EGR Pros/Cons Info Request

EGR is an emissions device....and a bad one at that...quite a few newer more efficient engines don't have one at all, in theory the EGR valve takes burnt exhaust gas and runs it through the intake manifold again....the idea being to burn some of the fuel that was not burnt the first time...this reduces emissions to some degree from unburnt exhaust gas...that's the theory. In actuality I have found all the valve really does is foul up the intake manifold, if you have ever taken he manifold off I am sure y have seen the layer of black soot....quite a bit of that is due to the EGR valve....there should only be soot downstream of the combustion chambers. So I would eliminate the valve myself if you don't have to worry about emissions, or if you are exempt. Hell, I would eliminate it anyway, even if I have to have one on there to pass a visual inspection I would block the hose, or weld the valve shut, or something....I can't stand my intake being fouled up by EGR valves...I make a practice of blocking them off one way or another, call me an anti-enviromentalist if you will. One other effect the EGR valve has is that you engine warms up slightly faster(similar to those cars where they put a tube over the exhaus manifold to vent hot air to the air intake)

p.s. it isnt actuated under full throttle or similar conditions presumably because it would force too much exhaust gas(which has little or no oxygen) into the cobustions chambers, thus leaning out the fuel mixture with potentially catastrophic results....or at least thats the way I understand it

need is a subjective word, but no, it wont hurt your car to run without one, in fact it will keep the intake side of the engine cleaner and cooler, check your state laws before actually removing it though, I really doubt any cop will ever hassle you about it, with the car as old as it is, I doubt most cops even know that there was emissions equipment then(started in 67 if I'm remembering correctly)

you're good to go then...I love having a '66 even if I had to go through an emissions test with it, I still wouldn't need any equipment because there was none in '66...so 66 and older are automatically exempt in every state(except maybe CA, who knows what nazi laws they have there)

wicked93gs said:

you're good to go then...I love having a '66 even if I had to go through an emissions test with it, I still wouldn't need any equipment because there was none in '66...so 66 and older are automatically exempt in every state(except maybe CA, who knows what nazi laws they have there)

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actually the PCV valve is part of the emissions system, and in 66 probably the only emissions equipment, but it actually helps ring seal to some extent. BTW, some california cars in 66 had emissions control devices, not sure what, if any, they would be for a mustang but don't think that just because it's a 66 it automatically didn't have emissions equipment

Yeah, California DSO cars had PCV and Thermactor in '66. Of course if you were any where near the L.A. basin during the '60s & '70s you can understand the effects of NOx in the atmosphere, and the benefits of EGR.
EGR can be a good thing. It helps control cylinder temperatures during lean cruise, and increases fuel mileage. It is inactive under medium to heavy load, and idle. It does nothing detrimental to performance, when the car is tuned correctly. Different cam designs have varying amounts of "natural" EGR as well.

true....doesnt hurt performance at all...but I would still rather have a clean intake manifold, as far as lean cruise...I tend to tune my cars to cruise at 14.9-15.1 AFR...I don't like my engines ever really running leaner than that...tends to cause them to run rougher than I like

Keep 'em both until doing an H/C/I swap.

Platonic Solid said:

So EGR improves gas mileage? What about PCV, does that improve gas mileage too? I've actually been considering installing open emission breather caps on the valve covers and plugging the related carb and air cleaner connections.

Environmental concerns are not in question here as the car will never see more than a few hundred miles per year. Heck, I'm sure I produce more harmful emissions with my lawnmower, not to overlook the gas that I spill every time I use the retarded "safety-valved" gas can (what a joke).

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the PCV system evacuates combustion gasses, water vapor and nitric acid vapor, in the crankcase. It is definitely benificial, especially for the kind of use you plan. Run your engine to operating temps for at least 30 minutes or so before parking again and the PCV system will do a good job of keeping things like bearing material from getting eaten away.
When tuned correctly either way (PCV or no PCV), there will be no change in fuel mileage. The PCV valve is a "metered vacuum leak" so, if the carb is jetted for a PCV system, it will run rich without a PCV valve. An engine that is jetted for a non-PCV system would run dangerously lean if a PCV valve is added.

Personally, I don't get excited about NOx, but I do get excited about combustion temperatures (and the two go hand in hand). Ever hear a car ping under light load? That's related to combustion temps. When the air fuel ratio reaches stoich, CO and HC are low, but combustion temps and NOx are at their highest. The recirculated exhaust gasses don't burn, so they help cool the cylinders, and stave off detonation. This allows running more advance for the lean mixture (lean mixtures burn slower due to the extended distances between burn-able particles) and in an engine designed for an EGR system, will give a very slight improvement in "freeway" or light load gas mileage. Honestly the fuel mileage is really minor.
From my perspective, the biggest benefit is the reduced cylinder temperatures. On the super charged EFI engine in my '66 (which came out of my old '90GT) I kept the EGR specifically for this reason. It helps bring the temps back down after a hard boosted run.
From my experiences, if the engine is not designed for EGR, it's really not helpful, and adding it is a waste of time. The EGR will be naturally developed by valve overlap, and piston dwell time.
Bottom line, every part of an engine is engineered as a package. Keep that "package" together, and it is efficient. Mix the wrong components, and even the most expensive parts won't perform well.

If it were me, I'd keep both systems unless making a H/C/I change, at which time I'd talk to the mfg of the parts and get their recommendations as to the EGR. As for PCV, I'd keep it for sure.

well...I would say it also depends on the engine...for example, in the neon...under cruise my EGTs were in the 1400 degree range....not cooling anything in the combustion chambers(or at least I wouldn't think so) but then, that was turbo...even NA, I would think ambient air would be cooler than the 600 degrees NA EGTs usually are, so much for logic I guess

Ah, OK, I see what you're saying, Wicked.
What you're missing is that "combustion temperatures" and "exhaust gass temperatures" are similar but separate entities. You could have reasonable combustion temps with high exhaust gas temps in the exhaust manifold runners(such as a rich mixture that keeps burning in the exhaust, or late ignition timing that allows the gasses to exhaust while still burning).

While the theory can seem complex and difficult to understand, the practical aspect is much simpler. Just choose known good combinations, follow instructions, and pay attention to detail. As more experience is gained, more options are available.
I've always been a huge fan of K.I.S.S. (not the rock band )

It *was* the nature of the beast years ago. A lot of short hop, daily driving would let the engines develope sludge and carbon deposits. Combines with leaded gas, poor base oil configurations, average lack of maintenance (and understanding of the importance to the finer details of tuning), etc., and the combustion chamber of the average car was a pretty dirty place
If you were to have the passages cleaned out now, and kept up with good driving habits, maintenance and tuning practices, I doubt they would plug again.