EGR valve
Intermediate
Joined: Jul 2010
Posts: 49
Likes: 18
From: Grand Rapids Michigan
Originally they were a device to improve emissions during the engine warm-up phase.. They diverted exhaust gasses from one bank thru a "stove" in the intake manifold and into the opposite bank's exhaust. It was active during a cold start and helped the engine get off choke faster .
Essentially they were like the old heat riser valves upgraded with better materials to improve durability because they were part of the warrantied emission system. Many folks wired them open, especially if they rattled during the opening event.
Once the engine reached operating temperature they opened andwere non functional. Your car will operate OK without it. But if your state has emission testing, you may need it.
Essentially they were like the old heat riser valves upgraded with better materials to improve durability because they were part of the warrantied emission system. Many folks wired them open, especially if they rattled during the opening event.
Once the engine reached operating temperature they opened andwere non functional. Your car will operate OK without it. But if your state has emission testing, you may need it.
Tech Contributor
Joined: Aug 1999
Posts: 14,373
Likes: 6,371
From: At my Bar drinking and wrenching in Lafayette Colorado
Originally they were a device to improve emissions during the engine warm-up phase.. They diverted exhaust gasses from one bank thru a "stove" in the intake manifold and into the opposite bank's exhaust. It was active during a cold start and helped the engine get off choke faster . Essentially they were like the old heat riser valves upgraded with better materials to improve durability because they were part of the warrantied emission system. Many folks wired them open, especially if they rattled during the opening event. Once the engine reached operating temperature they opened and were non functional. Your car will operate OK without it. But if your state has emission testing, you may need it.
You're thinking about the EFE valve. The EGR has nothing to do with engine warm-up or re-routing exhaust through to the opposite bank to get the engine off the choke faster.The Exhaust Gas Recirculation (EGR) system helps reduce the amount of nitrogen oxides (NOx) in the exhaust gases. Nitrogen oxides are normally formed in the process of combustion in the engine cylinders, and their formation increases dramatically at higher combustion temperatures, thus increasing undesirable engine emissions. The EGR system reduces the combustion temperature by diverting a small portion of the exhaust gases back into the intake manifold. Exhaust gases are no longer combustible, so diluting the intake air with exhaust gases makes the air/fuel charge less combustible, thus lowering combustion temperatures and NOx emissions. The EGR only does this exhaust injection when the engine is at part-throttle light cruise after the engine is warmed up, so it has no effect on maximum power or idle (the EGR is triggered by "ported" vacuum and the engine's EGR Thermal Vacuum Switch).
Lars
Last edited by lars; Dec 8, 2020 at 08:26 PM.
8th Gear
Joined: Dec 2020
Posts: 8
Likes: 11
From: North Carolina
On a properly tuned engine at cruise the EGR will actually increase fuel economy. Later on computer controlled engines with computer timing control, 4 way catalytic convertors, knock sensors and variable valve timing NOx was easily controlled. Engineers used EGR strictly for cruise fuel economy. Now of course they don't need them even for that but back in the C3 day's EGR was the only way to get NOx and still have a drivable car
Last edited by RLI; Dec 8, 2020 at 12:37 PM.
Melting Slicks
Joined: Dec 2009
Posts: 3,229
Likes: 656
From: Thunder Bay
If you are not required to have it for an emissions check where you live, I would recommend getting rid of it. I have had my '79 for over 25 years. In the early days I tried very hard to keep it original, including all the emissions devices. The EGR valve gave me more trouble than any other system on the car. It would stick open on a regular basis. When it does it is basically a huge vacuum leak. I tried several valves, but the problem occurred with all of them. I finally gave up and removed it. The car runs much better without it. I know lots of guys have been able to get their cars to run well with a functioning EGR. I'm not one of them.
Le Mans Master
Joined: Jun 2019
Posts: 7,649
Likes: 2,466
From: Indiana
If you are not required to have it for an emissions check where you live, I would recommend getting rid of it. I have had my '79 for over 25 years. In the early days I tried very hard to keep it original, including all the emissions devices. The EGR valve gave me more trouble than any other system on the car. It would stick open on a regular basis. When it does it is basically a huge vacuum leak. I tried several valves, but the problem occurred with all of them. I finally gave up and removed it. The car runs much better without it. I know lots of guys have been able to get their cars to run well with a functioning EGR. I'm not one of them.
my 79 egr worked perfectly...but my design 79 was in fact a positive back pressure valve which means it was a constant vacuum leak when working properly.. there were actually 3-4 designs in my year
https://www.corvetteforum.com/forums...x-power-2.html
see post 22
Last edited by interpon; Dec 8, 2020 at 09:43 PM.
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