Do we really need the EGR system on our cars? I's main purpose is to reduce engine heat and emmissions, but there are ways of getting rid of heat that works well (hood vents ect.) So my question is how many have gotten rid of thier EGR system, how does the car operate with out one ( temp gauage ) ? and if I do get rid of my EGR system how do I go about making the changes so my computer is not looking for the EGR and throwing codes at me?

Well actually the EGR vavle preheats your intake and makes your engine run hotter. I have removed the TB heater and put a cap in between the manifold and EGR vavle on my 94 cavalier Z24 and it made a huge difference in under hood temperatures. and power. If you remove the EGR your computer will throw a code for it but if you can deal with the light then it will hurt nothing else. gas mileage, power, etc.

If you just block your EGR valve, you won't throw any codes. Only reason you'll get a code is if your EGR solenoid is disconnected/not working. If the solenoid is bad, you can shut off the code by jumping 2 wires on the solenoid which "tricks" the ECM into thinking it works.

So, if you don't want to use the EGR :

Just block off the valve by installing a solid gasket at either connection to the valve or the plenum.

My EGR has been blocked on my 86 V6 since I bought it, no heat problems, car runs fine. One thing you may have to do is back off your timing a couple degrees to avoid detonation, but it seems that most don't have that problem.

Dave

Boy.... some misinformation was just posted here.

EGR does NOT preheat the intake, EGR does NOT make the car run hotter.

EGR is exhaust gas recirculation, under light load it reintroduces a small amount of exhaust gases back into the intake to DISPLACE air/fuel mixture. This is done to act as a buffer since exhaust is already burnt and is for all intents now inert gas (usually about .3% O2 under these conditions left vs. 21% in the incoming air). This slows and cools the combustion process to keep it under 1500 degrees where NOx is produced.

This reduces NOx emissions under low load part throttle conditions.
This has ZERO effect of WOT power. This has ZERO effect on driveability if it's functioning correctly.
It also has about zip to do with underhood temperatures... it's to reduce combustion temp only and not while sitting still. It may help reduce underhood temps a wee bit in a Fiero due to airflow issues that are unique to our cars and the fact that it will effectively cool exhaust gas temps some.

This does have a major effect that a lot of people here ignore ... it saves exhaust manifolds from cracking. As a mechanic, one of the main things I used to see that went with a cracked exhaust on this vintage vehicle was almost always a non functioning EGR system.

So, I say yes... our cars need it, it's also breaking federal emissions regulations to remove or disable it, and the computer systems are programmed to calculate proper fuel mixture assuming that it is in place and functional.

Can you remove it or disable it without the feds showing up at your door? Most likely... But I think most people remove it "Cause that's just some %^&* they bolted on it don't need"... not understanding why it's there and what it does anymore than they understand an O2 sensor or Catalyst, or Evap Canister. It is all there doing something to make the air you breath better, and if the car has all those items functioning correctly, none of them will effect driveability in a bad way.

[This message has been edited by Scott-Wa (edited 03-18-2004).]

I have blocked off EGR on many engines with good results. EGR supplies a metered amount of exhaust gas by way of the EGR valve into the intake manifold except during idle and full throttle conditions. This reduces emissions by reducing combustion temperatures. All it is there for is emission reduction. Many people here on the forum say an engine is designed to run with EGR if it had it from the start, and they have melted/broken parts to back it up. I believe it was and still is a problematic device from the start ( it dates back to the early 70's). I have never thought introducing exhaust gas back into the intake ever helped performance, so that is why I block it off. Just my .02

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Tim
Red 88 Formula Auto 2.8 100K+ Miles - Hypertech - No Cat - No EGR

Murphys Law - "Nothing is as easy as it looks, Everything takes longer than you expect, And if anything can go wrong - it will, At the worst possible moment!"

