What exactly is the Egr for? What does it do for the engine? Is it needed to run right? Can I pass emissions without it? The PO unplugged the vac line to it and capped off the tube from the exhaust! Would it help or hurt my mileage to hook it back up? Any info/help would be greatly apreciated, thanks

 

It meters a small amount of exhaust back into the intake to cool the combustion slightly..keeps the NOx emissions down and allows for a slightly leaner mixture to be run. Some engines manage to pass emissions without them (unless you have a visual check), others not.
If it's functioning properly (!) it has little effect on power or mileage. I'd say differently regarding the 1970's versions..they were bad...but modern implementations are much improved.

 

Theoretically, the EGR valve is there to allow a metered amount of exhaust gas into the intake stream to "dampen the fire" and reduce NOx emissions (NOx is a product of elevated combustion temperatures - the nitrogen gas in the atmosphere is literally made hot enough to dissociate into atomic nitrogen - from molecular - and combine with oxygen in various forms.)

The EGR is "necessary" on high compression engines, because they run higher combustion temperatures.

On lower-compression engines (like ours,) the EGR's "reduction" in NOx comes at a price of a massive increase in HC and CO (products of incompleat combustion - HC is unburned fuel, CO is partially-burned fuel) due to the decrease in combustion temperatures.

(I still don't understand how routing 1200-1500*F exhaust gas into the chamber reduces temperatures, but I'm no petrochemical engineer.)

The EGR valve is of specious utility when it is useful, simply because the rerouted exhaust gas contains particulate carbon - which craps up everything in the intake (don't believe me? Unbolt your throttle body and flip it over!)

ChryCo was supposedly able to do away with the EGR for 1991 by altering cam timing slightly to promote "reversion" in the exhaust port, which retained a portion of the exhaust gas to achieve the same result. (This makes slightly more sense - at least you're not crapping up the intake with carbon, and you're able to delete a failure-prone part.)

However, a water/MeOH fog would be better, more effective, easy to add to the infrastructure in place, and it's older (and more proven!) technology, and is would have the beneficial side effect of keeping your intake tract clean - and potentially allow for the elimination of the catalytic converter as well, plus allow greater engine output (the water/MeOH fog system was originally devised to improve high-altutude performance of piston-engine aircraft in WWII...)

Why don't we use it? Because people can't be bothered to maintain their vehicles worth a damn anymore. And, FMVSS and EPA regs enable this (by disallowing deletion of systems that do more harm than good, or are not the best option for handling the problem with which they're associated.)

 

Adding a small amount of inert gas (exhaust.. it's free and available) displaces some oxygen and slows down the combustion event, lowering it's peak temperature. Sort of like partially smothering a fire.
Later Chryslers accomplished the same thing by tweaking intake/exhaust valve overlap allowing the intake stroke to pull back just a bit of exhaust.

 

But it's adding a hot gas - that strikes me as being like adding hot water to a pot of water on the stove to make it cooler.

And, leaning out combustion tends to increase combustion temperatures, because there is less fuel awaiting atomisation to absorb head from the system (essential thermodynamics.)

That's why using water/MeOH is so effective - and it allows you to run leaner if you like (you can get closer to LBL without damage,) because it adds something to the system that effectively absorbs heat from the system. The water also helps to steam-clean internals (carbon deposits have an affinity for water - water gets absorbed, flashed to steam, and literally blows deposits off of surfaces) and MeOH is itself a minor fuel and assists in combustion (akin to propane enrichment on a Diesel - a little trick I used to use to get trucks off of the scales when they'd been downchecked for excess particulate emissions.)

So, you have to fill the water tank. How hard can that be? Not very, based on my own experience (I've run water/MeOH on several vehicles in the past, and installed it on dozens more.)

As I said, the primary reason that systems like that are disallowed comes back to the idea that people can't maintain their vehicles worth a damn anymore - I was talking to one person years ago who didn't know that engine oil required changing - and had run the same fill for 40,000 miles! (It can be done, but it's a stonking bad idea and can cause a whole pantload of problems...)

