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View Full Version : Why is an EGR system good automotive design?



Stephen Tashiro
10-21-2011, 8:27 PM
The principle of operation of the EGR system in an automobile engine is to recirculate a small amount of exhaust gas into the intake in order to reduce the oxygen content of the intake gas and thus reduce the combustion temperature. Is this more effective than simply making the mix leaner by injecting less fuel?

I'm replacing the EGR valve on my 90 Corolla (a pain in the neck job) and I notice how small the the tube for the recirculated gas is. It's only a few millimeters in diameter. It's also a good candidate for a tube that will get clogged with carbon. It makes me wonder how much good the EGR system really does.

Chuck Wintle
10-21-2011, 8:33 PM
it reduces the level of nitrogen oxides in the exhaust. Good automotive engineering...no idea.

Kevin W Johnson
10-21-2011, 10:39 PM
Making the mix leaner actually causes the engine to run hotter. Too lean, and you burn valves and pistons, score cylinders, etc. To rich, you burn up catalytic converters, thats why its so important to have a miss condition corrected immediately.

Jim Underwood
10-22-2011, 11:18 PM
it reduces the level of nitrogen oxides in the exhaust. Good automotive engineering...no idea.

Which, in turn keeps the engine from pinging, which is in reality, pre-ignition. Which is not a good thing...

JohnT Fitzgerald
10-23-2011, 9:57 PM
The small tube might just be vacuum line, which activates the EGR. The actual flow of gases would be in the openings (ports) on the manifold.

Larry Edgerton
10-24-2011, 6:49 AM
The small tube might just be vacuum line, which activates the EGR. The actual flow of gases would be in the openings (ports) on the manifold.

Not sure about Honda's but the EGR was a problem when I supercharged my Miata because the manifold was under pressure and it had a metal tube that ran from the EGR valve to the manifold. I welded it shut and left the EGR in place so it did not throw a code.

Myself I do not see the EGR as sound engineering, but I am looking at it from a performance standpoint. I have eliminated them an many cars with no ill effects.