SpiritOf76

My buddy has an Edelbrock 37011 he says I can have for $150.


He told me it is for an engine with EGR, which he says he removed from his, which was also a '76 like mine. He has an L82, but it is all worked over. I don't really go to him for any advice or info, for some reason I do not trust his "knowledge".


I have a '76 all stock. I know EGR stands for Exhaust Gas Recirculation, and the basic idea of it... I guess my question is, is it necessary? Can it be eliminated? If yes or no, is that a good intake for starting my L46 build up?


Thanks.

resdoggie

Throw it away and buy a cover to block the hole.

SpiritOf76

Is it that simple? I'm reading of some idle/acceleration issues without it.

resdoggie

I don't recall any issues on my stock L-82 at the time with oem heads and when I removed it after installing a Performer 2101 intake, egr delete. But to try, remove and plug the vacuum hose on the egr and ensure the egr is closed. Then go for a scoot and see if there are any driveability problems.

SpiritOf76

So is the EGR just nonsense smog equipment?

gungatim

recirculating exhaust gas in the combustion chamber is done for a few reasons. none of them are for performance. some will argue a properly working system does not harm performance. whether it does or not, you do not NEED it for a properly functioning engine, and you CAN safely eliminate it. That may NOT, however, satisfy your state's emission laws.

FWIW, many, if not most owners ditched the EGR and the A.I.R. pumps many decades ago...it's rare to see them intact these days outside of the restoration crowd.

NewbVetteGuy

I'd love to see more discussion on this; I don't know much but I've been trying to learn.

My understanding is that there's two parts of the air / exhaust flow involved in these smog systems. -"EGR" and "AIR"

The super ridiculous part involves the AIR pump literally taking air and pumping it into the exhaust stream to dilute the pollutants and a "poor man's hack" to passing emissions -a poor man's hack given to us straight from GM; I think it's sometimes discussed as the added oxygen helping the catalytic converter to perform some sort of breakdown reaction, but it's actual use is simple dilution. -I've heard that the air pumps at redline RPMs steal 5-6 hp from turning the pump; like 1/2 hp or less at idle. (I think I've seen a post from "Grumpy Vette" that said up to a 15 hp loss with a high performance engine is possible, but I don't understand how this would steal more HP from a higher HP engine; it seems like the loss is just from turning the pump which would be RPM dependent and not engine HP dependent.) -Hmm.... Update: I guess if at high RPM your exhaust flow is your limitation because your exhaust is slightly undersized, pumping more air into the exhaust via the smog pump would just exacerbate the problem and the associated losses COULD be HP dependant. (Airflow through the the engine is directly tied to HP so anything that limits your ability to flow out the exhaust would be a problem.)


The second recirculation component is the Exhaust Gas Recirculation, which, just like it sounds, takes exhaust gas and dumps it back into the intake so that it can be burned again to reduce pollutants a little bit more. The EGR has an added benefit of improving fuel economy because it reduces pumping losses at low RPM- at low RPMs the throttle blades of the carb are mostly closed so they don't pass much air and the vacuum in the cylinder creates vacuum induced drag that makes the engine less efficient. EGR is essentially the original late 60s early 70s "dynamic displacement" technology as the exhaust gasses are partially filling the cylinders and taking up space that would be otherwise occupied by more fuel and more air- this reduces power at idle but it isn't needed at idle and it improves fuel economy. This tech also reduces engine temps and makes early detonation / pinging less likely. It's my understanding that EGR does NOT reduce performance at wide-open throttle when all components are properly operating as exhaust gas is not recirculated at wide open throttle; only partial throttle /low RPMs.


-Supposedly one of the reasons the original exhaust was so restrictive from the factory is that they wanted increased back pressure because it made the flow of exhaust gas into the intake that much easier. -Maybe this is another "Smog ERA urban legend", though; not sure.


Pumping air into the exhaust is dumb and steals power. EGR has got some decent benefits you should think about a bit first.


Note: My confidence interval that all the above is correct is maybe 75% so hopefully this can kick-off a conversation with someone more knowledgeable.

Adam

NewbVetteGuy

There's multiple generations of the Edelbrock Performer (3 I think); each successive generation has better flow and power. If this is the modern 3rd gen (I have no idea how to tell); then $150 is probably worth it. You'll save a ton of weight vs. the L48 iron intake that's currently on your 76 and the Performer will fit our C3 hoods with a normal height air filter. (The Performer RPMs and Air Gaps involve hacks to make them fit.)



Adam

NewbVetteGuy

Between throwing away your smog equipment (including those OEM rams horn manifolds you already got rid of by going to headers), replacing your iron intake with an aluminum Performer, and possibly getting a set of aluminum heads (per the other thread), you could have some nice weight savings in a hurry in your 76 as an added bonus.

Take off the spare tire and replace it with a AAA card, get a composite rear leaf spring, and an aluminum radiator and you'd have some serious weight reduction in a hurry. (I'm good at convincing other people to spend their money; lol!)


Adam

SpiritOf76

OK, so I'll run for a while without the EGR and see what happens.

I'm 2 out of 3 on that 2nd part: Got the aluminum radiator, and no spare tire (not by choice, just don't have one!) composite rear leaf is on my L-O-N-G wish list, along with that intake manifold and heads.

Shark Racer

The idea is that it helps unburnt fuel in the exhaust stream burn up. It's not a "hack" cooked up by GM, a large majority of makes and models on cars have A.I.R. pumps - even my 2006 Porsche Cayman S had one. They were eliminated on GM V8s in the mid 2000s, although I've heard they're starting to come back. We're getting close to the point where we're regulating ant farts.

