I'm preparing the parts to convert my '64 Valiant to a SuperSix. A '79 Aspen was the donor, so it's set up for EGR. I was going to install a blocking plate, but got to thinking that maybe it would be a good idea to install the EGR valve. With exhaust gas recirculation, I might be able to advance the timing a little more and perhaps pick up a bit of mileage and performance. Opinions?

Mileage yes, performance no. Only reason I know of for EGR is polution control... to burn anything that didn't combust the first time around. But conseqently, you are also feeding the cylinder with a mixture that won't burn any more because it already did the first time around, and you loose performance.

It is the equivalent of eating your own feces.... and that doesn't sound too tasty does it?

Actually, the cat has the job of burning anything the engine doesn't (hydrocarbons).
EGR's purpose is to lower cylinder temperatures to control NOx (oxides of nitrogen) emissions by injecting an inert gas.
The most convenient inert gas for this purpose is exhaust gas, so they pipe a little of it back in.
This is only used under cruise conditions, when the engine is probably a little lean (factory calibrations), lean mix = high cylinder temp.
WOT disables the vacuum operated valve, so it doesn't affect that mode.
Part throttle response should improve (assuming proper tuning), along with mileage.

I realize EGR wouldn't offer a direct performance increase, but it should allow more spark advance. Right now, I can only get about 2* advance before it begins pinging on 87 octane.

I'm not concerned about WOT conditions, since I seldom do that, but what about a torque increase at half throttle with another 3*-4* of advance available?

I'd say the increased advance would be tempered by the diluted charge, cancelling out most of the gain.
I don't have figures to back me up, though. Anyone else?

Hi all,

One of the leading components of engine exhaust is water vapor. Part of why EGR works at all is this water vapor is chemically active in combustion.
Quoting from http://not2fast.wryday.com/thermo/water ... mistry.txt

"As a side note - Volvo recently released some SAE papers documenting the use
of cooled EGR to both reduce detonation and return to a stoic mixture under
boost in the 15 psi range - while maintaining approximately the same power
output. Notice - they reduced fuel and still get the same power output.

When you consider that EGR consists primarily of nitrogen, CO2, and water ( to
the tune of about two gallons formed from each gallon of water burned ), you
might draw the conclusion that it also was not "inert". They peaked their
tests at about 18% cooled EGR - which would work out to about 36% water
injection and got about the same results under similar conditions that the
early NACA research got."

So, while I wouldn't go out of my way to add EGR, it may not be as bad as it sounds.

Greg

This discussion has veered way off track and the info being presented is theoretically unsound and not based in fact.

That Volvo setup used COOLED EGR, which is not at all the same as the hot EGR with which production cars are equipped. Cooled EGR is still a lab experiment, not yet on production cars, hence the SAE paper. The EGR system found on the slant is a "very hot" setup -- the exhaust admitted into the intake tract is super hot and contains almost no water on a unit volume basis. EGR as implemented on virtually all cars has *NOTHING* to do with water injection, which is a totally different, separate deal.

"Increased performance" from having an EGR system on a pollution-uncontrolled slant-6; this idea has absolutely no basis in reality. The exhaust as inducted *is* inert, it *does* reduce cylinder pressure and increase induction temperature, which *does* reduce performance. Period.

The thing about increasing the spark advance to get better performance is real, but only relative to the '71-'72 cars that had severely retarded spark as their one and only NOx control strategy. The '73 addition of EGR allowed the spark to be advanced *back to normal levels*, which gave back *SOME* of the performance. To put it in other words, the EGR system reduced performance LESS than a super-retarded spark did, while achieving these two strategies' common goal of reducing NOx emissions.

THe original poster's car will run best if he blocks off the EGR.

I'd still run EGR; if your engine is already detonation sensitive, it will allow more advance which will give you a little extra responsiveness and mileage. With gas as high as it is, it's nice to run the cheap stuff.
Also, I enjoy breathing, so if you can reduce emissions with minimal or no performance penalty, by all means do it!
Like it or not, our cars are "gross polluters" with no emission control for the most part. We should all be conscious of our impact on our surroundings.

