 air/fuel ratio) and when the engine is ran at stoicheometric the cats are something like 99% efficient at converting HC's, CO's, and NOx into inert gasses.

Arod said:

So in order to reduce the 3 main emission components from a SI engine, NOx HC's and CO's, the engines were ran rich which reduces NOx however this resulted in lots of HC's and CO's being emitted from the engine. This is where the air pump and catalytic converter come into play. Keep in mind that NOx is already reduced. The excess HC's and CO's in the exhaust stream need excess air to burn inside the 2 way cat. So the air pump pumps excess air into the exhaust system to provide the extra O2 so that the excess HC's and CO's can combine into (CO2 and H2O) chemicals that are found everywhere. It takes the 2 way cat to achieve this along with running the engine rich and introducing excess air into the exhaust. It doesn't just start happening in the exhaust.

The new cats are 3-way cats so they don't need the air pump, however they do require the engine to run at as close to stoicheometric as possible(14.7:1 air/fuel ratio) and when the engine is ran at stoicheometric the cats are something like 99% efficient at converting HC's, CO's, and NOx into inert gasses.

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Your statement is simply incorrect.

EPA required a 90% reduction in tailpipe emissions for new 1975 and 1976 motor vehicles. The manufacturers were forced to REDUCE CO and HC by the early 1970's and this resulted in LEAN air/fuel mixtures that INCREASED the amount of NOx formed. The manufacturers then started adding EGR to reduce NOx as required by the federal government in 1973.


Starting in 1975 and up until about 1980 oxidizing catalytic converters (2 way cats using palladium and platinum) were used to help reduce the HC and CO. Catalytic Converters are pretty efficient (but not 99%- 75% efficient maybe on NOx, a little better for CO and HC- and that's with high quality cats) when the air/fuel mixture is balanced. TOO rich or TOO lean and the catalyst doesn't work very well at all. Beginning in 1980 they switched to 3 way converters that had a separate area that used rhodium to break down NOx into Nitrogen and O2. The 3 way converters also need the air to perform the same chemical oxidation for HC and CO. On many vehicles, they were able to eliminate the air injection simply because they were able to run lean enough mixtures (notice MOST TBI chevys don't have air injection?) with the introduction of fuel injection. Other manufacturers like FORD kept air injection on most all their V8's until 1995, since they ran them richer (hence less oxygen left over after the burn process) for drivability reasons.

Also on vehicles equipped with air injection: When the engine is cold, air is injected upstream into the exhaust manifolds to allow the HC and CO present to blend with the additional oxygen along with the heat of the exhaust manifolds to indeed start the reduction of the two gasses. The heat generated as the burn continues also helps to heat up the catalyst. As the vehicle warms, the air is then diverted downstream where it is chemically combined with the HC and CO to form the components you stated (CO2 and H20).

Please have an understanding of the systems before trying to altering history, physics and chemistry. We are here to increase the knowledge, not add to any misconceptions.

Also- The Clean Air Act of 1963 formed the EPA and though them you can obtain most all this information.

I agree with both sides on this. Now it took me a little while to read though all the replies so if I missed it at 3 in the morning I am sorry. But, I'm not sure if Mitsu does it the same way GM does, but I know the main problem with blocking the EGR was the ecu still thinks it's opening and still advances the timing (like stated). This advanced timing also causes a hotter combustion chamber and the chances of hurting tops of pistons increased slightly. Now I do have basically every emissions device removed on my Fiero but I also have a not stock engine (not even the right one for the car) and tuning with a hacked gm ecu so I have control of all the settings. I am not against removing emissions devices for emissions reasons, but at least in GM standards, other things should be done to complement that mod.

Justin

EMX5636 said:

I agree with both sides on this. Now it took me a little while to read though all the replies so if I missed it at 3 in the morning I am sorry. But, I'm not sure if Mitsu does it the same way GM does, but I know the main problem with blocking the EGR was the ecu still thinks it's opening and still advances the timing (like stated). This advanced timing also causes a hotter combustion chamber and the chances of hurting tops of pistons increased slightly. Now I do have basically every emissions device removed on my Fiero but I also have a not stock engine (not even the right one for the car) and tuning with a hacked gm ecu so I have control of all the settings. I am not against removing emissions devices for emissions reasons, but at least in GM standards, other things should be done to complement that mod.

Justin

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you HAD to bring this god D@MN thread back from the dead, didnt you.... anyways, doesnt our cars retard timing to reduce knock (when knock is sensed by the knock sensor) so it really wouldnt matter because the timing would advance, and then retard to the most advanced it can be without getting knock? actually, dont answer that, just let this thread rip.

MyBeatGSX said:

For the record. My EGR is blocked off and my car failed the computer test (not egr related) and was then kicked to an old style sniffer test which it passed with flying colors.

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That is because at an idle, the EGR is closed. EGR only opens under load. If an EGR opened at idle, you would have poor idle, rich smelling exhaust, possible stalling, etc.