| :1) NO. As I mentioned in the writeup, the exhaust manifold is under considerably more pressure than the intake manifold. I know this because I have put a pressure gauge on the exhaust manifold to confirm what I have heard everywhere else. I was seeing as high as 50psi in my exhaust manifold with an older BB set of turbochargers when running about 22psi of boost. Because of this, the exhaust blows into the intake, not the intake blows out the exhaust. Hmm. Interesting. So then what would keep those same exhaust gasses from blowing back through exhaust valves when the piston finishes pushing the spent fuel out but the valves are still open...in fact open long enough that they overlap with the intake valves. Also, how do you account for those members here who've had rich AFRs that were eventually tracked down to a stuck open EGR valve? That would seem to imply that fresh air under boost is bypassing the combustion process and making its way out through the EGR into the exhaust. Again, this is not a challenge because I'm sure the complexity of this issue allows an explanation that fits both scenarios. I'm just curious about it and wonder if you can explain it. Thanks. :2) You dont seem to understand what I put in the writeup. A stuck open EGR when the plenum is under idle will cause the plenum to suck exhaust gases from the manifold and recirculate it through the engine. This will lower MAS readings and cause the engine to run poorly, dependent on how much of a bleed there is. To test this, hook the EGR directly to any vacuum port on the manifold and watch to see how poorly the engine idles and runs while cruising.
:The volume of exhaust gas that is allowed into the intake is variable dependent on throttle position. When you first crack the throttle open, there is a good bit of vacuum pulling the EGR open. As you open the throttle even more, there is less vacuum felt at the throttlebody chamber port and the EGR begins to close.
:As for the inspections thing, again, I dont think you read all of my post. I specifically mentioned about the visual inspection. I certainly didn't mean to imply that the EGR is supposed to be open at idle. It should only open up during steady state cruising. What I'm still confused about is how exhaust gasses entering the plenum through the EGR can lean out a mixture when the gasses are inert? I read the post. I was just stating my experience for those that are considering removing their EGR. If you do in a smog check II zone, and then your tech will probably find it even if they're inexperienced.
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