Actually some of the members of this board do have to test their cars regularly. One truck member if I remember right passed with flying colors and he had no EGR, Cat. Convertor, but maintains his slant on a regular basis. You can't compare our cars to modern day standards, they weren't built for that, but if you're willing to add all the nice things that are on a modern mill, you would probably see better emissions and less power.
If you want a 'gross polluter' go check your lawn mower, any peice of diesel construction equipment, most two stroke motor applications, and most USA citizens with a 1980-1988 chevy...


-D.Idiot

I know the standards were different then; hopefully we're all learning from the past instead of living in it.
I mean no disrespect to anyone - kudos to everyone for trying to keep their cars in better than factory condition -that's why we spend so much time here!
We've learned a lot about handling/brakes/tires in the last 30-40 years and we use that knowledge freely to upgrade our cars to "modern" standards (or beyond); let's apply what we've learned about engines, too.
Modern cars are pretty impressive when you consider how well the average family sedan performs, and how clean they are.
Just adding EFI has worked wonders for many of us by enhancing power, driveability, mileage, and reducing emissions throughout the drive cycle.

See, but the thing is, the first-generation emission controls fitted to cars of the '70s and '80s like the later Slant-6s did little to reduce emissions in the real world. The Federal emissions certification tests (not the same as your yearly smog check, this—it takes three days and several thousand dollars) of the day were so grossly unrepresentative of any real-world driving conditions that the automakers had no choice but to "design to test", that is, make their cars so they'd pass the cert tests and deal with the enormous driveability and response/reliability problems in the aftermarket with TSBs. On the whole, EGR as implemented on the slant-6 was a kludge designed to get the engine through the NOx portion of the Federal cert test. In the real world, it does not enhance efficiency, it worsens it.

Well, 64convert, you wanted opinions; looks like you've got some to pick from.

Great discussions!

I think what I'm going to do is try it both ways. It's something that can be done in the real world without too much expense and a few minutes of effort. I'll be the test bed and report on the findings.

I'd still welcome more opinions...this makes good reading.

In order to try it both ways, you'll need to set up the whole EGR system. It's a lot more than just a valve and a vacuum hose! You'll need the EGR vacuum amplifier, CCEGR switch/valve and, if you are trying to have the least-primitive EGR system possible, the inhibit switch that prevents EGR in 1st and 2nd gear.

Once you've got this all set up, *then* it becomes a matter of connecting or disconnecting the EGR valve's vacuum hose to try it both ways. Be sure to keep careful track of fuel mileage.

I'll first say that 90% of what I say is based off of opinion, not fact(I"m 18, give me some slack ).

I've read that cars from the 70's with their emissions were prone to running badly, many cars not working well off the showroom. My 73 is lucky in having a very basic system, and only having an EGR. I've disconnected it and connected it and really can't tell the difference, and I'm not even sure if I have it connected right(I bought a hose and connected the only two vacuum connections I had un-used). The Slants are not horrible on emissions for the 70's, you don't see them with black smoke coming out they're back, at least not very often. If you're worried about the environment though then putting modern emission items on your car will help. As said earlier technology has came a long way and with money and efort if you stick modern emission items on a car you can get better performance as long as you don't stick the cat converter on your pipe. Personally with the quality of emissions controls from the 70's I hope to take as much out as I can to make my car run better, then I want to add feul injection and generally make my car more efficient. In my opinion a well running car's better for the environment then one with emissions equipment that has to have the gas predal pressed down at a stop light to keep it running and stalls often, or sounds like like someone took a hammer to the engine.

Thinking about it, my car's pretty advanced for it's time. I've had quite a few people be suprised that it's an electronic ignition for a 73. Bet they'd be really suprised about a 50's mechanical feul injection vehickle that I've seen(and wanted).

_________________
My car may be slow to sixty, but at least it's been reliably slow to sixty for more than thirty years.