One other very important thing that I have not seen mentioned here is the timing issue. In the stock chip, there is a timing table which advances timing slightly any time the EGR system is commanded on. If you remove the EGR system but don't change the chip programming, you could end up with holes in your pistons over time because the Fiero does not have a knock sensor to listen for the detonation you might get when there is no EGR. Or, you could retard your distributor timing a little to compensate but this would hurt your overall power and gas mileage.

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power corrupts. absolute power corrupts absolutely.

Custom Chip Burning | Fiero Engine Conversions | Turbocharging | www.gmtuners.com

Someone, please help me understand how introducing hot exhaust gasses reduces combustion temperatures. Let see, what is the other source feeding the intake, fresh external air. Much cooler than exhaust gas I would think.

Seriously, I'd like to know.

Larry S.
BTW: I've been running my 150,000 mile '86 GT with the EGR blocked 1hr 45min / day, 5 days / week, for the last 3 years. Why? I can't shell out $100 for the tube. The result? No overheating. 32 mpg. The car still runs like a champ.

[This message has been edited by swanthog (edited 03-18-2004).]

Cracked manifolds are more as a result of the 'loose' muffler/cat. From the y-pipe down, the exhaust is mounted on springs, which let the cat/muffler/etc move as the car is driving. The manifolds are bolted to a fairly solid engine block, so like a piece of wire that you hold at one end and move the other, the manifolds will eventually break (Fieros are not the only cars that suffer from the cracked manifold problem, there is a welding shop near where I live that 'specializes' in manifold repairs). You now see on cars made today a flexiable exhaust tube that is usually inserted before the cat to isolate the manifolds from the movement of the rest of the exhaust system. There was a post on here some time ago with someone on here that installed this system on their Fiero as well.

As for defeating the EGR - what's the point in the first place? Unless there is a proven benifit to doing it, why not leave it on? (runs and hides behind firewall)

Tim

quote Originally posted by swanthog: Someone, please help me understand how introducing hot exhaust gasses reduces combustion temperatures. Let see, what is the other source feeding the intake, fresh external air. Much cooler than exhaust gas I would think. Seriously, I'd like to know. Larry S. BTW: I've been running my 150,000 mile '86 GT with the EGR blocked 1hr 45min / day, 5 days / week, for the last 3 years. Why? I can't shell out $100 for the tube. The result? No overheating. 32 mpg. The car still runs like a champ.

My car is the same way, runs great and strong at 165000 miles...no EGR

As far as the engine temperatures, let me take a crack at this...don't know if it's correct:

If you introduce the exhaust gases (inert basically) into the intake, you won't get as big of a burn since you have more inert gas present than normal....dang, that still doesn't make sense...then you'd be wasting gas. Somehow it must not burn as hot as it would with normal air and no EGR. At least I gave it a shot .

Dave

quote Originally posted by Scott-Wa: EGR is exhaust gas recirculation, under light load it reintroduces a small amount of exhaust gases back into the intake to DISPLACE air/fuel mixture. This is done to act as a buffer since exhaust is already burnt and is for all intents now inert gas (usually about .3% O2 under these conditions left vs. 21% in the incoming air). This slows and cools the combustion process to keep it under 1500 degrees where NOx is produced.

Swanthog, this should answer your question.
Now one of mine has not been answered, maostly because I did not ask properly. If I were to remove the EGR from my car what would be the best way to compesate for the removed system? I was thinking reprogramed chip, or even a knock sensor, anyone add one to a 2.8 before that is not running turbo?

Hello,

Introducing hot exhaust gases actually provides cooler burning in the cylinder because (1) exhaust gas slows fuel from burning. Imaging if you mix fuel and 02, you get flames (you've seen a blow torch). Well, if you remove some fuel, you'll get less flames...same goes if you remove 02, you'll get less flames, but if you mix in an inert gas, you'll get the same heat, but with a larger flame (Same heat output, but over a larger area). Since Cylinder volume doesn't change, by inserting exhaust gas, the flame (peak temperatures) in your cylinders is less (cooler) and NOx is reduced. Nitrogen Oxides are the only pollutant the device controls. The hotter the temperature, the higher the NOx (The output is related to temperature squared, so the hotter you get, it's pretty much 4 times that for NOx output) so by cooling things down, even a little, you reduce NOx. Now at WOT, lots of gas, lots of air, but you need lots of power, so the EGR closes until you back off.