(Grammar note - "it's" is a contraction for "it is," "its" is the proper possessive form. Sorry to be nitpicky, but it's just who I am. Precision of expression is important!)

 

I'm sure the overall increase in temperature isn't quite drastic as that - though it is indeed counter-intuitive. I believe EGR holds an advantage in winter during warm up. Also the principle is that the exhaust gasses are mostly not oxygen, the excess of which causes a lean mixture. In EGR the fuel-to-gas ratio is the same by simple volume, but since there is less oxygen it's more akin to running rich.

Indeed. Two coworkers of mine seem to have let their cars fall into similar fates. One didn't change the oil at all for the year he owned it, but an accident rendered that irrelevant; another's the bank (or whomever) would not reposess it when he declared bankruptcy because the engine had siezed.

 

That's one of the reasons EGR became necessary... mixtures were leaned out to lower other emissions, but that raised NOx levels by increasing combustion temperatures. 2500 deg F is the magic temp for NOx formation.
It isn't the physical temperature of the exhaust gas that cools combustion, it's choking the combustion event itself by displacing some of the oxygen, even though that does further lean the mix a bit.
You cool off a woodstove by closing the air dampers. Same principle in effect here.
Crude? You bet.

I agree 100% with you that there are other more effective means to accomplish this, but they all involve the vehicle owner having to take an active role in maintenance. Good luck with that, lol.
The manufacturers prefer passive devices (as opposed to those requiring operator involvement) even though they may be less effective because they are required to certify the emissions device will remain operational for 75K miles or some such period. They can't certify that when relying on the owner to keep refilling a tank.
Some people don't bother even to change oil, much less fill a "smog tank" periodically.
I'm waiting to see what the compliance level is with the diesel urea solution tanks. I bet it's pretty bad, at least on a noncommerical use level.

 

Before EGR, experiments showed that adding a small amount of inert gas to the mixture spaced the molecules slightly apart, causing a cooler burning and less NOx formation. It did not appreciably lean the mixure, just made it burn cooler. HC and CO levels dropped slightly too.
the inert gas used was Helium - but it was impracticle - the world supply of Helium wasn't enough.
About 1964 Chrysler was banned from selling some engines in CA due to excessive NOx. A guy that worked at LA Trade Tech - Evan Arnold, sent Chrysler the fix - he drilled a tiny hole in the manifold crossover, letting a small amount of inert exhaust gas into tne intake. They used his idea!
They called it a FLOOR JET.
They sent him a nice check - and a new Station Wagon. He saved the day! We often went to lunch in his new wagon.
Problem was the jets wore bigger, causing rough idles.
Eventually it evolved into a separate valve, controlled by vacuum and thermostats inhibiting opening until it was needed.
Today the valve is gone, the cam is ground to provide just a tad of residual exhaust.

 

Fine as it goes.

My primary problem is that, if I can remove extra components and retune the engine slightly to improve aggregate emissions, then get out of my way and let me do it!

No, not everyone can do this sort of thing. But those of us who can? Let us do it! I don't like having extra components on my engine that can be eliminated - and net a positive effect in doing so.

Hell, since I'm subject to regular emissions testing anyhow, how about you provide a sliding discount on registration according to emissions improvement? (Oh - and stop making the damned test cost more than the renewal, that's just STUPID. Paying an annualised sales tax is bad enough, having an effective biennial surcharge on that sales tax - even though it doesn't go to the state - is extortionate. Throw in that you pay more if you pass, and I have to wonder what they're thinking. It can't possibly cost eight dollars to send the certificate to Sacramento - it's done electronically in bulk, and probably costs about a dime each...)

I'm not opposed to emissions monitoring and reduction in theory or principle - I just can't stand the implementation, as it's intolerably silly and mostly backwards.

