I'm certain that this has been covered before but I'm exhausted searching. I want to know why someone would specifically block off one end of the EGR tube. When I search "block off EGR tube" I get alot of hits discussing blocking off the "EGR". I just want to know about blocking the tube. Why do it and what does this do to the emissions control system, performance, mpg, etc?
Thanks
indydriver in L.A.

If the system is working, there is a mistaken belief that it hurts performance but since it closes at anything over 50% throttle, it's doesn't really.

If it's broken, well its a huge leak.

Without it working you are unlikely to pass the NOX part of the test if they do it there.

It doesn't matter if you block off the tube or the EGR itself, It will disable it's function.
Some disable it because of vacuum leaks (The EGR tube is notorious for cracking over time)
Some think it helps performance or gas mileage. Because back it the 70's on carb'd motors it did make a difference. On the later cars (1982 and newer) it does not provide any gain.

The EGR allows inert gases from the exhaust into the cylinders to aid in reducing head temps. Head temps go up as you get leaner. The engine typically runs on the slightly lean side for emission purposes. When head temps rise, The level of NOx rises. The EGR reduces head temps and reduces NOx emissions.

As noted above it only works during cruising and has no effect on power at WOT.

[This message has been edited by Oreif (edited 03-04-2009).]

OK, this all makes sense now. When my mechanic did the smog test on my new Fiero, he found the EGR tube blocked off with a piece of foil, or shim stock. He also found the cracked EGR tube. So the shim was to dissable the system to allow the car to run ok but it did cause it to fail emissions test.
Thanks all.
indydriver in L.A.

quote Originally posted by indydriver: I'm certain that this has been covered before but I'm exhausted searching. I want to know why someone would specifically block off one end of the EGR tube. When I search "block off EGR tube" I get alot of hits discussing blocking off the "EGR". I just want to know about blocking the tube. Why do it and what does this do to the emissions control system, performance, mpg, etc? Thanks indydriver in L.A.

EGR means exhaust gas recirculation, it is a half-assed way to get a motor to emit less NOX (oxides of nitrogen). NOX is the major component of photochemical smog in large cities. EGR valves were mandated by the EPA back in 1973. From 1900 to 1973, cars didn't even have EGR valves- because emission laws were nonexistant.

Over in Europe and Japan, they still don't use EGR valves or CAT converters on their engines, and they still burn leaded fuel. Only in USA are emission standards so strict. It's a political tree-hugger issue.

By putting exhaust gas into the intake tract, the combustion event is cooled somewhat. Think of it like taking ashes out of the bottom of a wood burning stove, and throwing it on the fire- it will tend to put the fire out and cool it.

It DOESNT' cool the intake charge, because exhaust gas is definitely hotter than air/fuel mixture.

A lot of bad things then happen- power goes DOWN. The intake manifold becomes sooted up, and on the 3800 engines with plastic intakes, the heat cracks them. I for one don't want to put that garbage back into my engine.

another way to look at it is, if someone redirected a small portion of your homes sewage, back into your drinking water- for emissions purposes.

I have been unplugging EGR valves on my own cars for about 30 years now- the cars have never failed to run BETTER. In the old days, this would require running premium fuel, because the car many then ping under load. But on my ' 01 Monte 3800, I can run regular, the modern OBD2 systems manage the spark and retard the timing, when the EGR is unplugged.

you don't have to block the tube- just pull the connector on the electric EGR valve- done deal. It will throw a CEL code, but who cares- the car will run better at part throttle- WAY better.

quote Originally posted by no-EGR: dude, I don't know how to say this, so I'll just say it bluntly- you're wrong there. I ran my GTP for 5 years with EGR unplugged, it makes more power at part throttle, way better driveability- and the same mileage. I also ran (2) Saturn 1.9 DOHC commuters to 220,000 miles each, with EGR unplugged the whole time. They had WAY more power with EGR off. Why do you think places like Intense put EGR delete right in their computers ? An engine was designed to burn fuel, not reburn exhaust. If it wasn't for the stupid emission laws, that EGR valve would not even be on there.

of course it make more power at part throttle - but - who cares? its part throttle.
EGR is inactive - and has ZERO affect on full throttle.

EGR delete is an option because many just dont want to install one.

EGR is an item which improves milage on light throttle. if you dont drive at light throttle much - you'll never miss it. I dont miss mine. Havent had an EGR connected for a over 5 years now. I removed mine for the same reason most do: dont want to fix the broken EGR system.

there are no gains to removing a working EGR. tho, there are plenty gains with removing a broken EGR system.
part throttle power is moot - much like the old Spinal Tap "It goes to eleven" - its all equal at WOT

This has been debated for years now. Here is my recent story...
I had my 87 2.5, 5-speed in for emissions testing. It failed on the CO emissions at idle and cruise. Without getting into what I did to get it to pass as I think the bottom line was the O2 sensor that was not quite right. In the process, I completely blocked off the EGR valve with a plate and plugged the vacuum line. Not only did it pass emissions testing the CO was almost nonexistent the NOX was unchanged and the seat-o-the pants dyno shows significant increase in power.