(2) For as hot as EGR gas is, it's actually slightly cooler then what is in combustion chamber after firing, so injecting it does cool without adding to the fire. However, this effect is minor, the fact that it doesn't burn in key.

In my industry, (Large Gas Turbines), the goal is lots of fuel, lots of air, but to spread that combustion over a large area to reduce peak flame temperatures and thus reduce NOx.

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Ben
1986 Buick Regal T-Type
1993 Pontiac Grand Prix 3.4L DOHC
1988 Pontiac Fiero GT
1971 Chevy Caprice 4dr Htp
1991 Chevy S-10 2wd LB

quote Originally posted by Mickey_Moose: As for defeating the EGR - what's the point in the first place? Unless there is a proven benifit to doing it, why not leave it on? (runs and hides behind firewall) Tim

Going to make a custom exhaust, just trying to see if there is a easy way to remove the system and boost performance, the answer is looking to be no, but the information here is proving to very useful and a good reference point for other ideas that I have.

Great88Fiero,

Thanks for the explanation.

Let's see if I'm getting this right so far. It seems that by adding an inert gas, which is by definition inflammable/inactive, you are displacing oxygen. Reduced oxygen results in a cooler flame. In your explanation, you say that the same heat is achieved with less oxygen. How is this so?

I like the torch analogy but it's been a while since I've used an Oxyacetylene rig. Isn't the flame more focused(less area) and intense when more oxygen is added? And in contrast, less focused( more area) and cooler with less oxygen?

Larry S.

[This message has been edited by swanthog (edited 03-18-2004).]

Even if you are lucky enough to have an 85 2.8L computer that you can add a knock sensor to, you are still going to have to have the knock retard code enabled in a custom chip. You can't just bolt all that stuff on and expect it to work with the stock chip. So if you are going to get a chip done, have the person doing the chip remove the timing advance in that table I gave you earlier. The problem with a knock sensor is that there has to be detonation before the knock sensor will pick it up, and the computer has a chance to retard timing. If this is occuring all the time then there is still a slight chance that damage can occur. Better to remove the EGR timing advance on the chip if you are removing the EGR.

To simplify what someone earlier said about EGR operation, the EGR valve introduces an INERT gas to the intake charge. The inert gas will not burn and displaces volume of burnable gases in the combustion chamber. Therefore, less fuel is burned (fuel= air/gasoline) and as a result less heat is produced. The reason why you don't get worse gas mileage with EGR operation is because the stock chip is set up to work with the EGR and the ECM is constantly monitoring O2 voltage and will try to maintain an overall air/fuel ratio of 14.7:1. So, in all actuality, your engine might run a little more effecient with an EGR system as far as gas mileage is concerned, although the gains will be minimal.

Darth Fiero has got it.

When you replace 02 with exhaust gas, the 02 sensor will see the engine get a little rich and will put a little less fuel into the cylinder, thus keeping it's perfect combustion ratio. Now, the ECM may lean out the injector if the EGR is told to open, so the O2 sensor may never see a change, that's for the ECM guru's to step and say (The ECM adjusts the timing for the EGR, it may adjust the fuel tables too). If that is the case, then just cutting out the EGR will effect engine operation, as it expects to see that exhaust in the cylinder.