 

The "visual" check should be done away with. If your motor meets the numbers, it shouldn't matter how you accomplished that.

 

I've been saying exactly that for fifteen years.

- If you find a better way to reduce NOx, why not do it?

- Why should you fail for not having the "fuel fill restirctor" in the fill pipe - tell me just where you can find leaded fuel anymore? (If you put Diesel in your gasoline-engined car, you shouldn't be driving in the first place.) I haven't seen "regular" gasoline since about the time I came out to CA - in 1990. Last place I saw it was driving through Kansas, and that was over a dozen years ago!

You know, things like that.

 

It's possible to tune it so it passes without some of the devices. BUT it doesn't last long. The devices are to cut the emissions down even when it's out of the fine tune necessary.

But - if you'd rather dispence with the requirement of the devices - cat, pump, etc, it could be made so you'd have to get it tested more often - like once a month, once a week, or so to make sure it stays in the state of "perfect tune."

I was part of the lubbying in Sacramento to get the interval down to 2 years - some politicians wanted it done every 6 months, some every year.

The $8 covers the cost of the computers and the data base records. If I remember right, the politicians wanted $50.

Government always grows - that's why it's so important to vote - get the money grabbing freeloading politicians out!

 

"Cost of the computers?" They're paid for - should be low to nothing.
"Database records?" It's automated, ergo zero labour.

My Jeep gets forced into "Test Only" stations - last time I had to do it, it was $90 for a $50 renewal (and another $8 for the "certificate" - if I've got to pay for a cert, dammit, I want a copy to go with the report!)

As far as I'm concerned, every station is "Test Only" - given my experience, I can barely trust them to properly identify the #1 spark plug, and don't tell me he knows what he's doing when he stalls my clutch on an unloaded dyno (if you're going to be stupid, how about you let me drive?)

And, I keep having to take my FSM in for smog, because the VECI saying that the vehicle is "pre-OBD" isn't enough. I keep getting docket for a "Nonfunctional CEL/MIL" - there's a window, it's a holdover from using the OBD-I GM V6-171 engine and control system. I've had to explain that little datum so many times that I'm about to have it tattooed on my forehead. There's not a bulletin or list that goes around? I pay CA enough, they should be able to distribute something (if they're not going to fully inform all of their people, then I shouldn't have to pay so much for the damned tags.)

Voting? Yeah - every election. I'm marking my ballot right now, in fact (after a run-in with the NBP in 2008, I've registered "Permanent Absentee." Not because I'm afraid of those nitwits, I just don't feel like having to go through that much paperwork again anytime soon. Even though it was four-on-one and very clearly self-defense, I spend the next four months leading with legal crap - but they're doing five years for ADW, ten more for voter intimidation, and I'll probably have moved out-of-state by the time those halfwits are loose.)

Politically, I'm too far to the right to be a Libertarian these days, but that seems to be pointless in CA - not simply for relative geographic location is this called the "Left coast."

However, when my wife and I leave the state, we promise to not bring CA with us. We'll be leaving because we've had enough - why start the cycle of asininity all over again?

EDIT - Besides, doesn't the testing interval run semi-annually, annually, or biannually depending on location? Or did they finally get that mess under control? (As if Smog Check II isn't bad enough.)

It's not the idea of Smog Check I have a problem with, it's the execution. The problem with letting politicians and functionaries write the rules is that they often have no idea of the subject matter they're trying to control (and they won't listen to me, because I don't have more letters after my last name than in it...)

 

Sounds like you've had some bad experiences. Yours is modified from stock? There are prodedures to get it approved, then it's easy after that.

The computer system is much more than your home computer, it has to hold all the records for all the cars in California.

Yes, politicians wrote the laws, they only understand bribery and extorsion.

Good luck on your move to a backwoods state where they don't have inspections.

 

No emissions or safety inspections here in WI unless you are near the Milwaukee area. Plates are $75/year. That's it.
Plus we have cheese and beer.