The primary point of EGR is to lower combustion temperatures with the leaner calibrations and more advanced (at cruise) ignition timing commanded in the late 70s. If you look at a lambda vs emissions chart, it will explain it pretty well.

CO emissions increase as AFRs decrease (richer)
HC emissions increase as AFRs move away from stoich (leaner or richer). These are basically unburnt fuel.
NOx emissions increase as AFRs increase (leaner).

The goal, then, is to minimize CO and HC by maintaining a close to stoich fuel mixture and use auxiliary emissions control systems/designs, like EGR, to minimize NOx emissions. Some modern engines have eliminated the need for EGR through valve timing or cylinder head design. They disappeared from the LS V8 motors around 2001.

Minimizing pumping loss is an interesting point, but I'm not sure how significant EGR's contribution to that is. Generally speaking, at lower loads the engine VE is lower so the cylinder theoretically doesn't "need" as much mixture volume in the cylinder.

Shark Racer

And the lamda vs emissions picture:

NewbVetteGuy

Wow; awesome post!

QQ: Is it possible to eliminate the AIR pump and still keep the EGR capability or are both managed by the smog "AIR" pump?


Adam

resdoggie

In general, how much usable fuel is in exhaust gas that gets reburned to make it worthwhile to have an egr? Like the air pump, another useless device, it pumps air into the exhaust system to make it look like it's reducing exhaust emissions by dilution of the exhaust gas with fresh air. Really??? So you can see why most folks trash the early attempts at emission control because they weren't that effective, added weight to the car which further offsets any benefits, expensive to repair and just looks ugly!

Shark Racer

They're separate systems. AIR injects fresh air into the exhaust system at the exhaust manifolds near the exhaust ports. EGR picks up exhaust air from channels in the head and intake manifold, between the exhaust ports of the center cylinders(2-4, 3-5).

EGR isn't used for re-burning fuel at all. As I said, it's meant for pushing inert gas through the motor to lower combustion temperatures. I'm not sure about the pumping loss suggestion but I'd like to learn more about that theory.

They definitely do help with emissions, particularly EGR and NOx.

jb78L-82

I recently "disabled" the EGR valve on my 1994 mustang GT convertible (31,000 miles) which operates (unlike the C3 EGR) at all throttle inputs off idle since it caused engine pinging at moderate to WOT. All pinging disappeared AND the effect on NOx on the emissions cycle test was 2 PPM increase...really???? Give me a break! The 78 EGR has been gone since 1985...forever. The theory is that using inert EGR gases reintroduced into the intake charge lower combustion temperature HOWEVER, reality is that 500 degree unburned exhaust INCREASED the intake air temp SIGNIFICANTLY and caused pinging. The AIR pump and EGR on a C3 are completely worthless and lowering emissions on 35+ year old cars driven 1/10 of 1% of the time is ridiculous. Throw that crap in the trash!

Theory versus reality...they are not often the same....

cardo0

Edelbrock 37011 for $150? Thats a polished intake thats lighter, flows better than your stock intake and would cost $450 new. It will work with the EGR port in use or blocked. Pick it up but inspect it for cracks or machining.

EGR valves are vacuum operated and should not affect WOT power at all if you choose to use it connected. EGR does lower cylinder temps and emissions as it is even used on the power plant scale as i witnessed.

You will soon become familiar your states smog laws and requirements. Nevada cars beyond a certain age only have to pass the sniff test so mine is long gone. But i would have no problems reinstalling it if needed. Some history here is that by 1996 the LT4 engines had no EGR because the overlap of the stock cam had enough overlap to meet the EGR/emissions requirements. And that was a fairly mild cam (203/210 @ 0.050", lift with 1.6 rocker ratio 476/480, lsa 115 degrees).

Buy it.

centuryoldracer

The air pump adds oxygen to the exhaust to help complete combustion of the un spent fuel in the exhaust system, it does not dilute the mixture, it promotes complete burning of the mixture even though it is doing it in the exhaust system, and not the combustion chambers. Remember that 1/3rd of the fuel goes out of the combustion chambers un burned. This is to keep the pistons from melting. The unburned mixture is acting like a cushion if you will between the piston, and the combusting fuel.
The EGR recirculates exhaust to cool combustion (because it won't burn a second time), and lower Nox emissions. It is completely closed at idle BTW.
Removing it will actually promote pinging because the combustion temps will be higher.
Bottom line though is that as others mentioned adding a aluminum intake, and a properly jetted carb while removing the EGR, and air pump will improve performance.
If you leave it stock, removal of the air pump won't have any affect on drivability, however removing the EGR may if no other tuning/jetting is done.
Edit, and possibly timing. Remember that each car engine reacts a little differently depending on age of the engine, oil consumption, compression ratio, etc.Even gearing, and weight will affect tuning.

gungatim

actually it injects more than oxygen, it is atmosphere, so nitrogen, co2, etc. whatever it sucks. that is assuming the filter is not clogged and the pump is not worn out, and the valves are all working properly...

OP: for more discussion, just do a search. been discussed/argued about many times on this forum...

jb78L-82

For all the EGR proponents out there, please help me understand why not a single engine builder I have ever spoken to has once ever said that inclusion of the EGR valve will not effect performance one bit AND will increase combustion efficiency? Theory versus reality.....

EGR's do lower Nox emissions but like most things in life, it is not a free ride. Unfortunately, like many issues today, there is a lot of spin to try and convince everyone that what is being stated about emissions reducer has only upsides but zero downsides...NOT true!