For something that you can see, lets pretend it takes 1 gallon of Air to burn 1 gallon of Fuel. You pour them both in a 2 gallon container and it burns, and say an average temperature at 1000 degrees. What the EGR does it like adding empty space to that 2 gallon container...so now that 2 gallon container will only hold 3/4 of a gallon of Fuel and 3/4 of a gallon of Air (1.5 gallons total - 1/2 gallon with no Air/Fuel is there from the EGR, it just takes up space). It all burns, but now average temperatures are lower, say only 800 degrees because you now only have 1.5 gallons of Air/Fuel burning in a 2 gallon container.
Of course, Fuel=Power, so yes, the EGR does take power from the engine. However, with a cooler flame, you can add timing, thus gain power. Second, the EGR is only used at part throttle, so whenever you stomp on it, it closes you have all the power you need. There are various other little tweaks, but overall the EGR system works well. Another thing to note is the volume of exhaust is very small, so instead of talking about a 1/2 a gallon in the above example, it's more like a tablespoon.

I hope that makes things a bit clearer.

three words...

can of worms...

the opinions on ths are much like that of an a**whole, everyone has one, and everyone thinks there's is the |3est.

i took mine off when i first got the car. car never sees over 210, (have winaldl) i luv without it ill get a pic for u if u want on what i did to

pred1tor83, the facts on the stock chip speak for themselves. Almost 10 degrees of timing advance when the ECM "thinks" the EGR is on. If you are not having any problems then kudos to you, but I am just putting the information out there. If you don't want to heed my warnings then that is your business. I am just trying to save people from potential unnessessary major engine work down the road.

I have heard this piston burning thing for sometime when you disconnect the egr. I would like to hear from just one person that has his engine burn the top of the piston from disconnecting the egr.
Don

As stated the EGR only reduces NOx emissions. The reason you have NOx emissions is because the air/fuel ratio is set to 14.7 to reduce other emissions. In other words when the engineers found that the 14.7 A/F was great for reducing other emissions, It caused higher head temps which created the NOx. The EGR was added to reduce the head temps. Removing the EGR without changing the ECM could cause a hotter burn leading to pre-dentonation (pinging/knock) which can put a hole in the piston or burn the valves. You may not see the problems except on a very hot day. The EGR was removed off of my original 2.8L but the timing and fuel were redone to allow for it. I did it because you can get slightly better highway gas mileage, better part throttle response, and you have less problems with cracking EGR tubes. But that is about the only real gain.
At WOT your A/F is closer to 12.5 so you don't need the EGR during it.

If you remove the EGR and do the correct mods to compenate for it, You will have better throttle response, But it's not going to make the car any faster since WOT (wide open throttle) will stay the same.
The removing of the EGR started back with carb'd engines. The EGR would cause less power due to less vacuum below the carb and higher intake temps. So back in the day, you would remove the EGR, block off the exhaust crossover which caused the intake to stay cooler, and use larger jets to get back to the 12.5 A/F to get more power. With EFI, this isn't the case because you do not rely on the manifold vacuum to draw in the air/fuel mixture. The MAP (or MAF on other engines) sensor tells the ECM what the pressure is and fuel is metered accordingly. The Fiero EGR set-up does not have the hot exhaust gasses running thru the intake like the old ones. The EGR is mounted on the "Y" pipe and the inert gasses actually cool slightly because of the EGR tube. The other thing is you don't have a huge amount of inert gasses being sucked in so the intake won't see any real temp gains from it.

[This message has been edited by Oreif (edited 03-18-2004).]

I'm not sure if you're in an E-Check county, but just in case...

Over the summer I replaced the 2.8L engine with a new crate 3.1L. I pretty much the only things that were left on/in the engine from before were the intakes, timing chain cover, alternator, exhaust system, and some vacuum lines. I used new spark plugs, distributor, ignition coil, etc. So this was a well running new engine with new everything that would be replaced in a tune up. When I went to get an e-check, I failed due to high NOx. I went over all the vaccum lines again, and it turned out the EGR solenoid didn't have any vacuum running to it, and the EGR system wasn't working. Once I fixed that, I passed Echeck.