Now for the other side of the coin. I used to sell remanufactured engines for several large name rebuilders. I have seen failures due to detonation caused by what we assumed were a malfunctioning EGR. A lot of things can cause a lean condition resulting in detonation. (Knocking and pinging). With a carbureted engine I would have to say that to run lean enough to pass emissions and not detonate, you may need an EGR valve to compensate. With a modern fuel injected computer controlled engine it is my belief that the need for and EGR is not as great. If you have an engine with a knock sensor then probably you would not need and EGR valve for sure.

Our stock Fiero engine management system does not have a knock sensor but with the O2 sensor, it should not allow the engine to run so lean as to detonate. This is all assuming an otherwise properly maintained and functioning fuel management system.

Just my .02 worth.

Anyone care to chime in with a more scientific approach?

[This message has been edited by RCW (edited 03-04-2009).]

Like no-EGR said, if you're gonna do it, unplug the EGR solenoid instead of just block it off, there's a vacuum sensor in there, so then at least the computer will know the EGR is not operational, and should adjust timing accordingly.

You might even have better WOT performance with a working EGR system, because it will keep cylinder temperatures down, so that when you actually floor it, it will be less detonation-prone.

your car will have more power and better part throttle driveability, without EGR. Also require less throttle valve angle to achieve a given power level.

EGR is so detrimental to engine performance, that if it opens at idle, the engine will simply stall- EGR is locked out by the computer at idle, WOT, and during open loop warmup for this reason- at WOT the car wouldn't have much power with EGR, because the higher exhaust pressure would fill the intake manifold with exhaust gas, and actually push the fuel out the intake and resist fuel flow into the engine. On some designs EGR is locked out during A/C compressor on mode, because the added strain of A/C plus EGR would cause severe driveability problems

EGR is BS, just unplug the connector, you won't regret it- it's Big Brother's way of getting into your life, by getting under the hood of your car. EGR is no different than Cat Converters, which basically filter exhaust gases with a restrictive honeycomb in the exhaust tract, and rob even more power.

pull the EGR plug, and "adjust" your converter with a sledgehammer and iron bar- knock the guts out of it, and MIG weld it back in place.

[This message has been edited by no-EGR (edited 03-04-2009).]

quote Originally posted by no-EGR: dude, I don't know how to say this, so I'll just say it bluntly- you're wrong there. I ran my GTP for 5 years with EGR unplugged, it makes more power at part throttle, way better driveability- and the same mileage. I also ran (2) Saturn 1.9 DOHC commuters to 220,000 miles each, with EGR unplugged the whole time. They had WAY more power with EGR off.

WOW, Are you way off. Even your previous explaination of how an EGR works is inaccurate and filled with wrong information.

"In the old days, this would require running premium fuel, because the car many then ping under load."

True, If you had no clue what you were doing. To correct the ping under load you just needed to re-tune it properly. While you seem to have an idea on how an EGR works, You seem clueless on how it interacts with other systems of the engine.

"But on my ' 01 Monte 3800, I can run regular, the modern OBD2 systems manage the spark and retard the timing, when the EGR is unplugged."

In case you don't know it, retarding the timing advance REDUCES power. Especially when it senses pinging/knocking under load. Many OBDI cars do not have knock sensors so disabling the EGR incorrectly could cause damage to the engine.

"Over in Europe and Japan, they still don't use EGR valves or CAT converters on their engines, and they still burn leaded fuel."

That is WRONG. Japan stopped using leaded gasoline about the same time as the U.S. I can tell you for a fact that when I lived in Japan in the mid-80's they did NOT have leaded gas at the gas stations. Some Eastern Europe countries still use leaded gas but not Western Europe.
There are only a handful of countries still using leaded gas and most are in the process of phasing it out. South Africa stopped using leaded gas in 2006.

"you don't have to block the tube- just pull the connector on the electric EGR valve- done deal."

Considering he has a stock 2.8L it does not have an electronic EGR your inaccurate advice will NOT work. So to disable it you can plug the vacuum and/or block the tube. It will not throw a code because the EGR solenoid will still function properly, It just won't turn on the EGR. You do need to re-program the computer so that it doesn't run too lean and ping under load.

"Why do you think places like Intense put EGR delete right in their computers ?"

Because if you build a high performance engine, You are building for peak performance not emissions. This mean the A/F ratio's are curved for max power not emissions. In order to operate the fuel/air mix properly you need to program it for the EGR delete so that it does not affect the A/F ratio or the timing timing advance. On a stock engine the programming is set up for emission contol. Just pulling the connector off the electronic EGR or blocking the EGR or plugging the vacuum on an older EGR is FOOLISH if you do not re-program the computer or re-tune it properly. With OBDI you risk pinging under load and with OBDII it will retard the timing advance resulting in LESS POWER.


Bottom line, If you disable the EGR system on a newer vehicle PROPERLY it will have no effect on power or gas mileage. If you don't believe it, Find a Dyno shop and run it once with the EGR hooked up and and once without the EGR hooked up. Any "butt dyno" gains are just a "placebo" effect.

The ONLY reason the older 70's cars gained power and gas mileage was because the EGR was controlled by a thremal vacuum switch. This caused the EGR to stay open longer than needed. Also many intakes used an exhaust crossover port which ran under the carb heating it up. So if you disconnected the EGR, Blocked the crossover port and re-tuned the carb, You gained more power and gas mileage increased.

[This message has been edited by Oreif (edited 03-04-2009).]