Just figured I'd let you know that if you remove the EGR system without trying to correct the NOx emissions somehow, you're going to have a hard time passing echeck. The EGR system really does lower NOx emissions.

In any case, goodluck!

-Jeff

quote Originally posted by Oreif: The EGR was removed off of my original 2.8L but the timing and fuel were redone to allow for it.

Oreif, I am curious to what exact changes you made. I am looking to eliminate my EGR system with a custom exhaust and would like a few options. I was thinking of a custom chip for my car to compensate for the EGR being removed but would need to find a new way to determin timeing advance, that part is got me stumped since the EGR seems to be a big part of timeing on the Fiero from what Darth Fiero posted.

quote Originally posted by OH10fiero: Oreif, I am curious to what exact changes you made. I am looking to eliminate my EGR system with a custom exhaust and would like a few options. I was thinking of a custom chip for my car to compensate for the EGR being removed but would need to find a new way to determin timeing advance, that part is got me stumped since the EGR seems to be a big part of timeing on the Fiero from what Darth Fiero posted.

There is a flag in the program as to when the EGR turns on. If you set it so the EGR doesn't ever come on, the timing advance doesn't happen. I don't remember what exactly what was changed. I had the chip programmed at a speed shop. They also did some other minor changes to the fuel and timing curve.
Come to think of it, The chip is still in my ECM. I'm just not using it with the carb'd engine.

quote Originally posted by Oreif: There is a flag in the program as to when the EGR turns on. If you set it so the EGR doesn't ever come on, the timing advance doesn't happen. I don't remember what exactly what was changed. I had the chip programmed at a speed shop. They also did some other minor changes to the fuel and timing curve. Come to think of it, The chip is still in my ECM. I'm just not using it with the carb'd engine.

Anyone have sugestions as to where I can get a custom chip to do this?

quote Originally posted by OH10fiero: Anyone have sugestions as to where I can get a custom chip to do this?

Most speed shops or places that do high performance engine work (Tuner shops) have the equipment.
Some dyno shops also have the equipment, but these tend to cost more as they re-tune the car on the dyno hence the dyno time fee's.

We will be burning our own ECM chip to use with the turbo we're putting on my 2.8 and yes, the EGR will be history. If you're not going to address the programming when you pull that EGR, I'd leave on and make sure it's working correctly.

Depending on dyno results and demand, we may make that (not street legal) chip available. If we do I'll post the info. As soon as I can get my hands on an extra 2.8 (this is a hint guys and it don't have to be a good engine) to use as mule for fitting things, we'll be making a high-flow intake manifold that engine. We build them now for MR2s, see trueleo.com.

I do custom chips for the Fiero 2.8. I can remove the EGR stuff if you like. Info is on my website: www.gmtuners.com

quote Originally posted by Darth Fiero: I do custom chips for the Fiero 2.8. I can remove the EGR stuff if you like. Info is on my website: www.gmtuners.com

Cool, thats just what I was looking for, thanks.

To those who have gotten rid of theier EGR sysytems, how do you the change?, what are some of the noticeable changes you can remember?.
I have to get a new exhaust for my GT and the hack shop that did the exhaust for the guy that owned the car before me used cheap material and the damn thing is falling apart in 6 locations. Want a few on hands opinions before I order a chip and have a new exhust put on.

Ok I disconnected mine for the fact that at 45 to 50 mph steady speed I could feel the car surging back and forth and you could watch the tach and see that it was not steady. also if you hand operated the throtle when car is sitting you could hear a slight miss in the exhaust. I took it to Pontiac and they had a Fiero expert and he said that the egr valve was not working right. he put a new one on and it did the same thing, so he disconnected it and it ran perfect. he told me he could not block it off but when I got home to disconnect it and forget it. I did this and it ran perfect. PS this was on my 84- 4 banger. I know this is a clean air thing and I go along with it. But anyone telling me that putting dirty exhaust into good clean fuel will make it run better I don't go that route. Also EPA did not require egr on large trucks and buses. you know why! because they needed that extra power.
Also if you fool the computer by fixing the egr solenoid valve on the V-6 to trick the computer then your timing will be advanced as usual and run better. All of you know that increaseing the timing makes the engine run better ( but not to much). So for me I have the egr disconnected on my V-6 and it runs perfect. I know I am violating the law, but laws are made to be broken. someday I think egr will be a thing of the past with the development of new fuel. All i can say try it both ways and if you can tell no difference then leave it hooked up.

Darth Fiero, how did you get the data on the EGR? I have been wondering about fuel curves on the V6 - any info on this?

When the egr is working properly, you should see a slight increase in fuel mileage. When the EGR is active, the ecm adds about 10 degrees of timing and pulls almost 25% of the fuel. Other than pumping loss/friction, you are running with 25% less engine than when the egr is not active. The feedback from the oxygen sensor will not fully compensate for this cut in the fuel and cylinder temps get kind of high. Just adding high octane to cover the spark knock is only half the problem. With as many people here who can burn a custom chip (some will do it for just the cost of the chip- about $5.00) there is no need in taking the chance.

no, our cars do not NEED the EGR. but, I would rather have a working EGR than not. but, I also do not find the cost of repairing the EGR worthwhile. so, if its working, I leave it in, and even maintain it, if its not working, I remove it. completely.

quote Originally posted by OH10fiero: To those who have gotten rid of theier EGR sysytems, how do you the change?, what are some of the noticeable changes you can remember?. I have to get a new exhaust for my GT and the hack shop that did the exhaust for the guy that owned the car before me used cheap material and the damn thing is falling apart in 6 locations. Want a few on hands opinions before I order a chip and have a new exhust put on.

I bought an 87 V6 with a toasted solenoid and blocked off EGR. I bought a new solenoid and reconnected the EGR and noticed no changes in engine performance/economy.

Dave

So, if the EGR solenoid is disconnected, the ECM therefore should know it isn't working, and NOT use the EGR added spark advance table. Right or wrong?

I put a new $120 solenoid on (old one rusted solid), and it worked for awhile, then got flaky. About once a day the car would have a high idle after the SES light came on. Usually, the light would go back out, but not always. This annoying, unexpected high idle has not happened since I disconnected the solenoid to try to isolate the problem. The EGR added spark advance table is interesting.

quote Originally posted by ScottF: So, if the EGR solenoid is disconnected, the ECM therefore should know it isn't working, and NOT use the EGR added spark advance table. Right or wrong?

this will also light the engine light - and I would hope the ECM would not use the EGR advance table

This is my 3rd v6 fiero (and I BEAT THE HELL out of these cars...) with NO egr... none have blown up.
As far as doing the correct thing.. I agree if you can do it cheap.. but the things always rusted out on me or the tube rusted a hole in it....
Now that I'm rich (kidding) and fiero is a summer only car.. perhaps I would reinstall an egr system..
BUT!!! I would rather invest in the correct CHIP....they do not rust out as easily..

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The ECM receives a signal from the egr solenoid that it is receiving vacuum and to adjust for the advance. If the ECM does not receive this signal from the solenoid then it will not do any advance for ignition. So if you fool the ECM to think it is getting vacuum then it will advance the timing as if it were working. I have explained this several times how to jump two wires together to fool the ECM. It works like a charm I assure you.
Don

Anyone know what the maximum advance the ECM can crank into the system?? Is that in the ECM tables somewhere? If we start with 10 degrees, and add 'normal' advance values, and the EGR adds another 9.5.....................

'60's Mopars will tolerate about 40 total, and I assume that's typical. But since the EGR only activates under relatively light loads, did GM design it to push the envelope, and run much higher advance settings under those conditions?? Maybe 50 degrees? If the EGR is disconnected, are we running only about 30 total advance? Can the computer be fooled so you can just measure total advance with a light like you can with a conventional engine? Gotta try it, I guess.